Forced convection boiling in a microchannel heat sink

Micromachining technology was utilized to fabricate a transparent microchan nel heat-sink system by bonding glass to a silicon wafer. The micro heat si nk consisted of a microchannel array, a heater, and a temperature sensor ar ray. This integrated microsystem allowed simultaneous qualitative visualiza tions of the flow pattern within the microchannels and quantitative measure ments of temperature distributions, flow rates, and input power levels. Boi ling curves of temperature as a function of the input power were establishe d. No boiling plateau was observed in the boding curves, consistent with ou r previously reported data but different from results reported for macrocha nnel heat sinks. Three stable boiling modes, depending on the input power l evel, have been distinguished from the flow patterns, Local nucleation boil ing was observed in microchannels with a hydraulic diameter as small as 26 mum at the lower input power range. At the higher input power range, a stab le annular flow was the dominant boiling mode. Bubbly flow commonly observe d in macrochannels, could not be developed in the present microchannels. Co nsequently, no bailing plateau was detected in the boiling curves.