Thermal and flow analysis of a refrigerated truck for cold chains under various conditions in practical use

Heat infiltration from frequent door opening of refrigerated trucks during delivery for cold chains has a significant impact on food quality and energy consumption. This study investigates the flow and heat transfer characteristics inside a 15 m³ refrigerated truck. Detailed analysis was conducted during the transient state after opening the truck door under several different practical conditions. The numerical method was validated using experimental data and showed an acceptable agreement. Initially, the flow inside a refrigerated truck body with no load and the fan off was investigated after opening two doors. Subsequently, the effects of the number of doors opened, fan operation, and amount of cargo loading were analyzed. When the truck was empty and the fans were operating with all doors opened, the forced flow region was located at the top and the natural convection region was located below. The temperature and infiltration heat increased significantly after the outside air was drawn in by the fans. When the fans were turned off, natural convection was dominant, and a rapid increase in temperature occurred when the inflow of outside air increased. When only one door was closed, the circulation of cold air was maintained, suppressing air inflow and rapidly increasing the air temperature. The rate of temperature increase was approximately 23 % slower for the half-loaded case than for the no-load case. The results of this study can contribute to reducing energy consumption by optimizing the operating strategy and geometry that can minimize the heat loss after opening the doors.