Enhanced flow boiling of HFE-7100 in silicon microchannels with nanowires coated micro-pinfins

Abstract

Promoting the thermal performance of the microchannel heat sinks with dielectric fluids has attracted significant attention owing to its great potential in achieving direct cooling of electronics with high power density. However, hostile thermophysical properties such as low thermal conductivity and latent heat of dielectric fluids impose great challenges. Here we report an experimental study of the HFE-7100 flow boiling in silicon microchannels with nanowires coated micro-pinfins (SiNW-pinfin) over a wide range of working conditions. The proposed microchannels can sufficiently regulate the two-phase regime transition and augment the heat transfer rates by enhancing nucleation boiling and regulating multiple flow patterns into annular flow. The flow boiling heat transfer coefficients (HTCs) of HFE-7100 can be further enhanced up to 84.6% and 57% compared to these in SiNWs and μ-pinfin microchannels (two demonstrated highly efficient configurations) with high heat and mass fluxes, respectively. The critical heat fluxes (CHFs) of the proposed microchannels are also promoted up to 61% and 20% compared to these in conventional plainwall and nanowire coated microchannels. In addition, the drawback of delayed onset of nucleate boiling (ONB) of HFE-7100 in the conventional plainwall and μ-pinfin microchannels has been overcome by integrating SiNWs. The supercapillary hierarchical structure could further reduce the pressure drops up to 42.9% compared to the separated two-phase flow achieved in μ-pinfin microchannels with slightly decreased CHFs.