Heat transfer during forced air precooling of perishable food products

Abstract

An experimental investigation has been carried out to study the heat transfer during forced air precooling of orange and tomato at different cooling velocities of cold air at 4–5 °C. The air velocity has been varied from 1.2 to 4.4 m s−1. It was found that air velocity had significant bearing on the cooling rates of food products below the dimensionless temperature, T ¯ , of 0.6. The limiting cooling air velocity for orange was 3.5 m s−1 and that for tomato was 2.6 m s−1. The increase in cooling air velocity beyond the above values did not affect the cooling rate significantly. The heat transfer coefficient, h, during cooling of tomato was higher than that for the cooling of orange by between 9 and 30 per cent. A correlation has been developed to predict the heat transfer coefficient, h, for different velocities of cooling air. This correlation predicts the experimental results in an error band of ±7.5 per cent.