Experimental study of pool boiling heat transfer on mini-pillar surfaces with different hydrophobic dot arrays

In this study, we conducted experimental research on the pool boiling performance of mini-pillar surfaces with different hydrophobic dot arrays. The experimental results show that the distribution and total area of hydrophobic dot arrays on pillar tops significantly influence the boiling performance of mini-pillar surfaces. In comparison with the mini-pillar surface without wettability modification, introducing hydrophobic dot arrays on the pillar tops can improve the bubble nucleation density and diminish the wall superheat at boiling onset. Therefore, the boiling performance of mini-pillar surfaces can be gradually improved by increasing the total area of hydrophobic dot arrays at low heat fluxes. However, a further increase in the total area of hydrophobic dot arrays may lead to the reduction of the bubble departure frequency at high heat fluxes, which is not conducive to the segregation of the liquid and vapor pathways. The experimental results indicated that when the total area of hydrophobic pillar tops accounts for 10.24 % of the projected area of the mini-pillar surfaces, an optimal enhancement is achieved, and the optimal enhancement of boiling performance on the mini-pillar surfaces with hydrophobic dot arrays results from a suitable balance between promoting the bubble nucleation and maintaining higher bubble departure frequency.