Numerical Simulation Of Airflow And Temperature In Ginseng Drying Room

Ginseng is a precious medicinal material in China.Due to high water content,the fresh ginseng rots easily,and thus it generally needs to be dried.The coal-fired drying is a common method of dewatering.It is known to all that the coal-fired drying performs characteristics of serious pollution and high energy consumption.Compared with coal-fired drying,the heat pump drying is environmental-friendly and energy-saving.However,there are few studies on the process of ginseng drying by the heat pump.The airflow in the drying room and heat transfer between air and ginseng cannot be known clearly.To settle this issue,the mathematical model and numerical solution method are studied in this paper.Subsequently,characteristics of airflow distribution and heat transfer between air and ginseng in the ginseng drying room are investigated.The detailed research works are concluded as follows:Fristly,a real heat pump drying room in Baishan City of Jilin Province is taken as physical model.This room is divided into two areas including air flow area and ginseng stacked area.The turbulent is exhibited in the air flow area,and the ginseng stacked area is a porous media one.Based on the turbulent flow and heat transfer theory,and the law of the fuild flow and heat transfer in macroscopic porous medium,a mathematical model of ginseng drying with heat pump is established.In the proposed model,the special treatment is not required for the boundary condition between two areas,which facilitates the further research of efficient numerical solution techniques.In the proposed mathematical model of ginseng drying,the complex computational domain and complex flow & heat transfer processes owing to gas-liquid phase change and turbulent flow are involved.Due to these problems,the solving is generally low efficient by traditional numerical algorithm,for example,SIMPLE algorithm.To reduce the cost of numerical simulation,based on the CFD/NHT open source software OpenFOAM which is widely used in the world,the high efficient pressure-velocity coupling algorithm IDEAL proposed by our research team is extended to solve the mathematical model.Then,based on the extended IDEAL algorithm,numerical results obtained from the proposed mathematical model is validated by the field industrial production data.Finally,on the basis of the proposed mathematical model and the extended IDEAL algorithm,the airflow and temperature in the drying room in different drying stages are analyzed.Subsequently,the effects of factors including volume flowrate of air,inlet diameter,material thickness(porosity)and the number of partitions on the velocity and temperature unevenness coefficients,are also analyzed comprehensively.