Subcooled convective boiling in structured surface microchannels

摘要

Experiments are performed to investigate subcooled flow boiling, on side wall cavities with angles of 60°, 90° and 120° with bottom-wall asymmetrical heating, for a microchannel heat sink containing 75 parallel 100μm × 200 μm channels. The heated surface is made of a Cu metal sheet with/without 2μm thickness diamond film. Tests and measurements are conducted with de-ionized water, de-ionized water + 1 vol.% MCNT additive solution, FC-72 fluids over a mass velocity range of 820-1600 kg m~(-2) s, inlet temperatures of 15 (8.6), 25 (13.6), 44 (24.6) and 64℃ (36.6℃) for DI water (FC-72) and heat fluxes up to 800 W cm~(-2). Flow morphologies, boiling incipience, two-phase heat transfer coefficients and critical heat fluxes are obtained and presented. Both cavities' structured and sputtered diamond ultrathin film surfaces in nanofluid flow boiling in a microchannel are shown to significantly enhance heat transfer through the promotion of bubble ebullitions and to reduce boiling incipience. A significant increase in critical heat flux (CHF) is also found.