Enhanced Heat Rejection of Microscale Geometries in Convective Flow Boiling Evaporators

Four surfaces have been designed, fabricated and tested under convective flow boiling (CFB) conditions in an open loop configuration. They contain features in the 10 micron range and were tested with flow velocities under 3 mm/s. To accomplish these flow rates, this work utilizes a constant pressure potential driving flow, instead of the constant flow rate imposed with a syringe pump. This limited device flooding. The evaporation surfaces were tested to the point of dry-out at three different pressure potentials: 150, 650, and 1150 Pa, across a range of powers from 25 W/cm2 to 50 W/cm2. Temperature data was collected from an IR Camera and showed that fluctuations in the wall temperatures exceed 5 °C in more than 50% of the tests and reached differences as high as 23 °C. The wall temperature instabilities in CFB indicate that one temperature may be inaccurate and that by including time as a variable a better understanding of the behaviour at this scale may be revealed.