Study On Optimization Of Quasi-two-stage Compression Medium And High Temperature Heat Pumo System Based On Mixed Refrigeration

Industrial production process will produce plenty of 30~60 ℃ waste heat which is often unable to use and directly discharged into the environment resulting in lots of energy waste and environmental thermal pollution.The research of medium-high temperature heat pump technology can broaden the application range of heat pump technology.This technology can recover industrial waste heat to enhance the energy level and product the hot water above 80℃,while these hot water can be re-used for industrial production or heating and bring significance in saving and emission reduction effect.Due to the high condensing pressure,high exhaust temperature and other reasons,the coefficient of heat production is often lower while making high temperature water heating by conventional medium-high temperature heat pump.From two aspects of refrigeration and system,enthalpy of supplementing gas in medium-high temperature heat pump system based on screw type of mixed refrigerant was conducted.In the aspects of refrigeration,the environmental characteristics,safety characteristics,working pressure and unit volume heat production are taken as the selection principle of pure refrigeration in medium-high temperature heat pump.After comparison the better quality of the pure working material in multifaceted was selected.By writing the programming language,the calculation of the thermal cycle in mixture of pure components and mixed refrigeration in the heat pump system is realized.According to the calculation results,,the ratio of the mixed refrigerant with better performance for medium and high temperature heat pump is determined considering to the physical and chemical properties such as the environment and safety.It can be found while the ratio of R134 a and R245 fa was 0.2/0.8、0.3/0.7、0.4/ 0.6 the thermodynamic cycle can obtain a good affect in medium and high temperature heat pump system.On the other hand,based on the selected three kinds of mixed refrigeration,the REFPROP software was used to quantitatively determine the temperature slip law of the mixed refrigeration in the temperature range of the bubble dew point.In the aspect of system optimization,the mathematical model of compressor system with economizer system,gas supplement of economizer calculation,evaporator and condenser are established,and these mathematical models are combined into heat pump system model.Based on the model,write simulation program and optimize the calculation for the heat pump system in the selected conditions.The simulation results show that the system COP and the heat capacity are higher than that the ordinary heat pump system;with the compressor inner volume ratio increasing from 1.2 to 1.8,the system COP is increasing and the volume per unit volume of heat showed a downward trend;in the range of 5~8℃,the higher the heat transfer temperature difference,the higher the system COP and the heat.At the same time,the mathematic model of the compressor air supply position of the compressor is set up.By analysis the first-order inner volume ratio was selected and was taken into the mathematical model to obtain the better position of the compressor air supply in heat pump system.In order to establish the actual heat pump system,the concrete data of each component selection under the selected working condition are calculated as the theoretical basis for the construction of the experimental platform.In addition,comparing the experimental data of the heat pump system in experimental platform with the simulation data of the same working conditions show that the simulation error is about 8~10%,which can basically verify the accuracy of the simulation calculation.In this thesis,the heat pump system simulation program was compiled into a user interface GUI program,the GUI program has been successfully run.