Experimental and Numerical Investigation of Airflow Inside Refrigerated Shipping Containers

Abstract

During transportation of fruits and vegetables, factors such as temperature, air exchange, humidity levels, packaging design and stacking arrangements in the reefer (refrigerated shipping container) are extremely important to maintain the cold chain. In this study, the airflow distribution inside two types of refrigerated shipping containers (T-bar floor and flat floor) used for transporting fresh fruit handling were investigated. Computational fluid dynamics (CFD) model of airflow was developed and experimentally validated. Measurements of air velocities were taken from 222 sample positions inside a full-size reefer. The validated model was then implemented to study the effects of container designs and operational conditions on airflow pattern and distribution. High and low evaporator speed scenarios of the two reefer designs (T-bar floor and flat floor) were investigated. The result showed that airflow distribution in the two container designs were markedly different. Good agreement was found between measured and predicted values of air velocities. The air exchange rate in the rear part of the reefers for the two designs were compared. For the flat floor reefer, the air exchange was 0.2 m3 h−1 while for the T-bar floor, it was 0.6 m3 h−1. Also, in the primary recirculation region, (between 3 and 8 m from the inlet side) the average vertical air velocity was higher in the T-bar floor reefer (0.04 m s−1) than in the flat floor reefer (0.01 m s−1). As a result, reefer with T-bar floor design exhibited a noticeable reduction of air recirculation zone and enhanced uniform vertical air movement compared to the reefer with flat floor design.