When loading the reefer sea container, in addition to checking the original quality of the goods and specifying it on the manifest, the goods in the reefer sea container must be well and evenly placed for reasonable stowage to establish a good wind circulation in the cabinet. To promote refrigeration efficiency, avoid the unbalanced cooling caused by the cold air short circuit and reduce the refrigeration efficiency.
For perishable fruit and vegetable cargo, packaging that can circulate air in the middle of the cargo and take away the gas, water vapour, and heat generated by the breathing of the shipment should also be used. It has good strength and can maintain normal stacking in a high-humidity environment. Yard height and allows vertical airflow.
The freezer of the reefer sea container is placed at the bottom of the cabinet’s front end, sends air to the door side, and then circulates through the wardrobe and returns from the air return at the top of the front end.
This method will naturally result in lower temperatures at the air outlet and adjacent areas in the reefer sea container, higher temperatures on the far door side, lower temperatures on the bottom and higher temperatures on the upper part.
Generally speaking, the temperature in the middle part is relatively low and uniform, and the temperature difference at the door end is significant, especially since the temperature at the top of the door end is the highest. Therefore, the loading volume at the door end should be the smallest during actual loading. Therefore, the cargo is suitable for trapezoidal stowage, and the cargo volume decreases from the front end of the freezer to the door end.
In the refrigeration of the reefer sea container, the circulating fan forces the air to pass through the condenser, which also acts as an evaporator in the cold circuit and returns to the cargo through the grille.
Generally, for goods that have been pre-cooled, air only needs to flow around the goods. The goods themselves do not emit heat, and cooling only dissipates the heat that penetrates the insulating material from the outside. When transporting fruit and vegetable goods, the air flows through the goods. Fruits and vegetables can produce breathing heat, and cooling will dissipate this heat. The inner wall of the reefer sea container has groove lines and ripples, which can promote good airflow in the cabinet. Even if the goods are stacked against the wall due to improper storage, part of the air can still flow through, which is beneficial to dissipate heat.
The goods should be stowed within the warning line in the reefer sea container, and the stacking should not interrupt the airflow in the reefer sea container to ensure that the air in the reefer sea container can circulate the goods.
Shippers usually use International Cold Chain Technology (ICCT) related transportation conditions to request entrusted transportation, including specific reefer sea container settings such as temperature, ventilation and humidity.
For example, when the reefer sea container transports fruits and vegetables because it is necessary to remove the carbon dioxide and ethylene produced by the respiration of the goods from the container. For this reason, the front end of the reefer sea container is equipped with vents and new air baffles so that the external fresh air can use. In addition, through the baffle into the cabinet, the internal air can also escape from the cabinet.
This kind of air exchange is caused by the pressure difference between the circulating fans. Fresh air is sucked in on the suction side of the fan and dissipated on the pressure side. Usually, the amount of fresh air supplied per hour is not more than twice the cabinet’s internal volume. It will be affected by fan pressure difference and cargo stowage method.
Regarding the condition of the cargo, temperature inspection should be carried out before loading.
For refrigerated goods, such as fruits and vegetables that have plant respiration, self-heating, and premature maturity after picking, record mould, withering, dehydration, wilting, fading, soft spots, peeling and peeling, abrasions, frostbite and other abnormal phenomena;
Frozen goods should be checked for signs of discolouration, dehydration, drying, shifting, stinking, dark spots, and thawing.
In addition to the goods themselves, we must also pay attention to whether the pallets and packaging are in good condition to assess whether they can adapt to the entire transportation process.
The reefer sea container has long shipping routes, often crossing tropical, temperate, and frigid zones. Therefore, it changes in seasons, day and night and cargo conditions. During the voyage, the ambient temperature outside the reefer sea container and the condensation temperature of the condenser will also change.
When moist air flows over the surface of the cooling coil, condensate will be precipitated, causing frost and ice on the evaporator surface. Especially when refrigerating fruits and vegetables, the high humidity in the box tends to make the frosting more serious. Therefore, the refrigeration device has a regular defrosting function.
During defrosting, a certain degree of temperature increase in the cabinet will be recorded, and continuous temperature records will show periodic changes consistent with the defrosting interval.
Generally speaking, this short-term temperature increase will not affect the actual temperature of the cargo, nor does it mean that the refrigeration is abnormal.
The temperature, defrost interval and duration of average electronic data records should have overall regular stability. Suppose the temperature of the loaded goods is higher than the set requirement or even thawed. In that case, the reefer sea container may continue to activate the defrost function frequently (if the refrigeration unit fails, the temperature data record usually shows a gradual rise to the outside ambient temperature the process of).
Uneven air temperature distribution in the reefer sea container often results in a loss of cooling efficiency. In addition, changes in the inner wall, outer wall and surrounding environment of the reefer sea container can also cause cooling loss.
When investigating cargo damage accidents, in addition to checking the temperature recording instrument data in the reefer sea container, it is also necessary to conduct an in-depth investigation and analysis of external factors such as routes, storage, and cargo management to determine the proximate cause of the accident and claim compensation from the responsible party.
The times are developing rapidly, and the logistics management technology of refrigerated containers is also constantly advancing. Furthermore, with the continuous reduction of the cost of IoT chips, critical new technologies such as Fieldbus control systems, 5G technology, and recent satellite communication equipment are more deeply applied in the reefer sea container transportation.
In the small control room, the sensors and controllers in the reefer sea container can intelligently and efficiently complete real-time operation status monitoring, accident diagnosis and even troubleshooting, making remote monitoring and information sharing of all parties ubiquitous and omnipresent. So, the delivery quality of reefer sea containers has also been continuously improved, and the worldly life will be better.