Multi-parameter analysis of air flow velocity on peach precooling efficiency using CFD

Abstract

In the present work, a three-dimensional computational fluid dynamics (CFD) model was established to simulate the heat transfer process at different air-inflow velocities, and to predict the spatial and temporal variations of temperature distribution during forced-air cooling (FAC). Based on the conventional evaluation system, a more comprehensive multi-parameter evaluation system was proposed to determine an optimal precooling strategy of various air-inflow velocities. The current system employed a novel heterogeneity index to quantify the overall uniformity (OHI), and added a detailed theoretical calculation procedure of the cumulative moisture loss during the forced-convection cooling (M, mg). By analysing the effect of different airflow rates on SECT, precooling uniformity, moisture loss, and energy requirement, an airflow rate in the range of 1.5 - 2.5 m·s-1 was recommended as optimum for harvested peach precooling. Any further increase in air-inflow velocity led to excessive energy cost since it generated a relatively low decrease in SECT and overall heterogeneity index, so as moisture loss. At the same time, the moisture loss of peach primarily occurred in HCT, which was inversely proportional to airflow rate and cooling uniformity. An increasing power-law function relationship existed between energy consumption and airflow rate. The present work demonstrated the effect of various air-inflow velocities on peach precooling efficiency, and provided an integral evaluation system to optimise the precooling strategy of other horticultural fruits.