The cooling of marine diesel engine covers for distant areas are -
- Jacket and cylinder head cooling
- Piston cooling
- Charge air cooling
- Fuel injection valve cooling
- Lube oil cooling
- Jacket and cylinder head cooling includes turbocharger cooling, exhaust valve cooling. Normally fresh or distilled water is used, chemical compounds may be used to prevent corrosion.
- Piston cooling may be or may not be in the same circuit as jacket cooling water. The circulating pipes are separated. Fresh water or distilled water is generally used Lube oil may be used in some engines for Piston cooling
- Charged air uses seawater for cooling as the temperature required of the cooled air is around 40 degrees Celsius
- Fuel injection valve cooling have a separate cooling water circuit (freshwater) low viscosity oil may also be used( distillate fuel )and it is crucial to maintain the cleanliness of this coolant and provide chocking.
- Lube oil coolers use sseawater for cooling.
Advantages of fresh water cooling
- It is inexpensive, has high specific heat as compared to oil, has low viscosity has cleaning ability and has easy access to difficult reaches.
- It has easy availability and the pH value can be controlled
- Capable of higher temperature in operation.
- It has the specific heat capacity of nearly twice that of oil.
Disadvantages of fresh water cooling
- May contain salt which is deposited and can obstruct flow.
- Main cause corrosion and scale formation to restrict heat dissipation.
- It requires treatment.
- Leakage Can contaminate the Lube oil system leading to loss of lubrication and possible overheating of bearing.
- Water also required a separate tank and pumping system
Advantages of Lube Oil Cooling System
- No separate Pumping system is required.
- Leakage within Crankcase has no serious consequence.
- No chemical treatment is required.
- The moving part gets automatically lubricated.
Disadvantages of lube oil cooling system
- It is expensive
- It has low specific heat (as it requires a higher quantity of lube oil to give same cooling capability as water)
- If Lube oil is exposed to overheated components it will form carbon layer as insulation and result in poor heat dissipation
- Oxidation of the oil on contact with hot surface leads to reduction in lubrication property. It has the lower maximum temperature to prevent formation of carbon.