Comparative analysis of apple and orange during forced convection cooling: experimental and numerical investigation

Abstract

The main theme of this paper is to make improvements in heat transfer during cooling of food products in forced convection environment. In the present study the effect of air velocity during precooling of spherical food products i.e., apple and orange is seen. The experiments are performed on an air blast apparatus and results are compared using simulation with a 3D CFD model. Models are developed and solved with the later one more likely to be close to experiments and hence this model is studied at 5 different velocities (0.5, 1.0, 2.0, 2.5 and 3.0 m s-1) for both samples. It is observed that cooling is improved significantly up to a particular speed for both apple and orange and increasing the speed above their respective critical speeds i.e., 2.5 m s-1 for apple and 2.0 m s-1 orange, does not enhance the cooling significantly and hence is not advisable to increase the speed above their critical speed as it leads to loss of energy which in turn increases the overall operational cost. The half cooling time and the seven-eight cooling time consequently decreases by 45.91% and 44.61%, respectively, for an individual apple with an increase in air-inflow velocity from 0.5 to 3.0 m/s and 44.27% and 43.31% respectively for orange. The food sample is rotated about its axis slowly at 2 rad s-1 and its effect is also seen. It is observed that there is significant amount of increase in the cooling rate and also the cooling is uniform.