In modeling the drying process of a skim milk droplet subjected to a hot gas flow, ignoring the effect of solid particles in reduction of evaporation surface before the crust formation and porosity variation within the droplet, causes the predicted surface temperature of droplet deviate from the experimental values. In the present study, a new drying model is developed in which the effects of variable porosity within the droplet as well as the reduced area of the evaporation surface due to the presence of solid particles are accounted for. Based on this model, a Finite Volume code is developed to calculate the droplet porosity at all drying stages and also taking into account the effect of solid particles in reducing the evaporation area of the droplet by calculating the diffusion coefficient of porous medium. Using this model leads to a better prediction of droplet temperature with a maximum error of 2% compared to experimental results. This model also has a good prediction of droplet mass reduction with an average error of about 10%. Also, a parametric study is performed to investigate the effect of the principal parameters such as air temperature, air velocity and droplet initial diameter on the drying time and morphology of obtained dry particles. Peclet number is a criterion for determining the morphology of dried particles. Numerical results show that with increasing the hot air velocity and temperature, the Peclet number increases but the initial droplet size does not have much effect on the Peclet number. Based on this observation a new correlation is introduced between the Peclet number and the characteristics of the dryer air flow.

在模拟脱脂牛奶液滴在热气流下的干燥过程时，忽略了固体颗粒在结壳形成之前减少蒸发表面的影响和液滴内的孔隙率变化，导致液滴的预测表面温度与实验值有偏差值。在本研究中，开发了一种新的干燥模型，其中考虑了液滴内可变孔隙率的影响以及由于固体颗粒的存在而导致的蒸发表面面积减少。在此模型的基础上，开发了有限体积代码来计算所有干燥阶段的液滴孔隙率，并通过计算多孔介质的扩散系数来考虑固体颗粒对减少液滴蒸发面积的影响。与实验结果相比，使用该模型可以更好地预测液滴温度，最大误差为 2%。该模型对液滴质量减少也有很好的预测，平均误差约为 10%。此外，还进行了参数研究，以研究空气温度、空气速度和液滴初始直径等主要参数对干燥时间和所得干燥颗粒形态的影响。颗粒数是确定干燥颗粒形态的标准。数值结果表明，随着热风速度和温度的增加，Peclet数增加，但初始液滴尺寸对Peclet数没有太大影响。基于这一观察，在派克莱特数和干燥器气流特性之间引入了新的相关性。