Effect of process, box and product properties on heat and mass transfer during cooling of horticultural products in pallet boxes

摘要

During cooling of fruit and vegetables, non-uniform distribution of the temperature and moisture causes a variability of the fruit and vegetable quality after storage. Knowledge of local condition of airflow, temperature and humidity in the boxes provides possibilities for reducing losses and improving product quality. Traditional tools based on global energy balances cannot be applied to optimize the cooling process. In this study, a mathematical model is developed to compute the local airflow atdifferent positions in individual pallet boxes in a cold store and incorporate the effect of process, box and product properties on cooling rate and moisture loss. The model consists of the full system of conservation equations of momentum, energy and species for the two-phase air-product matrix. A finite volume code (CFX, Harwell, UK) is used to solve the model equations. The results show a strong dependence of the local cooling rate and moisture toss on the airflow rate. Forced direct cooling improvedthe temperature uniformity during the cooling phase but caused a high weight loss. Conduction cooled boxes have a slow cooling rate. The results lead to an improved understanding of the cooling process for horticultural products.