Numerical Simulation Technology Development And Application Research For Hot-air Drying Of Shiitake Mushrooms In Drying Oven Scale

As a nutritious and high-value edible mushroom,shiitake mushrooms have been increasingly consumed by people.However,their high water content after fresh picking makes them highly susceptible to spoilage and deterioration.Hot air drying technology has the advantages of low equipment cost and easy operation,and is currently widely used in the drying process of shiitake mushrooms,to facilitate their long-term preservation,storage,and transportation.Recently,with the continuous improvement of computer performance and simulation software functions,numerical simulation technology is increasingly being applied to the study of hot air drying at the drying oven scale.However,the current numerical simulations of the drying oven scale are mainly concerned with the distribution of the flow field and the temperature field,without considering the changes in moisture evaporation within dried material during the drying process.This results in a significant deviation from the actual drying process,making it difficult to meet the design and optimization requirements of actual industrial production.In order to solve this problem,this study first investigates the drying characteristics of shiitake mushrooms under fixed drying conditions based on drying kinetics experiments at material level.A drying kinetic model of shiitake mushrooms under fixed drying conditions with different air temperatures,relative humidities,and air velocity is obtained.After that,a drying kinetic derivative model for variable drying conditions is derived.Through this model,we can determine the functional relationship between the moisture evaporation rate of shiitake mushrooms and the drying time,air temperature,relative humidity,and air velocity,and predict the moisture ratio variation of shiitake mushrooms under variable drying conditions.Subsequently,a shiitake hot air drying simulation technology integrated with the material and drying oven at the drying oven scale based on drying kinetics experiments is developed by coupling this functional relationship with the heat and mass transfer equations.A comprehensive consideration has been made of the interactions between moisture evaporation of the material and variation of the physical field within the drying oven in this technology.Thus,the numerical simulation is able to achieve coupling between the material and the drying oven.Finally,based on this simulation technology,the reasons for the uneven distribution of shiitake moisture content are studied,the influence of different inlet condition parameters on drying non-uniformity is analyzed,and the inlet condition parameters of the drying oven are optimized,and the internal structure of the drying oven is improved.By optimizing the inlet drying parameters and improving the design of the drying oven,the non-uniformity of moisture ratio during the drying process can be reduced by 25.84%.Besides analyzing the distribution of physical fields within the drying oven and optimizing drying conditions and structure parameters,this research also provides a valuable reference for investigating and optimizing the drying conditions of other materials,which is of great importance to the industrial development of the drying industry.