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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Micro Liquid Film Heat Transfer and Critical Heat Flux of Flow Boiling in Micro-Channels

Get access (open in a dialog) DOI: 10.1615/IHTC15.fbl.009333
pages 2761-2773

摘要

Critical Heat Flux (CHF) during flow boiling in microchannels is a topic of great interests because it limits the heat fluxes that can be reliably dissipated. Unlike the situation in macro-scale channels where CHF occurs near when vapor quality goes to one, CHF in microchannels is usually due to local dryout of the thin liquid film. In a confined space formed by the micro-channel, bubble nucleates at fairly large superheat and the flash growth of the elongated bubble or bubble slug leaves a very thin micro film. At high heat fluxes and moderate mass flow rates the film can evaporate completely before upstream liquid floods in and hence gives rise to CHF. In this article, a fully unsteady-form model is developed for the micro liquid film. We solved the equations using a special numerical scheme with stabilization treatment on nonlinear terms, and conducted film and two-phase flow coupled simulations of the flow boiling in microchannels. The simulation determines automatically the instantaneous distribution of film thickness and the developing of drying spot during bubble growth. The model is validated with experimental results in literatures. The originally proposed unsteady-form formulations have potential applications in the other studies where the heat transfer of micro liquid films is involved.