New effective Nusselt-Reynolds correlations for food-cooling applications

This paper presents new correlations between the Nusselt and Reynolds numbers for food products being subjected to water and/or air cooling applications. In the theoretical part we assume that the problem of cooling a cylindrical or spherical product can be reduced to I-D hear conduction in the radial direction, subject to convective cooling at the surface. By developing new models for this problem, and the experimentally measured temperatures at the centers of the products, the convective heat-transfer coefficients were obtained as an inverse problem. These heat-transfer coefficient values together with some literature results, were used to arrive at the Nusselt-Reynolds correlations. It is concluded that the present correlations are practical tools to determine convective heat-transfer coefficients for the products during cooling in water and air media. (C) 1997 Elsevier Science Limited. All rights reserved.