Performance Analysis And Parameter Optimization Of Economizer System Coupled With Scroll Compressor

The air source heat pump system using the vapor injection technology can effectively reduce the exhaust temperature of the compressor under high pressure ratio(low temperature conditions in winter and high temperature conditions in summer)and improve the comprehensive performance of the system.Compared with the traditional heat pump system,the economizer system coupled with scroll compressor using vapor injection technology increases the process of vapor injection and mixing,and the parameters affecting the system performance are increased.This leads to difficulties in design,manufacture and operation control of economizer system coupled with scroll compressor.In order to analyze the types of parameters affecting the performance of the system and their influencing rules,lumped parameter models are established for the vapor injection scroll compressor,economizer,heat exchangers and throttle elements in the above-mentioned systems.For the accuracy of the model,a partition lumped parameter model for heat exchanger is established.According to the import-export relationship of the parameters between the components,the component models are combined into the system models under winter and summer conditions,and the simulation calculation is carried out by programming.According to the types and parameters of each component of the system,an experimental prototype was set up,and a test-bed of economizer system coupled with scroll compressor was built.The test-bed was used to carry out experiments under multiple conditions in winter and summer.According to the comparison between the calculated value and the experimental value under the same working condition,the simulation error is less than 10%.According to the thermodynamic model of the vapor injection scroll compressor,it can be concluded that the relative injection pressure,the relative mass flowrate ratio of vapor injection,the injection enthalpy and specific volume ratio of the first-stage compression can affect the performance of the system.The open-loop sequential calculation algorithm of closed-loop system is used to solve the system model in winter simulation working conditions(the outlet water temperature is set at 40? and the ambient temperature is-25? to-5?)and summer simulation working conditions(the outlet water temperature is set at 10? and the ambient temperature is set at 39? to 45?).The variation of system performance parameters with the studied parameters under various operating conditions can be obtained.With the increase of relative injection pressure and the relative mass flowrate ratio of vapor injection,compressor power and system heating capacity both show an upward trend,while cooling capacity increases first and then decreases,with a peak value.As the injection enthalpy increases,the discharge temperature rises slightly and the reliability of the system decreases as a consequence.EER improves as the specific volume ratio of the first-stage compression increases.To obtain the maximum of COP,it is better to maintain the relative mass flowrate ratio of vapor injection to be between 0.4 ~0.7 and to keep the specific volume ratio of the first-stage compression to be 1~1.3.