Influence of regional artificial cavity layouts on flow boiling in micro heat sinks with stepwise-decreasing pin-fin heights

Novel heat sink configurations and associated flow boiling physics were examined. Specifically, the influence of regional artificial cavity layouts on flow boiling in micro heat sinks with stepwise decreasing pin-fin heights was investigated. Four heat sinks with stepwise decreasing fin heights were compared. One of them has microcavities only in the downstream region (DPFH-1D), the other has microcavities both in middle and downstream regions (DPFH-2D), and another has microcavities in all regions (DPFH-3D). Additionally, the fourth one has no microcavities (DPFH) and was used as reference case. Under various heat fluxes (212 – 462 kWm −2 ) and mass fluxes (151 and 222 kg m −2 s −1 ), tests were conducted at an approximately constant inlet temperature (≈77°C). DPFH-1D provided the best overall thermal performance and the highest two-phase heat-transfer coefficients, although DPFH-3D yielded slightly lower wall-superheat values at the two highest heating powers. The maximum heat-transfer-coefficient enhancements of DPFH-1D reached 286.2% and 528.4% at 151 and 222 kgm −2 s −1 , respectively. Despite producing the highest pressure drop, DPFH-1D’s PEC value remained above 1 throughout dataset, with a maximum of 3.49. Downstream microcavities most effectively promoted capillary liquid retention and surface rewetting, whereas upstream and middle microcavities provided limited additional benefits at low and moderate heat loads.