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-tra nsfer coefficient, h(p), between a stationary particle and a fluid str eam over a wide range of slip Reynolds numbers (1<Re<600) and local so lids fraction. The results have terms of Reynolds number Prandtl numbe r and local voidage, and compared with the previously published correl ations of Rant & Marshall (1952) and Agarwal (1988). This comparison s howed that the Rant particle data, though for higher solids fractions only the predictions at lower Reynolds numbers, less than ca. 100, wer e accurate. However at these reduced voidages Agarwal's correlation, b ased 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. A ll rights reserved.