Boiling heat transfer and critical heat flux evaluation of the pool boiling on micro structured surface

We study the effectiveness of microstructured surfaces in enhancing the boiling heat transfer (BHT) and critical heat flux (CHF). A set of experiments is designed with thirteen prepared samples: twelve with a microstructured surface, and one with a bare surface. The samples are fabricated using microelectromechanical systems (MEMS) techniques. The samples are tested using pool boiling experiments in saturated and atmospheric pressure conditions. The experimental results show that BHT increases with the surface roughness, defined as the ratio of the rough surface area to the projected area, but this enhancement gradually slows. The heat transfer coefficient of the structured surface is more than 300% that of the bare surface. The increase in the heating surface area due to the roughness ratio improves nucleate BHT due to the enhancement of convective heat transfer. The structured surface shows a 350% improvement in CHF over the bare surface. However, through analysis of the capillary flow rate on the structured surface, a critical gap size that limits the CHF is found. The critical gap size is discussed analytically and compared with experimental data. Designs for optimal boiling performance are proposed by studying the role of microstructured surfaces in both BHT and CHF.