Cooling Systems on Ships

The systems on board ships are cleverly designed to operate at maximum efficiency and be able to run for hours. The most common loss of energy from a ship’s engine comes in the way of thermal energy. Any escape of thermal energy must be lowered or removed by a cooling medium, such as central air conditioning systems, to avoid non-functioning, breakdown or damage to the engine.

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There are two cooling systems used on ships for this purpose:

Seawater cooling system: direct sea water used in the cooling system of the engine as a medium for heat exchangers.

Freshwater or central cooling systems: fresh water used in a closed circuit to cool the engine room machinery. Fresh water returning from the heat exchanger after cooling this engine is cooled by seawater.

Central Cooling Systems – how do they work?

As discussed above, all machines that work on ships use a central cooling system that utilises freshwater to cool. The system consists of three different circuits:

Sea water circuit

Sea water is used as a coolant in large sea water cooled heat exchangers to cool fresh water from the closed circuit.

Low-temperature circuit

A low-temperature circuit is used for low-temperature zones of machinery and the circuit is directly connected to the main sea water central cooling; then the temperature is lower than the high temperature (H.T circuit). L.T circuit consists of all auxiliary systems.

The total amount of low temperature or L.T fresh water in the system is maintained in equilibrium with H.T. fresh water by the cooling system expansion tank that is common to both systems.

High-temperature circuit (H.T)

The H.T circuitry in the central cooling system mainly consists of the jacket water system of the main engine where the temperature is high. The HT cooling system water is circulated by the electric cooling water pump, one in service and one standby.

Advantages of the central cooling system

Low maintenance costs: As the system is running with fresh water, cleaning, maintenance and replacement of components is reduced.

Less corrosion: Because the sea water system is located only in the centre, there is less corrosion of pipes and valves. Proud to serve the marine industry, get a Brass Ball Valve at a site like

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Improved high speed liquid heat exchange: Higher speed is possible in freshwater systems, which results in reduced pipe installation costs.

Cheaper materials: As there is a significant reduction in potential corrosion, cheaper materials can be used as expensive ones are not needed for valves and pipes.

Constant temperature level is maintained: Because the temperature is controlled regardless of the temperature of sea water, a stable temperature is maintained which helps in reducing engine wear.

Ideal for unmanned machinery space: The greater reliability and temperature control systems offered by the central cooling system makes it an ideal choice for unmanned engine rooms.


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