苹果片太阳能低温吸附干燥工艺优化与模型研究

Studies on Characteristics and Model of Solar Low-temperature Adsorption Drying for Fresh Apple Slices

摘要:

以新鲜苹果片为研究对象，采用本单位研制的太阳能低温吸附干燥(LSAD)系统为实验设施，探讨干燥温度、相对湿度、干燥介质流速、载样量、切片厚度对苹果片太阳能低温吸附干燥特性的影响。结果表明，苹果片太阳能低温吸附干燥过程可以分为三个阶段:即调整、恒速、降速干燥阶段；其中干燥温度对苹果片干燥的速率影响最显著，如50 ℃比10 ℃节时达65.9%,各因素对苹果片干燥的影响的主次顺序为干燥温度>相对湿度>干燥介质流速>切片厚度>载样量，苹果片太阳能低温吸附干燥优化的工艺条件为：干燥温度50 ℃、相对湿度20%、干燥介质流速0.9 m/s、载样量7.5 kg/m2、切片厚度3 mm；采用数学软件选用3种模型对实验数据进行计算拟合，苹果片干燥数学模型与Page模型拟合程度最高，苹果片太阳能低温吸附干燥数学表达式为MR=exp(-0.00557*t^1.76669)；此模型的建立为应用太阳能低温吸附干燥生产脱水苹果片提供理论支撑。

Abstract:

Using fresh apple slices as the research object and the low-temperature solar adsorption drying (LSAD) system developed in our company as the experimental facility, the effects of drying temperature, relative humidity, drying medium flow rate, sample loading amount and slice thickness on the LSAD characteristics of apple slices were investigated. The results showed that the LSAD process could be divided into three stages: Adjustment, constant speed, and decelerating drying stages. The drying temperature had the most significant effect on the drying rate of fresh apple slices e.g. drying at 50 ℃ reduced the drying time by 65.9% than at 10 ℃. The primary and secondary influences of the variables on the drying of apple slices were drying temperature > relative humidity > flow rate of drying medium > slice thickness> sample loading amount. The optimum process conditions for LSAD of apple slices were: drying temperature 50 ℃, relative humidity 20%, flow rate of drying medium 0.9 m/s, sample loading amount 7.5 kg/m2, slice thickness 3 mm. The mathematical software was used to select and fit the experimental data by three models, and the mathematical model of apple slice drying had the highest fitting degree with Page model. The mathematical equation for LSAD of fresh apple slices was MR = exp (-0.00557*t^1.76669). The establishment of such a model provides the theoretical support for the application of LSAD to the production of dehydrated apple slices.