Measurements of particle-liquid heat transfer in systems of varied solids fraction

The heat-transfer coefficient between particle and liquid in a flowing food mixture is an important parameter which controls the heating and cooling rate of the particles. Experiments have measured the heat-transfer coefficient, h(p), between a stationary particle and a fluid stream over a wide range of slip Reynolds numbers (1<Re<600) and local solids fraction. The results have terms of Reynolds number Prandtl number and local voidage, and compared with the previously published correlations of Rant & Marshall (1952) and Agarwal (1988). This comparison showed that the Rant particle data, though for higher solids fractions only the predictions at lower Reynolds numbers, less than ca. 100, were accurate. However at these reduced voidages Agarwal's correlation, based on accurate single-particle data, proved tobe more successful in predicting h(p) and as such is more applicable to food flows than the correlation of Ranz and Marshall. (C) 1997 Elsevier Science Limited. All rights reserved.