A Numerical Study on Heat and Mass Transfer Coupled with Respiration Reaction within Stacked Spherical Postharvest Produce: Spatial Distribution and Temporal Variation

Abstract

Reaction rate of respiration in postharvest horticultural produce is dependent on coupling effects of heat and mass transfer. The present work is aimed to develop a numerical model of heat and mass transfer coupled with respiration reaction for forced-air cooling (FAC) and modified atmosphere (MA) storage of postharvest produce. Wind tunnel model with a single bin of stacked spherical produce therein is used as a benchmark case to analyze spatial distribution and temporal variation of heat and mass transfer characteristics. Competitive diffusion of O2 results in the highest O2 partial pressure around 8 kPa between produce surface and core at 10 min during FAC combined with MA. With positions of such peaks moving inward, similar O2 partial pressure around 4 kPa is obtained in the vicinity of produce core at 30 min. This indicates comparative effects of convective removing and reaction consumption of O2. During the same process, under simultaneous effects of low temperature and O2 content, peak values of respiration heat between produce surface and core are generally below 60 W/m3 at 10 min, while two peaks in each produce individual basically merge together with reduced values to around 40 W/m3 at 20 min.