Effects of Channel Dimension, Heat Flux, and Mass Flux on Flow Boiling Regimes in Microchannels
T. Harirchian and S. V. Garimella, “Effects of Channel Dimension, Heat Flux, and Mass Flux on Flow Boiling Regimes in Microchannels,” International Journal of Multiphase Flow Vol. 35, pp. 349-362, 2009.
Experiments are conducted with a perfluorinated dielectric fluid, Fluorinert FC-77, to investigate the effects of channel size and mass flux (225–1420 kg/m2s) on microchannel flow boiling regimes by means of high-speed photography. Seven different silicon test pieces with parallel microchannels of widths ranging from 100 to 5850 lm, all with a depth of 400 lm, are considered. Flow visualizations are per- formed with a high-speed digital video camera while local measurements of the heat transfer coefficient are simultaneously obtained. The visualizations and the heat transfer data show that flow regimes in the microchannels of width 400 lm and larger are similar, with nucleate boiling being dominant in these channels over a wide range of heat flux. In contrast, flow regimes in the smaller microchannels are dif- ferent and bubble nucleation at the walls is suppressed at a relatively low heat flux for these sizes. Two types of flow regime maps are developed and the effects of channel width on the flow regime tran- sitions are discussed.
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