The majority of refrigerated transports overseas is carried out with reefer containers. Nowadays the predominant type is the integral reefer container. There is a built-in cooling unit that is screwed in the face of the container. Three phase current is necessary for the operation of such containers.
Cool air flows through or around the goods inside the container. This cool air is blown in by the grating in the ground and exhausted on the container ceiling.
Subsequently, the circulation fan presses the air through the air cooler, which is simultaneously the vaporizer of the refrigeration circuit, and back through the grating into the container. Regarding pre-cooled frozen foods it is sufficient if the air just flows around the goods since heat of the goods itself doesn’t need to be discharged. Merely the heat from outside penetrating through the isolation needs to be discharged. However, during the transportation of fruits, air has to flow through the fruits, because they generate heat through ripening that has to be discharged.
The goods in the container have to be stored in a way that the airflow is not cut off, so not higher than the red “load-limit-line”. Furthermore stream short cuts due to free space in front of the door should be avoided (here perhaps the grating needs to be covered).
A pre-cooling of the container before loading should only be applied if the container is loaded through a sluice (e.g. of a cold house) so that the temperatures in front of the container doors is the same as inside the container. Otherwise water condensates during the opening of the doors and the pre-cooled container, which might damage the goods.
The Dr.-Ing. Yves Wild GmbH consults shipping companies, shipyards and manufacturers in regard to all questions concerning the construction and operation of reefer containers and the equipment of ships for the transport of reefer containers. In case of refrigeration damage we investigate the causes that led to damage of the goods. Mr. Dr. Wild is author of the article “Kühlcontainer im Containerhandbuch” (reefer containers in the container manual) of the “Gesamtverband der Deutschen Versicherungswirtschaft e.V. (GDV)” (association of German insurance companies).