Enhanced flow boiling heat transfer characteristics of R134a on graphene-Cu nanocomposite coating on copper substrate

This study presents the flow boiling heat transfer characteristics of graphene-Cu nanocomposite coated copper surfaces. First, recently reported studies regarding efforts to enhance flow boiling heat transfer are discussed, then related studies on the impacts of using nanocomposite coated surfaces on flow boiling heat transfer characteristics are reviewed. Experimental investigations explore the effects of graphene concentration and feed mass flux of a refrigerant (R134a) on the heat flux and the heat transfer coefficient. The test chamber is a rectangular channel of 60 mm width, 3 mm height, and 460 mm length, and the dimensions of the graphene-Cu composite test plates are 10 mm x 10 mm. The feed mass fluxes used in the experiments are 240 and 480 kg/m(2)s, while the wall heat flux are varied from 0.1 to 20 W/cm(2). Based on the experimental analysis, the heat flux slightly increased before the onset of nucleating bubbles. Subsequently, the values drastically increased as the wall superheat continued to increase. Additionally, in experiments with higher graphene concentration, higher heat flux and heat transfer coefficient were demonstrated, and the increase in feed mass flux promoted flow boiling heat transfer.