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Refrigeration systems for cargo ships

Refrigeration is used onboard a general cargo vessel in air conditioning systems , to cool bulk CO2 for fire fighting systems , to preserve perishable foodstuffs during transport or storage and in the carriage of some liquefied gases and bulk chemicals.


Summarized below various refrigeration system components, working process and maintenance guideline:
  1. Automatic direct expansion refrigeration- vapour compression

    2. The basic components of any refrigeration system (Figure 11.1) working on the vapour compression cycle, are the compressor, condenser, expansion valve, evaporator and the refrigerant fluid which is alternately vaporized and liquefied during the refrigeration cycle. The temperature at which a fluid boils or condenses, is known as the saturation temperature and varies with pressure....more

  2. Choice of refrigerants

    3. Theoretically, almost any liquid can be used as a refrigerant if its pressure/temperature relationship is suitable for the conditions. Although no perfect refrigerant is known, there are certain factors which determine a refrigerant's desirability for a particular duty and the one selected should possess as many as possible of the following characteristics.....more

  3. Refrigeration systems - Chamber cooling arrangements

    4. To avoid having an extended refrigeration circuit for cargo cooling, a brine system can be used. The brine is cooled by the evaporator and in turn cools grids or batteries. Grids provide cooling which relies on convection and conduction but air circulated through brine batteries provides a positive through cooling effect. .....more

  4. Refrigeration system components

    5. Marine condensers are generally of the shell and tube type, designed for high pressures. There may a few coil-in-casing or other types still in use. The coolant passes through the tubes with refrigerant condensing on the outside......more

  5. Refrigeration system compressors

    6. Refrigeration compressors are usually either reciprocating, or of the rotary screw displacement type. Centrifugal and rotary vane compressors have also been used.....more

  6. Refrigeration systems expansion valves

    7. The expansion valve is the regulator through which the refrigerant passes from the high pressure side of the system to the low pressure side. The pressure drop causes the evaporating temperature of the refrigerant to fall below that of the evaporator. .....more

  7. Monitoring instruments,CO2 measurement & Heat leakage and insulation test

    8. All necessary cargo temperature readings are obtained on modern reefers and container ships on a data logger which makes an automatic record. The temperatures and pressures relating to refrigerant gas and liquid, cooling water, brine and the ambient are also required. Most of these are obtained from direct reading instruments. .....more

  8. Marine condenser assembly

    9. The temperature of the refrigerated spaces with a direct expansion system is controlled between limits through a thermostatic switch and a solenoid valve which is either fully open to permit flow of refrigerant to the room evaporator, or closed to shut off flow. The solenoid valve is opened when the sleeve moving upwards due to the magnetic coil hits the valve spindle tee piece and taps the valve open.....more

  9. Comparison between refrigerants R717 ammonia & R744 carbon dioxide

    10. The ammonia used for refrigeration systems based on the use of a compressor, condenser, expansion valve and an evaporator (Figure 11.2) is dry (anhydrous) in that there is no water in solution with it. It has the chemical formula NH3 but as a refrigerant, it is coded with the number R717....more

  10. Container cooling system

    11. The air is cooled either by brine or direct expansion batteries and the containers are arranged so that one cooler can maintain a stack of containers at a given temperature. The temperature of the return air duct for each container is monitored.....more



Other useful articles :
  1. Methods of refrigeration

    2. Refrigeration is essentially the removal of heat through the process of evaporation. We choose to refrigerate commodities such as fruits and vegetables because we want to prolong their “practical shelf life” – the time from harvest until the product loses its commercial value.
    More .....

  2. Reefer cargo stuffing

    3. it is essential that all products are treated correctly prior to stuffing. Even though the temperature, ventilation and humidity are all optimal during the entire voyage, products will only arrive in perfect condition if the pre-treatment has been performed correctly. Successful shipping begins at the product sourcing area.
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  3. Growing demand for container refrigeration

    4. On deck refrigerated containers are generally serviced by clip-on air cooled electric motor drive cooling units. The units are plugged into the ships electrical system by way of suitable deck sockets.
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  4. Frozen products packaging requirement

    5. Proper packaging procedures will help protect frozen cargo during transport. Frozen products do not require air holes in the top and bottom of the cartons. Air flowing around the load is sufficient to remove heat that has penetrated the container. The cartons should be stacked directly on top of each other to take advantage of their strength in the corners.
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  5. Packaging & stowage guideline for reefer cargo

    6. Packaging plays an important role when it comes to protecting the cargo. The packaging material must be able to support a stacking height of up to 2.4 metres (7’10’’). The material should be able to withstand humidity without collapsing, and should allow the passage of an adequate vertical airflow through the cartons in order to maintain the desired temperature..
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  6. Choice of packaging for various commodities

    7. Goods should be well stowed within the package, evenly distributed and properly secured. Items completely filling the case or carton contribute to the strength of the whole package. Items which do not completely fill the package must be cushioned against shock or vibration.
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  7. How to keep cargo fresh ?

    8. Proper ventilation of fresh, chilled products is necessary to remove the heat, carbon dioxide and other gases produced by the cargo. Heat is removed by continuously circulating the internal air, whereas carbon dioxide and other gases are removed by replacing the internal air supply with cooled fresh air..
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  8. Loading precautions for refrigerated cargoes

    9. Refrigerated cargoes include meat carcases, carton (packed) meat, fruit, cheese, butter, fish and offal. Ships are specifically designed for their carriage, with separate spaces in holds and ’tween decks, each fitted with suitable insulation and individual control of ventilation. Ordinary general cargoes may be carried in the spaces at other times, the temperature being regulated accordingly for the type of cargo being carried.
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  9. Role classification societies maintaining seaworthiness of vessels

    10. classification societies publish rules and regulations which are principally concerned with the strength of the ship, the provision of adequate equipment, and the reliability of the machinery .
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  10. Periodic survey requirement by classification societies

    11. To maintain the assigned class all steel ships are required to be surveyed and examined by the Society’s surveyors at regular periods. The major hull items to be examined at these surveys only are discussed here..
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