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MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS - 1963
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ORNA-1678
CONF-6509 46-3
L
MASTER
NOV 8:
AN ACOUSTIC INSTRUMENT FOR VASURIG SUBCOCLING IN BOILING SYSTEMS
H. Kariluke, R. P. Wichner, and H. W. Hoffman
Reactor Division
LEGAL NOTICE
This report mo prepared u an account of Government sponsored work. Naithor the United !
States, aor the Commission, nor any person acting on behalf of the Commission:
A. Makes any warranty or representation, exprossed or implied, with respect to the accu-
racy, completoncas, or usefulness of the information contained in this report, or that the uso
of any information, apparatus, method, or procoso disclosed in this report may not infringo
privately owned rights; or
B. Assumes any liabilities with respect to the use of, or for damages resulting from the
ute of any information, apparatus, mothod, or proceus disclosed in this report.
As used to the above, "person acting on behalf of the Commission" includes any om-
ployee or contractor of the Commission, or omployee of such contractor, to the extent that
much employee or contractor of the Commission, or employoe of such contractor properos,
i disseminates, or provides access ts, any Information pursuant to be employment or contract
with the Commission, or his employment with such contractor.
For presentation at the Fourth High-Temperature Liquid-Metal
Heat Transfer Technology Conference to be held September 28-29, 1965,
at Argonne National Laboratory, Argonne, Illinois.

RM BASKD POR ANNOUNCEMBET
IN NUCIKAR SCLLICE ABSTRACTS
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OAK RIDGE NATIONAL LABORATORY
Oak Ridge, Tennessee
Operated by
UNION CARBIDE CORPORATION
for wie
U. S. ATOMIC ENERGY COMMISSION
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AN ACOUSTIC INSTPUMENT FOR MEASURING SUBCOOLING IN BOILING SYSTEMS:
H. Kartluke R. P. Wichner, and H. W. Hoffman
Oak Ridge National Laboratory
Oak Ridge, Tennessee
ABSTRACT
An acoustic instrument capable of indicating the degree of under-
saturation in a known fluid at unknown local temperature and pressure
conditions is described. This incipient-boiling detector (developed
by Aeroprojects Incorporated) has been tested with water and shown to
be effective as a means for monitoring the Ilow in pressurized water
reactors where boiling is undesirable ana dangerous. The current
study is directed to evaluating this device for possible similar appli-
cation in liquiä-metal cooled Tast reactors. Preliminary tests in
liquid potassium are discussed. The results were inconclusive; further,
experiments with a higher power oscillator are planned.
"Research sponsored by the v. S. Atomic Energy Commission under
contract with Aeroprojects Incorporated and the Union Carbide Corporation.
Project Engineer, Aeroporjects Incorporated, West Chester, Pennsyl-
vania.
"
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****
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INTRODUCTION
Aeroprojects Incorporated has been studyins, under a cortract with the
U. S. dtomic Energy Commission, an acoustic instrument (named an incipient-
boiling detector) capable of inäicating the degree of undersaturation in a
known fluid without knowledge of existing local teraperature and pressure con- .
ditions. This is accomplished by producing cavitation at the face of a small
probe immersed in the fluid and relating the power required to effect this
cavitation to the difference between ambient pressure-temperature conditions
and those necessary for boiling. Further, the instrument can be sealed into
a system through a force-insensitive mount developed by Aeroprojects which
minimizes losses in the energy transferred to the probe and; hence,' allows
the ultrasonic generator to be located in a rooni-temperature region far I'rom
a hot system. Thus, the incipient-boiling detector enables monitoring of
liquid-cooled channels in nuclear reactors where bçiling is undesirable or
dangerous.
De Prisco et al.1 described the incipient-boiling detector in 1962 and
gave preliminary results with water at several pressure levels; interest at
that time centered on pressurized water reactors. Recently, application to
alkali metal cooled fast reactors was suggested. Because Aeroprojects has no
liquid-metal facilities, the Engineering Development Branch of the Division
of Reactor Development and Technology, U. S. Atomic Energy Commission, has
requested that the Oak Ridge National Laboratory, test this instrument in an
alkali liquid-metal environment..
APPARATUS
A bench setup for testing the incipient-boiling detector with atmospheric
water is shown in Fig. 1. A magnetostrictive transducer driven by an ultra-
sonic, generator causes mechanical vibration in the coupler rod on which it is
mounted. This vibratory motion is transmitted to a small probe (reed) immersed
in a water pool through a pair of force-insensitive mounts. A piezoelectric
sensing element is fastened to the coupler rod at a nodal point; the output
signal is read on an oscillcscope. Further details of this device and the
T
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ALSIAI
CHIN
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theoli arr.
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| Trace Clear
No Cavitation
50-kcps
Driver:
Coco.moscope
'Poak Volcmeter.
Laboratory Stand ::
and Clamps
Fig. 1. Bench Setup for Incipient-Boiling Tests with Atmospheric Water.
$
Warning
11
13.
Trace Shoring
CavitaciorNoise
Filter

associatea electronic system can be found in Rei. I.
When cavitation occurs in the liquid, a noise signal is superimpcsed on
the normal trace of the sensor output; this condition is illustrated in the
upper portion of Fig. 1. The peak voltace and the power to the transducer
are also recorded at the caviüavion threshold. The sensitivity appears high, .
and small changes in the power input are sufficient to cause the appearance
or disappearance of the "hash" observed on the oscilloscope screen.
Tests with liquid potassium were conducted in a 2-in.-diam, type 347
stainless steel, pool-boiling capsule. Auxiliary instrumentation included a
calibrateå Bourdon gage for pressure measurement and liquid and vapor region
thermocouples contained in thermowells penetrating the capsule from the top.
EXPERIMENTAL RESULTS
Figure 2 shows typical results obtained by Aeroprojects during operation
of the incipient-boiling detector with atmospheric water at known temperatures.
- The scatter in the data has been ascribed by De Prisco as probably due to the
randomness in the factors involved in cavitation rather than to any inability
in detection. In particular, the performance of this instrument was best
immediately after the water pool had been sparged with air and, hence, when
cavitation nuclei were present in large numbers. Tests have also been made at
overpressures up to 5.7 atm with similar results.
Preliminary results with potassium are given in Fig. 3; the observed sys-
tem pressure is plotted against the measured liquid temperature. For comparison,
the saturation pressure corresponding to the liquid temperature is also shown;
the helium overpressure was 0.4 psi. The sequence of the experiments was as
follows: ,
1. The test was initiated at a liquid temperature of 1198°F (superheat =
66°F); with the vibrator at the resonant frequency, the temperature was sys-
tematically increased to 1265°F. The data taken during this sequence are in-
dicated by the open circles with right-haná tabs. Occasional bumping was noted;
the pressure surges accompanying these bumps (indicated by the vertical dashed
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200 do
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Fig. 2. Power and Peak Transducer Voltage at Carritaticii Threshold for.
er at Atmospher.. re ana Var.:c:.
lines) varied vetween 1.0 and 3.5 psi. Since the pressures were measured on
a high-inertia Bourdon-tube gage, the peak pressure was probably much higher
than the observed value. During this cycle, the occurrence of bubbles (noted
both by the sound emitted from the system and by the pressure surges) was
sensitively indicated by changes in the oscilloscope trace.
2. The vibrator was then turned oil, and the performance of the system
was observed as the liquid temperature decreased from 1280°F down to w1100°F.
(open triangles with left-hand tabs). Bumping was also noted during this
period; however, the frequency may have been slightly less than found with
the vibrator on.
3. At a liquid temperature of ~1100°F, the vibrator was again turned on
and the temperature further decreased to ~050°F (open circles with left-hand
tabs). Frequent, mila bumping (0.5 psi) was immediately observed. .
4. With the vibrator on, an increasing temperature sequence was again
started (iilled circies with right-hand tabs). At liquid temperatures between
1060 and 1075°F, a period of steady boiling was o'oserved (half-filled circles
with right-hand tabs). This condition was characterized by pressure fluctua-
tions of barely discernable amplitude (<0.1 psi) and was clearly noted on the
oscilloscope.
5. As the temperature was increased further, smooth boiling ceased; and
at 1200 °F, bumping was again detected. The sequence was terminated at a liquid
temperature of 1395 °F.
DISCUSSION
The data described in the above section were obtained in a first examina-
tion or the performance of the Aeroproject incipient-boiling detector in an
alkali liquid-metal environment; the results of the test were inconclusive.
However, the maximum power capability of the oscillator driving the acoustic
generator was only 8 watts and, perhaps, insufficient to effect cavitation in
a liquid in which cavitation nuclei ere at best not plentiful. This study will
be repeated shortly with a 100-waut oscillator.
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On the positive side, this instrument provides a sensitive means for
detecting boiling in the liquid pool.
The preseri discussion is intended only to generate an awareness of the
incipient-boiling detector. A critical evaluation of its usefulness with the
alkali liquid metals as a measure of the subcooling or as a means for reducing
the superheat required for boiling must await further experiments. Other
uses ~ 2.., as a phase regime indicator or a flow meter - suggest themselves
and may be investigated.
ACKNOWIEDGVENTS
The ultrasonic vibrator and the associated generation and detection in-
strumentation were provided by Aeroprojects Incorporated.
REFERENCES
2: 4. ***
C. F. De Prisco et al., "Ultrasonic Instrumentation in Nuclear Applications:
I. Ultrasonic Detection of Incipient Boiling and Cavitation," USAEC Report
NYO-10010, Areoprojects Incorporated; March 1962.
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