Experimental Study of Refrigerant (R-134a) Condensation Heat Transfer and Retention Behavior on Paraffin-Coated Vertical Plates and Fin Structures

Condensation of refrigerant R-134a is experimentally investigated on a paraffin-coated copper surface and compared to condensation on a plain copper surface. Heat transfer and visualization experiments are conducted for vertical-plate samples and for two different fin structures at various degrees of subcooling. A one-dimensional heat conduction model is used to interpret the condensation heat transfer measurements, while liquid retention behavior is quantified with the aid of image processing. The experimental results on vertical plates show that the heat transfer is enhanced on the coated surface with a maximum increase of 27% in the condensing heat transfer coefficient. On fin structures, the liquid retention was reduced by up to 28% on a coated surface. The heat transfer and retention behavior vary with surface material, degree of subcooling, and fin geometry.