EFFECT OF SURFACE WETTABILITY AND SURFACE ROUGHNESS ON SiO2 AND COPPER HYBRID THIN-FILM-COATED SURFACES FOR NUCLEATE BOILING PERFORMANCE

Abstract

The present scenario shows that the usages of electronics equipment are very extensive because of its performance and compactness. The concept of boiling heat transfer is applied to cool the equipment for better thermal management system. In the present experimental investigation, the copper substrates were coated by SiO2 and copper hybrid thin film by the radio frequency sputtering method. The thickness of the coating was selected as 250 nm, 500 nm, and 750 nm. The contact angle of the SiO2 and copper-coated hybrid surface was measured by goniometer, and structural studies were conducted by images from a scanning electron microscope and a stylus profilometer. The wettability of surfaces was improved significantly because of active nucleation sites created by thin-film coating. The nucleate boiling test was carried out by the pool boiling experimental setup for deionized (DI) water at saturation temperature and atmospheric pressure. The critical heat flux (CHF) and boiling heat transfer coefficient (HTC) were calculated, and compared with bare copper substrate. The results showed that the critical heat flux was enhanced by 45%, 53%, and 62%, whereas the boiling heat transfer coefficient was 63%, 97%, and 130% for 250-nm-, 500-nm-, and 750-nm-thick surfaces, respectively. The reason for this enhancement was due to increased nucleation site density which deals with the bubble formation and departure. The critical heat flux and boiling heat transfer enhancement at low wall superheat reveals a better heat transfer mechanism for an effective thermal management system.