Environment-friendly Solar Drying System Of Chinese Wolfberry With Thermal Storage

in order to improve the current situation of energy consumption and serious pollution emission in crop drying industry,a regenerative solar drying equipment consisting of a air collector,a heat storage device equipped with paraffin phase change material,an adiabatic drying box and a ventilation/wet device is proposed.The performance of solar drying system was studied,and the drying tests of sweet potato and other crops were carried out to verify its drying performance,compared with the drying test of natural air drying.In this paper,a overall design scheme of the solar drying is proposed and the feasibility of heat storage system is studied.Moreover,in order to realize the intelligence of solar drying process,reduce the burden of manpower and improve the drying quality of crop products,the temperature control system with PLC is introduced.The solar drying platform mainly includes collector,accumulators,oven,and control system.According to the material’s heat energy balance,the total area of the collector panel is 4 m2,the fixed inclination angle is 30 degree and the heat conversion efficiency is 40%.In order to improve the imbalance of the heat supply,the accumulator composed of phase change material-paraffin and serpentine copper tube heat exchange structure is constructed.Moreover,a frequency control system with PLC as the core is introduced to adjust the drying temperature,so as to realize the function of the solar drying system to control the temperature parameters.On the basis of building a solar drying platform,the performance of the drying platform was studied by several experiments.Firstly,through the no-load temperature test of the drying system,it shows that the inner temperature of the drying chamber can reach 40～45℃,which could meet the working requirement of low-temperature drying.Secondly,in the drying experiments of potatoes,the results show that the efficiency of the solar drying is better than that of the sun drying.Thirdly,the drying experiments of sweet potatoes is carried out with heat storage system,compared with the natural sun drying.the result proves that the experimental period(14h)of solar drying equipment was shorter than that of natural sun drying(23h),meanwhile,the working time of the solar drying system with accumulator was prolonged by another 2 hours,and the maximum temperature rise could reach 15“C.The solar drying experiment of the Chinese wolfberry showed that the drying rate of this solar drying device was significantly higher than that of natural drying,which proved the feasibility and practicability of the solar drying of the Chinese wolfberry.