Simulation And Optimization Research On Comprehensive Performance Of Two-stage Compressed Air Source Heat Pump Systemby

As a kind of renewable energy,air source heat pump has been widely used in China because of its economy,high energy efficiency and environmental protection.The air source heat pump can meet the needs of people in most areas for heating in winter and cooling in summer.When the ambient temperature is low in winter,when it is used for heating,it will have problems such as increased exhaust temperature,increased compressor pressure ratio,reduced system heating capacity,and reduced performance.To solve this problem,this paper studies a two-stage compressed air source heat pump system with an intercooler.Using a two-stage compression cycle can reduce the compression ratio of a single compressor,and its inter-stage structure can reduce the throttling and superheat loss of the system.Improve system performance.Simulated analysis of the effect of operating parameters on system performance under low-temperature heating conditions,established its analysis model under low-temperature heating conditions,obtained suitable operating parameters,and established the thermodynamics of the system under different operating conditions The simulation model is established,and a PID-dichotomy control algorithm is applied to the iterative calculation of the system model to improve the calculation speed and accuracy of the model.It simulates the application of the system in different regions.Its research content mainly includes the following aspects:Using the pressure and enthalpy diagram of R134 a and its related physical property parameter models,under low-temperature heating conditions,the heat exchange amount,supercooling degree,superheating degree,and shunting ratio of the intermediate heat exchanger are simulated and analyzed.Performance impact.An analysis model of the system under low-temperature heating conditions was established.Through simulation calculations,the effects of split ratio,condensing temperature and condenser subcooling on system efficiency and loss coefficients of system components were analyzed.The distributed parameter method was used to establish the thermodynamic simulation model of the system under different operating conditions.The system has three operating conditions.When the outdoor ambient temperature in winter is lower than the equilibrium point temperature,the system is a two-stage compression heating condition;winter outdoor When the ambient temperature is higher than the equilibrium point temperature,the system is in single-stage compression heating mode.In summer,the system is in single-stage compression refrigeration mode.The model considers the changes of the thermodynamic parameters of air and refrigerant,the structure of the heat exchanger,etc.,and can more realistically reflect the actual operation of the heat pump unit.A PID-binary combination control algorithm is established to iteratively calculate the system model,and a system-wide cyclic distributed parameter model based on the PID-binary combination control algorithm is formed.Using the relevant experimental data,the accuracy of the model under different operating conditions was verified,and the calculation speed of the model was analyzed.Based on the established thermodynamic simulation model of the two-stage compressed air source heat pump system,the meteorological data of Zhengzhou City are used to change the parameters such as the intermediate pressure and condensation temperature during the simulation process to analyze the influence of the parameters on the overall performance of the system,and The application of different regions was simulated and analyzed,and the design parameters of the heat exchanger and the cylinder volume ratio of the compressor in each region were given.In view of the large amount of waste of condensing heat during the summer operation of the system,a dual-stage compressed air source heat pump system with condensing heat recovery is proposed.The new system has eight operating modes to meet the different needs of people in different seasons.This paper establishes a system-wide cyclic distributed parameter model based on PID-dichotomy control algorithm,which is a fast,stable and reliable simulation model.The research results in this paper can provide some theoretical guidance for the design of the dual-stage compressed air source heat pump under different working conditions,and provide a reference for the promotion and application of the dual-stage compressed air source heat pump in different regions.