When exporting refrigerated goods, many shippers pre-cool the cold shipping containers to the set temperature. However, this practice may have adverse effects on both the goods and the container, and is not a scientific approach. It may result in less than high-quality container refrigeration (freezing) transportation.
The reason is that pre-cooling the container before loading will cause a large amount of high-temperature and humidity air from outside to enter the cabinet and mix with the low-temperature air inside when the cabinet door is opened to prepare for loading. This will cause a large amount of water droplets to condense on the inner wall of the container. These water droplets will not only drip onto the outer packaging of the goods and affect the appearance of the packaging, but also affect the operation of the container refrigeration system, which has a negative impact on the quality of the goods.
Because this condensed water must be removed by the evaporator in the container refrigeration system, the condensed water will freeze when it passes through the evaporator, resulting in a brief defrosting process for the refrigeration system.
On the other hand, the evaporator must also remove three types of heat: heat directly entering when loading the cargo through the cabinet door, heat entering through the cabinet wall and entering the cabinet, and heat generated by fresh or live cargo due to metabolism. It can be imagined that the more extra heat and humidity the cold shipping container needs to remove, the less the refrigeration capacity will be for the cargo itself.
Refrigerated containers are divided into external and internal types, and the temperature can be adjusted within a specific range. The internal type container can start the freezing unit at any time during transportation to keep the container at a specified temperature, while the external type container relies on the refrigeration unit equipped on the container-specific vehicles, ships, and special yard vehicles to provide refrigeration. It is suitable for transporting butter, chocolate, frozen seafood, condensed milk, and other items in summer.
Refrigerated containers are containers designed specifically for transporting refrigerated or low temperature goods that require a certain temperature. Currently, there are two basic types used internationally: one is an internal concealed mechanical refrigeration container with a refrigeration unit, and the other is an external mechanical refrigeration container with inlet and outlet vents on the end wall and no refrigeration unit, which is supplied with cold air from the refrigeration device of the ship.
Refrigerated containers have a higher cost and operating expenses. During use, attention should be paid to the technical condition of the refrigeration equipment and the temperature required by the cargo in the container. In order to improve the cooling effect, the internal walls, tops, and bottoms of the entire cold shipping container are covered with insulation materials.
Therefore, it is best not to pre-cool the container when exporting refrigerated goods, especially in high-temperature regions and during the summer season. The best approach is to pre-cool the goods and quickly load them into the container through the insulation passage between the cold storage and the cold shipping container.