Visualization Investigation on Flowing Condensation in Horizontal Small Channels with Liquid Separator

A simultaneous visualization and measurement experiment was carried out to investigate condensation flow pat- terns and condensing heat transfer characteristics of refrigerant R14 lb in parallel horizontal multi-channels with liquid-vapor separator. The hydraulic diameter of each channel was 1.5 mm and the channel length was 100 ram. The refrigerant vapor flowing in the small channels was cooled by cooling water. The parallel horizontal mul- ti-channels were covered with a transparent silica glass for visualization of flow patterns. Experiments were per- formed at different inlet superheat temperatures （ranging from 3~C to 7~C）. Mass velocity was in the range of 82.37 kg mZs1 to 35.56 kg m-2s1. It was found that there were three different flow patterns through the mul- ti-channels with the increase of mass velocity. The flow patterns in each channel pass almost tended to be same and all of them were annular flows.＇ The efficiency of the liquid-vapor separator with U-type was related to vapor mass velocity and the pressure in the small channels. It was also found that the heat transfer coefficient increased with the increase of the mass velocity while the cooling water mass flow rate increased. It increased to a top point and then decreased. It increased with the increase of superheat in the low superheat temperature region.