The Study On The Effect Of Process Parameters On The Drying Quality Of The Solar Assisted Heat Pump Drying System

Solar energy is a natural,safe and environmentally friendly renewable energy.China's solar energy resources are abundant.Solar radiation has a wide area and long radiation time.The total annual emission is about 5000MJ/m2.Solar energy can be used is far more abundant than conventional fossil fuels such as coal,oil and natural gas.But the flow density of solar energy is low,and the night and rainy weather is short of solar energy.The radiation is unstable and intermittent.It is difficult to control the drying process directly by using solar energy.As a new energy saving and environment-friendly drying technology,heat pump drying system greatly saves energy and has a wide range of regulation compared with conventional energy drying.The combination of solar energy and heat pump technology can flexibly switch drying mode according to actual drying needs.The solar collector system receives solar energy,provides low temperature heat source for heat pump evaporator terminal,and promotes high grade heat source by means of heat pump,used for crop drying.It is beneficial to save energy,to reduce energy consumption,improve the drying quality of the products,and has broad application prospects.The main research content and conclusions are as follows:(1)A new type of shell-and-tube heat storage device is designed to compensate for the intermittent shortcomings of solar energy.A three-dimensional,unsteady,liquid paraffin containing natural convection is established.A thermal storage unit is studied in this model.The three-dimensional numerical simulation of the regenerative process of the heat storage unit of the regenerative heat exchanger was carried out.the heat storage unit thermal storage and release performance under the conditions of the natural convection or not,different heat storage unit placement,unit with or without fins were analyzed and compared,which provides a theoretical foundation for the development and optimization of energy storage devices and integrated systems.(2)The experimental platform about heat pump assisted solar energy drying system is built in order to investigate the drying characteristics of mushroom.(3)According to the initial conditions of drying and the division of the process stage,the material balance calculation and heat balance calculation are carried out,and the heat load required for the drying process is analyzed and calculated.(4)The effect of heat pump drying on the drying quality of letinous edodes was studied.Based on the traditional drying process of the letinous edodes and theoretical analysis,the process stage of variable temperature drying is determined.The evaluation index of the letinous edodes qualityis established.Four different heat pump drying conditions were designed.The effects of different heat pump drying conditions on the recovery,shrinkage,color,flavor and other qualities of letinous edodess were investigated,and the general rule of the drying process of the letinous edodes is further obtained.