Numerical investigation of the protective mechanisms of air curtain in a refrigerated truck during door openings

Abstract

Warm air infiltration during door openings of refrigerated delivery trucks can account for approximately 34% of the overall refrigeration load, with this share estimated to be higher for longer and/or more frequent door openings. An increase in refrigeration load can have a direct impact on the energy usage (higher thermal loads require greater energy consumption). Many sources in the literature suggest that the use of an air curtain to reduce the impact of warm air infiltration during door openings. However, the majority of these studies focus on air curtain use in large cold rooms and warehouses. The main purpose of this study is to investigate the protective mechanisms of an air curtain against natural infiltration in a refrigerated vehicle during door openings. This study analyses the airflow behaviour in the refrigerated truck body with and without the protection of an air curtain during door openings. Different air curtain velocities have been tested for this particular investigation to study the influence of discharge velocity on energy performance. The airflow analysis suggests that natural infiltration is mainly caused by cold air flowing out from the lower part of the opening as warm air infiltrates in from the upperpart to fill the space. It has been found that an air curtain at optimum velocity (3.1 m/s in this study) can help reduce the energy consumption by almost 48%.