A periodic stepped fin microchannel heat sink (PSFMC) is developed to stabilize microchannel flow boiling operation and thereby improve the two-phase heat transfer performance. Flow boiling experiments are performed on the 25mm x 25mm copper based heat sink using de-ionized water as the coolant. The flow boiling performance of this heat sink is benchmarked against a conventional straight microchannel heat sink (SMC). Unlike the SMC where the confined flow passages lead to bi-directional expansion of elongated vapor slugs, PSFMC facilitates expansion of vapor bubbles or slugs in the span-wise direction at the interconnected sections. Flow reversal effects are minimized and the pressure and temperature measurements are more stable compared to SMC. The improved boiling stability coupled with higher bubble nucleation activity causes the PSFMC to provide an enhanced two-phase heat transfer performance compared to SMC particularly under the lowest mass flux of 57 kg/m2s.
Keywords microchannel heat sink, two-phase cooling, stability, stepped fin, heat transfer