Performance Of Liquid-separation Plate Condenser And Its Application To Heat Pump System

In the conventional plate condenser,there exists a problem of the condensate accumulation in the middle-low channel with the thickened liquid film,leading to the increasing of thermal resistance and worsen heat transfer.This paper applies liquid-separation condensation in plate condenser.The flow channel is divided into multiply paths.The condensate is drained away from the vapor-liquid separation units,while the refrigerant with high vapor quality continues condensing in the next path.It is expected to achieve heat transfer enhancement.The study was carried out as following:Firstly,two types of liquid-separation plate condensers（the variable corrugation amplitude liquid-separation plate condenser had different corrugation amplitude in the second path,while the variable plate width liquid-separation plate condenser had different plate width in the second path）were proposed.A general mathematical model was built by employing the empirical correlations of heat transfer coefficient and pressure drop in the refrigerant side and water side.The program was compiled to calculate the performance of each path.The verifications with the experimental data of the conventional plate condensers indicated that the errors were within±25%.Secondly,the variable corrugation amplitude liquid-separation plate condenser was targeted to investigate the effects of different path length and corrugation amplitude on the performance evaluation parameter（PEC）and exergy efficiency.The results showed that in the case of equalized refrigerant mass flow rate in the first path and the second path,the optimal structure was obtained when the path length ratio（PLR₂）was 0.4 and the corrugation amplitude ratio（CAR₂）was 0.72.The influence of variable working conditions on its performance was further studied.As the inlet mass flow rate was in the range of 0.045-0.009 kg/s and vapor quality of 0.7-1,its PEC was always greater than one.The heat load and the exergy efficiency were 2.2%-4.9%and 0.8%-7.4%higher than the conventional plate condenser,respectively.Thirdly,the variable plate width liquid-separation plate condenser was selected to investigate the effects of liquid-vapor separation efficiency.It was found that higher liquid separation efficiency led to better performance.When the liquid-vapor separation efficiency was 100%and the mass flow rate was 0.08-0.12 kg/s,PF and the exergy destruction were 14.6%and 2.6%-6.1%lower than the conventional plate condenser with the same heat transfer area,respectively.When the mass flow rate is 0.1 kg/s,the exergy destruction was superior only when the vapor quality was higher than 0.45.Finally,the variable corrugation amplitude liquid-separation plate condenser was applied to the heat pump system.The mathematical model of the heat pump system was established with R134A as the working fluid.The structure of liquid-separation plate condenser was optimized by using the system COP as the objective.The system COP and heating capacity of heat pump system with the optimal structure in liquid-separation plate condenser were both increased by 3.5%compared with the conventional heat pump system.Under the same operating conditions and the same value of COP,the heat pump system with liquid-separation plate condenser could have 18.2%less heat transfer area.When varying the evaporation temperature in the range of 3-10 ^oC,the COP and subcooling of liquid-separation heat pump system is 2.3%-6.9%and 2.6-7.2 ^oC higher than the conventional heat pump system.Above all,the performances of two types of liquid-separation plate condenser were better than the conventional plate condensers.The heat pump system with liquid-separation plate condenser had superior COP and heating capacity.This study provides the new ideas for the development of plate condenser,amd it is also of significance to the academic research and engineering application.