Effects of an air curtain on the temperature distribution in refrigerated vehicles under a hot climate condition

Refrigerated vehicle plays an essential role in the cold-chain applications. It directly affects the quality and shelf life of specialized perishable goods. However, the cold energy dissipation caused by natural convection through an open door during partial unloading breaks the isothermal cold environment and notably elevates the air temperature inside the refrigerated container. This temperature rise is harmful to the remaining food. In this study, an air curtain was introduced near the container doorway to attempt to reduce the cold energy dissipation caused by partial unloading. A numerical model was established to explore the effects of the key parameters of the air curtain such as the airflow rate, nozzle width, and jet angle on the air flow and temperature evolution inside the refrigerated container after the door is opened. The numerical results show that the key parameters need to be tailored to form a stable and effective air curtain for preventing the internal cold energy loss or external hot air invasion. An effective and stable air curtain was formed to make the inner air temperature increase only by about 3 °C from the initial temperature of 5 °C after the door was opened, when the jet velocity was set to 2 m/s, the nozzle width was set as 7.5 cm, and the jet angle was set between 0 deg and 15 deg. This work can offer significant guidance for the introduction of an effective air curtain in a refrigerated vehicle to avoid the failure of cold-chain transportation.