A refrigerator ship is a type of ship

Ship

Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

 typically used to transport perishable commodities which require temperature-controlled

Air conditioning

An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle...

 transportation, mostly fruit

Fruit

In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...

s, meat

Meat

Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...

, fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, vegetable

Vegetable

The noun vegetable usually means an edible plant or part of a plant other than a sweet fruit or seed. This typically means the leaf, stem, or root of a plant....

s, dairy product

Dairy product

Dairy products are generally defined as foods produced from cow's or domestic buffalo's milk. They are usually high-energy-yielding food products. A production plant for such processing is called a dairy or a dairy factory. Raw milk for processing comes mainly from cows, and, to a lesser extent,...

s and other foodstuffs.

Reefer ships may be categorised into three types:

1. Side-door vessels have water tight ports on the ships hull, which open into a cargo hold. Elevators or ramps leading from the quay serve as loading and discharging access for the forklifts or conveyors. Inside these access ports or side doors, pallet lifts or another series of conveyors bring the cargo to the respective decks. This special design makes the vessels particularly well suited for inclement weather operations as the tops of the cargo holds are always closed against rain and sun.
2. Conventional vessels have a traditional cargo operation with top opening hatches and crane
   Crane (machine)
   A crane is a type of machine, generally equipped with a hoist, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of...
   
   s/derricks. On such ships, when facing wet weather, the hatches need to be closed to prevent heavy rain from flooding the holds. Both above ship types are well suited for the handling of palletized and loose cargo.
3. Refrigerated Container vessels are specifically designed to carry containerised unit loads where each container is an individual refrigerated unit. These ships differ from conventional container ships in design and power generation equipment.

A major use of refrigerated cargo hold type ships was for the transportation of bananas but has since been partly replaced by refrigerated containers that have a refrigeration system attached to the rear end of the container. While on a ship this is plugged into an electrical outlet (typically 440 VAC

Alternating current

In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

) that ties into the ship's power generation. Refrigerated container ships are not limited by the number of refrigeration containers they can carry unlike other container ships which lack sufficient refrigeration outlets or have insufficient generator capacity. Each reefer container unit is designed with a stand-alone electrical circuit and has its own breaker switch that allows it to be connected and disconnected as required.

Refrigerated cargo is a key part of the income for some shipping companies. On multi-purpose ships, Refrigerated containers are mostly carried above deck, as they have to be checked for proper operation. Also, a major part of the refrigeration system (such as a compressor) may fail, which would have to be replaced or unplugged quickly in the event of a fire. This being the case, no provisions for refrigerated cargo power connections are made below the hatch covers that enclose the top of the hatches aboard a ship. Modern container vessels stow the reefer containers in cellguides with adjacent inspection walkways that enable reefer containers to be carried in the holds as well.

Modern refrigerated container vessels are designed to incorporate a water-cooling system for containers stowed under deck. This does not replace the refrigeration system but facilitates cooling down of the external machinery. Containers stowed on the exposed upper deck are air-cooled, while those under deck are water-cooled systems. The water cooling design allows capacity loads of refrigerated containers under deck as it enables the dissipation of the high amount of heat they generate. This system draws fresh water from the ship's water supply, which in turn transfers the heat through heat exchangers to the abundantly available sea water.

There are also refrigeration systems that have two compressors for very precise and low-temperature operation, such as transporting a container full of blood to a war zone. Cargoes of shrimp, asparagus, caviar and blood are considered among the most expensive refrigerated items.

See also

• Cold chain
  Cold chain
  A cold chain is a temperature-controlled supply chain. An unbroken cold chain is an uninterrupted series of storage and distribution activities which maintain a given temperature range...
  
  
• Reefer (container)
  Reefer (container)
  A refrigerated container or reefer is an intermodal container used in intermodal freight transport that is refrigerated for the transportation of temperature sensitive cargo....
  
  
• Refrigeration
  Refrigeration
  Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work, but can also be done by magnetism, laser or other means...
  
  
• Refrigerator car
  Refrigerator car
  A refrigerator car is a refrigerated boxcar , a piece of railroad rolling stock designed to carry perishable freight at specific temperatures. Refrigerator cars differ from simple insulated boxcars and ventilated boxcars , neither of which are fitted with cooling apparatus...
  
  
• Refrigerator truck
  Refrigerator truck
  A refrigerator truck is a van or truck designed to carry perishable freight at specific temperatures. Like refrigerator cars, refrigerated trucks differ from simple insulated and ventilated vans , neither of which are fitted with cooling apparatus...
  
  

External links

• "Floating Island Ship to Make Ice in the Tropics" Popular Mechanics, January 1935
• "Ship Keeps Cool When Heat Is On" , June 1949, Popular Science article with drawings explaining refrigerated ships for transporting bananas built shortly after WW2
• ReeferTrends News site dedicated to the Reefer industry
• Reefership Information & Schematics of different Reeferships
• Crosstree Interesting information on refeership ocean transport.
• Article Article on various reefer ship types.