Propulsion Struggles

[Lmj266]

Hey Guys !

Im posting here as I am having a bit of a struggle with a propulsion related question. It asks,

State the differences between a normal Jacket Water Cooling System and a Centralised Jacket Water Cooling System.

From whats in my notes it gives a brief description of the operation of each system but not enough to state any difference between the two and I am struggling to find answers on the internets. Hopefully someone would be able to give a newbie a hand! Thanks,


Lmj266

[lazygenius]

A central coming system cools engines/compressors with fresh water, which in turn is cooled in a central cooler by sea water. This is low temp cooling on one side of the heat exchanger and sea water on the other side.

"Normal" jacket water cooling is not so normal anymore, and central cooling systems are more the norm on newer ships. A "normal" system uses sea water in the engines/compressors/etc. Not so desirable as the centralized system as you add the inherent risk of debris fouling the system, replacing anodes is a more frequent job as the sea water becomes more corrosive as you heat it.

[Dosedmonkey]

To me, Jacket water (JW) means, High Temperature (HT) cooling water, for the engine jacket, at around 80 celcius.

This jacket water is normally cooled by either sea water (SW), or Low Temperature (LT) fresh water (which in turn is cooled by sea water further from the engine) by heat exchanger (tube or plate type).
LT FW water can also be referred to as Secondary Cooling Water.

As you can see there is different names, for the same systems.

There is some small engine vessels/craft directly cooled by sea water, but I would not call it normal for Merchant Navy.

Personelly there is no such thing as a normal system! But the most common on large Merchant Vessels is to have HT > LT > SW, But your HT Jacket Water can be individual to each engine, or split in other ways. Depends on the design. Just keep it simple and study as if there is a single engine!

So...

Centralised cooling system, refers to a closed loop, LT & HT system from looking through different sources, being cooled by sea water via heat exchanger. But I would not refer to direct sea water cooling as "normal" for certain.