Comparative study of pool boiling heat transfer on different subtractive surfaces

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 modi-fication on key parameters such as critical heat flux (CHF) and heat transfer coefficient (HTC) were in-vestigated. 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 re-sults 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.(c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

The preparation of micro-nano hybrid structured copper surfaces through sandblasting and ultrasonic wet etching techniques has been investigated for its impact on nucleate pool boiling. The study found that the hybrid structure exhibits improved critical heat flux and heat transfer coefficient compared to smooth and individual micro or nano structured surfaces. The enhancement mechanisms are attributed to the combined effects of roughness, surface area ratio, and wettability.