火龙果热泵干燥数值模拟及试验

Numerical simulation and experimental study of pitaya during heat pump drying

目的:提高火龙果干制品的品质。方法:基于多孔介质理论和菲克定律,建立火龙果传热传质与固体力学多物理场耦合的数学模型,并研究火龙果在热泵干燥过程中的温度与含水率的变化规律。结果:考虑体积收缩的模型计算精度更高,达到干燥标准时,模拟值与试验值的最大相对误差为9.2%。火龙果片在干燥初期温度分布由表面向中心逐渐降低,后期达到平衡,而水分分布呈相反趋势。火龙果片在热泵干燥过程中的温度、湿度梯度力是导致其收缩变形的主要因素。不同干燥温度和切片厚度下火龙果片的干基含水率的计算值与试验值变化趋势一致,相对误差均<10%,证明了模型的准确性。结论:试验建立的多物理场耦合的数学模型能够准确模拟火龙果热泵干燥过程。

Objective:To improve the quality of dried pitaya products.Methods:Based on the porous medium theory and Fick s law,a mathematical model of the coupling of heat and mass transfer of pitaya fruit with multiple physical fields of solid mechanics was established,and the variation of temperature and moisture content of pitaya fruit during the heat pump drying process was studied.Results:The calculation accuracy of the model considering volume shrinkage was higher.The maximum relative error between the calculated value and the test value was 9.2%after reaching the drying standard.The temperature distribution of pitaya slices decreased gradually from the surface to the center in the early stage of drying,and achieved a balance later,while the water distribution showed an opposite trend.The temperature and humidity gradient forces in the heat pump drying process were the main factors leading to the shrinkage deformation of pitaya slices.The calculated values of dry base moisture content of pitaya slices under different drying temperature and slice thickness were consistent with the experimental values,and the relative errors were all less than 10%,which proved the accuracy of the model.Conclusion:The mathematical model established by the experiment can accurately simulate the heat pump drying process of Pitaya.