Authors

Abstract

To promote the application of solar energy-heat pump combined drying technology in forage processing and enhance the drying efficiency of alfalfa, an experimental study was conducted. The research utilized a solar energy-heat pump drying system and a mesh belt dynamic drying device to investigate the drying characteristics of alfalfa. Drying characteristic curves were obtained, and the drying model and parameters were determined through model comparison. The study also analysed the impact of factors such as hot air velocity, temperature, alfalfa stacking thickness, turning angle of the spinner rack, and conveyor belt speed on the drying characteristic curves and parameters of alfalfa. A predictive model for alfalfa moisture content was developed, and the effective moisture diffusivity and activation energy were calculated. The findings revealed that alfalfa does not exhibit a constant speed drying stage, and its drying primarily occurs during the deceleration drying stage. The Logarithmic model was found to accurately describe the moisture change pattern during the dynamic drying process of alfalfa, with a model fitting coefficient R^2 exceeding 0.994, with an effective moisture diffusivity ranging from 2.776×10-10 m2/s to 4.7324×10-9 m2/s, and an activation energy of 37.02 kJ/mol. The study suggests that increasing the hot air velocity and temperature, reducing the conveyor belt speed, and adjusting the alfalfa stacking thickness can further enhance the drying rate and reduce the drying time.

Abstract in Chinese

为推动太阳能-热泵联合干燥技术在饲草加工领域的应用，改善苜蓿干燥效率和效果，借助太阳能-热泵干燥系统及其网带式动态干燥装置对苜蓿进行了干燥特性试验研究，获取了干燥特性曲线，并通过模型对比确定了干燥模型及参数。分析了热风风速、温度、苜蓿堆积厚度、转架偏转角度、输送带移动速度等因素对苜蓿干燥特性曲线与参数的影响，得到了苜蓿水分比预测模型，同时计算得到有效水分扩散率和活化能。结果表明苜蓿无恒速干燥阶段，其干燥主要发生在降速干燥阶段，Logarithmic模型可以精准描述苜蓿动态干燥过程中的水分变化规律，模型拟合决定系数R2大于0.994。有效水分扩散率介于2.776×10-10m2/s～4.7324×10-9m2/s、活化能为37.02 KJ/mol，可通过增加热风风速、温度、降低输送带移动速度、苜蓿堆积厚度，进一步增大干燥速率，缩短干燥时间。