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CFD simulations have been widely used in the study of precooling process of fresh fruits and vegetables. This work established a quasi real three-dimensional model of Fuji apples, by comparing the wall shear stress, drag coefficient, separation angle and recirculation length of an apple with those of an equal-diameter sphere over a large Reynolds number range (10~30 000), and whether an apple can be directly replaced by an equal-diameter sphere in the study of CFD models was verifed. Moreover, to achieve the optimal CFD model of contact points between apple and apple (or the wall of boxes) and fully consider heat transferring by contact among apples, two apples contacting with each other were studied. From the accuracy of simulation results of the drag coefficient and temperature distribution along a line from the center of an apple to the center of another apple, the optimal size range of four different ways of the contact point modifications (e.g., reduction, expansion, smoothing, bridge) for different Reynolds number range was determined. The results showed that an apple can be replaced by an equal-diameter sphere in academic research, and the maximum relative deviation was about 15% for all the physical parameters in the whole range of Reynolds number; the accuracy of bridge methods was the best in four different ways of the contact point modifications. The predicted results were consistent with the measured results by comparing simulation results with those of experiments, and the maximum root-mean-square error and average relative error for produce temperature were 1.514 and 21.07%, respectively. © 2016, Chinese Society of Agricultural Machinery. All right reserved.
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