Food Science Department, Faculty of Agriculture, Cairo University, 12613 Giza, Egypt.
Chemical Engineering Department, Faculty of Engineering, Cairo University, 12613 Giza, Egypt.
J Adv Res. 2015 Mar;6(2):171-8. doi: 10.1016/j.jare.2013.12.001. Epub 2013 Dec 5.
Two identical prototype solar dryers (direct and indirect) having the same dimensions were used to dry whole mint. Both prototypes were operated under natural and forced convection modes. In the case of the later one the ambient air was entered the dryer with the velocity of 4.2 m s(-1). The effect of flow mode and the type of solar dryers on the drying kinetics of whole mint were investigated. Ten empirical models were used to fit the drying curves; nine of them represented well the solar drying behavior of mint. The results indicated that drying of mint under different operating conditions occurred in the falling rate period, where no constant rate period of drying was observed. Also, the obtained data revealed that the drying rate of mint under forced convection was higher than that of mint under natural convection, especially during first hours of drying (first day). The values of the effective diffusivity coefficient for the mint drying ranged between 1.2 × 10(-11) and 1.33 × 10(-11) m(2) s(-1).
两个相同的原型太阳能干燥器（直接式和间接式）具有相同的尺寸，用于干燥整个薄荷。两种原型都在自然和强制对流模式下运行。在后一种情况下，环境空气以 4.2 m/s 的速度进入干燥器。研究了流动模式和太阳能干燥器的类型对整个薄荷干燥动力学的影响。使用了十个经验模型来拟合干燥曲线；其中有九个模型很好地代表了薄荷的太阳能干燥特性。结果表明，在不同操作条件下，薄荷的干燥处于降速期，没有观察到干燥的恒速期。此外，所得数据表明，强制对流下薄荷的干燥速率高于自然对流下薄荷的干燥速率，特别是在干燥的最初几个小时（第一天）。薄荷干燥的有效扩散系数值在 1.2×10(-11)和 1.33×10(-11)m(2)s(-1)之间。
