Reefers ships not only transport eatables but sometimes they are also can be used to carry very precious cargoes which cannot be compensated for by money such as blood to a war zone. Obviously the need to carry such cargoes at their proper temperature range is of utmost importance.
The arrangement used for refrigerating such bulk quantities of cargo could be having a refrigerated cargo hatch but this type of system is quite inefficient and is used lesser these days.
The more popular method of refrigerating cargo is to use reefer containers which have their independent refrigeration systems and just need a power input which is supplied from the ship generators.
Another concept which is gaining popularity these days is the use of liquid carbondioxide to produce ultra low temperatures for several weeks at a stretch. This offers the benefit of saving fuel costs though the cost of liquid carbondioxide isn’t low either but then just imagine the benefits of transporting without any need for electric power for the reefer containers. Also this method is environmental friendly and literally maintenance free as compared to the conventional refrigeration systems which have moving components such as compressors which need regular maintenance and repair.
The picture shows such reefer containers of MAERSK Company stacked in a series. You can clearly see the refrigeration equipment on one end of these containers which is used to control the temperature inside the container.
In some of the ships a water cooling system is used to cool the hatches which store cargo. The water has already been cooled to a preset value and helps to keep the hatches at a controlled temperature. This system is useful since the heat generated in the hatches is enormous and conventional compressor based refrigeration systems have a hard time cooling them.
In the end it can be said that due to reefer carriers, people in one part of the world can really savour and enjoy the delicacies of foodstuff which grow in other parts of the world. Also the use of reefer in transporting live saving fluids such as blood helps a great deal in the humanitarian aspects of a war.