Bubby behavior and heat transfer characteristics of bionic microchannels in the subcooled flow boiling process

Microstructures on the sidewall or bottom wall, have shown excellent heat transfer performance in the single-phase convective heat transfer of microchannel heat sinks. For increasing the heat flux, phase-change heat transfer was highlighted as an effective approach. However, more complicated mechanisms of boiling heat transfer make less study focused on the microchannel with microstructure. In this work, a bionic microchannel with concave cavities and bionic ribs was proposed to enhance the boiling heat transfer. Numerical simulations, along with the volume of fluid (VOF) analysis combined with a phase-change model, were used to investigate the effect of the microstructure on the behavior of bubbles in the subcooled flow boiling. The results showed that the microstructure promotes bubble nucleation and the occurrence of more small bubbles around big bubbles. Thus, it enhances boiling heat transfer. Meanwhile, the microstructure was found to be beneficial in maintaining a stable liquid film evaporation under annular flow and suppressing boiling instability. Ultimately, compared with rectangular microchannels, the reported wall temperature and inlet pressure are more stable in the proposed bionic microchannel, the heat transfer coefficient and critical heat flux of the bionic microchannel were found to be 1.45 times higher, with mass flux G of 498 kg/(m2 center dot s) and heat flux qw of 600 kW/m2.