Complete suppression of flow boing instability in microchannel heat sinks using a combination of inlet restrictor and flexible dampener

Abstract

Flow boiling suffers from the issue of instability due to the high rate of bubble generation in confined spaces within microchannel heat sinks. The cyclic changes in flow regimes lead to prolonged periods of dry out due to the backflow of vapour at high heat fluxes. Poor management of excess vapour and the resulting crowding at the outlet plenum drastically deteriorates the thermal and hydraulic performance of microchannel heat sinks. This study incorporates the simple design of a flexible membrane type pulsation dampener at the outlet port to address the aforementioned issues. The flexible dampener expands to accommodate the excess vapour, thereby minimising backflow and dryout within the channels. The heat sink design with the flexible dampener drastically reduces the fluctuations with lower surface temperature and pressure drop in compassion to the baseline case. Next, we combine the flexible dampener design with the inlet restrictor and compared the performance with and without the flexible dampener. The fluctuations/backflow are completely mitigated in this case, however, at the cost of a slight increase in pressure drop. Nonetheless, a quantitative comparison in terms of performance evaluation criteria suggests that the pulsation dampener can largely minimise the pressure drop penalty due to inlet restrictors while ensuring complete suppression of instability.