Effect of dense packed micro-/nano-porous thin film surfaces developed by a combined method of etching, electrochemical deposition and sintering on pool boiling heat transfer performance

Abstract

The transportation of quick latent heat during phase change heat transfer (boiling) guides its prospective application in various heat transfer devices. The stability of the fabricated cavity/porous surfaces with the base substrate is a significant concern for the degradation of boiling performance. Therefore, a new three-step surface fabrication method (wet etching, electrochemical deposition, and sintering) is proposed in this work. Initially, the three micro/nanostructured surfaces (ES#3, ES#2, and ES#1) are fabricated by using wet/chemical etching. The best-performing wet/chemical etching surface (ES#3) is further used as a cathode for next-of-surface fabrication, i.e., electrochemical deposition. The electrochemically deposited surface (ES#4) is sintered in a predefined atmosphere to increase the bonding between the coated surface (copper-alumina) and the etching surface (ES#3). The higher boiling performance found on the final surface (ES#4) is due to the proper bonding between the ES#3 and electrodeposited copper-alumina nanoparticles. A decrease in the intermediate resistance due to proper binding boosts the percentage of heat transmission by keeping the temperature constant between the top surface of the heater and the tip of the fin. For ES#4, the critical heat flux (CHF) improvement over bare copper is 98%. Comparing the ES#4 coated surface to the bare copper surface results in a 260% increase in heat transfer coefficient (HTC). The effect of various macro and micro-scale constraints on pool boiling heat transfer phenomena is also investigated. Following multiple testing cycles, the decrease in superheat temperatures, surface morphology, and wettability for ES#4 is significantly lower, which indicates healthier stability of ES#4 surface.