c/EPA
" T.'il S'/I'PS
Environmental Protection
Agency
Laboratory
Research T
EPA 600/7-79-166
July 1979
Development of
Droplet Sizing
for the Evaluation
of Scrubbing Systems
Interagency
Energy/Environment
R&D Program Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of, and development of, control technologies for energy
systems; and integrated assessments of a wide-range of energy-related environ-
mental issues.
EPA REVIEW NOTICE
This report has been reviewed by the participating Federal Agencies, and approved
for publication. Approval does not signify that the contents necessarily reflect
the views and policies of the Government, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/7-79-166
July 1979
Development of Droplet
Sizing for the Evaluation
of Scrubbing Systems
by
Hector Medecki, K.C. Wu, and D.E. Magnus
KLD Associates, Inc.
300 Broadway
Huntington Station, New York 11746
Contract No. 68-02-2111
Program Element No. EHE624
EPA Project Officer: D. Bruce Harris
Industrial Environmental Research Laboratory
Office of Energy, Minerals, and Industry
Research Triangle Park, NC 27711
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
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DISCLAIMER
This report has been reviewed by the Office of Research
and Development, U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the
contents necessarily reflect the views and policies of the
U.S. Environmental Protection Agency, nor does mention of
trade names or commercial products constitute endorsement or
recommendation for use.
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ABSTRACT
The measurement of entrained droplets and their concen-
trations in gas streams is an important requirement in
pollution control technology. The use of a hot-wire
sensor can successfully measure the desired parameters for
droplets in the size range from 1 pm to 600 ym.
The development and characteristics of the DC-2
Droplet Counter is reported herein. Extensive testing in
the laboratory are described and the comparison with results
from the Brink impactor is presented. A correlation of
results for these two measurement techniques is achieved.
Field tests at four different sites are also described.
111
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CONTENTS
Abstract iii
Figures v
Tables vii
Acknowledgments viii
1. GENERAL BACKGROUND 1
Principle of Operation 2
Program Plan for Improved Performance 6
2. CONCLUSIONS AND RECOMMENDATIONS 9
3. DEVELOPMENT OF THE PROBE 10
General Background 12
4. THE DC-2 23
General Description 23
Implementation of Temperature Measurement 26
Implementation of Velocity Measurement 26
Droplet Counting 31
Physical Characteristics and Use of the DC-2 31
Data Analysis 35
5. PRINTER/CONTROLLER 41
General Description 41
Functions of Front Panel Switches 41
Interfacing with Two DC-2's 46
Probe Multiplexer System 46
6. LABORATORY INVESTIGATIONS 49
Calibration Tests 49
Laboratory Tests with the Impactor 54
7. FIELD TESTING 76
Colbert Pilot Plant 76
Water Treatment Plant in New York 78
Shippingport Power Plane 78
Cooling Tower of the High Flux Beam Reactor
, at Brookhaven National Laboratory 84
References 91
Appendix
A. Tabulation of Laboratory Tests 92
iv
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FIGURES
No,
1 Principle of Operation of the Sensor 3
2 Electrical Signal from Sensor 4
3 Mechanical Model of Sensor 13
4 Aspirating Probe 16
5 Protected Probe 18
6 Disposable Sensor Probe 22
7 Temperature Conversion Block Diagram 27
8 Sensor Temperature Characteristics 28
9 DC-2 Velocity Measurement Network 30
10 View of the DC-2 Front Panel 33
11 Printout Illustration 42
12 Printer Panel Layout 43
13 Schematic of the DC-2 Interface with
Printer/Controller 47
14 Schematic of DC-2 Interface with Multiplexer
System 48
15 Droplet Calibration Apparatus 51
16 Capture Size vs. Dj_/d 55
17 Laboratory Setup 56
18 Average Number Concentration for Impactor
and the DC-2 Data (Test No. 216) 62
19 Average Number Concentration for Impactor
and the DC-2 (Test No. 212) 63
20 Cumulative Entrainment Volume for Impactor
and the DC-2 Data (Test No. 212) 64
21 Cumulative Entrainment Volume for Impactor
and the DC-2 Data (Test No. 216) 65
22 Salt Collected on Stage 1 66
23 Salt Collected on Stage 3 67
24 Pressure Drop along the Impactor 71
25 Temperature Drop along the Impactor 72
26 Schematic of the Demister Scrubber at the
Colbert Facility 77
27 Distribution at the Prescrubber Demister
Inlet at the Colbert Facility 79
28 Distribution at the Prescrubber Demister
Outlet at the Colbert Facility 80
v
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FIGURES (Continued)
No.
29 Distribution at the Exit Demister Inlet at
the Colbert Facility 81
30 Distribution at the Demister Outlet at the
Colbert Facility 82
31 Demister Cross Section at the Treatment
Plant in Wantagh, New York 83
32 Test Section of a Duct at Shippingport, Pa. 85
33 Average Number Concentration for the Demister
Sections at Shippingport, Pa. 86
34 Average Cumulative Entrainment Volume as a
Function of Diameter for the Demister
Sections at Shippingport, Pa. 87
35 Average Cumulative Entrainment Volume as a
Function of Droplet Size in the Exhaust
of the Cooling Tower at Brookhaven National
Laboratory 89
36 Droplet Number Concentration Measured in the
Exhaust of the Cooling Tower at Brookhaven
National Laboratory 90
VI
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TABLES
No.
1
2
3
4
5
6
7
8
9
Internal Sizing Distribution for Module 1 37
Internal Sizing Distribution for Module 2 38
Internal Sizing Distribution for Module 3 39
Internal Sizing Distribution for Module 4 40
050 for Brink Impactor 59
Cascade Impactor Stage Parameters 70
Rate of Change in Radius for Water Droplets
at 293°K and P^-PQ = 0.1 mmHg 73
Supersaturation Ratio, Pr/P^,, for Water
Droplet at 293°K 74
Rate of Change in Radius for Water Droplet
at 293°K 74
VII
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ACKNOWLEDGMENTS
The work reported herein was performed by KLD Associates,
Inc. under Contract No. 68-02-2111 from the Environmental
Protection Agency, Research Triangle Park, North Carolina.
Mr. Bruce Harris was the Project Officer for the EPA and
his support and suggestions are acknowledged.
The field testing of the instrumentation was performed
at three sitesthe Colbert Pilot Plant in Muscle Shoals,
Alabama; the Shippingport Power Plant in Shippingport,
Pennsylvania; and Brookhaven National Laboratory in
Upton, New York. Mr. Robert Statnick of EPA made the
necessary arrangements at the Colbert Facility,
Mr. Dennis Martin of York Research was responsible for the
arrangements at Shippingport, and Messrs. Seymour Protter,
Michael Brooks and Daniel Oldham assisted us at Brookhaven.
Their support is gratefully acknowledged. The cooperation
of all individuals at the plants was outstanding and con-
tributed greatly to the success of the field testing.
Vlll
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SECTION 1
GENERAL BACKGROUND
The measurement of size and concentration of liquid droplets
in the gas stream of scrubbers and mist eliminators is a require-
ment in pollution control technology. The capability of making
such measurements will lead to improved performance of such
devices and to a better understanding of the processes involved.
Several methods of measuring droplets in such devices can be
suggested, but one measuring device, which uses the heat trans-
fer principle, appears most advantageous because of its
simplicity and capability for in-situ measurements without sample
extraction.
The technique uses a hot wire exposed to the flow with en-
trained liquid droplets. As a droplet attaches to the wire, an
electrical signal is generated. The analysis of this signal
provides information on droplet size. By electronically
processing the signal, the droplets can be sorted into diameter
ranges and the droplet distribution function determined.
Another parameter required for the computation of droplet concen-
tration is the gas stream velocity which is obtained from the
same sensor operating as a hot wire anenometer.
In 1974, KLD Associates, Inc. developed and successfully
demonstrated an instrument using this hot wire principle. The
device, which is designed as the DC-1 Droplet Counter, sorts the
droplets into six size ranges. The laboratory and field studies
provided extensive insight into the droplet distribution in de-
misters. Originally, the measurement range for such devices was
thought to be 20 um to 500 ym. However, the field studies with
the DC-1 clearly showed the importance of measurements in the
range from 1 ym to 100 ym. In addition, the field studies
indicated several areas for improving the operation of the in-
strument; these improvements are summarized below:
Allocation of more than six droplet diameter ranges
for a better description of droplet size distribution.
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Reduction or elimination of adjustments to be per-
formed by the operator.
Elimination of calibration curves, providing the
result of the measurements in digital form and
engineering units (metric system).
Improvement of the probe ruggedness, since this is
the only element with limited life, subject to
breakage and contamination.
In the present report, the work performed in the improve-
ment of the DC-1 is presented. The result of this effort is
a second-generation instrument designated the DC-2 Droplet
Counter.
PRINCIPLE OF OPERATION
The operation of the heat transfer droplet sensor is based
on the cooling caused by a droplet attaching to a hot wire.
The concept is schematically shown in Figure 1, where the hot
wire sensor and its longitudinal temperature distribution are
shown before (a) and after (b) a water droplet (cross-hatched
circle) attaches. The electrical resistance of the wire is a
function of the wire temperature which in (a) is high and sub-
stantially uniform along the wire. In situation (b) the por-
tion of the wire covered by the droplet is cooled to approxi-
mately the droplet temperature. A constant electrical current,
which flows along the wire to heat it, shows a measurable
voltage drop at the wire support when a droplet is attached to
the wire. The voltage encountered before droplet attachment
(a) is reduced for condition (b) in direct proportion to the
cooled length of wire; i.e., the droplet diameter. The elec-
trical energy delivered to the wire evaporates the water,
leaving the sensor dry and ready for further interaction.
The above description of the principle of operation of the
instrument is an idealization, and in actual practice, the
electrical signal is rather complex. A typical electrical
signal obtained during a droplet-hot wire interaction is shown
in Figure 2. Reduction of the voltage implies cooling of the
wire. An initial fast decay of the signal is observed; it
corresponds to the initial lateral contact of the droplet and
wire with a basically radial cooling of the wire. The duration
of this portion is of the order of a few microseconds. The
less steep signal following the initial contact is caused by
the droplet centering around the wire and by the longitudinal
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Support Support'
Hot Wire
Hot-|-
Ambient
Temp.
Wire Longitudinal
Dimension
(a) Temperature before Attachment
Wire Temp.
Hot+
Ambient
Figure 1
Wire Longitudinal
Dimension
(b) Temperature after Attachment
Principle of Operation of the Sensor
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Voltage
Droplet
Wire
Contact
Longitudinal
Cooling
Droplet Heating
Droplet Evaporation
Time
Figure 2; Electrical Signal from sensor.
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cooling of the wire beyond the area covered by the droplet.
During this time, a warming of the droplet-wire takes place,
raising the signal until the boiling temperature is reached;
the droplet shrinks due to evaporation and disappears. The
voltage in the wire then returns to the initial level prior
to interaction of the droplet.
For the purpose of determining the droplet diameter, only
the signal during the droplet contact is relevant and this
portion is processed in both the DC-1 and DC-2 instruments.
The processing is performed electronically, separating the front
of the signal and frequency filtering it. After the analysis
of a droplet is started, the processor does not accept a
second droplet until the first droplet is fully evaporated
and the hot wire sensor is restored to the proper operating
temperature.
The calibration of the instrument (i.e., sensor output
versus droplet diameter) is performed by simultaneously taking
a microscopic picture of the droplet and measuring the corres-
ponding electrical signal from the sensor (voltage drop). The
apparatus for this purpose will be described later. Many
calibrations may be obtained for different settings of
operating conditions and signal processing; however, an opti-
mum calibration was obtained as a compromise among many con-
flicting requirements, some of which are:
One sensor and one operating .temperature should
cover the total droplet size range from 1 ym to
600 urn.
The calibration curve should be monotonic.
Air turbulence signals should not introduce false
counting.
The calibration curve should be independent of the
droplet velocity relative to the sensor.
These requirements were achieved in the implementation of
the DC-2 Droplet Counter, and its use in the field proved this
approach to be sound.
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PROGRAM PLAN FOR IMPROVED PERFORMANCE
A program to upgrade the characteristics of the droplet
counter was undertaken. The major areas of work to improve
its performance may be separated into five tasks as discussed
below:
Improve Probe Life and Reliability
The objective was to improve the design of the
probe by making it more durable in a field
environment. Three probe configurations were
investigated: the aspirating probe, the supported
probe and the replaceable probe. The following
improvements were implemented:
a) The construction of the probe was modified
to reduce damage during handling and
installation. The configuration was modified
to reduce the possibility of breakage due to
large solid particles moving with the flow;
b) Techniques of cleaning the sensor while
operating in slurries and deposit-prone
contaminants were developed;
c) Effect of corrosive environment on the probe
components was investigated in both laboratory
and field tests;
d) A replaceable probe was designed, built and
tested in the laboratory.
Improve the Functional Characteristics of the
Instrument
The objective was to provide increased capability
of the droplet counter/measuring device. This
objective was accomplished by:
a) Increasing the storage capacity of each storage
bin from 999 to 10,000 counts;
b) Increasing the number of bins characterizing
droplet size to fourteen (14);
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c) Providing a buffered output for the measured
data. Such output may be then interfaced
with an external recording and display
device:
d) Providing a display of flow velocity and
temperature in engineering units;
e) Controlling the selection of the droplet
size range of each bin by changing
modules on the front panel;
f) Extending the capacity and control of the
sample interval timer by providing several
selectable time limits to a maximum of
1,000 seconds.
Modification of the Physical Characteristics and
Construction of the Instrument
The objective was to better adapt the droplet/
counter/measuring device to field work by making
it more transportable and convenient to use.
The device was redesigned as a small package
with space for cables and probes. Based upon
the new design which incorporated all the
electronic improvements discussed above, two
(2) units were built for the EPA after receiving
approval from the EPA Project Officer
Develop a Printer/Controller
The objective of this phase of the effort was
to provide the measured data in the form of
printed hard copy. In addition, the controller
was to automate the operation of the instrumen-
tation and be able to simultaneously monitor two
DC-2's. The device is also capable of controlling
up to 12 hot-wire probes in a multiplex mode of
operations. The Printer/Controller was used
extensively in the laboratory and field tests of
this project.
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0 Laboratory Test and Field Validation
The objective was to calibrate and validate the
two droplet counter/measurement devices result-
ing from the modifications as discussed
above in preparation for delivery to the EPA.
The following work was performed in the
laboratory in order to ascertain the performance
of the improved instruments:
a) A calibration of the instruments was performed;
b) The instruments were made to operate with
sprays simulating those encountered in
typical facilities;
c) Design modifications were incorporated to
improve the performance under the simulated
conditions
d) An extensive test and measurement program
was performed with a Brink impactor in the
KLD laboratory. The primary purpose of these
tests was to generate data for comparison with
the measurements simultaneously recorded with
the DC-2.
After the operation of the instruments was optimized
in the laboratory, a program of field validation
was undertaken. Four facilities were selected and
approved for field measurement bv the EPA
Project Officer.
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SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
A prototype instrument had been previously built and
successfully used in the field for measuring droplet size and
concentration in gas flows. The device operated on the heat
transfer principle described in Section 1. Under the program
reported herein, a second generation of the instrument was
implemented and demonstrated in the field. From the work on
the improved version of the instrument, the following conclu-
sions and results were reached:
» Water droplets from 1 to 600 microns in diameter,
flow velocities up to 10 meters per second and gas
temperatures between 0°C and 100°C can be readily
measured by the improved instrument (DC-2). The
distribution of droplet sizes is subdivided into
14 size ranges by the device.
The involvement of the operator is reduced to a
minimum and no auxiliary equipment is required to
perform the measurement.
« The instrument is particularly suitable for field
use because of its portability and the small size
of the sampling probe.
The probe is the only component which requires
care during handling and use. Special effort was
devoted to ruggedize this component. Furthermore, a
replaceable sensor was designed and successfully
tested in the laboratory.
« The Printer/Controller enhanced the operation of
the DC-2 in the laboratory and in the field. The
printed data facilitates the reduction and
interpretation of results.
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The results from the laboratory and field studies
provided some specific conclusions with respect to the
measurement of droplet distributions:
« The data obtained with the Brink impactor was
higher than the data from the DC-2.
This conclusion was reached after careful
attention to minimize the data scatter in the
impactor results.
Measurements from the Brink impactor can be re-
lated to the DC-2 measurements using an equiva-
lence factor, K, which is applied over the size
range of 1 ym to 10 vim. The equivalence factor
represents the aerodynamic influence on the
capture area of the wire and other phenomena
which characterize the difference in the two-
measurement procedure. The aerodynamic
influence was investigated and defined for the
size ranges between 1 ym to 10 urn.
Laboratory measurements with the impactor
exhibited substantial scatter even with care-
fully controlled procedures. If the droplets
were water without trace elements as a diagnos-
tic, the scatter in the data was unacceptable and
meaningful results could not be obtained. By
using a 10% solution of NaCl, more reliable
results were achieved.
From a series of qualitative tests, it was con-
cluded that the scatter in the impactor results
is caused by evaporation/condensation within the
impactor. Small changes in environmental condi-
tions can significantly alter the measurements
with the impactor.
« The DC-2 was used at four different field sites,
and the device performed well. The Shippingsport
Power Plant has a limestone scrubber, and the
entrained liquid in the exhaust flow provided the
most difficult test conditions. However, with the
correct procedure, meaningful results were achieved
with the DC-2.
10
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As a result of this research project, several recom-
mendations can be made with respect to future activities in
droplet measurements:
- Further field testing should be performed with the
DC-2 and Brink impactor. These measurements should
be compared and the reliability of the two proce-
dures established. The test sites should be
selected to encompass many different test environ-
ments to establish a range of applications for
both devices.
Guidelines and procedures should be developed for
the operation of the DC-2 and the impactor for
droplet measurements at various types of facili-
ties. These procedures should be documented in a
handbook for use by a field team.
0 The replaceable probe for the DC-2 provides many
advantages for operating the equipment in the
field. The development of this equipment should
be completed and introduced as a field operating
procedure.
11
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SECTION 3
DEVELOPMENT OF THE PROBE
GENERAL BACKGROUND
The probe is the component which performs the droplet
measurement when inserted into the flow under investiga-
tion. The probe has the shape of a thin cylinder and is
connected to the electronic processor with a single coaxial
cable. Attached to the probe is a sensor composed of a
platinum wire, five microns in diameter and one millimeter
long. The sensor detects droplets while the remaining part
of the probe provides a means of mounting and protecting the
sensor.
The diameter of the platinum wire was selected as a
compromise between its mechanical strength, requiring a
large wire diameter, and the minimum droplet diameter to be
measured, requiring a small wire diameter. The sensor is the
only component of the droplet counter subject to damage, con-
tamination or destruction. The improvement of the probe, in
particular the sensor, will result in a more useful and
reliable instrument.
Sensor as a Mechanical Structure
The reliability of the sensor and its mount is directly
related to the accuracy of its measuring capability as well
as its structural soundness. Studies were conducted to test
the sensor's reliability for measurement and handling.
The mechanical model of a typical sensor is shown in
Figure 3. The main supporting structure is a rigid metal ring
built around the sensor and at the end of the probe. The
diameter of this ring is approximately one centimeter (.4
inches), which is large enough to prevent the accumulation of
water which may eventually clog the sensor. The sensor is
mounted across the ring on two prongs (b). The prongs, each
3 mm long, provide both mechanical support and electrical con-
tact. The sensor, originally a silver plated platinum wire,
12
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Figure 3: Mechanical Model of Sensor
13
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is soldered at the two prongs. The silver coating is then
removed from a section of the wire with nitric acid exposing
one millimeter of sensor (S). It is this exposed section that
is sensitive to and measures droplets. The remaining unexposed
platinum wire (a) serves as additional support for the sensor.
The dimensions of the sensor and its surrounding supports are
presented in Figure 3.
This mechanical model was tested for its response to:
Vibrations (acceleration),
Aerodynamic flow,
Collision of solid particles
In all practical situations, accelerations along the axis
of the sensor and support cannot produce breakage. The sensor
is much more sensitive to accelerations along directions
perpendicular to the sensor axis. The sensitivity depends
on the initial tension of the wire which is basically taut
after the silver coating is dissolved, but acquires a certain
amount of slack when heated. An additional limitation is
introduced by the flexure of sensor supports (b) in Figure 3.
The flexure increases the separation of the prong tips. The
widening gap between the prongs eventually becomes larger
than the length of the sensor, thus breaking it. The study
indicates two separate solutions to the lateral acceleration:
Very light supporting prongs so that the
longitudinal strength of the sensor prevents
its separation
Strong prongs with large sections to minimize
the deflection
For relative ease of construction and to minimize the
electrical resistance of the connection, the second approach
was taken. Also slack in the wire greatly improves the
sensor integrity. Furthermore, it became apparent that the
use of tapered prongs reduces deflection for a given value of
lateral acceleration.
Extensive testing showed that a substantial gain in probe
ruggedness may be achieved by mounting the supporting ring on
a resilient structure. This substantially reduces the level
of acceleration transmitted to the sensor. This feature was
incorporated in the disposable sensor probe.
14
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The effect of air flow and the turbulence normally
associated with this flow may cause oscillation of the sensor.
The amplitude of this oscillation increases with the slack in
the wire. Other factors inducing sensor vibrations with
associated flexure fatigue include the random attachment of
water droplets on the sensor and the collision of solid
particles with the sensor. The requirement of a taut sensor
able to survive a strong gas flow contradicts the requirement
of a slack sensor, necessary to withstand large lateral
acceleration. A compromise between the conflicting require-
ments should allow a deflection of the sensor center point of
the order of 50 microns. However, the technique used to build
the sensor does not allow for such close control.
The collision of solid particles with the sensor requires
it to be slack to withstand the impact without breaking. The
maximum force which may be applied to the sensor before it
breaks is approximately .5 gms. With the above mentioned 50
microns of slack, breakage occurs when a 100-micron diameter
particle moving at 10 meters per second directly collides
with the sensor. At a relative velocity of 1 meter per second,
solid particles within the diameter range of a quarter of a
millimeter may destroy the sensor. There are no obvious
solutions to eliminate or reduce the risk of such collisions.
The use of a deflecting rod located upstream of the sensor and
mounted parallel to it was one of the approaches tested. This
solution, however, had limited success. The function of this
rod was to deviate the large solid particles or, at least, to
reduce their velocity to a safe value prior to collision with
the sensor. In practice, however, the excessive collection of
water on the rod prevented the proper interaction of drop-
lets with the sensor.
The Aspirating Probe
The aspirating probe shown in Figure 4 uses the same
platinum wire sensor adopted for the open probe. This sensor
is mounted across a small tube having a 1 mm to 6 mm inside
diameter (.040 to .25 inch). A vacuum pump is used to create
a gas flow along this tube.
Tests with the aspirating probe in the field and labora-
tory showed that the possibility of damaging the sensor during
handling and operation is almost entirely eliminated. It was
also shown that, with a proper design of the conduit entrance,
the amount of noise due to air turbulence may be substantially
reduced.
15
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o\
Enlarged Section of the Entrance
Suction
Figure 4: Aspirating Probe
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Several problems are associated with the aspirating probe,
a description of which follows.
To remove a droplet having a diameter of 600 microns from
the sample flow and move it past, the hot wire sensor requires
an air flow velocity of approximately 30 meters/second (100
feet/second) around the sensor. However, this velocity is
too high to assure proper interactions of droplets and sensor.
Large droplets are shattered. Interaction time of the small
droplets and sensor is too short, greatly reducing the signal
output. The reduction of aspiration flow velocity below
30 meters/second prevents the detection of large droplets. As
an example, a flow of 3 meters/second (10 feet/second) does
not allow for detection of droplets 150 microns or larger.
Another problem associated with the operation of the
aspirating probe at a high flow velocity is that the count
rate may exceed the maximum counting rate of the instrument,
which is 500 droplets per second. An attempt to solve this
limitation was made by using a dilution stage. Such a stage
mixes a measured droplet-carrying flow with a measured clean
air flow, thus reducing the droplet concentration to a level
which is compatible with the instrument count rate. The sensor
is designed to operate on this diluted sample.
The implementation and operation of a dilution stage is
a rather involved procedure. Measurements performed in the
laboratory showed poor repeatability. Differences in the
temperature of the mixing gases affected the measurements.
Furthermore, in order to create a good sample dilution, strong
mixing of the two flows is required. The turbulence necessary
for this mixing affected the results of the measurement of
small droplets. The results of this study were presented
to the contract monitor and it was decided that further work
with the aspirating probe should be discontinued.
Protected Probe
In order to increase the sensor life, a new probe configu-
ration was implemented. The basic idea was to have a sturdy
body with an enclosure to protect the sensor when not .in use.
Several configuratons were implemented and tested. The one
finally selected is shown in Figure 5. It consists of tubing
having a diameter of 10 mm (.39 inch) and a length of 30 cm
(12 inches). A hole is bored in one end of the tube where the
sensor is located. A BNC connector provides the electrical
connection. A thin 12 mm (.5 inch) diameter tubing slides
17
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OPEN POSITION
oo
CLOSED POSITION
Figure 5: Protected Probe
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along the probe closing the opening and protecting the sensor
when not in use. The support for the sensor is short and
strong to minimize the amplitude of vibration of the sensor when
the probe is subject to impact during handling.
To use strong cleaning substances such as hydrochloric
and other inorganic acids, the probe is constructed from
corrosion-resistant materials. The body of the probe and
support of the sensor is made with stainless steel and the
insulating material is ceramic.
Techniques to Clean the Sensor
A study of techniques to clean the sensor after it has
been operating in slurries and deposit-prone mists and sprays
was undertaken. These techniques may be grouped into three
approaches:
Heating,
« Mechanical cleaning,
Liquid cleaning.
Some of the contaminants which accumulate on the sensor
may be removed by heating the probe above the contaminants'
boiling or decomposition temperatures. Unfortunately, the
contamination may include substances which become baked onto
the sensor under the effect of heat. This results in a crust
which is difficult to remove by other methods. Hence, it was
concluded that heating the probe is not an acceptable cleaning
technique.
The mechanical approaches included ultrasonic and sand
cleaning techniques. The ultrasonic cleaning was performed by
submerging the contaminated sensor in a cleaning fluid and
subjecting it to an ultrasonic agitation. The enhancement of
the fluid cleaning effect was negligible when low ultrasonic
power was used. To be effective, the ultrasonic agitation
technique required high power. The extent of this power, how-
ever, is capable of destroying the sensor due to mechanical
vibration. An attempt to solve this problem was made by
designing sensors with a smooth transition between the exposed
platinum wire and the silver supporting wire. While sensors
of this design did last longer than short transition sensors,
they also tended to fail, probably due to flexural fatigue.
All the ultrasonic cleaning was performed at a frequency of
30 KHz. If the assumption that sensors break due to flexural
fatigue is valid, the use of higher frequencies, and thus
substantially lower vibration amplitudes may achieve the
19
-------
cleaning of the sensor without breaking it. Such an extension
of the work was not pursued.
Sand cleaning techniques were performed by dropping sand
on the contaminated sensor and also by sand blasting the
sensor with a small air jet containing fine particles. The
dripping technique was successful, but required relatively large
particles and consumed excessive time. The sand blast approach
consumed much less time, and was particularly effective for the
removal of dry deposits. The sand blaster is mounted in a
small jar with a rubber stopper one inch in diameter. The
probe, air jet tube and ventilation tube are mounted on the
stopper. The sensor must be rotated to expose all areas to the
jet stream of sand. Sticky coatings on the sensor such as
grease tended to collect the sand, stopping the cleaning
action. The best results were achieved with alundum grade 400
which is used to grind optical glass. It was discovered that a
slight increase of the sensor's resistance (~.04Q) during the
cleaning operation was a good indication that the bulk of the
contaminants were removed. Care should be observed to keep
the grinding sand dry.
Liquid cleaners are used either to dissolve the contami-
nants or to decompose them through chemical reactions.
A variety of organic grease and mineral oil type con-
taminants are easily removed with a sodium hydroxide solution,
which is a good general-purpose cleaner. Greases and oils may
also be removed with carbon tetrachloride. Carbon and soot
may be removed with commercial liquids used to clean carbure-
tors .
The operation of the probe exposed to tap water shows
accumulation of white crystals, mostly sulfates. Solutions
of hydrochloric acid 10% prove to be very effective to remove
these crystals. As mentioned previously, to submerge the
probe in such a corrosive medium, a corrosion proof probe was
built using stainless steel for the body and sensor support.
The sensor itself uses silver and platinum which are able to
withstand the acid. As a dielectric insulator, a ceramic
material was used.
Some of the contaminants encountered during the field test
of the instrument are soluble in plain water or boiling water.
Such is the case of the ammonia sulfate crystals typical of the
pilot scrubber at the Colbert Steam Plant in -Alabama. Water
is also effective for the removal of sodium chloride crystals.
20
-------
From the described work on sensor cleaning, it has been
concluded that sand blasting as well as liquid cleaning may be
used to deal with almost all contaminants. The selection of
the most effective liquid cleaner requires some systematic
search.
Work on Disposable Sensors
Work in the field showed that the cleaning of the con-
taminated sensor is a time consuming operation, especially
when dealing with limestone solutions. In order to expedite
the measurement procedure, direct replacement of the contami-
nated probe with a new one was adopted as a standard procedure.
The convenience of having an inexpensive sensor which can be
replaced in the field, saving most of the probe's supporting
structure, is obvious and a study was undertaken.
The disposable sensor was built on a two-prong plug.
The most important consideration was to have good mechanical
supporting characteristics and low electrical resistance of
the contacts. The corrosion resistance of the materials was
not important, since it operates for a short time and it is
disposable. Figure 6 shows the disposable sensor probe
successfully tested in the laboratory.
Tests were performed with these probes in the laboratory
without any problem or deterioration of performance as compared
to other types of probes. A probe having the socket mounted on
a resilient mount is presently being investigated by KLD. This
will effectively reduce the acceleration of the sensor below
the breaking point when the probe body or protective ring is
impacted during handling or use. The cost of the disposable
sensor material is negligible and only the cost of labor for
its construction is relevant.
The laboratory work demonstrated the feasibility of the
disposable probe, but only limited field experience was possi-
ble. KLD recommends that future activities include extensive
field testing of the disposable probe.
21
-------
Sensor
Figure 6: Disposable
Sensor Probe
22
-------
SECTION 4
THE DC-2
GENERAL DESCRIPTION
The DC-2 is a modified and advanced version of the DC-1
model. The droplet counter/measuring device was extensively
investigated in the following areas:
0 Temperature flow measurement,
9 Velocity flow measurement,
e Droplet counting,
e Modifications of the physical characteristics
and construction of the instrument.
The use of the DC-1 droplet counter requires the operator
to determine the precise measurement of the probe's resistance
under various conditions of gas flow, velocity, temperature1
and instrument settings. A built-in meter (incorporating a
'wheatstone tri igo) is used to perform these measurements in
the DC-1 as follows (see Ref. 1):
« Setting the DC-1 dial on "TEMPERATURE," the sensor
resistance is measured as the temperature of the
gas is obtained. This is accomplished by means of
a calibration curve showing sensor resistance versus
gas temperature.
Setting the dial on "VELOCITY," the sensor
resistance is first measured for a no-flow con-
dition (zero velocity). This is achieved by
enclosing the sensor within a shielded container.
The sensor resistance is again measured by exposing
the sensor to the flow under study. The gas flow
velocity is obtained from a calibration curve,
depicting gas flow velocity versus the ratio
between shielded and exoosed sensor resistance.
23
-------
e After obtaining the sensor resistance for the
gas temperature inside the stack, an overheat
condition is set on the Wheatstone bridge at a
resistance 1.75 times this resistance. The DC-1
is then set to count. The electronics automati-
cally maintain the sensor temperature at 192°C
above the gas temperature. At this time, the
measurement of the droplet diameter occurs. The
counting is allocated to six droplet diameter
ranges determined by the particular plug-in dis-
tribution module selected.
The convenience of reducing the operator's involvement,
as described above, to a minimum became evident after using
the DC-1 Droplet Counter in the field. To achieve this,
each one of the steps required to perform the measurements
was investigated. Possible schemes for their automatic
operation were devised and compared. The most suitable were
selected.
The success of automatic operation of the droplet counter
depends on the following:
e To fabricate sensors so that a precise correla-
tion between absolute temperature and sensor
resistance is achieved. The fabrication of a
calibrated sensor requires that a specific resis-
tance be achieved at the ambient temperature at
which the etching takes place.
To replace operator handled calibration curves by
automatic electronic processing. For this require-
ment, the highly non-linear relationship between
gas flow velocity and electrical output is
linearized by an appropriate circuit.
e To automatically balance the Wheatstone bridge during
the measurement of the flow temperature. It should
be emphasized that the measurement of the gas
temperature itself has no relevance for the
measurement of droplet size and concentration.
However, this temperature is required to set the
operating condition of the sensor at a specific
and constant temperature above the stack tempera-
ture, thus achieving the proper cooling effect from
the interacting droplets.
24
-------
All the above aspects were successfully accomplished in
the course of the project, resulting in an instrument which
performs the entire measuring sequence automatically.
The operator of the DC-2 is only required to locate the
probe on the facility and switch the power on. By pressing
the START button, the following automatic sequence takes
place:
The sensor is cold. Its resistance, indicative
of the gas temperature, is measured with an
electronic circuit by balancing the i^hearsitoiie
bridge. The number of steps required to
achieve this balance is a direct indication of
the temperature. The temperature is displayed and
stored in digital form. The entire measurement
takes less than a second.
At the completion of the temperature measuring
cycle, the Wheatstone bridge becomes imbalanced.
The electronic feedback circuit heats the sensor,
increasing its temperature a prescribed amount
above the measured gas temperature. The electric
power required to keep the sensor temperature at
this level is proportional to the cooling due to
gas-to-sensor relative velocity. The electrical
power is digitized, stored and displayed. This
measurement requires less than a second.
o The pulses generated by the cooling of the sensor
under the impaction of the droplets are analyzed
for amplitude. Each is then categorized into one
of 14 droplet size intervals, plus a total. The
time required for this process depends on the
number of droplets being counted or the time limit
setting. During the counting period, a "C" appears
on the display. On reaching a time or droplet
count limit, an "H" (HOLD) appears on the display.
e If the "START" button is pressed while the instru-
ment is measuring velocity or counting, a time
delay assures that the sensor cools and reaches
equilibrium with the surrounding gas prior to the
measurement of the temperature.
25
-------
« When the time or droplet count limit is reached,
the power to the sensor is disconnected, extending
its life and preventing the accumulation of
deposits.
IMPLEMENTATION OF TEMPERATURE MEASUREMENT
The stack temperature is available directly at the DC-2
output display, via the front panel slide select switch. The
operator simply sets the switch to "TEMPERATURE", presses
the "START" pushbutton, and reads out the temperature directly.
The readout is in units of degrees centigrade, with a range
of 0°-100°C and a resolution of 1°C.
Figure 7 depicts a block diagram of the "Temperature
Conversion Logic." In the DC-2 unit, a ladder network (not
to be confused with the interval size module) controlled bv a
counter and comparator, replaces the potentiometer/null meter
employed in the DC-1. When the "START" button is pressed,
both the binary and decade counters are automatically incre-
mented to the point where the ladder resistance equals the
sensor resistance. The counters contain the available stored
temperature information for display purposes. The etching of
the platinum wire requires 4 ± .040 at 25°C to insure a match
in thermal characteristics to the matched ladder network.
Figure 8 depicts the sensor conductance versus temperature
characteristics. The linear approximation curve resulting
from the ladder network is also displayed. Sources of error
in the temperature readout and their associated percentage
of error are as follows:
Linear approximation ±4%
Resistance of ladder ±1%
« Resistance of probe ±1%
DC drift in the comparator ±1%
These errors, of course, will not always cumulate in bhe
same direction. An RMS average is more realistic, resulting
in a full scale-percent error of ±4.35%.
IMPLEMENTATION OF VELOCITY MEASUREMENT
Several improvements for velocity measurement have been
incorporated in the DC-2. First, the measurement was automated,
In addition, the measurement range and accuracy were improved
by three changes:
26
-------
+ 5 VDC
8-Bit Ladder
Network
Binary Counter
(8 bits)
Decade Counter
(3 decades)
(To Display Multiplexing)
Figure 7: Temperature Conversion
Block Diagram
27
-------
274-,
264-
254-
244-
234-
224-
214-
204-
194-
184"
174
Sensor and Cable Conductance (]
0 (i
Linear Approximation
10 20
Figure 8:
30 40 50 .60 70 30 90
Sensor Temperature Characteristics
100
28
-------
The probe temperature was elevated (overheat
mode).
« Constant probe temperature was employed instead
of constant probe heating current.
« A precise linearizer circuit was used to compensate
for the response of the sensor.
e A special circuit was incorporated to compensate
for droplets which strike the probe and tend to
cause velocity measurement errors.
The DC-2 Droplet Counter provides a direct indication of
the flow velocity in digital form. It is displayed by
setting the slide switch to "VELOCITY". The readout is in
meters per second. The range is between 0 to 10 with a
resolution of .1 meter per second.
In measuring velocity with the DC-1, a constant heating
current is employed, whereas with the DC-2, the sensor is
maintained at a constant temperature. A feedback power
amplifier maintains a sensor temperature of approximately
250°C above the ambient temperature. ^.his automatic setting
is performed in two steps:
The Wheatstone bridge is balanced, as described above,
for the gas temperature measurement.
The sensor is heated by short circuiting half of
the bridge resistance, n, (see Figure 9) and
connecting a power amplifier on the feedback loop.
The sensor is heated until its increase in resistance
restores the bridge balance.
From the principle associated with the operation of the
hot wire anemometer, it is known that the cooling effect of
a gas flow depends on the temperature difference of the sensor
and gas and on the velocity of the gas. The voltage, VB, is
directly proportional to the energy released from the sensor
because of the gas flow. This voltage ranges from .8 volts at
zero velocity to 1.3 volts at a velocity of 10 meters per
second. An amplifier is used to subtract the voltage at
zero velocity. The amplifier also scales the electrical
signal which is fed to a squaring network. This results in a
relationship of linear voltage versus gas velocity.
29
-------
Power
Amplifier
800 mv
1300 mv
Scaling
Amplifier
and D.C.
Restoration
0 V
5 V
Squaring
Network
0
2.5V
Voltage
Controlled
Oscillator
0-]
»
l
.00 PPS
1-Second Gate
3-Decade
Counter
To
Display
Multiplexing
Figure 9 : DC-2 Velocity Measurement
Network
30
-------
To digitize the gas velocity information, the linearized
signal acts on a voltage controlled oscillator whose
frequency is zero for no flow and increases to 100 pulses per
second for a flow of 10 meters per second. The output from
the voltage controlled oscillator is accumulated during one
second. The information is stored and displayed in meters
per second. The presence of large numbers of droplets in the
gas flow has a cooling effect which may be interpreted by the
instrument as an apparent higher gas flow velocity. To
compensate for this error, a special circuit was conceived
and incorporated into the DC-2. The basic idea is the
separation of droplet signals, with characteristic spikes,
from the constant level electrical signal created by the gas
flow. The droplet signals are integrated and the correction
is subtracted from the total bridge voltage.
DROPLET COUNTING
The operation of the DC-2 in the count mode differs
from the operation of the DC-1. The DC-2 is automated
with three droplet TOTAL LIMITS and three TIME LIMITS.
Furthermore, the number of droplet size intervals was
increased from six to 14.
The operator of the DC-2 does not have to make any
potentiometer/null meter measurements as is necessary
with the DC-1. When the operator presses the "START"
button, the temperature ladder network is automatically set
to the probe resistance as previously described. At the end
of the temperature conversion cycle, lasting for less than
one second, the DC-2 automatically goes into the count mode.
This starts with the overheat mode, which is described in the
velocity flow section. The overheat is held throughout the
entire count cycle and is released when the preset limit is
reached. Overheating of the probe only occurs during the
count mode, thus augmenting the life of the probe. The
storage capacity of each of the size intervals for droplet
diameter was increased to 10,000.
PHYSICAL CHARACTERISTICS AND USE OF THE DC-2
Particular attention was devoted to better adapt the
Droplet Counter to field work by making it more transportable
and convenient to use. The DC-2 consists of the device itself,
five probes, four modules for different droplet size ranqes and a
coaxial cable approximately 15 feet long. All components are
neatly contained in a portable case. The dimensions of the
case are :
31
-------
Length: 36.5 cm (14 1/2 inches)
Width: 15.1 cm (6 inches)
Height: 15.3 cm (5 27/32 inches)
Weight: 4 kgm (10 Ibs.)
The case and card bucket are made of drawn aluminum.
The circuit cards are wire-wrapped and made of glass epoxy.
The instrument is powered from 125 VAC (±15%), 60 Hz line,
requiring 2.5 watts of power. The electronics were
designed with low power CMOS logic. The digital display
is a liquid crystal type, chosen for its superior performance
in bright ambient light.
A view of the instrument panel is presented in Figure 10,
Use of the Instrument
In order to collect data on droplet size and concentra-
tion, the instrument must be powered from a 110-volt, 60-Hz
line. The coaxial cable and probe are connected with the
instrument OFF. A toggle switch is used to activate the
instrument; no warm-up period is required. The probe is
inserted into the flow under study. It is important to
realize that the DC-2 monitors the flow conditions and drop-
let population practically on a single stream line. Whenever
average conditions over the facility cross section are
desired, an appropriate set of sampling points must be
adopted.
It is important to position the sensor axis perpendicu-
lar to the gas flow to obtain valid gas flow velocity and
droplet population data. In certain facilities, the flow
direction is not known; e.g., flow rotation generated by
spinners, blowers or flow barriers. A proper sensor
positioning is achieved by observing the velocity reading
while reorienting the sensor direction. The maximum
measured gas velocity corresponds to a sensor oernendicular
to the flow direction.
The probe should be handled with care to avoid damage or
destruction of the sensor due to impacts. Droplets and gas
flow do not damage the sensor.
32
-------
U)
Kl.l) .'.I .. . -kl ! . INC
; f - r IMIJ I Ljrj ijTAriorj. MY
Figure 10: View of the DC-2 Front Panel
-------
Selection of the Droplet Distribution
Four sizing modules are made available to the operator as
shown in Tables 1,2, 3 and 4. Two of them cover the entire
droplet diameter range of the instrument, while the other two
emphasize detection of smaller droplets. The operator selects
the module which best describes the facility conditions and
inserts it in the holder at the left side of the front panel.
The removal of the module is performed by pushing upwards
through a slot at the side of the module holder. A series of
numbers are printed at the exposed side of each network.
These numbers represent the droplet diameter in microns.
The readout select switch points to the interval number on the
right and the corresponding droplet diameters on the left.
The interval size represents the smallest droplet diameter
for each interval. The electronics also keeps a count of
the total number of droplets.
The total number of droplets to be counted is selected
by a toggle switch which allows for the selection of 100,
1,000 or 10,000 total number of droplets.
If so desired, the instrument can be operated on a time-
limit basis by selecting, with another toggle switch, 10,
100, or 1,000 seconds.
The droplet counting process will stop whenever the total
selected number of droplets or time limit is reached, which-
ever happens first. When this occurs, the letter "H" appears
in the display, signifying that the system is in hold, awaiting
another cycle initiation.. The following data is available
for readout:
TEMPERATURE of the gas,
VELOCITY of the gas flow,
TIME interval,
TOTAL number of droplets and the
number of droplets in each one of the 14 size INTERVALS.
Handling and Maintenance
A few precautions are necessary in handling the DC-2 to
achieve maximum performance and prevent damage to the sensor.
The probe should never be treated roughly, nor should the
operator attempt to touch the sensing wire. The sensing wire
may be broken if the aerosol stream contains large solid
particles.
34
-------
For best operation, the probe should be kept clean. A
medium power magnifier may be used to determine the state of
cleanliness of the sensor, and liquid cleaners are the best
means of removing contaminants.
The electronics of the DC-2 is all solid state and
highly reliable. If the unit does not perform, first check
the fuse that is located in the bottom of the box near the
power ON switch. If the fuse is not open, place the Readout
Select Switch in the TEMPERATURE measuring position and press
the START button. If the probe is operating properly, the
number in the display will count to some finite value and
remain there. If the probe is faulty, the number in the
display will not reach a fixed value, but will continually
cycle from zero to a maximum.
DATA ANALYSIS
The DC-2 Droplet Counter is capable of providing a
large amount of data which is usually presented in tables
or, more often, on graphs. A volume or mass distribution
emphasizes large droplets and de-emphasizes or ignores the
small ones. On the other hand, a description of the number
of droplets puts the emphasis on the smaller droplets, which
are more numerous. A third presentation, seldom used, depicts
the surface of the liquid droplets versus its diameter. In
this case, the emphasis is a compromise between the other two
methods.
In principle, it is possible to convert from one dis-
tribution to another, but in practice, care should be
exercised to prevent the introduction of large errors due to
averages and approximations. An obvious example is the
difference between direct average diameter and the diameter
of the average volume.
The droplet distribution may be displayed by computing
and summarizing the number of droplets or by summarizing
the volume of these droplets. The droplet concentration, n^,
corresponding to each droplet size interval is computed by
the expression:
Drop/cm3 (i = 1'14)
v
35
-------
where
Nj_ = Droplets counted in the itn channel
v = Flow velocity (cm/sec)
t = Time interval (sec)
I = Sensor length (.1 cm)
Di = Average droplet diameter for the i*-n channel (cm)
d = Sensor wire diameter (5x10""* cm) .
In plotting the distribution of the number of droplets versus
droplet diameter, each of the values of nj_ is divided by the
width of the droplet size interval, ADi, in microns. This
ordinate is then plotted corresponding to values of the
related average droplet diameter, Dj_. To simplify the com-
putation, all the constants are grouped together by a
factor, Ki or Kj_v, presented in Tables 1, 2, 3 and 4. This
allows for the following expression:
where nj_ is the number of droplets per unit volume of gas per
unit diameter range for the itn size interval.
For the volumetric distributions, Vj_, in the ifc" size
interval, the expression becomes
By writing in terms of the constant, Kj_v, of Tables 1 through 4,
V. =
With the above formulas, the data from the DC-2 can be readily
reduced to produce number concentration or volume distribution.
Other quantities often encountered in particle sizing, such as
mass mean diameter, surface mean diameter, etc., can be
derived from the existing data without difficulty. In
Section 6, Laboratory Testing, these formulas are applied to
make comparisons with the mass measurements from the Brink
impactor. Also discussed in Section 6 are the effects of
flow conditions on the capture size of the hot wire.
36
-------
Table 1: Internal Sizing Distribution for Module 1
Size
Enterval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Droplet
Diameter
(microns)
1.0-1.6
1.6-2.6
2.6-4.1
4.1-6.6
6.6-10
10 - 17
17 - 27
27 - 43
43 - 69
69 - 110
110 - 176
176 - 281
281 - 450
> 450
Di
(microns)
1.3
2.1
3.35
5.35
8.3
13.5
22.0
35.0
56.0
89.5
143.0
228.5
365.5
585.0
Ki
( l ]
ycm2microny
2.6 x 104 '
1.4 x 104
8.0 x 103
3.9 x 103
2.2 x 103
7.7 x 102
3.7 x 102
1.6 x 102
6.3 x 101
2.6 x 101
1.0 x 101
4.0 x 10°
1.6 x 10°
6.3 x 10'1
Kiv
f micron^
\ cm2 }
3.0 x 104
6.8 x 104
1.6 x 105
3.] x 105
6.6 x 105
9.9. x 10-
2.1 x 106
3.5: x 10
5.3 x 106
1.0 x 107
1.7 x 107
2.8 x 107
4.1 x 10 7
5.6 x 107
37
-------
Table 2: Internal Sizing Distribution for Module 2
Size
Interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Droplet
Diameter
(microns)
1-36
36 - 70
70 - 105
105-139
139-174
174-209
209-243
243-278
278-313
313-347
347-382
382-416
416-450
> 450
Di
(microns)
18.5
53
87.5
122.0
156.5
191.5
226.0
260.5
295.5
330.0
364.5
399.0
433.0
468.0
K. \
( l }
\ cm micron /
1.2 x 102
5.0 x 1C1
3.0 x 101
2.3 x 101
1.7 x 101
1.5 x 101
1.3 x 101
1.0 x 101
9. 5 x 10°
8.8 x 10°
7.7 x 10°
7.3 x 10°
6.7 x 10°
6.0 x 10°
Kiv
( micron2 \
I cm2 )
y-.o x ios
4. 0 x 106
1.2 x 107
2.3 x 107
3.6 x 107
5.5 x 107
7.6 x 107
9. 6 x 107
1.3 x 108
1.6 x 108
2.0 x 10 8
2.4 x 108
2.8 x 108
3.3 x 108
38
-------
Table 3: Internal Sizing Distribution for Module 3
Size
Interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Droplet
Diameter
(microns)
1 - 1.4
1.4-1.8
1.8-2.5
2.5-3.3
3.3-4.5
4.5-6.1
6.1-8.2
8.2-11
11-15
15-20
20-27
27-37
37-50
> 50
Di
(microns)
1.2
. 1.6
2.15
2.90
3.90
5.3
7.15
9.6
13.
17.5
23.5
32.0
43.5
60
Ki
1
cm micron
4.0xl04
3.8xl04
2.0xl04
1.6xl04
9.4xl03
6.0xl03
4.0xl03
2.4xl03
1.4xl03
8.9xl02
S.OxlO2
2.7xl02
1.6xl02
7.7X101
Kiv
micron^
cm*
3.7xl04
8. IxlO4
l.lxlO5
2.1xl05
2.9xl05
S.OxlO5
7.9xl05
1.2xl06
1.7xl06
2.6xl06
3.6xl06
4.8xl06
6.£xl06
8. 7x1 O6
3T9
-------
Table 4: Internal Sizing Distribution for Module
Size
Interval
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Droplet
Diameter
(microns)
1-3
3-5
5-7
7-9
9-11
11-13
13-15
15-17
17-19
19-21
21-23
23-25
25-27
> 27
Di
(microns)
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Ki
1
£
cm micron
7.1xl03
5.6xl03
4.5xl03
3.8xl03
3.3xl03
2.9xl03
2. 6xl03
2.4xl03
2.2X103
2.0xl03
1.9xl03
1.7xl03
1.6xl03
l.SxlO3
Kiv
micron^
cm^
3.0xl04
l.SxlO5
5.2xl05
l.OxlO6
l.SxlO6
2.7xl06
3.8xl06
S.lxlO6
6.7xl06
8.4xl06
l.OxlO7
1.3xl07
l.SxlO7
1.7xl07
40
-------
SECTION 5
PRINTER/CONTROLLER
GENERAL DESCRIPTION
The Printer/Controller was designed to work in con-
junction with one or two DC-2 Droplet Counters and a Probe
Multiplexer. It provides the user with a summary printout of
data measured by the Droplet Counters. This eliminates
recording the data manually.
The front panel controls make the printer/controller a very
versatile instrument. The controls consist of Month and Day
thumbwheel switch, Number of Runs switch, Print Mode switch,
Time Interval switch, Limit Select switch, Start switch, Paper
Feed switch and Clock Control switches. The functions of these
switches will be discussed in greater detail later in this sec-
tion.
At the beginning of each Print Cycle the Serial Number,
Date and Time information is printed out. Other information
being printed out is Temperature, Total number of droplets
counted, Elapsed Time (time required to count droplets),
Velocity and Droplet Distribution. When in the MUX Mode, the nrin-
ter will also print out the number of the probe being monitored.
The Clock Module provides the time information while Month
and Day information is set manually with thumbwheel switches.
The droplet distribution information is received from the
Droplet Counter with respect to the Distribution Module being
used. An example of a typical printout is illustrated in
Figure 11.
Printing is done by a mosaic printer capable of printing
all characters that can be formed within a 7 by 5 dot matrix.
The printer is mounted in such a way that access to the paper
and ribbon only requires the removal of a cover plate.
FUNCTIONS OF FRONT PANEL SWITCHES
Figure 12 is an illustration of the front panel of the
Printer/Controller. The function of the panel switches are as
follows:
41
-------
Serial Number
Date
Droplet
Distribution
in MICRONS
Total Number of
Droplets Counted'
Elapse Time in_
Tenths of Seconds
Velocity in
.Decimeters per Second
Temperature in
Centigrade
Multiplexer Probe
being Monitored
Time
SN1.-4/76 11 06 54
1-1 4M 00710
1.4-1 8M 00881
1.8-2.5M 01416
2.5-3.3M 02827
3.3-4.5M 02099
4.5-6.1M 01010
6.1-8.2M 00507
8 2- 11M 00208
11- 15M 00137
15- 20M 00098
20- 27M 00063
27- 37M 00032
37- 50M 00011
> 50M 00001
'TOTAL 10000
S.T.0.1S 01226
VEL CM/S 00070
EMP/C 00030
MUXPRB12 00000
Fiaure 11: Printout Illustration
42
-------
Hrs. Min. Sec.
f^l
DC-2
111
Coru-eclcr
/
2
3
1
Month
Day
MUX
Conn.
C A
M K MUX
DC-2
tt2
Print Mode
(flight
o
No. of Runs
15 30
10 1 Hr.
5 2 Hr.
Time Int.
SN 1-0^22 11 15 33
1-1 6M 02 164
1. 6-2 6M O193't
2. 6-4 1 M 0 1 2 3 1
4. 1-6 6 M 01019
6. 6-10 M 00804
10-17 M 00791
1727 M 00501
Power Fuse
Switch
Start
Limit Select
Paper
Feed
Figure 12 . Printer Panel Layout
-------
1. Limit Select switch determines when printer operation
begins with respect to the Droplet Counter or Counters
a) In the £1 position, the printer is activated
whenever either one of the two DC-2's goes into
HOLD.
b) In the $2 position, the printer is activated only
when both DC-2's have reached HOLD.
2. Print iMode Switch - This is a four-position switch
selecting the following print mode operations:
a) Manual Mode (M) - Each print cycle has to be
initiated by depressing and releasing Start
switch.
b) Continuous Mode (C) - Once the print cycle is
initiated, the printer will operate continuously
until it is stopped manually or by the Number of
Runs switch.
c) Automatic Mode (A) - This mode of operation is
ideal for long-term unmanned testing operations.
After initiating the first print cycle, all other
print cycles are under the full control of the
Number of Runs switch and Time Interval switch.
d) MUX Mode - Initiation of first print cycle again
is required and the remainder is dependent on
the setting of the Number of Runs switch. The
setting of the Number of Runs switch is dependent
on the Number of Probes being monitored by the
Multiplexer. Printout of Probe data will be con-
tinuous. Each time a set of Data is required, a
new print cycle must be initiated.
3. Month and Day Switch - The Month and Day information
which is to appear on the printout must be manually
set up with these thumbwheel switches.
4. Number of Runs Switch - The setting of this thumb-
wheel switch determines the number of cycles that
will be printed out when the Print Mode Switch is
in Continuous, Automatic or MUX.
44
-------
5. Time Interval Switch - This switch allows the print
cycles to be spaced with respect to elapsed time.
It is functional only when Print Mode Switch is in
Automatic.
6. Start Switch - To initiate printer operation, this
switch must be depressed and released. The depressing
of the Start switch will put the DC-2's into the count
mode and allow them to collect Data.
7. Paper Feed - To advance paper, depress and hold until
desired amount of paper has been advanced and then
release.
8. Clock Controls - The setting of the Clock Module and
Display is accomplished by six Front Panel switches.
Their functions are as follows:
a) Hours Set - The setting of the Hour is done by
depressing and releasing the HRS pushbutton
until desired hours reading is displayed.
b) Minutes Set - Minute setting is done by depressing
and releasing MIN pushbutton switch until desired
Minutes reading is displayed.
c) Seconds Set - To set the seconds, the SEC push-
button must be depressed and released when
desired seconds reading is displayed.
d) Reset - By depressing and releasing switch marked
"R," the Clock Module and Display are set to
0 hrs., 0 min. and 0 sec.
e) Run/Set Switch - This switch prevents the accidental
changing of the Time while clock is running. In
the RUN Position, Clock Set switches are inhibited.
f) Run/Stop Switch - Controls operation of Clock
Module when Run/Set switch is in the Set position.
45
-------
INTERFACING WITH TWO DC-2's
The Printer/Controller can be used with one or two
DC-2 Droplet Counters. Figure 13 is a schematic of the
interface hookup o£ one and two Droplet Counters with the
Printer/Controller. If two counters are connected to the
printer, the outputs of each are distinguished by the
serial number code on the printout. Each DC-2 functions
separately and independently.
PROBE MULTIPLEXER SYSTEM
The Probe Multiplexer, when used with the DC-2 and
Printer/Controller, expands the probe monitoring capability
from one to 12 probes. Selection of probes to be monitored
is done with a 12-position pushbutton Selector Switch.
Only one probe will be able to transmit data to the DC-2
at a time. The determination as to which probe will be
monitored is controlled by the Selector Switch and the
electronics within the Probe Multiplexer. When more than
one selector button is depressed, probes are monitored in a
descending order, starting with the highest number probe
selected.
The data collected by the probe is transmitted to the
DC-2 and then printed out by the Printer/Controller in a
similar manner as described at the beginning of this
section.
The Probe Multiplexer electronics receives its DC power
from the Printer/Controller via the Probe Multiplexer Inter-
face cable which is supplied with the Printer Interface.
Therefore, any power failure in the Printer/Controller will
cause a loss of power in the Probe Multiplexer. Once
power has been restored, probe monitoring will again start
from the highest number probe selected.
Figure 14 is a schematic of the interface hookup of
the DC-2 with the Multiplexer system.
46
-------
To Probe -«*-
DC-2
DC-2
tfl
D
MUX
DC-2
»2
Printed
Controller
Interface
To Probe
To Probe -«-
DC-2 jfl
DC-2
DC-2
D
Printer/
Controller
MUX
DC-2
If 2
Fiqure 13 . Schematic of DC-2 Interface with Printer/Controller
-------
oo
DC-2
To Probes
1-12
MULTIPLEXER
DC-2
ttl
Printer/
Controller
MUX
DC-2
02
Figure 14: Schematic of DC-2 Interface with Multiplexer System
-------
SECTION 6
LABORATORY INVESTIGATIONS
Extensive laboratory investigations were performed
using the DC-2 and the hot wire probe. The laboratory
studies concentrated on two main topics:
» Calibration Tests
The objective of this effort was to calibrate the
DC-2 for a range of operating conditions using
laboratory equipment. The procedures and apparatus
used for these tests are described in this section.
In addition, several analytical studies were per-
formed in support of the calibration effort. The
most important result from the analytical studies
was the analysis of the capture size of the wire.
» Laboratory Tests with the Impactor
The objective of these tests was to accumulate
laboratory data using a Brink impactor and to then
make comparisons with the measurements from the
DC-2. Extensive tests were performed to achieve this
objective and these tests are tabulated in
Appendix A along with the test purpose and configura-
tion of the experimental apparatus. Again, certain
analytical studies were performed in support of the
experimental work. Both the experimental and
analytical results are discussed in the following
section.
CALIBRATION TESTS
A special apparatus was designed and built by KLD to
perform the calibration of the DC-2. The approach adopted
for calibration is optical. As an interacting dronlet makes
contact with the hot wire sensor, it is observed under a
microscope. A photographic camera records the image of both
the sensor and the droplet. By adopting this technique, a
permanent record is obtained to study the attachment mechanism
and to provide the calibration data. Since the interaction
49
-------
time is short, an electronic flash is used to stop the motion
at the instant of droplet-sensor contact. Thus, no appreci-
able shrinkage due to evaporation takes place and accurate
calibration data is obtained. The duration of the flash is
approximately one microsecond, which is compatible with the
time a droplet, with a diameter range of interest, moves and
shrinks. The electronic flash provides a bright background
for the hot wire. Both wire and droplet appear dark with
sharp boundaries, making a clear contrasting photograph.
Figure 15 shows the arrangement of the main components. The
camera is a Polaroid with Type 107 film. Optics capable of
magnifying the subject up to 100 times its actual size were
used. Magnification limits were set by the length of the
wire (~1 mm) and the diagonal dimension (10 cm) in the
photographic plane. A standard Leitz compound microscope was
used, and the microscope specimen holder was adapted for the
support of the probe. The micrometric positioning setup was
used to position the sensor in the microscope field.
Simultaneously, as the photograph of the interacting
droplet was taken, an oscilloscope picture of the electrical
signal was also recorded. Measurements from each pair of
pictures were recorded, obtaining droplet diameter size in
microns and corresponding peak electrical signal in volts.
An important aspect of this calibration is the generation
of water droplets. A variety of devices were investigated to
create water droplets within the diameter range of interest.
The ideal droplet generator should provide a monodisperse
aerosol of adjustable droplet sizes. Instruments with these
characteristics are available, but their cost and complexity
do not always justify their use. Therefore, KLD designed and
constructed a cost-effective device capable of generating
droplets using a compressed air-driven spray. Droplet dia-
meter sizes were controlled by adjusting the pressure; low
air pressure emphasizes large droplets while high pressure
creates a fine mist or small droplets. In order to measure
the electrical signal peak amplitude over the wide random
range of droplet sizes, a two-beam scope was used with a
different gain for each trace.
The sensor was mounted ?way from the. apparatus creating
the spray (within 1 foot) so that one interaction every few
seconds was obtained. This period between droolets allowed
time for setting the calibration anoaratus and avoided multiple
droplet interactions.
50
-------
Film
Holder
Photographic
Camera
O
Probe
Electronic
Flash
r
=0
o
Figure l.r>: Droplet Calibration Apparatus
-------
Temperature Calibration
The temperature calibration was performed by immersing
the sensor in water with temperatures ranging from melting ice
to boiling water. A precision mercury column thermometer was
used as a control. Temperature readings were displayed on
the front panel of the DC-2.
An important condition to be satisfied when using the
sensor as a thermometer is that the electrical current should
only heat the sensor negligibly. On the other hand, such
current is necessary to operate the Wheatstone bridge which
measures the temperature. (A large current improves the sig-
nal-to-noise ratio of the electronic circuit.) The effect of
sensor self-heating was investigated by repeated measurements
with several gas velocities. The temperature reading should
remain independent of gas velocity.
Gas Velocity Calibration
The calibration of the DC-2 operating as a hot wire
anemometer was performed with the use of a Thermo System Cali-
brator Model No. 1125. This instrument generates a turbulence-
free flow whose velocity may be controlled to 1%. Additional
equipment required for this measurement consisted of a micro-
manometer for the measurement of the decrease in pressure
across the calibrated orifice, a mercury thermometer to
correct the flow for temperature difference, and finally a
supply of compressed air.
Analysis of Capture Area
As presented in the Data Analysis of Section 5, the drop-
let concentration, nj_, corresponding to the itn interval can
be computed with the expression:
Ni
ni = . o ," , -M (i = 1,14).
1 v t H (Dj_+d )
The denominator in the equation represents the volume
sampled and is based on the assumption that all sizes of
droplets have sufficient inertia to maintain a linear trajec-
tory. This assumption, however, may not be accurate for
particles smaller than the diameter of the wire. Flow prob-
lems of this type have been investigated in aerosol filtra-
tion (Ref. 2 and 3) using a two-dimensional analysis for the
52
-------
flow past an infinite cylinder. Although an exact descrip-
tion of the stream lines and droplet trajectories is not
possible, the interception mechanism can be evaluated for
limiting cases. As a convenience in the analysis, the non-
dimensionalized capture size function, f, is defined as
Sampled Volume = vtfcd f (Dj_d) .
Then, with the streamlin.es characterized by the Reynold
Number based on the wire diameter (i.e., vd/v) , the capture
size of the fiber can be determined. Inertial impaction occurs
because the droplet deviated from the fluid motion in
accordance with Stokes1
fluid; namely,
Law for a sphere in an unbounded
stk
= v _
where
v
w
Stk -
v = flow velocity
t - dimensionless time = time multiplied by
UD = particle velocity.
Some limiting solutions of the foregoing equation are tabu-
lated below and provide insight into the capture size func-
tion, f(Did), when normalized by (l+Dj_/d).
Flow Condition
1) Stk -»- ~
Particles follow a straight
trajectory
2) Stk =0; no particle inertia
a) Potential flow
b) Oseen flow
f (Dj_ , d ) / (l-f-Di/d
1 -
ll+Dj/d)2
Di
T2(lp/)'
2.002 - In (Re)
53
-------
In Figure 16, the capture size function is plotted as a
function of the dimensionless droplet size. For the case of
Oseen flow, the Reynold Number is assumed to be 0.3. For
small droplets (Dj_/d10ym. For small droplets between 1 to 10 ym, the more
complicated expressions for f(Dj_,d) should be used.
For the experimental studies performed in the laboratory,
the number of droplets below 10 ym was large and KLD applied
the modified values of the capture size function to the
measured data. The effect of the capture size function on the
final experimental results is discussed in the next section.
LABORATORY TESTS WITH THE I.M.P ACTOR
As reported in Appendix A, a large number of experiments
were performed in the laboratory during the period from
June to December 1977. The objective of this work was to
accumulate data and to compare measurements made with the
Brink impactor and the DC-2. Once the experiments were
initiated, a secondary objective emerged; namely, to better
understand the flow behavior in the impactor and its effect
on the measured data. Several qualitative experiments were
performed to accomplish the secondary objective.
To minimize measurement error, a closed system with a
steady flow was used in the laboratory (Figure 17). The
droplets were generated using a rotating disc, and the speed
of the disc was carefully controlled with an optical tacho-
meter. Several designs-of this droplet generator were
developed and refined to achieve the required stable droplet
distribution. The final design utilized a small volumetric
pump with a controlled motor speed to continuous!/ pump the
liquid to the center of the rotating disc. As shown in
Figure 17, the rotating disc was enclosed in a plastic box.
This approach provides a reliable and rep^atable source of
entrained droplets.
The droplets were entrained in the flow and drawn through
the impactor using a peristaltic pump with a stable but
adjustable speed. The flow was monitored using a calibrated
orifice and manometer. Most of the experiments were performed
with a flow rate of .03 cfm (.85 liter/min) for which a sub-
stantial amount of calibration data is available for the
54
-------
Stk -»
Potential flow Stk = 0
Viscous flow Stk =0, Re = .3
Figure 16: Capture Size vs. Dj/d
55
-------
CTl
I' r i.11 t:o r/Coi i L ro 1 br
A
IZZH3
LX'-2
Caljbratcd
Ori flee
pump ^-=
I i. !..
DC- 2
l!ni|).'.ictor
Probe
ManoineUer
Probe Pl.ow
Spray
Ficjurc -1-7: l.al^oratory Set-up
-------
impactor. Other flow rates were used to investigate the
effect of flow velocity on the measurements.
The impactor was operated with a cyclone and one to five
stages, depending upon the type of experiment. Instead of
using the stainless steel targets of the standard impactor,
aluminum foil cups were used as targets. This approach
simplified the procedure and increased the accuracy of the
measurement. The aluminum foil cups were especially useful
for the fourth and fifth stages of the impactor when the
operating time was less than 20 minutes.
Depending upon the type of test, measurements with the
DC-2 were performed upstream (A) and/or downstream (B) of
the impactor (Figure 17 ). The DC-2 data was automatically
recorded using the Printer/Controller described in Section 5.
For this application, a special hot wire probe was designed
and built as an integral part of the 4.8 mm diameter glass
tube, which v.'?.= placed in the flow line. The hot wire was
mounted perpendicular to the longitudinal axis of the tube to
achieve a well defined flow condition about the wire. For
the prescribed flow conditions (.85 liter/min), the air
velocity at the probe was .73 m/sec.
Experimental Procedure
To obtain the desired accuracy in the data, careful
laboratory procedures had to be established early in the test
program. The sources of data scatter had to be identified
and, where possible, techniques used to minimize the errors.
For example, the system was operated with pure water or a 10%
NaCl solution. The tests with pure water identified some
sources of measurement errors in the impactor. For example,
the DC-2 at location A indicated a stable droplet distribu-
tion, but the impactor results were erratic. The length of
the sampling time has a pronounced influence on the measure-
ments with the impactor, and the scatter of data was found to
be unacceptable. These problems were attributed to evapora-
tion and/or condensation taking place at various points in the
impactor. Because of these problems with the impactor, the
quantitative studies with pure water were discontinued early
in the research.
The impactor measurements with a salt solution were more
dependable, but still exhibited scatter (see Discussion of
Results). To control the scatter in the data, carefully
57
-------
controlled techniques for measuring the samples at each
stage were used. As mentioned above, small aluminum foil cups
provided better accuracy and convenience when weighing the
samples at each stage. As a check upon the data, periodic
measurements of the accumulated liquid were made and the
evaporation history in the ambient environment was plotted.
This procedure supplied data with respect to the total amount
of liquid collected per stage when the test was completed but
before the samples were dried and weighted. Such measure-
ments were used to verify the data obtained from the dried
sample of the NaCl residue.
Depending upon the number of impactor stages, a "time
delay" was observed as the impactor achieved steady-state
conditions. After the initial period of approximately
45 minutes, the measured droplet distribution became stable
within ±10%. Numerous tests were performed to understand this
phenomenon and develop acceptable experimental procedures.
The "time delay" effect is attributed to the condensation/
evaporation phenomenon occurring inside the impactor.
Also, a procedure had to be established with respect to
the total sample period for a generic experiment. Again, a
series of tests were performed to establish this methodology,
and a sample period of 20 to 40 minutes was used for the
majority of the experiments.
The performance and data analysis with the Brink
impactor was based upon the best information available.
Efficiency curves, which accounted for wall losses at
different stages, are given in Table 8 of Reference 4, and
the cyclone efficiency curve appears as Figure 24 of
Reference 5. These two reports are based upon a particle
density of 1.35 gm/cm3 and 1.0 gm/cm3, respectively. For
the present study, the 10% NaCl solution has a density of
1.05 gm/cm3 approximately. The values of 050 used in this
study have been properly adjusted for any differences in
density. Moreover, the diameter of each impactor nozzle was
measured carefully to be sure that it was within the tolerance
of the published value. The DSQ for the present study is
given below in Table 5.
58
-------
Table 5: 059 for Brink Iinpactor at
.85 liter/min Flow Rate, 22°C,
751.84 mm Kg and Particle
Density 1.05 gm/cm3
Stage 050
Cyclone 17.00 urn
1 5.27 ym
2 3.61 urn
3 2.29 urr.
4 1.07 urn
5 0.74 urn
The DC-2 was operated in the standard manner. As
expected, salt accumulated on the hot wire, and after several
minutes of continuous operation, the response of the instru-
ment would degrade. To define a convenient sampling time, the
instrument was operated for various periods. Based on these
tests, a sampling time of approximately 100 seconds was
adopted for the DC-2. With this procedure, the effect of the
salt accumulation was negligible. It was also observed that
by leaving a contaminated sensor in the flow, a self-cleaning
action occurred when the sensor was cold. With a time delay
of five minutes between sample periods of 100 seconds, the
response of the sensor was unaffected and the probe was
seldom replaced.
Discussion of Results
The results from the laboratory tests permit a direct
comparison of droplet number and volume distributions as
obtained with the Brink impactor and the DC-2. In addition,
extensive data was accumulated with respect to the operating
characteristics of the impactor. In this subsection both
these topics are discussed.
The experimental data consistently shows that the
measurements with the DC-2 were lower than the impactor
measurements in the region from 1 to 10 ym. Some of the
difference in the measurements can be attributed to the
aerodynamic influence on the capture size of the wire as
discussed under the Calibration Procedures. In addition,
tests were indicative of condensation occuring in the impactor.
59
-------
However, it is not possible to quantify completely all the
effects which contribute to the differences in the measure-
ments, nor was such a quantification within the scope of the
present research.
To achieve a meaningful comparison of the data from the
many tests, KLD examined approximately four similar experiments
with the impactor and averaged the results for each impactor
stage. The simultaneous measurements with the DC-2 for
each experiment were average for each of the 14 size intervals.
All of this data in the form of a number concentration, ~,
was plotted as a function of droplet diameter. Then an
equivalent factor, K, was defined as
K =
n-for Impactor
r\i for DC-2
The computed values of K are tabulated below:
Inter-
val
No.
1
2
3
4
5
6
Size
Range
1 - 1.6
1.6 - 2.6
2.6 - 4.1
6
10
4.1
6
10 - 17
Ratio of
.Impactor
to DC-2
5.0
2.8
2.0
1.6
1.2
1.0
Kaero
Aerodynamic
factor
2.5
1.8
1.2
1.0
1.0
1.0
AK=K-Kaero
2.5
1.0
0.8
0.6
0.2
0
As shown, the values of K approach one after the fifth
size interval. The factor, K, includes the aerodynamic
effect on the capture area. The aerodynamic effect can he
computed and is represented by the column labelled Kaero
in the above table.
been tabulated.
The difference AK-K-Kaero has also
60
-------
The tabulated values of K were applied to various sets
of experimental data to demonstrate the consistency of
results. In Figures 18 and 19, the results from two
experiments are compared. The dashed curve represents the
measured number concentration with the impactor whereas the
solid curve is for the DC-2 data after the factor K is ap-
plied. A similar comparison is shown in Figures 20 and 21
for the results in terms of the accumulated volume concentra-
tion .
The foregoing curves are in acceptable agreement and the
results from the two techniques of measurement can be related
using an equivalence coefficient, K. It should be emphasized
that the agreement emerged only after very careful laboratory
work to minimize data scatter and by averaging results from
several tests.
During the experimental work, theoperational characteris-
tics of the impactor became evident and it is worthwhile to
document some of the observations for the benefit of other
researchers. Although the Brink impactor has been evaluated
on a theoretical basis by others and can be calibrated using
known solid particles, its use for entrained liquid droplets
is based upon assumptions which may not be justified. The
complex flow at various stages can result in condensation or
evaporation depending upon the operating environment. During
many tests, the collection of significant amounts of liquid
on the walls of the impactor was observed. These problems
can cause scatter in the data and control of the scatter is a
difficult t a "?]: in the laboratory and certainly more difficult
in the field. If the liquid is without trace elements, the
measurements with the impactor are significantly less
reliable and of little quantitative value.
A typical example of the scatter in the laboratory data
is shown in Figures 22 and 23 for stages 1 and 3. In each
diagram, the weight of the dried NaCl residue is plotted as
a function of sampling time. In theory, the accumulated
salt should be a linear function of the sampling time. For
stages 1 and 3, there is an obvious increase in the accumu-
lated salt with time, but the slope of this curve cannot be
accurately defined. Several attempts were made to provide
better insight into the data. For example, all the tests on
a particular day with known environmental conditions were
grouped and studied. - Unfortunately, this grouping tended to
reduce the scatter at some stages but not at all stages.
61
-------
KEY:
10 r
4 .
0
CP
c
a:
01
E
5
0
^
0
a
, >
o
>
3
2
1Q3!
Q 1
8
7
6
5
4
3
101
Impactor
DC-2
Figure
456
Diameter (ijm)
10
11
18
Average Number Concentration for Irnpactor and
the DC-2 Data (Test Mo. 216)
62
-------
KEY:
impactor
DC-2
I
4567
Diameter (urn)
10
11
Figure 19:. Average Number Concentration for Impactor and
the DC-2 (Test No. 212)
63
-------
e
o
c
,H
0
JJ
c
1)
e
E
r-l
c
cu
0)
>
r-l
4J
(3
. !
3
c
5
o
IS3
KEY:
Impactor
DC-2
4567
Diameter (in u)
10
11
Figure 20 : Cumulative Entrainment Volume for Impactor
and the DC-2 Data (Test No. 212)
64
-------
u
c
5
0)
3
r-l
0
4J
c
0)
c
4J
c
u
0)
3
E
3
U
10s
9
8
7
6
5
4
3
ICT
KEY:
_..«. _. Impactor
DC-2
i i
4 5
Diameter
I
10
11
Figure 21: Cumulative Entrainment Volume for Impactor and
the DC-2 Data (Test No. ?U',)
65
-------
6.0-1
5.5-
5.0-
4.5-
Salt
Weight
(mg)
4.CL
3.5_
3.0-
2.5-
2.0-
1.5-
i.o-
0.5-
O.C-
0
20
~r
40
T
60
~T~
80
Time (Mins.)
Figure 22: Salt Collected on Stage 1
66
-------
o.io-
0.09 -
0.08-
0.07-
0.06-
Salt
Weight o.o5-
(mg)
0.04-
0.03-
0.02-
0.01-
0.00.
I
20
40 60
Time (Mins.)
I
80
Figure 23: Salt Collected on Stage 3
67
-------
Several experiments were performed with the Brink impac-
tor inside the box where the droplets are generated. This
approach was adopted with the assumption that scatter would be
minimized if the impactor is in equilibrium with the sample
flow. It should be emphasized that the procedure was equiva-
lent to the field practice of placing the sample train in the
flow for long "soaking" periods. The results from these ex-
periments were disappointing since no appreciable reduction
in the scatter was observed.
KLD performed several experiments to gain better insight
into the phenomenon causing data scatter. A glass tube was
constructed to resemble the impactor, and by visually
monitoring the flow inside the tube, varying conditions of
evaporation and/or condensation were observed. When the two-
phase flow was introduced into the tube, wall condensation
was very evident. The condensation on the wall could be
correlated with the droplet distribution at the outlet of
the tube. The distribution at the outlet did not stabilize
until the condensation on the walls achieved a stable condi-
tion. If a light source is placed near the tube (causing an
undetectably small temperature difference), the condensation
phenomenon was greatly altered with evaporation on the side
exposed to the light and condensation on the diametrically
opposite side. These qualitative experiments demonstrated the
sensitivity of the internal flow to extremely small changes in
wall conditions. Further study to quantify this effect is of
interest and possible, but such an effort is beyond the scope
of this project.
Analytical Considerations
Several analytical studies were undertaken in support of
the experimental effort. . The objective of the studies was to
provide additional insight into the thermodynamic and aero-
dynamic conditions in the impactor. The procedures used for
the studies are briefly reviewed in this subsection.
An idealized pressure and temperature distribution in the
impactor can be determined using a one-dimensional flow
theory for a compressible, isentropic flow. The temperature
and pressure ratios at a cross section with velocity, v, are
given by
68
-------
-i
where A is ratio of specific heat (A ~ 1.4)
M is the Mach number
To is the stagnation temperature
Po is the stagnation pressure.
These equations are used to obtain the idealized pressure
and temperature conditions in the impactor for a given set of
nozzle geometries. The nozzle dimensions, the jet velocity
at each nozzle exit, as well as the pressure drop are pre-
sented in References 4 and 6. For r.he Brink impactor, these
parameters are given in Table 6 for stages n tnrouah 6.
The resulting temperature and pressure distributions are
given in Figures 24 and 25. The first three stages, which
have a jet velocity less than 10 m/sec, show negligible
temperature and pressure drop. Temperature difference of
0.5°C to .'. .5°C and pressure drop of 3 to 17 mm.Hg are found in
stages 4, 5 and 6.
A second analysis was used to qualitatively describe the
growth or reduction in droplet size. It is well known that
aerosol particles, when in supersaturated atmosphere, may act
as nuclei, enhance condensation and growth. A droplet passing
through an impactor undergoes a similar process. In theory,
droplets may grow or shrink inside an impactor.
A complete analysis on the history of a droplet passing
through an impactor could be achieved numerically. However,
such a complete study was not undertaken during this contract.
Rather, an idealized and simplified model was used for the
condensation/evaporation rate of droplets in the impactor
environment.
For a spherical motionless droplet, assuming stationary
condensation/evaporation and ideal behavior of the vapor, the
rate of change of the droplet radius can be described by
[Maxwell's equation:
69
-------
TABLE {
Cascade Impactor Stage Parameters
Modified Brink Model B Cascade Impactor
Stage No. of
No. Jets
0 1
1 1
2 1
3 1
4 1
5 1
6 1
D.-Jet
Diameter
(cm)
.3598
.2439
.1755
.1375
.0930
.0726
.0573
S-Jet
to Plate
Distance
(cm)
1.
0.
0.
0.
0.
0.
0.
016
749
544
424
277
213
191
S
D.
3
2
3
3
3
2
2
3
.02
.07
.10
.08
.98
.93
.33
Reynolds
Number
326
481
669
853
1263
1617
2049
Jet
Velocity
(m/sec)
1
3
6
9
21
35
58
.4
.0
.0
.7
.2
.3
.8
Cumulative Frac-
tion of Impac-
tor Pressure Drop
at each stage
0
0
0
0
0
0
1
.0
.0
.0
.0
.065
.255
.000
-------
-5
tt,
-10
Stage 1
~T~~
Stage 2
f~~
Stage 3
4
Stage 4
Y
Stage 5
\
f
Stage 6
Outlet
'N
\
\
\
Nozzle outlet of previous stage
H
10
15
20
25
30
\
-15
r ~~i 1 1 1 1 1 1 1 1 c -P .9 I
1 -H U 1
1 ' 1 0( l/> ',
L . c £ vt \
lit | | t 1 1 t 1 r-^->> M M < 1
r\ W a) fljr-itN n^a1 mvD'b-P
J\. II C tj> Q) (U
rH -*ty O m (U QJ i 4J4J4-)4-)-M4JT)O
2CJ-oWWWWWWs
(U .
f
i i i i i i |l
x(cm)
35
Figure 24: Pressure drop along the impactor (760 mmHg is used as inlet pressure)
-------
0 ,
- . 5-
NJ U
o
-l.Or
-1.5-
f
1
1 t
i
1
1
Nozzle outlet of previous stage
-1-
'""''\r--j
Q)
. 1
N
I\l
O
ry
F
kl <"
U c
U 0
^H
U
>i
U
1
t
QJ
tji
*T3
4J
tn
-
o
Q)
CS)
t
r-H
QJ
CP
03
to
t
fN
Q)
in
(0
4->
to
t
ro
0)
On
(0
10
t
T
0)
cr«
13
-P
t/1
i
t
in
0)
cr>
0)
4J
to
t
vD
0)
CT>
(0
4-1
00
'
t
TI 4->
Q) 0)
^ 4J
H 3
O O
0
^
oi,ci^>- j ^uayt; u uuco.t;'-
~~V "\ /""-N /'
f / \
' / \
1 '
/ l !
V
vi >i
Q) O rH 1
: J -H u b
.-H 03 0)
c e to
M M .<
,
1
i
i
^j _j j i
5 10 15 ^"20
Figure 25. Temperature drop along the impactor. (20
25 i 30
°C is used as inlet temperature)
x (cm)
-------
dr
dt
r =
t =
D =
M =
PL =
R =
P =
where r = radius of the droplet
time
vapor diffusivity
molecular weight of the vapor
density of the droplet
ideal gas constant
vapor pressure at the drop surface calculated
from the drop temperature
POO = vapor pressure in the air stream.
By assuming Pco-P0 = 0.1 mmHg , the rate of change of the
droplet radius, dr/dt, for typical conditions is given in the
following table. As shown, dr/dt is most significant for
small droplets.
Table V: Rate of Change in Radius for
Water Droplets at 293°K and
POO-PQ = 0.1 mmHg
0.25
0.50
1.0
2.5
5.0
10.0
dr , i -.
(urn/sec)
11.40
5.72
2.86
1.14
0.56
0.28
The evaporation of small droplets in a saturated atmos-
phere was also investigated. The vapor pressure on the surface
of a droplet of radius, r, is given by Kelvin's equation:
r
- = exp
'RTpLr'
where a = surface tension.
73
-------
The evaporation effect on dr/dt can be calculated
accordingly. The supersaturation ratio, Pr/Poo/ for various
values of r is given in Table 7 and dr/dt at 293°K is pre-
sented in Table 8. Again, the small droplets have the most
significant rates of change.
Table R: Supersaturation Ratio, Pr/Poa,
for Water Droplet at 293°K
r (ym)
Pr/pc
0
0
1
2
5
10
.25
.50
.0
. 5
.0
.0
1.
1.
1.
1.
1.
1.
0044
0022
0011
00044
00022
00011
Table 9: Rate of Change in Radius
Water Droplet at 293°K
for
r (urn)
0.25
0.50
1.0
2.5
5.0
10.0
dr . . .
"7T (ym/sec)
dt
9.
2.
0.
0.
0.
40
36
59
094
0236
0.0059
The above calculations are based on the assumption that
the droplet is pure water and Maxwell's equation applies.
Theoretical consideration on the concentration change at the
surface of the droplet as well as the evaporation/condensation
constant lead to
74
-------
dt
MD
PLRT
D
.rva
+ 1
where a = evaporation/condensation constant for a liquid
RT
= 1/4 of the mean absolute velocity of
the vapor molecules.
For pure water, a = 0.034, and the above equation gives
a smaller value of dr/dt than obtained from Maxwell's equation,
Hence, the evaporation or growth of droplets in the
impactor appears possible for the small droplet sizes (D<10um)
and may account for the sensitivity of the impactor data to
environmental conditions. These studies did not include the
influence of the walls as condensation surfaces nor the
effect of re-entrainment of droolets from wet surfaces.
75
-------
SECTION 7
FIELD TESTING
An important objective of the research effort was to
demonstrate the use and suitability of the DC-2 under field
conditions. In all, four different sites were used in the
demonstration. At the Shippingport Power Plant, which has a
limestone scrubber, data was obtained with the DC-2 and was
to be compared with impactor data measured by an independent
source. Unfortunately, the impactor data is not available
and the comparison cannot be reported.
For each site, a test report was prepared and submitted
to the EPA Contract Monitor. In this section, the results
from each site are summarized.
COLBERT PILOT PLANT
A schematic of the demister scrubber at the Colbert
Pilot Plant in Muscle Shoals, Alabama is shown in Figure 26.
It consists basically of a duct where the flow carrying SO2
interacts with water within a prescrubber-demister . The
scrubber injects saturated ammonia and the resulting droplets
are recovered in a demister. This flow is created by means
of a centrifugal pump installed in the stack.
A total of 1260 measurements were performed at the four
available ports shown in Figure 26. The ports and the
corresponding number of measurements taken are:
Port
A. Prescrubber-Demister Inlet
B. Prescrubber-Demister Outlet
C. Exit Demister-Inlet
D. Exit Demister-Outlet
No. of Measurements
315
314
316
315
Each measurement includes gas temperature, flow velocity
and droplet size distribution.
76
-------
Exit
Demister
Prescrubber
H
S0^~
2
0
Section
1
1
I A Prescrubber ^
Section
1C D l
10 0
1 1 It
Flow
M»
| >' Demister ^ Scrubber
I Inlet Outlet
i 1
1
1
|
r
Inlet i
Outlet
Sulfates
and
Bisulfate
Bx-|
Saturated
Ammonia
Water
Stack
Figure 26 : Schematic of the Demister Scrubber at
the Colbert Facility
77
-------
Most of the measurements were performed with one probe
so as to monitor any degradation of its performance due to
the accumulation of contaminants. The only detected
accumulation was crystals of ammonia sulphate. A periodic
cleaning of the probe after 15 minutes of operation was
required for proper measurement. Crystals of ammonia sulphate
are highly soluble in water, so that the sensor was cleaned
simply by immersing in tap water for a few seconds.
For the performance of a single measurement (a total of
1000 droplets) the time limit was below 100 seconds, assuring
negligible deterioration of the sensor during a single
measurement. The measured droplet distributions are presented
in Figures 27, 28, 29 and 30.
WATER TREATMENT PLANT IN NEW YORK
Field testing at the New York site was made within a
demister located at the exhaust of diesel engines operating
with either fuel oil or methane. At the site, a scrubber was
used to clear, the exhaust gas of odors and carbon particles.
The function of the demister was to capture water droplets
after the scrubbing action took place.
A cross-section of the demister is shown in Figure -1.
Several thousand measurements were performed at this facility.
The main emphasis was to test the DC-2 viorformance under field
conditions rather than to evaluate the facility. It was
observed that conditions at the facility changed with time.
Furthermore, the spinner caused localized conditions in the
flow.
The measurements with the various instruments, i.e. one
prototype unit and two deliverable units were performed
simultaneously by locating their respective probes as close
together as possible. Measurements were taken over the cross
sections at various vertical locations with the sensor placed
perpendicular to the flow. The three instruments produced
results which are all rather similar. Differences, when
present, may be traced to either spatial or time fluctuations.
SHIPPINGPORT POWER PLANT
Field tests at Shippingport, Pennsylvania were made in
the demisters which are located at the exhaust of the coal-
fired power plant. The droplets were generated by venturi
78
-------
10.
E
c
o
H
U
+J
c
0)
u
s
4J
a
1-1
a
o
.1
i
8
10 12 14 16 18
Droplet Diameter (ym)
20
22
24
Figure 27:
Distribution at the Prescrubber Demister Inlet
Colbert Plant
79
-------
1000-
100
e
3.
<*i
c
O
X.
3 10
o
(
8
I
4 56
Droplet Diameter (ym)
Figure 28 : Distribution at the Prescrubber
Demister Outlet, Colbert Plant
80
-------
1000-
100-
c
n
C
o
\
c
c
JJ
'-(
£
o
c
o
CJ
JJ
o
r-~!
n
0
'-1
Q
1
_^-
-
^^
\
\
-A \
\\
\\
^ \\
\\\
\\
\
>
\
X \
\\
A
\v
\\
\\
\ \
\
^2. 5
4*
\
\ .
\^-^
v\ \
\\ \
\ \ \
\*(
^\^
\\
\
ft. froi
,2.0 ft
1.
/
/
1 \
\ \
\\
\ N
\
n wall
from \<
3 ft. fr
V
\
\
\ \
\
\\
\ \
all
om wall
Figure 29 :
4 5
Droplet Diameter (ym)
Distribution at the Exit Demister Inlet
Colbert Plant
-------
100
10
e
o
0
H
4-1
4J
c
0
o
c
o
u
a.
o
S-l
c
.1
Figure
Droplet Diameter (\J.m)
Distribution at the Demister Outlet
Colbert Plant
82
-------
De-entrainment
Spinner
Liquor
Inlet
Figure 31: Demister Cross Section at the
Treatment Plant in tfantagh,
New York
83
-------
scrubbers and the liquor contained limestone in suspension
to remove the major pollutant, S02- One double demister and
one single demister were investigated. The survey was made
downstream of the demister and covered the entire cross
section of the duct. Six access ports were available for the
measurement. The cross section of the duct and location of
the survey points are shown in Figure 32 .
The most serious problem encountered, during the field
work was the contamination of the sensor because of the
accumulation of limestone on the hot-wire probe. This con-
tamination problem was overcome by inserting the probe into
the c.uct only when the DC-2 was actively taking data and by
choosing the measuring time to be as short as 10 seconds.
Temperature, flow velocity and droplet concentration were
within the expected range of operation at the facility.
Large fluctuations were observed in the operating
conditions of the demisters. The fluctuations are inherent
to the operation of this type of demister and extend for
periods of minutes. Based on this observation, average.
values of the various measurements were used for the
computation of the results.
The average number and volume concentration for the
single demister and double demister are presented in
Figure 33 and 34. The single demister has a larger droplet
concentration than the double demister, as expected.
COOLING TOWER OF THE HIGH FLUX BEAM REACTOR AT BROOKHAVEN
NATIONAL LABORATORY
The objectives of this field test were to demonstrate:
the DC-2 Droplet Counter connected with the
Multiplexer and Pr i.nter/Controller . Four
multiplexer probes were used in these
experiments:
two DC-2 Droplet Counters interconnected with the
Printer/Controller.
For both types of experiments, all of the data was
recorded using the automatic mode of the Printer/Controller.
The equipment arrangements for the two configurations are
shown in Section 5 of this report.
84
-------
Port
6 5
2 1
B. S.
.1
2'
11 »! i > 14»^ J. '
12
XX X X XX
XX X X XX
XX X X XX
12'
Figure 32 : Test Section of a Duct at Shippingport,
Pennsylvania
85
-------
L-
E
o
a;
CT>
!M
Q)
ra
rH
Q
1-i
0
a
D
P
5
.-i
o
!M
O
f±
m
4-1
0)
o
!M
Q
u-i
0
.5
cj
2
10
10 !
10
10
10
io~J-
1
Fioure 33:
10 100 500
Drop Diameter,( urn)
Average Number Concentration for the
Demister Sections at Shippingport, Pennsylvania
36
-------
O
"
0
°
0
O
9
o
o
H
13
l-i
jj
H
JJ
fu
r-H
3
C
3
CJ
01
en
9
8
7
6
5
a
o
O
OSingle Demister
©Double Demister
0
0
o
o
10
I
10
100
Drop Diameter, urn
1000
Figure 34:
Average Cumulative Entrainment Volume as a
Function of Diameter for the Demister Sections
at Shippingport, Pennsylvania.
37
-------
The droplets were generated from domestic water with
a maximum of 1 PPM chloride chemical added for maintenance
purposes inside the cooling tower. The survey covered several
radial cross sections in two of the five exhaust cell units.
The investigation included measurements with the exhaust fan
on and off during the test.
The entire test program required approximately two hours,
but had to be scheduled over two days because of weather con-
ditions. Measurements were taken automatically every five
minutes and were printed out by the Printer/Controller.
Throughout the testing, all equipment operated properly.
No probe breakage occurred and no contamination was detected
either by the operation of the instrument or by observing
the sensors under a microscope. Typical results are given
in Figure 35 and 36. It is found that both number and volume
concentration are dominated by drops smaller than 30 ym.
88
-------
^.
n
O
"e
o
""
0
D
O
C
0
E
C
H
C
H
0)
.,-j
-U
(3
rH
D
£
5
CJ
0) )
0
^
10-7
9
8
7
6
5
4
3
2
10-8
9
8
7
6
5
4
3
2
ID'9
O O O
o
o
'
0
1
I o
M
^* i
o
1
1 I 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1
4 5 6 7 89 10 20
Droplet Diameter (ym)
40
60 80 100
Figure 35: Average Cumulative Entrainment Volume as a
Function of Droplet Size in the Exhaust of the
Cooling Tower at Brookhaven National Laboratory
89
-------
£
U
103
10 -
01
I 101
OJ
c
5
H
i->
5
o
u
a
I ID'2
e
-3
10
Figure
10
Droplet Diameter
100
jm)
Droplet Number Concentration Measured in the
Exhaust of the Cooling tower at Brookhaven
National Laboratory
90
-------
REFERENCES
1. Medecki, H., Kaufman, M., and Magnus, D., "Design,
Development, and Field Test of a Droplet Measuring Device,"
EPA-650/2-75-018, U.S. Environmental Protection Agency,
Research Triangle Park, N. C., 1976.
2. Fuchs, N. A., "The Mechanics of Aerosol," MacMillan
Company, 1964.
3. Davies, C. N., "Aerosol Science," Academic Press, New
York, N. Y., 1966.
4. Gushing, K. M., Lacey, G. E., McCain, J. D. and
Smith, W. B., "Particulate Sizing Techniques for Control
Device Evaluation: Cascade Impactor Calibrations,"
EPA-600/2-76-280, U.S. Environmental Protection Agency,
Research Triangle Park, N. C., 1976.
5. Smith, W. B., Gushing, K. M. and McCain, J. D.,
"Particulare Sizing Techniques for Control Device Evaluation,"
EPA-650/2-74-102, U. S. Environmental Protection Agency,
Research Triangle Park, N. C., 1974.
6. Harris, D. B., "Procedures for Cascade Impactor Calibra-
tion and Operation in Process Streams," EPA-600/2-77-004,
U. S. Environmental Protection Agency, Research Triangle
Park, N. C., 1977.
91
-------
APPENDIX A
TABULATION OF LABORATORY TESTS
Over the period from June 30 to December 28, 1977,
approximately 160 experiments were performed in the KLD
laboratory using the Brink impactor and the DC-2 to measure
droplet concentration. In Appendix A, these tests are
summarized in tabular form.
For each test, a purpose number is assigned in the
table. The definition of each purpose number (P.I...P.21)
is presented in tabular form at the end of this section.
Each test is further described by referring to a configura-
tion (C.1...C.29) which is defined by the sketches appearing
in this Appendix. For example, configuration C.5 consists of
a Brink impactor with a cyclone and three stages and a DC-2
probe located at the exit from the impactor.
The only other tabulated parameter requiring explanation
is the flow rate, which is given in inches of water. This
pressure drop is across a calibrated orifice and the flow
rate is obtained from the following equation:
AP = CO2
where AP = pressure drop
Q = flow rate
(cm of H20) _ (inch of H20)
C ~ UJ (liter/min)2 22^ (ft
92
-------
No. of
Flow
Rate
Droplet Liquid (inch of No. D.C.
Total
Test
Period Purpose
Test
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
Date
6/30/77
6/30/77
6/30/77
6/30/77
6/30/77
6/30/77
6/30/77
6/30/77
6/30/77
6/30/77
6/30/77
6/30/77
6/30/77
7/1/77
7/1/77
7/1/77
7/1/77
7/1/77
7/1/77
Conf ig.
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
C.I
Counter
DC- 2
SN-1
DC- 2
SN-1
DC- 2
SN-1
DC- 2
SN-1
DC-2
SN-1
DC-2
SN-1
DC-2
SN-1
DC-2
SN-1
DC-2
SN-1
DC-2
SN-1
DC-2
SN-1
DC-2
SN-1
DC-2
SN-1
DC-2
DC-1
DC-2
DC-1
DC-2
DC-1
Type
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
H70)
7/8"
1"
1 1/2"
2"
2 1/2"
O "
-J
3 1/2"
4"
4 3/4"
1 5/8"
1 1/8"
7/8"
3/4"
2"
2"
3/4"
3/4"
2 5/8"
2 5/3"
Samples
6
9
7
6
5
4
3
4
5
4
4
5
3
3
5
2
2
3
2
(sec. )
520
180
100
60
40
280
185
235
235
400
690
1480
1270
5<1.0
500
300
440
300
160
No.
P.I
P.I
P.I
P.I
P.I
P.I
P.I
P.I
P.I
P.I
P.I
P.I
P.I
P. 2
P. 2
P. 2
P. 2
P. 2
P. 2
93
-------
Flow
Rate
Total
Test
No. of
Test
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
133
139
140
Date
7/5/77
7/5/77
7/5/77
7/5/77
7/5/77
7/5/77
7/5/77
7/6/77
7/11/77
7/11/77
7/11/77
7/11/77
7/12/77
7/12/77
7/12/77
7/12/77
7/12/77
7/12/77
7/12/77
7/12/77
7/12/77
Conf ig.
C.
C.
C.
C.
C.
C.
C.
N.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
C.
1
2
3
4
5
6
7
A.
1
2
3
4
8
8
8
8
8
3
8
8
3
Droplet
Counter
DC-2
DC- 2
DC-2
DC-2
DC-2
DC-2
DC-2
N.A.
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
Liquid
Type
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
(inch of
H,0)
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
2"
1"
No. D.C.
Samples
1
2
2
3
3
3
2
N.A.
6
6
6
1
5
5
4
3
4
4
4
4
4
Period
(sec. )
40
60
90
200
240
270
140
N.A.
180
1200
2000
340
920
1200
430
550
580
800
700
900
Purpose
No.
P. 3
P. 3
P. 3
P. 3
P. 3
P. 3
P. 3
P. 4
P. 3
P. 3
P. 3
P. 3
P. 5
P. 5
P. 5
P. 5
P. 5
P. 5
P. 5
P. 5
P. 5
94
-------
No. of
Test
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
Date
7/12/77
7/12/77
7/12/77
7/13/77
7/13/77
7/13/77
7/13/77
7/13/77
7/13/77
7/13/77
7/13/77
7/14/77
7/14/77
7/14/77
7/14/78
7/19/77
7/19/77
7/19/77
7/20/77
7/20/77
Conf ig.
C.8
C.8
C.8
C.9
C.8
C.8
C.8
C.10
C.10
C.10
C.10
C.ll
C.ll
C.12
C.12
N.A.
N.A.
N.A.
C.3
C.3
Droplet
Counter
DC- 2
SN-2
DC- 2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
DC-2
SN-2
N.A.
N.A.
N.A.
N.A.
N.A.
Liquid
Type
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Pure
Water
Flow
Rate
(inch of
H-,0)
1"
1"
1"
3/4"
3/4"
3/4"
3/4"
3/4"
3/4"
1 1/2"
1 1/2"
2"
2"
2"
2"
N.A.
N.A.
N.A.
2"
2"
No. D.C.
Samples
4
4
4
5
5
7
5
4
4
3
6
4
5
5
5
N.A.
N.A.
N.A.
N.A.
N.A.
Total
Test
Period
(sec. )
1050
950
1300
260
110
310
120
1300
1300
320
60
2800
65
60
1050
1200
1300
840
1800
900
Purpose
No.
P. 5
P. 5
P. 5
P. 6
P. 6
P. 6
P. 6
P. 6
P. 6
P. 6
P. 6
P. 6
P. 6
P. 6
P. 6
P. 7
P. 8
P. 8
P. 8
P. 9
95
-------
No. of
Test Date
Conficr.
Flow
Rate
Droplet Liquid (inch of No. D.C.
Counter Type H2O) Samples
Total
Test
Period Purpose
(sec.) No.
161
162
163
164
165
166
167
163
169
170
171
7/20/77
7/20/77
7/20/77
7/21/77
7/21/77
7/22/77
7/22/77
7/22/77
7/25/77
7/25/77
7/25/77
C.3 N.A. Pure 2"
Water
C.3 N.A. 10% 2"
Saline
Solu-
tion
C.3 DC-1 10% 2"
Saline
Solu-
tion
C.3 DC-1 10% 2"
Saline
Solu-
tion
C.3 DC-1 10% 2"
Saline
Solu-
tion
C.4 DC-1 10% 2"
Saline
Solu-
tion
C.4 DC-1 10% 2"
Saline
Solu-
tion
N.A. N.A. 10% N.A.
Saline
Solu-
tion
C.14 DC-1 10% 2"
Saline
Solu-
tion
C.14 DC-1 10% 2"
Saline
Solution
C.13 DC-1 10% 2"
Saline
Solu-
tion
N.A. 900 P. 9
N.A. 1800 P. 10
6 3600 P. 11
9 7200 P. 11
21 3600 P. 11
17 7200 P. 11
19 3600 P. 11
N.A. 450 P. 12
13 2700 P. 13
12 1300 P. 13
17 2700 P. 13
96
-------
No. of
Test Date
Config.
Flow
Rate
Droplet Liquid (inch of Mo. D.C.
Counter Tvoe H-?0) Samples
Total
Test
Period Purpose
(sec.) No.
172
173
174
175
176
177
178
179
180
181
182
7/25/77 C.14 DC-1
7/27/77 C.14 DC-1
DC-2
7/27/77 C.14 DC-1
7/27/77 C.14 DC-1
7/27/77 C.14 DC-1
7/28/77 C.14 N.A.
7/23/77 C.14 DC-1
7/28/77 C.14 DC-2
SN-2
7/29/77 C.14 DC-1
7/29/77 C.14 DC-1
7/29/77 C.14 DC-1
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
10% 2"
Saline
Solu-
tion
8 1300 P. 13
8 600 P. 13
2 300 P. 13
5 600 P. 13
4 600 P. 13
N.A. 300 P. 14
14 1200 P. 13
6 300 P. 13
4 600 P. 13
14 2400 P. 13
12 1200 P. 13
97
-------
No. of
Test Date
201 8/1/77
202 8/1/77
203 8/1/77
204 8/1/77
205 8/2/77
206 8/2/77
207 8/2/77
208 8/3/77
209 8/3/77
210 8/5/77
Droplet
Config. Counter
C.15 DC-2
SN-1
DC-2
SN-2
C.15 DC-2
SN-1
DC-2
SN-2
C.15 DC-2
SN-1
DC-2
SN-2
C.15 DC-2
SN-1
DC-2
SN-2
C.15 DC-2
SN-1
DC-2
SN-2
C.12 DC-2
SN-2
C.15 DC-2
3N-1
DC-2
SN-2
C.15 DC-2
SN-1
DC-2
SN-2
C.16 DC-2
SN-1
DC-2
SN-2
C.17 DC-2
SN-1
DC-2
SN-2
Flow
Rate
Liquid (inch of No. D.C.
Type H20) Samples
10% 2" 4
Saline
Solu-
tion
10% 2" 12
Saline
Solu-
tion
10% 2" 3
Saline
Solu-
tion
10% 2" 6
Saline
Solu-
tion
10% 2" 10
Saline
Solu-
tion
10% 2" 7
Saline
Solu-
tion
10% 2" 10
Saline
Solu-
tion
10% 2" 6
Saline
Solu-
tion
10% 2" 8
Saline
Solu-
tion
10% 2" 12
Saline
Solu-
tion
Total
Test
Period Purpose
(sec . ) No.
300 P. 13
300 P. 13
600 P. 13
1200 P. 13
2400 P. 13
1300 P. 6
3600 P. 13
3600 P. 13
2400 P. 13
140 P. 15
98
-------
No. of
Test Date Config.
211 8/10/77 C.17
212 8/10/77 C.17
213 8/10/77 C.17
214 8/11/77 C.18
215 8/11/77 C.18
216 8/11/77 C.18
217 3/12/77 C.18
218 8/12/77 C.18
219 3/16/77 C.18
220 8/16/77 C.13
Droplet
Counter
DC- 2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
Liquid
Type
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
Flow Total
Rate Test
(inch of No. D.C. Period Purpose
H->0) Samples (sec.) No.
2" 8 2400 P. 13
2" 8 2400 P. 13
2" 16 4800 P. 13
2" 16 4800 P. 13
2" 5 1200 P. 13
p
2" 2 1200 P. 13
~2" 16 2400 P. 13
2" 6 600 P. 13
2" 4 1200 P. 13
2" 5 1200 P. 13
99
-------
No. of
Test Date Config.
221 8/16/77 C.18
222 8/16/77 C.18
223 8/17/77 C.18
224 8/17/77 C.18
225 8/17/77 C.18
226 8/18/77 C.19
227 8/18/77 C.19
228 8/18/77 C.19
229 8/19/77 C . 20
Droplet
Counter
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
DC-2
SN-1
DC-2
SN-2
Flow
Rate
Liquid (inch of No. D.C.
Type H?O) Samples
10% 2" 4
Saline
Solu-
tion
10% 2" 3
Saline
Solu-
tion
10% 2" 4
Saline
Solu-
tion
10% 2" 4
Saline
Solu-
tion
10% 2" 8
Saline
Solu-
tion
10% 2" 2
Saline
Solu-
tion
10% 2" 2
Saline
Solu-
tion
10% 2" 8
Saline
Solu-
tion
10% 2" 8
Saline
Solu-
tion
Total
Test
Period Purpose
(sec.) No.
1200 P. 13
1200 P. 13
2400 P. 13
2400 P. 13
4800 P. 13
2400 P. 16
2400 P. 16
2400 P. 16
3600 P. 17
100
-------
No. of
Test Date
301 8/2/77
302 8/2/77
303 8/2/77
304 8/2/77
305 8/2/77
306 8/2/77
307 8/3/77
308 8/3/77
309 8/3/77
310 8/4/77
Droplet
Config. Counter
C.21 DC-2
SN-1
DC-2
SN-2
C.21 DC-2
SN-1
DC-2
SN-2
C.21 DC-2
SN-1
DC-2
SN-2
C.22 DC-2
SN-1
DC-2
SN-2
C.22 DC-2
SN-1
DC-2
SN-2
C.22 DC-2
SN-1
DC-2
SN-2
C.23 DC-2
SN-1
DC-2
SN-2
C.23 DC-2
3N-1
DC-2
SN-2
C.23 DC-2
SN-1
DC-2
SN-2
C.12 DC-2
SN-1
DC-2
SN-2
Flow
Rate
Liquid (inch of No. D.C.
Type H20) Samples
10% 2" 8
Saline
Solu-
tion
5% 2" 3
Saline
Solu-
tion
Pure 2" 8
Water
10% 2" 8
Saline
Solu-
tion
5% 2" 8
Saline
Solu-
tion
Pure 2" 8
Water
10% 2" 8
Saline
Solu-
tion
5% 2" 21
Saline
Solu-
tion
Pure 2" 8
Water
10% 2" 10
Saline
Solu-
tion
Total
Test
Period Purpose
(sec. ) No.
2100 P. 18
2100 P. 18
2100 P. 18
2100 P. 18
2100 P. 18
2100 P. 18
2100 P. 18
-2 hrs. P. 18
2100 P. 18
~1 hr. P. 18
101
-------
Flow Total
Rate Test
No. of Droplet Liquid (inch of No. D.C. Period Purpose
Test Date Config. Counter Type H20) Samples (sec.) No.
311 8/4/77 C.12 DC-2 5% 2" 10 ~1 hr. P.18
SN-1 Saline
DC-2 Solu-
SN-2 tion
312 8/4/77 C.12 DC-2 Pure 2" 26 ~2 hrs. P.18
SN-1 Water
DC-2
SN-2
313 8/2/77 N.A. DC-1 10% 3 1/2" 2 2.1 P.19
Saline
Solu-
tion
314 8/2/77 N.A. DC-1 10% 3 1/4" 2 2.8 P.19
Saline
Solu-
tion
315 8/2/77 N.A. DC-1 10% 3" 3 4.6 P.19
Saline
Solu-
tion
316 8/2/77 N.A. DC-1 10% 2 3/4" 2 3.3 P.19
Saline
Solu-
tion
317 8/2/77 M.A. DC-1 10% 2 1/2" 2 2.5 P.19
Saline
Solu-
tion
318 8/2/77 N.A. DC-1 10% 2 1/4" 2 3.6 P.19
Saline
Solu-
tion
319 8/2/77 M.A. DC-1 10% 2" 3 7.4 P.19
Saline
Solu-
tion
320 8/2/77 N.A. DC-1 10% 1 3/4" 2 9 P.19
Saline
Solu-
tion
102
-------
No. of
Flow
Rate
Droplet Liquid (inch of No. D.C.
Total
Test
Period Purpose
Test
321
322
323
324
325
326
327
328
329
330
Date Config. Counter
8/2/77 N.A. DC-1
8/2/77 N.A. DC-1
8/2/77 N.A. DC-1
8/2/77 N.A. DC-1
8/2/77 N.A. DC-1
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
3/2/11 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
Type H20) Samples (sec.)
10% 1 1/2" 3 6.7
Saline
Solu-
tion
10% 1" 2 6.8
Saline
Solu-
tion
10% 3/4" 2 9
Saline
Solu-
tion
10% 1/2" 2 11.4
Saline
Solu-
tion
10% 1/4" 2 11.2
Saline
Solu-
tion
10% 3 1/2" 1 3.9
Saline
Solu-
tion
10% 3 1/4" 1 5.2
Saline
Solu-
tion
10% 3" 1 5.8
Saline
Solu-
tion
10% 2 3/4" 1 5.5
Saline
Solu-
tion
10% 2 1/2" 1 5.2
Saline
Solu-
tion
No.
P. 19
P. 19
P. 19
P. 19
P. 19
P. 19
P. 19
P. 19
P. 19
P. 19
103
-------
No. of
Flow
Rate
Droplet Liquid (inch of No. D.C.
Total
Test
Period Purpose
Test
331
332
333
334
335
336
337
338
339
Date Config. Counter
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
8/2/77 N.A. DC-2
SN-2
Type H20) Samples (sec.)
10% 2 1/4" 1 4.8
Saline
Solu-
tion
10% 2" 1 4.7
Saline
Solu-
tion
10% 1 3/4" 1 4.3
Saline
Solu-
tion
10% 1 1/2" 1 5.3
Saline
Solu-
tion
10% 1 1/4" 1 6.0
Saline
Solu-
tion
10% 1" 1 7.2
Saline
Solu-
tion
10% 3/4" 1 8.8
Saline
Solu-
tion
10% 1/2" 1 11.6
Saline
Solu-
tion
10% 1/4" 1 13.4
Saline
Solu-
tion
No.
P. 19
P. 19
P. 19
P. 19
P. 19
P. 19
P. 19
P. 19
P. 19
104
-------
Flow
Rate
Total
Test
No. of
Test
401
402
403
404
405
406
407
408
409
410
Droplet
Date Config. Counter
8/24/77 C.21 DC-2
SN-1
DC-2
SN-2
8/24/77 C.22 DC-2
SN-1
DC-2
SN-2
8/25/77 C.23 DC-2
SN-1
DC-2
SN-2
8/26/77 C.15 DC-2
SN-1
DC-2
SN-2
9/16/77 C.17 DC-2 &
Multi-
plexer
9/19/77 C.17 DC-2 &
Multi-
plexer
9/19/77 C.24 DC-2 &
Multi-
plexer
9/20/77 C.25 DC-2 &
Multi-
plexer
9/20/77 C.25 DC-2 &
Multi-
plexer
11/23/77 C.26 DC-2
SN-1
2 probes
Liquid
Type
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
10%
Saline
Solu-
tion
(inch of No. D.C. Period Purpose
H20) Samples (sec.) No.
2" 5 2400 P. 18
2" 5 2400 P. 18
2" 14 3000 P. 18
2" 9 4800 P. 18
2" 16 P. 20
2" 7 P. 20
2" 15 3600 P. 18
2" 10 3600 P. 18
2" 15 4200 P. 18
2" 5 1800 P. 21
105
-------
No. of
Test
411
Date Config.
11/23/77 C.26
Droplet
Counter
Liquid
Type
Flow
Rate
(inch of
H20)
No . D . C -
Samples
Total
Test
Period
(sec.)
Purpose
No.
DC-2
SN-1
probes
10%
Saline
Solu-
tion
2"
2400
P.21
106
-------
Definition of Purpose Number
No. Purpose
P.I Investigate the response of instrument for different
flow rates
P.2 Compare results given by DC-1 and that of DC-2 under
the same operating condition
P. 3 Investigate the output response of impactor by
using DC-2
P.4 Measure the pressure and temperature drop after the
cyclone--cyclone + 1 state, cyclone + 2 stages and
cyclone + 3 stages individually
P.5 Obtain the droplet distribution curves at the inlet
and outlet of a vertical brass tube
P.6 Investigate the distribution curves at the inlet and
outlet of a vertical glass tube for the study of
condensation/evaporization and delay effect
P.7 Obtain the evaporation rate of pure water on foil
target using the Cahn Balance
P.8 Investigate the evaporation rate of pure water on
paper target using the Cahn Balance
P.9 Use paper as absorbing material to investigate the
condensation effect behind the target
P.10 Investigate the evaporation rate and/or concentration
change for drops collected on stage 1 of an impactor
P.11 Exercise the combined operation of impactor and DC-1
P.12 Obtain the evaporation rate for a drop of saline solu-
tion using the Cahn Balance
P.13 Perform experiment for comparison of DC-2 against the
Brink impactor
107
-------
No. Purpose
P.14 Perform experiment for comparison of the DC-2 against
the Brink impactor with the impactor connected to the
spray box overnight to establish an equilibrium
initial condition
P.15 Compare the time required for measuring 100 drops by
DC-2 SN-1 and DC-2 SN-2
P.16 Perform experiment for comparison of DC-2 against
impactor by leaving the impactor inside the spray box
P.17 Investigate the distribution curve at the inlet and
outlet of an impactor with no targets inside the
impactor
P.18 Obtain distribution curves at the inlet and outlet of
the designed configuration for investigation of
collection efficiency and delay phenomena
P.19 Investigate droplet size distribution and rate of
counting for different flow velocities
P.20 Check the validity of measurement for two probes
P.21 Compare the mass of droplets collected by stage 1 of
impactor with the mass difference indicated by the
DC-2 measurements at the inlet and outlet
108
-------
Test Configurations of Equipment
ci
schematic of
hot-wire probe
air +
droplets
flow
C2
C3
cyclone alone
>
c
1
cyclone +
1 stage
C5
C6
cyclone +
3 stages
cyclone +
4 stages
C4
cyclone +
V2 stages
C7
cyclone +
5 stages
109
-------
C8
Cll
i
Vertical brass
tube
DC-2 is connected
to probe either at
inlet or outlet
Metal deflector is introduced
in the glass tube to reduce
turbulence in the flow
C9
C12
i
Vertical glass tube
Vertical glass
tube with metal
deflector
C13
CIO
-Z3Z
Z3E*
Cyclone + 1 stage
Horizontal glass tube
110
-------
C14
C17
Cyclone +
2 stages
Two probes are
connected
to 2DC-2's
CIS
CIS
C16
Cyclone +
3 stages
*" ^
C
1
2
3
4
Cyclone +
4 stages
0) >.
C19
* (D
C
1
2
3
4
5
Cyclone +
5 stages
111
-------
C20
C24
c
1
2
3
4
5
impactor without
targets
-------
TECHNICAL REPORT DATA
(Please read Inumctions on the reverse before completing)
1. .REPORT NO.
EPA-600/7-79-I66
3. RECIPIENT'S ACCESSION NO.
J. TITLE AND SUBTITLE
Development of Droplet Sizing for the Evaluation of
Scrubbing Systems
5. REPORT DATE
July 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHOH(S)
Hector Medecki, K.C. Wu, and D.E.Magnus
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
KLD Associates, Inc.
300 Broadway
Huntington Station. New York 11746
10. PROGRAM ELEMENT NO.
EHE624
1 1. CONTRACT/GRANT NO.
68-02-2111
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
13. TYPE OF REPORT AND PERIOD COVERED
Final: 6/75 - 3/77
14. SPONSORING AGENCY CODE
Research Triangle Park, NC
27711
EPA/600/13
15. SUPPLEMENTARY NOTES jERL-RTP project officer is D. Bruce Harris, Mail Drop 62, 919/
541-2557.
16. ABSTRACT
The report describes the development and characteristics of the DC-2
Droplet Counter as used to evaluate scrubbing systems. The measurement of entrai-
ned droplets and their concentrations in gas streams is important in pollution control
technology. The use of a hot-wire sensor can successfully measured the desired
parameters for droplets in the size range from 1 to 600 micrometers. The report
describes extensive testing in the laboratory and gives a comparison with results
from the Brink impactor. A correlation of results for these two measurement tech-
niques was achieved. The report also describes field tests at four different sites.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Pollution
Drops (Liquids)
Measurement
Testing
Evaluation
Gas Scrubbing
Counters
Pollution Control
Stationary Sources
DC-2 Droplet Counter
13B
07D
14 B
07A,13H
13. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
120
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
113
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