火龙果热泵干燥特性及收缩动力学模型分析

Drying Characteristics and Shrinkage Model Analysis of Pitaya Heat Pump Drying

为了优化火龙果热泵干燥工艺及提升干燥后产品的品质,本文研究了干燥温度、切片厚度和相对湿度对火龙果热泵干燥特性和体积比的影响,并确定了最佳收缩动力学模型,从而可以预测火龙果在不同热泵干燥条件下的体积变化规律。结果表明,干燥温度越高、切片厚度和相对湿度越小,干燥速率越大;其中,干燥温度对干燥速率影响最大,切片厚度影响最小;体积比随干燥温度的升高、切片厚度和相对湿度的减小而减小;对比分析5种薄层干燥模型,Quadratic模型可以精确描述火龙果热泵干燥过程中的体积收缩规律,计算值相对于试验值的平均误差为5.01%;在本文所述热泵干燥条件下,通过阿累尼乌斯方程计算出火龙果的收缩活化能为27.185 kJ/mol。本研究借助体积收缩模型优化热泵干燥工艺参数并获得更合适体积的干制品,可为火龙果在热泵干燥过程中体积收缩规律提供技术支持。

In order to optimize the pitaya heat pump drying process and improve the quality of dried products,the effects of drying temperature,slice thickness and relative humidity on heat pump drying characteristics and the volume ratio of pitaya were studied.The optimal shrinkage dynamic model was determined to predict the volume variation law under different heat pump drying conditions.The results demonstrated that the drying rate increased with the increase of drying temperature,the decrease of slice thickness and relative humidity.The drying temperature had the greatest effect on it while the slice thickness had the least.The volume ratio decreased with the increase of drying temperature and the decrease of slice thickness and relative humidity.Comparing and analyzing the five thin-layer drying models,the Quadratic model was determined as the most accurate to describe the volume ratio law in the pitaya heat pump drying process.The average error of the calculated value was 5.01%compared with the test value.Under the heat pump drying conditions described in this paper,the contraction activation energy of the pitaya was calculated to be 27.185 kJ/mol by Arrhenius equation.Based on the volume shrinkage model,the process parameters of heat pump drying could be optimized and the dry products with more appropriate volume could be obtained.This study could provide technical support for the volume shrinkage law of pitaya in the heat pump drying process.