Flow boiling characteristics of micro-grooved channels with reentrant cavity array at different operational conditions

Micro-grooved channels with reentrant cavity array (MGRA) was developed using the orthogonal Ploughing/Extrusion method (P/E) for the purpose of flow boiling heat transfer enhancement. The flow boiling tests were conducted using deionized water as working fluid with variation in the heat flux, mass flux (G = 170, 230 and 290 kg·m−2·s−1) and inlet liquid subcooling (△Tsub = 10, 25 and 40 °C). The heat transfer performance for the MGRA was compared with that for the micro-grooved channels (MG) without reentrant cavities on the side wall. The results indicated that the MGRA yielded higher heat transfer coefficient (HTC) than the MG due to the enhanced nucleation and interruption of the boundary layer. Despite the higher pressure drop, the MGRA took the advantage of mitigating the two-phase instability thanks to the sharp corner of the cavities and capillary-driven liquid intake. Increasing the mass flux increased the HTC while there existed an optimum inlet liquid subcooling for HTC maxima. The pressure drop increased with increase of mass flux while a reverse trend was observed for the inlet temperature.