Heat Transfer During Aircooling and Storing of Moist Food Products — II. Spherical and Cylindrical Shapes

Abstract

ABSTRACT HEAT transfer characteristics during aircooling of moist food products are analyzed taking into account the effects of the evapora-tion of the moisture film that usually exists on the product surface. The one-dimensional transient heat con-duction equation in spherical and cylindrical coordinates is solved. Charts useful in predicting the time-temperature histories and cool-ing loads are presented for the fol-lowing values of dimensionless parameters: Biot number, Bi: 0.1 to 10, Initial product temperature, tj : 2.5 (a 21 C) to 4.0 (~ 43 C) in increments of 0.5, Cooling air temperature, t^~: 1.25 (~ 2 C) to 2.25 (~ 15 C) in in-crements of 0.5, Relative humidity, $ : 0.0 to 1.0 in increments of 0.2. Relative humidity of the cooling air is an important parameter which decides the cooling rates. Surface evaporation effects are significant, particularly at low air humidities. The present analyses yield much better agreement with the experi-mental results compared to existing conventional methods.