Theoretical And Experimental Study On Cyclic Performance Of High Temperature Electric Heat Pump Based On Binary Mixture

China’s energy system is dominated by primary energy,which consumes a large amount of energy but has a low energy utilization rate.The consumption of a large amount of primary energy has caused huge environmental pollution and the greenhouse effect.Among them,industrial energy consumption accounts for 70%of China’s total energy consumption,but energy utilization efficiency is less than 50%,so the use of industrial waste heat recovery technology will significantly improve energy utilization efficiency and energy conservation and emission reduction effects.Because of its significant performance advantages,heat pump technology is gradually being used in the field of waste heat utilization.However,the temperature of industrial waste heat resources is mostly around 40 ℃,and most of the production process or central heating temperature requirements exceed 90℃.Therefore.it is subject to The temperature and pressure limit,the conventional heat pump working medium can not meet the high temperature conditions to ensure the safe and stable operation of the compressor,so the selection of new heat pump working medium suitable for high temperature working conditions is one of the main research directions of high temperature heat pump technology.Because non-azeotropic working fluid has the characteristics of heat transfer with sliding temperature,it is more suitable for the heat transfer process with large temperature difference.Therefore,this study established a mathematical model of non-azeotropic working fluid electric heat pump.Based on COP(coefficient of performance)and exhaust parameters The performance of different components and different ratios was compared with the heating capacity per unit volume to select a better working medium,and the change law of the heat transfer coefficient of the selected working medium during evaporation and condensation was analyzed.Finally,the experimental results were tested by using Selection of working medium heat pump performance.The research content includes:First,based on the energy balance and mass balance equations,a mathematical model of a high-temperature electric heat pump is built in the EES software,and REFPROP is called to calculate the physical properties of the non-azeotropic working medium.Second.R245fa,R142b.and R236ea are screened for high-temperature conditions and have comprehensive applications.Potential pure Freon,and then using R134a.R1234ze and R227ea as additional working fluids to take advantage of the characteristics of non-azeotropic working fluids to increase the COP of the heat pump and reduce the exhaust parameters of the compressor.This study is aimed at 9 combinations in different proportions.The performance parameters were compared and analyzed,and the mixed working medium R134a+R245fa(0.38/0.62)with better cycle perfomance was obtained,and the code was M;again,the selected non-azeotropic working medium M was analyzed for the evaporator and condenser substation.The heat transfer coefficient changes under the condition.The calculation results show that as the temperature of the inlet and outlet water on the condensation side increases,both the condensation heat transfer coefficient and the boiling heat transfer coefficient increase.When the temperature of the inlet and outlet water on the evaporation side increases,the condensation heat transfer coefficient and boiling heat transfer increase.The coefficients have all been reduced;finally,a comparative analysis of the cycle performance of the pure working medium XP140 and the mixed working medium M on the high temperature heat pump performance test platform Found that when the condensation temperature is low,refrigerant XP140 pure exhibits more excellent cycle characteristics,but when the water temperature of the condenser 80℃,the condensing pressure is higher than 2.1 MPa,unable to work at a higher condensation temperature.When the inlet water temperature of the evaporator is 60℃and the inlet water temperature of the condenser is 80℃,the exhaust gas temperature and the condensation pressure of the mixed working medium M reach 100.1℃ and 1560kPa,respectively,which has the potential to develop to higher condensation temperatures.Under temperature conditions,it shows better performance than XP140.At the same time,the heat transfer coefficients of mixed working fluids obtained by simulation and experiment are compared and analyzed.It is found that the change trends of the two are consistent,but the heat transfer coefficients obtained from experiments are lower than the simulated values.In summary,industrial waste heat utilization technology is an important way to improve the energy efficiency of energy systems and reduce energy consumption.Non-azeotropic working medium high-temperature heat pumps developed for industrial applications will have better application prospects in the industrial field due to their technical advantages.