Effect of thermal spray aluminum oxide coating on the long-term stability of pool boiling heat transfer enhancement

Abstract

Boiling stability is a crucial but frequently ignored attribute when developing modified surfaces to improve phase-change heat transfer. This study investigated pool boiling on copper surfaces with various durable micro-porous thickness aluminum oxide (Al₂O₃) coatings applied using thermal spraying that improved the pool boiling stability at high heat fluxes with deionized water as the working fluid. The experiments compared the effects of surface roughness and coating thickness on the pool boiling heat transfer enhancement relative to a copper surface. Each surface underwent continuous nucleate boiling for 60 h. The wettability, morphology, and surface oxidation were assessed before and after each test. The boiling heat transfer rates on the Al₂O₃ surfaces were very stable with little degradation. The standard deviation of the heat transfer coefficient on the coated surface was 0.951 kW/m²K, while that on the copper surface was 3.184 kW/m²K for the boiling curve stability test. The pool boiling CHF was significantly higher on the coated Al₂O₃ surfaces than on the copper surfaces. The CHF on the coated rough surface was 1681.1 kW/m², 54.6 % higher than on the copper surface. Thus, these Al₂O₃ coated surfaces demonstrate considerable potential for integration into applications that demand precise heat transfer and efficient thermal management.