A comparative study of flow boiling heat transfer and pressure drop in crescent pin-fin and smooth minichannel heat sinks

This study experimentally investigates flow boiling heat transfer and pressure drop characteristics in a minichannel incorporating smooth and crescent pin-fin surfaces. The crescent pin fins are designed to induce asymmetric flow disturbance and modify liquid–vapor interaction characteristics. The applied heat flux varies to cover subcooled boiling and fully developed flow boiling regimes. Experiments are performed using deionized water as the working fluid at an inlet temperature of 80 °C, with mass flux ranging from 180 to 360 kg/m 2 ·s and heat flux from 15.45 to 100.59 kW/m 2 . Local wall temperatures, heat transfer coefficients (HTC), and pressure drops are measured along the flow direction. High-speed visualization is employed to identify boiling patterns and flow regime transitions. The results show that HTC increases with both heat flux and mass flux, with the crescent pin-fin surface exhibiting enhanced performance due to increased heat transfer area, additional nucleation locations, and local flow disturbance introduced by the pin-fin geometry. A maximum HTC of approximately 12–12.5 kW/m 2 ·K was achieved for the crescent pin-fin surface at the highest mass flux and heat flux, compared to about 7–7.2 kW/m 2 ·K for the smooth surface under similar conditions. In terms of hydraulic performance, the crescent pin-fin surface exhibited higher pressure drop compared to the smooth channel due to increased flow resistance; however, it showed reduced pressure fluctuations and more stable flow behavior.