Analysis of flow boiling heat transfer characteristics in microchannels with hydrophilic/hydrophobic structured surfaces

This study employs computational modeling of straight microchannels with hydrophilic and hydrophobic surfaces to examine the influence of surface wettability on bubble morphology, flow field disturbance, and pressure distribution around bubbles in rectangular microchannels using the Volume of Fluid (VOF) approach. The analysis focuses on variations in average wall temperature under different mass flow rates and heat fluxes, as well as the effect of mass flow rate on critical heat flux (CHF). Findings reveal that the average wall temperature in hydrophilic microchannels exceeds that in hydrophobic ones, accompanied by more notable temperature fluctuations. The critical heat flux in hydrophilic microchannels is substantially higher, showing increases of 70% and 64%, respectively. When mass flow rate surpasses a certain threshold (above 400 kg/m²·s), the CHF growth rate in hydrophilic channels decelerates (from 29% to 11%), whereas it accelerates in hydrophobic channels (from 12% to 32%). These behaviors are closely linked to bubble morphology and their dynamic instabilities. The outcomes offer valuable insights for enhancing microchannel surface design to improve the thermal efficiency of two-phase flow systems.