Refrigerated container
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A refrigerated container or reefer is an intermodal container (shipping container) used in intermodal freight transport that is refrigerated for the transportation of temperature sensitive cargo.
While a reefer will have an integral refrigeration unit, they rely on external power, from electrical power points at a land based site, a container ship or on quay. When being transported over the road on a trailer they can be powered from diesel powered generators ("gen sets") which attach to the container whilst on road journeys.
Some reefers are equipped with a water cooling system, which can be used if the reefer is stored below deck on a vessel without adequate ventilation to remove the heat generated.
Water cooling systems are expensive, so modern vessels rely more on ventilation to remove heat from cargo holds, and the use of water cooling systems is declining.
The impact on society of reefer containers is vast, allowing consumers all over the world to enjoy fresh produce at any time of year and experience previously unavailable fresh produce from many other parts of the world.
[edit] Carbon dioxide based cooling
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Another refrigeration system uses liquid carbon dioxide (CO2) for cooling. This cryogenic concept was developed in response to rising fuel costs, and was an attempt to find an alternative to the standard mechanical refrigeration systems requiring maintenance, fuel and creating emissions. The CO2 reefer system can keep the container's cargo frozen solid as long as 30 days.
New "cryogenic" reefers are in service transporting frozen foodstuffs, but they have yet to gain wide acceptance (due, in part, to the cost of liquid carbon dioxide). Since cryogenic refrigeration is a proven technology and environmentally friendly, the rising price of fuel and the increased availability of carbon dioxide from Kyoto Protocol-induced capturing techniques may lead to common usage of cryogenic containers, especially in intermodal trade.
The cryogenic reefer container can be stored anywhere on any vessel that can accommodate "dry" (un-refrigerated) ocean freight containers. This is vitally important to the vessel operator because a typical dry freight load does not generate nearly the revenue of a refrigerated shipment. They can use many modes of transportation without an outside power source or a mechanical breakdown. Because a cryogenic reefer container doesn't need to be plugged in to a power source, it can be shipped anywhere, without electricity or fuel. This CO2 refrigeration technology has been used in railcars for years. The system has proven to be safe and reliable.
[edit] Redundant refrigeration
Valuable, temperature-sensitive, or hazardous cargo often require the utmost in system reliability. This type of reliability can only be achieved through the installation of a redundant refrigeration system.
A redundant ISO container system consists of a standard ISO container (i.e. intermodal container, integral primary and backup refrigeration units, and integral primary and back-up diesel generator sets.
The two sets of refrigeration units are mounted on one end of the ISO container used for intermodal shipping. This is a much more usable design than others which may try to have equipment on each end and load from the side of the container. The refrigeration units (and generator sets) will be electrically interlocked for automatic start and stop operation as required, such that only one can operate at a time to maintain the required temperature set points. Should the primary refrigeration unit malfunction, the secondary unit would automatically start. Refrigeration units with more highly reliable scroll compressors can also be used in order to maintain the desired temperatures.
The two sets of fuel-powered generator sets will power their respective refrigeration unit whenever necessary. The primary generator set will start automatically based on the status of the cord-supplied electrical power. If the primary generator engine cannot start after a pre-set time, the secondary generator will automatically start.
[edit] See also
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