Comparative study of pool boiling heat transfer on different subtractive surfaces

Abstract

• The subtractive micro-nano structured surfaces based on sandblasting were prepared. • The structured surface facilitates heat transfer depends on synergistic benefit of the influencing factors. • The characteristic parameters of the micro-nano surface have been quantitatively analyzed. • The visualization study has been carried out on the micro-nano structured surface. The preparation of stable surfaces to improve the heat transfer performance can make the equipment operate safely and bring significant economic benefits. Using sandblasting and ultrasonic wet etching techniques, copper surfaces were subtracted to prepare the microscale structures (MS) and nanoscale structures (NS) in this study. Then, these two special subtractive structures were composited together to form a hybrid micro-nano structured (HMS) surface. Nucleate pool boiling experiments were carried out on the prepared surfaces with different structures at atmospheric pressure. The effect of surface modification on key parameters such as critical heat flux (CHF) and heat transfer coefficient (HTC) were investigated. Through the quantitative analysis of roughness, surface area ratio and apparent contact angle, potential mechanisms affecting nucleate boiling were explored. Meanwhile, the surfaces were visualized and their enhancement mechanisms were analyzed from the perspective of bubble dynamics. The results show that compared with the smooth plain (SP) surface, the CHFs on NS surface, MS surface and HMS surface are improved by 22.8%, 48.2% and 33.8%, respectively. The maximum HTCs are improved by 42.9%, 83.7% and 77.6%, respectively. However, the boiling heat transfer performance of HMS surface is not improved compared with MS surface. According to the characterization results, this is the result of the combined effect of roughness, surface area ratio and wettability.