Evaporative Heat Transfer with R134a in a Vertical Minichannel

Zahid Anwar


Smart cooling solutions are required for modern electronic devices as heat flux is continuously increasing while component size is shrinking day by day. Two phase heat transfer within compact channels can cope with high heat flux applications. Two phase heat transfer in narrow channels was the subject of many studies from last decade. The mechanisms involved, however, are not fully clear and there is still room for further investigations to come up with a general solution. This article reports experimental finding on flow boiling heat transfer of R134a in a resistively heated, smooth vertical stainless steel minichannel. Experiments were conducted at 27 & 32 oC saturation temperature with 100-500 kg/m2 s mass flux and till completion of dryout. The effect of various parameters like, heat flux, mass flux, vapor quality and system pressure was studied. Results indicated that heat transfer was strongly controlled by applied heat flux while insignificant effect of varying mass flux and vapor quality was observed. Experimental findings were compared with various macro and micro scale correlations from literature, this comparison revealed Gungor and Winterton [10] correlation as the most accurate one for predicting local heat transfer coefficients.

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