Experimental Investigation of Nucleate Pool Boiling Heat Transfer of R134a on TiO 2 Coated TF Surface

Abstract Now-a-days, to save energy and to save environment are the great issues of the world. The enhancement of boiling heat transfer is one of the most important and advanced research fields to meet up the partial crisis of energy. But the way of research should be environmentally friendly. Various inferences have been drawn based on the existing parameters like operating pressure, temperature, boiling surface roughness, surface orientation, and types of working fluids or nano fluids by different researchers for enhancement of heat transfer rate. Here is an experimental study which is conducted to investigate the pool boiling heat transfer of environmentally friendly refrigerant R134a liquid at pool temperature 25 on flat copper surfaces. The surfaces are fabricated with titanium dioxide (TiO 2 ) thin film (TF) coating of thickness 100 nm and 200 nm. The Electron Beam Evaporator (EBE) is used to fabricate the thin film on test surfaces. The study is conducted on a set of values of heat fluxes of each experiment to clarify the effect of the heat flux on test surface. The surfaces are characterized with roughness, film thickness and scanning electron microscopy (SEM) & atomic force microscopy (AFM) etc. The results are compared with a plain copper surface and observed that the maximum enhancement heat transfer coefficient comes from 200 nm coating thickness of substrate and minimum from 100 nm. The heat transfer coefficient of coated surfaces was better than uncoated surface due to augmented roughness and increment of dynamic nucleation site density.