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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Experimental Study of Pulsed and Steady State Confined Subcooled Jet Impingement Boiling

Sridhar Abishek
Department of Mechanical Engineering, Curtin University

Ramesh Narayanaswamy
Department of Mechanical Engineering Curtin University AUSTRALIA

Vinod Narayanan
Department of Mechanical and Aerospace Engineering, University of California-Davis, Davis, California 95616, USA

DOI: 10.1615/IHTC15.evp.008439
pages 2501-2514


SCHLÜSSELWÖRTER: Boiling and evaporation, Thermal management, jet impingement, pulsation

Abstrakt

Jet pulsations have been found to have both enhancing as well as deteriorating heat transfer characteristics as compared to steady state jet impingement. While there is significant literature on the effect of jet flow oscillations on single phase impingement cooling systems, that on boiling characteristics of an impinging subcooled jet is very limited. The present research investigates the effect of low frequency externally induced jet pulsations on the associated transient as well as time-averaged heat transfer characteristics of boiling heat transfer using a subcooled jet of FC-72 in a submerged and confined geometry. A novel flow control mechanism was designed using solid state relays and solenoid control valves for the introduction of jet pulsations. Base line steady state experiments were carried out for two different inlet subcoolings of about 16.9 oC and 7.5 oC for jet Reynolds numbers in the range 3500-14000. Low frequency pulsating jet impingement heat transfer was studied for two different frequencies 0.25 Hz and 0.5 Hz, and amplitudes of about 36 % and 62 % of mean jet velocity, for a given mean Reynolds number and jet subcooling. Visual observation during the experiment revealed a periodic renewal of the boiling process where the bubbles on the heater surface were cyclically flushed downstream of the stagnation point almost in phase with the pulsating jet. It was found that jet pulsations had a significant effect on the temperature oscillations on the heat transfer surface. The magnitude of normalized temperature oscillations on the heater was larger for higher heat fluxes in the nucleate boiling regime as compared to relatively lower heat fluxes in the single phase convection controlled regime. However, the overall effect of jet pulsations was only minimal on the time averaged boiling characteristics, to the extent that the boiling curves due to both steady state and pulsating jet impingement were identical for most of the boiling regime, including critical heat flux. A slight deterioration in the heat transfer coefficients was obtained for lower heat fluxes in the single phase convection dominant regime of the boiling curve, for the range of parameters investigated in the present research.

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