Equivalent thermophysical properties and surface heat transfer coefficient of fruit layers in trays during cooling

Experimental engineering data and predictive equations are established for the equivalent thermophysical properties (thermal conductivity, thermal diffusivity, specific heat capacity and density) and surface heat transfer coefficient of bulk layers of fruits (strawberries, raspberries, apricots, peaches, grapes and apples) in trays. Both packed layers and uncovered trays are considered as a system of fruits and air. In the first case the influence of air inclusions and free convection in closed space is taken into account, while in the second - special attention is devoted to the effect of air infiltration between the fruits placed in trays and pallets. The regression equations derived give the relationship between the considered equivalent values and the velocity of longitudinal air how between the trays. The results are appropriate to be used for mathematical modelling and engineering calculations in real industrial heat transfer scenarios. (C) 1999 Elsevier Science Ltd. All rights reserved.