Flow Instability and Bifurcation in Gas-Loaded Reflux Thermosyphons

[+] Author and Article Information
P. F. Peterson

Department of Nuclear Engineering, University of California, Berkeley, CA 94720

N. Elkouh, K. W. Lee

Department of Mechanical Engineering, University of California, Irvine, CA 92717

C. L. Tien

Department of Mechanical Engineering, University of California, Berkeley, CA 94720

J. Heat Transfer 113(1), 158-165 (Feb 01, 1991) (8 pages) doi:10.1115/1.2910520 History: Received January 22, 1990; Revised May 31, 1990; Online May 23, 2008


In vertical gas-loaded two-phase reflux thermosyphons, the temperature and concentration gradients between the active and shut-off regions can create double-diffusive mixed convection flows. When the noncondensable gas molecular weight is greater than that of the vapor, different steady and time-dependent gas recirculation patterns develop, similar to those observed during Rayleigh-Bénard convection in vertical slots. Experimental results presented here show that bifurcations from axisymmetric to three-dimensional, then asymmetric, and finally multiple distinct gas-flow patterns occur as the Rayleigh number increases. Ultimately, a sudden transition to a large-amplitude oscillatory gas flow takes place. Detailed concentration maps and power-density spectra from point wet-bulb temperature measurements clearly chart these transitions. These results impact the design of many condensing systems where noncondensables are present.

Copyright © 1991 by The American Society of Mechanical Engineers
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