Experimental Comparison of Pool Boiling Performance between Cu-plain Surface and Functionalized Graphene Layers

Abstract

Functionalized-Graphene coatings have attracted considerable attention because this kind of materials offers many new and greatly improved properties for a wide range of applications. The purpose of this study is to provide experimental observation for pool boiling heat transfer on enhanced copper substrates by Graphene and Fluorinated-Graphene coatings using two different coating techniques, Chemical Vapor Deposition (CVD), and Electrophoretic Deposition (EPD) . HFE-7000 refrigerant is used as a working fluid in this study. It has been shown that the bubbles' density on Graphene coating surface (CVD) is 2 times higher than the bubbles density on Cu-plain, the bubbles density on F-Graphene surface (CVD) is 2.43 times higher than those on Cu-plain, and the bubbles density is 3.7 times on F-Graphene surface (EPD) more than the bubbles density on Cu-plain, and thereby this results in an enhancement in pool boiling HTC up to 20%, 80%, and 200% on Graphene & F-Graphene (CVD), and F-Graphene (EPD) respectively. It has also been proven that pool boiling Heat Transfer Coefficient (HTC) and Critical Heat Flux (CHF) by CVD are affected by the wettability change only, whereas pool boiling HTC and CHF by EPD are affected by two controlling parameters (the wettability change and the surface roughness). The surface morphology of (EPD) F-Graphene coating surface shows larger surface roughness compared to Graphene and F-Graphene surfaces by CVD attributing to more effective structures that result from applying F-Graphene by EPD. The results of this study can be further applied on two-phase heat transfer products to enhance their performance.