Experiment Investigation On Micro/Mini-channel Condenser With Liquid-Vapor Separator

Based on the design theory of heat exchanger and the working principle of liquid-vapor separation condenser,a condenser with liquid-vapor separator which is a U-type tube was designed.Based on the experimental study,the refrigerant R141b and R134a used as experimental working fluid,the heat transfer performances of the water-cooled and air-cooled condensing heat exchangers with liquid separation were investigated when the mass flow rate was 60?350 kg/m2s,the saturation temperature was 16? and 25?.The effects of steam mass flow rate,inlet superheat,cooling water flow rate and wind speed on the condensing heat transfer were analyzed.The heat transfer performances of each channel pass were analyzed emphatically.Based on the Nusselt condensation theory,the liquid film growth model in a horizontal rectangular tube was established considering the shear force at the liquid-vapor interface and the experimental results were used to correct the model.The change of the condensing flow pattern of the refrigerant R141b in the condenser with liquid-vapor separator was observed by the visualization experiments,the flow patterns observed in the experiment include annular flow,agitate flow,slug flow and bubbly flow.The condensate is separated in time by the U-type tube and it provided the basis for the effective separation of the condensate by the liquid separation structure.The change of condensation flow pattern due to the existence of liquid separation structure was observed.Because of the timely discharge of the condensate,the flow pattern inside the channel after the liquid-vapor separator was repeated,and this provided the basis for the increase of heat transfer coefficient in the condenser with liquid-vapor separator.With the increase of mass flow rate,the shearing force at liquid-vapor interface increased,and the flow pattern tended to annular flow.According to the condensation heat transfer experimental analysis,with the increase of mass flow rate,the shearing force at the liquid-vapor interface increased,and the film thickness decreased.The condensation heat transfer coefficient increased.With the increased of cooling water flow velocity,the wall temperature decreased,while the saturation temperature kept constant,and the temperature difference increased.The increase of condensation rate led to thickening of the liquid film on the wall and an increased of thermal resistance,resulting in the condensation heat transfer coefficient reduced.But in the wind cooled system,with the increse of wind speed,the heat trafer coefficient decreased.Becaues the convection heat transfer coefficient of wind side is limited,the wind speed faster,the heat exchange smaller.Compared with the non-liquid separation structure,the heat transfer coefficient of the condenser with liquid-vapor separator increased by 10%?20%,mainly because of the presence of liquid separation structure,making the vapor quality of the condenser increased.However,the diameter of the liquid separation tube determined its liquid separation ability.As the pipe diameter increased,the liquid separation rate increased and the condensation heat transfer coefficient increased.Based on the Nusselt condensation theory,the condensate film growth model in the horizontal rectangular channel can predicted the experimental results more accurately.The analysis of the influencing factors of the condensation heat transfer coefficient is same as the experimental results.