Experimental investigations of flow boiling heat transfer and flow behaviors in microgap channel

Boiling and Two-phase flow in microgap channel has been recently proposed for cooling the heat sources directly in application of thermal management for electronic devices. Many researches were carried out to investigate the mechanism of heat transfer in the microgap channel. In this study, the boiling heat transfer and gas-liquid flow on the heated surface in microgap is investigated experimentally by using Temperature- Sensitive Paint (TSP). Experiments are performed in a single rectangular channel having microgap of 10 mm width, 35 mm heated length and 0.5 mm height using FC-72 as a test fluid with inlet subcooling 13.9 K under atmospheric pressure conditions. TSP coated on the heated wall is used to obtain the local temperatures and subsequently local heat transfer coefficients. In addition, simultaneous flow visualizations are conducted to observe and explore the flow boiling in microgap channel. Flow rate of FC-72 is 200 mg/s and heated water at 339 K is used as a heat source for boiling of the test fluid. Observation of gas-liquid behavior and measurement of the temperature distributions on the heated surface could be achieved at the same time by TSP. As a result, the heat flux of the rear side of a boiling bubble is 1.2-1.5 times higher than that of the front side of a bubble.