4. Set the thermostat to the required temperature, pre-cool the car for 1.5 hours to remove the heat trapped in the car; turn off the refrigeration unit when loading and load the goods quickly.
When loading, the car must be pre-cooled or pre-heated first. Because the vehicle is parked in the open air, the car temperature is usually the outside ambient temperature. If the temperature of the transported goods is not the ambient temperature, the ambient temperature will affect the temperature of the transported goods when the goods are loaded into the car, resulting in changes in the quality of the transported goods. Therefore, the car must be pre-cooled to the required temperature before loading. However, the refrigeration unit must be turned off when loading (same as unloading). Many people do not turn off the refrigeration unit when loading and unloading goods, which is actually a very wrong operation.
The reason is: after we pre-cool the compartment, if we do not shut down the machine and open the compartment door, the fan of the evaporator of the refrigeration unit is working, the front of the fan is positive pressure, and the back of the fan is negative pressure, so the cold air blows out from the upper part of the compartment, and the lower part will quickly suck in the hot air outside, causing the temperature in the compartment to rise rapidly; if the machine is turned off and then the goods are loaded and unloaded, the fan is in a stopped state, the air flow stops, and the wind pressure inside and outside the compartment is consistent, so the speed of the external hot air entering the compartment is relatively slow.
5. The goods must be pre-cooled to the required temperature, and the temperature of the goods must be checked when loading; the refrigeration unit is used to maintain the temperature of the goods, not to reduce the temperature of the goods.
Many users of refrigerated trucks have a wrong concept, always thinking that the refrigeration unit on the refrigerated truck can arbitrarily freeze or heat the goods loaded in the compartment to the required temperature. Therefore, load the goods that are not up to the required transportation temperature into the compartment, and then set the refrigeration unit to the required transportation temperature, and reduce or increase the temperature of the goods to the required temperature after a certain period of time. However, the opposite is true. Not only can the temperature of the goods not be lowered (or raised), but the goods are damaged or deteriorated. Because the refrigeration unit of the refrigerated truck does not lower the temperature of the goods, but maintains the temperature of the goods. It is like the quilt we used to sell cold drinks in the past, which wraps the goods. When the external cold (heat) source enters the compartment through radiation, conduction, and convection, it is taken away by the cold air blown out by the refrigeration unit, isolating the heat source from entering the goods.
Therefore, when loading, the temperature of the loaded goods must be measured first. If the set point temperature of the refrigeration unit is higher or lower than the temperature of the goods, it is difficult for the temperature of the goods in the compartment to reach the temperature required for transportation. The storage temperature of the goods must be consistent with the transportation temperature. If the temperature of the goods changes frequently, moisture will be lost, which will cause the quality of the goods to change, thereby shortening the shelf life of the goods.
6. Even if the capacity of the unit exceeds the actual requirement, insufficient air circulation will be the main cause of the deterioration of the goods; any obstruction around the goods may lead to "hot spots".
A qualified refrigerated truck must ensure that the six sides of the compartment have good ventilation and there is no obstruction on the six sides of the goods; good air circulation can ensure that the goods are transported at the appropriate temperature requirements. The cold (hot) air blown by the refrigeration unit isolates the cold (hot) source from the outside entering the compartment from the cargo, thus protecting the cargo. If a certain position is blocked, the cold (hot) source in that part will directly enter the goods, causing the temperature of the cargo to change. Make sure the return air shutter is in good condition; do not block the evaporator inlet (return air); insufficient return air will cause irregular circulation of cold air and cause ice on the top cargo.