Design And Flow Field Analysis Of Solar Dryer With Energy Storage System

Drying can reduce the spoilage of agricultural products,it is an essential process in the conservation of agricultural products.The most common drying method,especially for agricultural products,is thermal drying,which involves simultaneous heat and mass transfer.Solar energy is a clean,free and environmental-friendly energy resource.The utilization of solar energy can effectively prevent the increase in traditional fossil fuel using and protect the environment.Closed solar drying have many advantages over open sun drying like improvement in product quality on the basis of color,texture and taste,decrement in drying time,reduction of the drying and storage losses.Therefore,in order to apply solar energy to the drying process of agricultural products,it is necessary to develop and research solar drying equipment.In this dissertation,the solar drying equipment is indirect solar dryer.The solar dryer mainly include heating system,drying system and thermal storage system.The thermal storage is used to overcome the intermittency and instability of solar thermal utilization.The process of heat storage and release is realized by using phase change material.The specific research content is as follows:1.The design of solar dryer.The solar dryer consists of heating system,drying system and thermal storage system.The heating system is composed of two solar collectors in series.The heating system converts solar energy into thermal energy of drying medium.Drying system is a place for heat exchange between wet materials and drying medium.The main component of the drying system is a drying box in which separated by three tray.The thermal storage system is used to store the energy in the form of thermal energy when the solar energy is abundant and release the stored thermal energy to the drying medium when the solar energy is insufficient.The thermal storage system is mainly consists of thermal storage box,phase change material and heat conduction copper tube.Thermal storage material is industrial semi-refined paraffin wax.The shape of heat-conduct copper pipe design as snake in purpose of increasing the heat transfer area and improving the heat transfer efficiency.2.The experiment of solar dryer.The indirect solar dryer performance is investigated in two different cases.The first case,the solar dryer was tested using PCM,and the second one when the device was tested free of PCM.The experimental results when using the PCM successfully maintains the drying temperature at approximately constant value for a long time.when it was free of PCM,the drying air temperature of indirect solar dryer change greatly with the change of solar intensity.When the dryer is used to dry materials,the temperature and wind speed of each measuring point in the drying oven are measured to provide verification data for later numerical simulation.3.Numerical simulation and structural optimization.Combined with computational fluid dynamics and FLUENT to study the process of drying in the drying oven.Numerical results such as the distribution of the temperature and velocity field in the drying box are provided.The accuracy of the simulation is verified by comparing with the experimental data.The structure of the drying oven was optimized by placing the deflector plate and changing the position of air inlet and outlet.FLUENT analysis software are used to verify,analyze and compare the design,by this method can provide corresponding theoretical basis and physical model for drying box optimization to reduce repeated experiment.