Experimental studies on nucleate pool boiling heat transfer enhancement for composite nano-structure coated copper heating surface

Abstract

The present paper is based on experimental studies on nucleate pool boiling heat transfer enhancement of different surfaces using water as a base fluid at atmospheric pressure. The test surfaces for the experiments include untreated, treated, and treated with Aluminum-silver oxide composite thin film surfaces having nano-layer thickness of 180 nm and 260 nm. The thin films are prepared on copper substrate by electron beam evaporation technique. The characterization of the heated surfaces is done by using optical surface profilometer for surface roughness and sessile drop method for contact angle measurement. The experiment is conducted in a closed boiling chamber and the heat flux is varied from 141.524 - 1244.101 kW/m2 in time steps. The enhancement of heat transfer coefficient is found as 22.8%, 17.27% and 11.81% from the 260 nm, 180 nm composite nanostructured coated and treated surfaces respectively compared to plain surface. Enhancement in nanostructured coated surfaces is found higher due to the capillary effect, increased wettability and high active nucleate site density and the increased rate of bubble frequency.