Optimization And Analysis Of Structural Parameters Of Wolfberry Vacuum Pulsation Drying Box

As an important step in the preservation and preservation of wolfberry,wolfberry drying has always been an important research object of wolfberry industry.Compared with the traditional drying method of wolfberry vacuum pulse drying has many advantages,such as no alkali,less pollution,good sterilization effect less pesticide residue and so on.In this paper,the problem of uneven temperature distribution in drying chamber of wolfberry vacuum pulse dryer is studied,and the structure of drying chamber is optimized by numerical simulation.The main research contents are as follows:According to the theory of numerical heat transfer,this paper analyzes the process of temperature transfer in the drying room,establishes the temperature transfer model of the drying box,simplifies the calculation model of the temperature field in the drying room,obtains the calculation model of the temperature field in the drying room composed of hot water,heat exchanger and wet vacuum,determines fluent as the numerical simulation tool of the temperature field in the drying room,and establishes the heat exchanger hot water flow model,continuous medium model and heat transfer model.According to the actual working condition of the dryer,the boundary conditions in the numerical simulation and the thermophysical parameters of the materials in the calculation domain are obtained.Taking the average absolute error as the evaluation index,the numerical simulation results of the temperature field in the drying room are compared with the measured temperature distribution in the drying room,and the accuracy of the numerical simulation scheme is analyzed.The results show that the numerical simulation scheme is accurate and reliable.Based on the analysis of the drying box structure,the hot water inlet flow rate,the height of the heat exchanger layer and the distance between the heat exchange tubes,are determined as the optimization objects of the drying box structure.Under the principle of ensuring that the heat exchange area is not changed,four parameters of each single factor are selected for single factor analysis,and the optimal parameters of each single factor affecting the temperature distribution of the drying room and each single factor affecting the drying room are obtained the influence degree of uniformity of internal temperature field.Then,three factors and three levels orthogonal test schemes are made for three factors,namely,the hot water inlet flow rate,the height of the heat exchanger layer and the distance between the heat exchange tubes.The nine groups of orthogonal parameters are combined for numerical simulation.The temperature nonuniformity coefficient and the average temperature are taken as the evaluation indexes of the orthogonal test results,and the influence of the three factors on the temperature distribution of the drying chamber is comprehensively analyzed to determine the temperature distribution the optimal combination of three factors is given.Finally,the structure of the oven was optimized according to the results of the orthogonal test.The experimental results show that the uniformity of the temperature distribution in the oven after the structure optimization is improved compared with the original oven.