Experimental Study On Low Temperature Evaporation Concentration System Of Coupled Air Source Heat Pump

In the engineering process of seawater desalination,traditional Chinese medicine concentration,wastewater treatment and food concentration,evaporation and concentration is an essential operation process,reducing the energy consumption of evaporation and concentration can improve the efficiency of the overall device operation.Multiple-effect evaporation and mechanical vapor recompression are the main technologies of evaporative concentration,but both require boilers or other methods such as electric heating to generate fresh steam to evaporate materials,which increases the energy consumption of evaporative concentration.The effect number of multi-effect evaporation is not infinitely increased,and when the effect number increases,the thermal energy utilization rate of the steam decreases.The specific volume of the steam in the mechanical vapor recompression technology is large,so the technical and technological requirements of the compressor are particularly high.In order to better save energy and improve the efficiency of evaporation and concentration,this paper proposes a new type of low-temperature evaporation and concentration system of air source heat pump,which conducts heat exchange and recovery of the steam generated by the evaporation of the raw material liquid,and conducts experiments to explore this.The system is mainly composed of air source heat pump,water ring vacuum pump and plate-fin heat exchanger using R134 a as the working fluid.The water ring vacuum pump extracts the pressure in the evaporation tank to reduce the boiling point of the raw material liquid.After the hot steam of the heat pump exchanges heat with the air through the plate-fin heat exchanger,the evaporation temperature of the heat pump working fluid is increased,the heating performance of the system is increased,and the frosting problem of the heat pump evaporation coil can be avoided.The main research contents of this paper are as follows:(1)The theoretical basis of the air source heat pump low-temperature evaporation and concentration system is explored.Through the research and analysis of the air source heat pump theory,it is concluded that under the condition that other external conditions remain stable,the evaporation temperature of the working fluid increases,and the heating coefficient of the heat pump increases.Increase.In this experiment,the steam generated by the materials in the evaporation tank is used to evaporate the working fluid of the heat pump after heat exchange with the air to improve the heating performance of the heat pump.(2)Build an air source heat pump low temperature evaporation and concentration system.Based on the air source heat pump,a set of low temperature evaporation and concentration system is formed by coupling the plate-fin heat exchanger and the water ring vacuum pump,which is divided into a heat pump working medium circulation system and a material circulation system.,vacuum system.The evaporation pressure of the material is reduced by the water ring vacuum pump to make it lower than the boiling point under normal pressure for evaporation and concentration,which not only saves energy,but also can be used for evaporation and concentration of heat-sensitive materials.(3)Analyze the energy flow of the system and evaluate the performance indicators of the system.The energy flow of this system is relatively complex.The energy flow of the system is divided into the energy flow of heat pump working fluid,the energy flow of raw material liquid(water)and the energy flow of air.The performance indicators of the system are expressed in terms of evaporation rate and COP.(4)The experiment explores the influence of the change of vacuum degree and the change of ambient temperature on the performance of the system.The experiment shows that with the increase of vacuum degree,the evaporation temperature of the material decreases,the power consumption of the compressor decreases,and the heating capacity increases.When the vacuum degree of the evaporation tank is 0.07 Mpa,the COP of the heat pump can reach 6.0,and the evaporation rate of the system is 22kg/h.With the increase of ambient temperature,the heating capacity,evaporation rate and COP of the system all increase.In the temperature,the COP of the heat pump reaches 5.3,and the evaporation rate of the system is 17.92 kg/h.