A reefer container, also sometimes called a refrigerated container, is an enclosed box unit designed to transport temperature sensitive cargo and can be used for everything from food to pharmaceuticals. Refrigerated containers normally need external power supplies in order to operate.
When refrigerated containers are loaded onto ships or similar transport, power is provided by the vessel. Some important facts to note include
- The refrigeration unit itself is often fitted in the front of the container to act as the front wall
- Some refrigeration containers are dual voltage but most work on AC, 3 phase power
- Operating control power is usually provided by a single phase transformer in order to step down AC supplies to 24 volt and 1 phase
The compressor section of the container contains the compressor (and HP switch) and a compartment for power cable storage. Power transformers are also commonly included. Modulating and suction solenoid valves are present to control the quantity of gas flow.
Most safety fittings will be limited to moisture liquid indicators, pressure relief valves and a filter drier, although some containers also have remote environmental monitoring which can include features such as compressor suction and discharge sensors, air temperature sensors, supply recorder sensors and ambient sensors.
The condenser section of the container contains the condenser fan and its associated motor, along with an air cooled condenser coil and a saturation sensor. Most units are air cooled, pulling air from the bottom and discharging it along the centre of the unit horizontally. It is possible to get water cooled considers and receivers but these are normally much more expensive.
The evaporator section of the container has the temperature sensing bulb and return recorder bulb sensor. The thermostatic expansion valve controls the flow of refrigerant and maintains the inside temperature at the desired levels. Assembly normally consists of an evaporator coil and heater, drain pan and heater along with defrost and heat transmission switches.
The evaporator fan will circulate air throughout the container by pulling air into the top of the refrigeration unit and then directing it through the evaporator coil. The air is then heated or cooled as needed and discharged out of the bottom of the unit back into the container.
There is also a fresh air make up vent which is designed to provide ventilation for cargo that needs fresh air circulation. The vent must be closed in order to safely transport frozen foods and other such goods.
The air exchange here depends entirely on the static pressure differential which varies depending on how the container is loaded.