Thermal performance of flat plate heat pipe array with surface wettability modification: An experimental and simulation study

Surface wettability has a significant effect on the heat transfer characteristics of the flat plate heat pipe array (FPHPA). In this study, an aluminum based FPHPA measuring 250 x 100 x 3 mm3, comprising of 9 independent channels, was developed to investigate the impact on wettability segmented modification through experiment and simulation. After chemical etching, the micro-nano structure of the surface can produce a hydrophilic effect, while hydrophobic effect can be achieved after spraying polydimethylsiloxane mixture, and the two modification methods passed the heat resistance and durability tests. The FPHPA, equipped with a hydrophilic evaporator, a hydrophobic adiabatic, and a condenser, exhibited enhanced heat transfer characteristics, lower wall temperature, a higher heat transfer limit, and reduced sensitivity to inclination angle. Simulation results revealed that the hydrophilic surface promoted bubbles to break away from the wall surface and improved the critical heat flux of the evaporator, while the hydrophobic surface had a faster droplet return rate and a thinner liquid film thickness, which improved the convective heat transfer coefficient of the condenser. Compared to conventional flat heat pipes, hybrid wetting modified FPHPA shows a higher overall effective thermal conductivity at thermal powers above 90 W. The findings from this study contribute to a better understanding of the heat transfer mechanism following surface modification and offer a practical method for modifying FPHPA.