Pool Boiling Heat Transfer Performance of R-134a on Microporous Al Surfaces Electrodeposited from AlCl3/Urea Ionic Liquid

Development of smart heating surfaces to enhance the performance of pool boiling heat transfer (BHT) has great significance in pool boiling applications. This paper presents the results of a study of improved pool BHT performance of R-134a on horizontal Al surfaces with microporous coating (diameter = 9 mm) at saturation temperature. Microporous Al coatings were fabricated by electrodeposition using AlCl3/urea ionic liquid (IL). The effect of various electrolyte temperatures (30°C, 40°C, 50°C, and 60°C) on the morphology, microstructure, porosity, thickness, and surface roughness of Al coatings was investigated. The pool BHT experiments were performed for increase in the heat flux, varying from 9.51 kW/m2 to 75.14 kW/m2. For the microporous Al coating electrodeposited at an electrolyte bath temperature of 30°C, 40°C, 50°C, and 60°C, the heat transfer coefficient (HTC) value was increased by 58%, 75%, 92%, and 109%, respectively, compared with the bare Al surface. The differences in the HTC augmentation for Al-coated surfaces can be explained by variations in the thickness of the microporous structure and in their surface characteristics such as porosity and surface roughness.