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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

Pressure Drop and Flow Boiling Heat Transfer of Refrigerant R-134a in Microchannel Heat Sink

Get access (open in a dialog) DOI: 10.1615/IHTC15.fbl.008792
pages 2631-2643

Sinopsis

Flow boiling in microchannel heat sinks is significantly influenced by capillary forces and by wall constrains affecting the flow pattern and the heat transfer. In this paper we presented experimental data on heat transfer and pressure drop at flow boiling of refrigerant R-134a in a horizontal microchannel heat sink. The primary objective of this study is to establish experimentally how the heat transfer coefficient and pressure drop correlate with the heat flux, mass flux, vapor quality and evaluate the effect of flow instability on flow boiling heat transfer in multichannels array. Experiments were conducted in a closed loop that re-circulates refrigerant. The copper plate of microchannel heat sink contains 21 microchannels with 335x930 ????m2 cross-section and fin thickness of 650 ????m at total plate thickness of 2.5 mm. The microchannel plate and heating block were mounted in the stainless steel container which had two sections divided by the partition wall for the local heat flux measurements. Distribution of local heat transfer coefficients along the length and width of the microchannel plate were measured in the range of external heat fluxes from 50 to 500 kW/m2; the mass flux was varied within 200-600 kg/m2s, and pressure was varied within 6-16 bar. For refrigerant R-134a flow boiling in the microchannel heat sink, the obvious impact of heat flux on the magnitude of heat transfer coefficient was observed. It occurs, when nucleate boiling is the dominant mechanism for heat transfer. The new model of flow boiling heat transfer, which accounts nucleate boiling suppression and liquid film evaporation, was proposed and verified experimentally in this paper.