| The solar-assisted heat pump drying system is one of the effective methods to solve the solar energy output instability,and it is also an important new drying technology.However,the structure of solar-assisted heat pump drying system is complex and the efficiency of waste heat recovery by evaporator is low.In order to solve these problems,this paper starts to view of the development and utilization of new energy and the drying demand of agricultural and sideline products.In this paper,presented a heat recovery and complementary energy on solar-assisted heat pump drying system has been proposed.Meanwhile,the heat and mass transfer model of material drying process has been established;the simulation system has been constructed and simulated;the optimization and experimental research have been carried out.The main work and conclusions of this paper are as follows:(1)The thin-layer drying characteristics of mango under different drying temperatures of 5 layers material were simulated by MATLAB software.Meanwhile,the variation curves of moisture content of mango,temperature and moisture content of hot air have been predicted.The simulation results show that when the drying medium passes through each layer of material rack in turn,the drying medium decreases and the moisture content of the air increases gradually,because of the evaporation of the material moisture.Furthermore,with the continuous drying of the material,the temperature of the material was increased gradually,and the moisture content of the material was decreased gradually.(2)Based on the analysis of mango drying characteristics and the requirement of material drying,a solar-assisted heat pump drying system has been designed,with the capacity of drying chamber is 9m3,air source heat pump is 3p,the total area of the a collector is 5.24 m2 and the area of heat exchanger is 5.5m2,and an actual of the performance analysis of the drying system was installed in Kunming has been carried out.The experimental results show that the maximum average COP of the system in the combined drying mode is higher than the heat pump drying mode is 23%.The relative of error between the predicted moisture content and the experimental moisture content is less than 15%.Therefore,the combination drying mode has more advantages than the heat pump drying mode.(3)The TRNSYS simulation software has been used to simulate the solar-assisted heat pump drying system in the whole year,the variation regulation of the parameters operating system,the performance and energy consumption has been analyzed.The system simulation results show that the lowest of COP system is 2.43 in January,and the maximum is 3.54 in July,the annual average COP is 3.03.The lowest of energy consumption in July and August is 4048.16 k J/h,and the highest of energy consumption in December and January is 6470.00 k J/h.The maximum relative error between the system simulation and the experimental results is 29%.Furthermore,the operating and control mode of the system has been optimized.When the irradiation intensity is greater than 0.323 k W/m2,the solar drying mode is operated;when the irradiation intensity is in the range of 0.163 k W/m2 to 0.323 k W/m2,the combined drying mode of solar energy and heat pump is operated;and when the irradiation intensity is less than 0.163 k W/m2,the heat pump drying mode is operated. |
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