Study on Heat Transfer Performance of R134a in Air-Cooling Liquid-Vapor Separation Condenser

In the process of in-tube condensation, the condensate film would accumulate continuously on the tube wall, increasing the thermal resistance. Inserting the liquid-vapor separation structure could help timely separate the condensate, improving the quality of the downstream flow and regenerating the thin liquid film effect in the inlet section. Then, the heat transfer coefficient inside the tube could be improved. In this paper, the overall heat transfer performance of the finned tube condenser with a U-tube liquid-vapor separator was investigated. The experimental conditions involved different wind speeds and different mass fluxes. The mass flow rates of the condensate separated through the separation tubes with diameters of 3 mm and 6 mm were measured. The experimental results showed that with the increase of the mass flux, the overall heat transfer coefficient of the finned tube condenser with the liquid-vapor separator increased, but when the mass flux was more than 250 kg•m-2•s-1, the heat transfer inside the tube basically presented single-phase heat transfer and the overall heat transfer coefficient decreased. Then, with the increase of the wind speed, the overall heat transfer coefficient increased. Finally, compared with the separation tube with diameter of 3 mm, the separation tube with diameter of 6 mm could increase the mass flow rate of the condensate separated by 20%∼50%. And as a result, the quality inside the tube was increased and the overall heat transfer coefficient was increased by 20%∼50%. © 2019, Science Press. All right reserved.