Results of an experimental and theoretical study of factors affecting self-sustaining hydrodynamic oscillations in boiling-water loops are reported. Data on flow variables, and the effects of geometry, subcooling and pressure on the development of oscillatory behavior in a natural-circulation two-phase-flow boiling loop are included

Jain, K. C.

English

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December 1969	 Brief 69-10620 
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Self-Sustained Hydrodynamic Oscillations 
in a Natural-Circulation Two-Phase-Flow Boiling Loop 
An experimental and theoretical study is reported 
(ref.) that attempted to determine factors affecting 
self-sustaining hydrodynamic oscillations in boiling-
water loops; it yielded a wide range of pertinent and 
consistent data on flow variables for this type of sys-
tem. The literature on past work is reviewed, and 
theoretical and experimental results are compared. 
Proper design of many systems of technological 
importance requires understanding of the behavior 
of heat-transfer systems in which the circulation is 
provided by the density difference caused by boiling 
in the heated 'section. The effects of geometry, sub-
cooling, and pressure on the inception and develop-
ment of oscillatory behavior in a natural-circulation 
boiling-water loop were studied. The following ranges 
of parameters were covered by the experimental study: 
Heat flux, Btu/hr-ft 2	 0.2-3.1 x 10 
Pressure, psia	 200-1500 
Inlet subcooling temperature, °F 0-62 
Test section, lengths, in. 	 48, 72, 96 
Internal diameters, in. 	 0.364, 0.625, 0.8125 
Riser, lengths, in.
	 48,60 
Internal diameters, in. 	 0.3125, 0.625, 1.049 
The critical power density was determined by an 
arbitrary criterion, since the steady-oscillation 
amplitude increases continuously with power. For 
large oscillations, periodic inlet-flow reversals were 
found, which could be compared to the steady inlet-
flow velocities. These phenomena are emphasized 
by lower system pressure and small-diameter test 
section and riser. Other parameters did not affect these 
phenomena in a distinct fashion. The frequencies of
the oscillations varied from 0.24 to 0.76 Hz and gen-
erally increased with increase in power, as did the 
flow amplitudes. 
Two theoretical models were investigated: one 
linear and one nonlinear. The linear analysis in 
frequency domain showed good ability to predict the 
oscillation threshold and the frequency associated 
with the initial oscillations. The predictions of the 
threshold power were correct within 5% for over 60% 
of the tested cases, and within 10% for over 80%. 
The nonlinear model had to be modified for satis-
factory prediction of the steady inlet-flow velocities. 
However, this modification and the original model 
failed to give reasonable predictions of the oscillation 
thresholds and frequencies. Neither form of the model 
satisfactorily predicted the amplitudes. It is thought 
that the one-dimensional formulation fails to take 
into account vaporization, which acts as a periodic 
forcing function, of superheated liquid near the lead-
ing edge of the two-phase region. The introduction of 
such a forcing function allows the computation of 
periodic bounded oscillations similar to those ob-
served experimentally, and also explains qualitatively 
the observed trends with parameter variations. 
Reference: 
1. Jam, K. C.: Self-Sustained Hydrodynamic Oscilla-
tions in a Natural-Circulation Two-Phase-Flow 
Boiling Loop. ANL-703, Argonne National Lab-
oratory, Aug. 1965. 
Notes: 
1. This information may interest workers with sys-
tems involving natural cycles of boiling water, such 
as specific power, water-purification, and desalin-
ization systems.
(continued overleaf) 
This document was prepared under the sponsorship of the Atomic liability resulting from the use of the information contained in this 
Energy Commission and/or the National Aeronautics and Space document, or warrants that the use of any information, apparatus, 
Administration. Neither the United States Government nor any per- method, or process disclosed in this document may not infringe pri-
son acting on behalf of the United States Government assumes any vately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000571 2020-03-16T18:24:43+00:00Z
	Inquiries concerning this information may be di- 	 Patent status: 
rectéd to:	 Inquiries concerning rights to commercial use of 
Office of Industrial Cooperation	 this information may be made to: 
Argonne National Laboratory 	 Mr. George H. Lee, Chief 
9700 South Cass Avenue	 Chicago Patent Group 
Argonne, Illinois 60439	 U.S. Atomic Energy Commission 
Reference: B69-10620	 Chicago Operations Office 
	
Source: K. C. Jain	 9800 South Cass Avenue 
	
Reactor Engineering Division	 Argonne, Illinois 60439 
(ARG- 10461) 
Brief 69-10620	 Category 02


Self-sustained hydrodynamic oscillations in a natural-circulation two-phase-flow boiling loop

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