微波干燥过程中南极磷虾肉糜的传热传质及形变参数模型

Heat and mass transfer and deformation parameter model of minced Antarctic krill during microwave drying

该文以南极磷虾肉糜作为媒介,基于电磁学、多相传输和固体力学变形模型研究了微波干燥仿真模型。通过在软件COMSOL Multiphysics中求解电磁方程、能量和动量守恒以及变形方程得到模拟结果。红外热成像仪用于拍摄样品表面温度分布,光纤传感器用于测定样品点的瞬时温度。经过180 s的间歇微波干燥,空间温度分布、瞬态温度曲线(RMSE=2.11℃)、含水率(干基,RMSE=0.03)和体积比与试验值有良好的一致性,说明仿真微波干燥是可行的。此外,微波模拟干燥过程中将虾肉糜视为形变材料与刚性材料,在温度和含水率方面显示了较明显的差别且前者与试验值更为接近,且未考虑收缩模型的温度和含水率的RMSE分别为9.42℃与0.08。该研究还对液态水和气体的内在渗透性(±50%)以及吸水膨胀系数(±50%)进行了敏感性分析。含水率对液态水的内在渗透性较敏感(RMSE=0.089),对气体的内在渗透性较不敏感(RMSE=0.023),体积比对吸水膨胀系数非常敏感(RMSE=0.053)。

Microwave drying is a technology for rapid dehydration of materials,which is widely used in the food industry.Compared with traditional convection drying,microwave drying for food has been found to result in improving the drying rate and final quality.However,microwave drying lead to a non-uniform temperature distribution in some instances,which can over-dry and even destroy food and its texture.Intermittent microwave drying can overcome these adverse effects and improve product quality.Although there are many experimental studies on microwave drying,there is no complete model of heat,mass transfer and shrinkage for microwave drying of Antarctic krill mince available in the literature.Therefore,in this paper,the simulation model was studied based on electromagnetics,multiphase transport and deformation using minced Antarctic krill as media.Microwave drying was carried out in a household microwave oven with a power of 100 W(rated power of 1000 W).The results of the simulation were obtained by solving electromagnetic equation,energy and momentum conservation and deformation equation by COMSOL Multiphysics.The model included multiphysics of Maxwell's electromagnetic heating,energy conservation,Darcy’s velocity,solid mechanics,mass conservations of water and gas,and phase change of melting and evaporation of water 6 s as one cycle was adopted in the simulation.The strategy for each cycle was that the first step was to calculate the electromagnetic field;the second step was to calculate the temperature,pressure,moisture concentration and vapor concentration by using the heat source term;the third step was to calculate the solid mechanics module based on the moisture concentration.After each cycle,the last calculation result was taken as the initial condition of the next calculation,and the dielectric property,thermophysical property,porosity and material size were updated for the next cycle(30 cycles in total).It could save calculation time by using the method to separation and circulation.Infrared thermal imager was used to photograph temperature distribution on the surface of the sample,and optical fiber sensor was used to measure the instantaneous temperature in the point of the sample.The spatial temperature distribution,transient temperature curve,moisture content and volume ratio were in good agreement with the experimental values during intermittent microwave drying for 180 s,and the RMSE of temperature and moisture content without considering shrinkage model are 9.42℃ and 0.08,respectively.Microwave simulation of microwave drying was feasible.In addition,the temperature and moisture content of minced shrimp treated as deformable material were significantly different from that of rigid material during microwave drying simulation,and the former was closer to the experimental value.Water loss was the main factor of material deformation.Intermittent microwave drying allowed the distribution of moisture,pressure and temperature within the material uniform.The sensitivity analysis of the input parameters including intrinsic permeability of water and gas(±50%)and water absorption expansion coefficient(±50%)showed that the water content was more sensitive to the intrinsic permeability of liquid water(RMSE=0.089),less sensitive to the intrinsic permeability of gas(RMSE=0.023),and the volume ratio was very sensitive to the water absorption expansion coefficient.