Composite microstructured surface with micro-cavities and micro-ditches on micro-pin-fins for enhancing pool boiling heat transfer

Abstract

In this study, a novel composite microstructured surface with micro-cavities and micro-ditches on micro-pin-fins was designed to enhance pool boiling heat transfer. To reveal the enhancement mechanism of the newly-designed composite microstructured surface, the pool boiling heat transfer performance on four types of microstructured surfaces was investigated in HFE-7100 under different liquid subcooling degrees. The experimental results show that the micro-pin-finned surfaces with micro-ditches at the side walls of each micro-pin–fin can enhance the rewetting ability of the surfaces, thereby enhancing the boiling heat transfer at high heat fluxes and improving the critical heat flux (CHF) in comparison with the base micro-pin-finned surface. Meanwhile, the wickability of the micro-pin-finned surfaces with micro-ditches was found to increase with increasing the number of micro-ditches. Furthermore, by fabricating both micro-cavities and micro-ditches on each micro-pin–fin, the composite microstructured surface with micro-cavities and micro-ditches is capable of not only utilizing the advantage of increasing the nucleation site density through the micro-cavity structures, but also enhancing the rewetting ability of the surface through the micro-ditch structures. As a result, the newly-designed multiscale composite surface can significantly improve the heat transfer coefficient (HTC) and the CHF simultaneously. Quantitatively, the achieved largest HTC and highest CHF are 5.12 W/(cm2·K) and 75.2 W/cm2, respectively, which are 6.24 times and 2.82 times, respectively, as high as those on a smooth surface at the liquid subcooling degree of 35 K.