Differences between Heat Exchangers and Coolers in Ships

Blog | November 23rd, 2018

Aboard seagoing ships, heat exchanger walls separate two fluid mediums. One watery load is hot and full of energy, and the second fluid is cool. The exchanger interface, a tubular array, is conducting heat, taking it from the boiling hot medium, and donating that energy straight to the cooler liquid. But wait, surely this is a vessel configuration that’s used in every land-locked boiler room?

Marine-Based Heat Exchangers: Based On Conventional Engineering Principles 

More accurately, tube and stack heat exchangers are used in regular boiler rooms. A curved and twisted array of tubes is held in place within a sealed tube, hence the tube-and-stack label. Metal baffles further reinforce the interior tubes while they also performing as heat channelling constructs. Technically speaking, this layout is used on larger vessels, but that heat exchanging architecture does occupy massive amounts of engine room space. Reducing the space occupied by the tube, there’s a second option. Known as a plate type mechanism, groups of closely aligned metal plates transfer thermal energy via their stacked components and an intersecting group of heat carrying tubes. Formed into corrugated plates, the components generate turbulence. Energy is exchanged, and the equipment efficiently pumps hot water throughout a cruising ship.

Applied Marine Heat Exchanging Technology: The Cooling Method

Big tubes and hot pipe stacks work well on land, but their two-phase method of cooling or heating a fluid source aren’t particularly efficient onboard a modern boat. Replacing the above approaches, marine engineers use marine cooling solutions. That means the initial fluid medium is there, right inside a low-pressure vessel, but it’s the local water, liberally located around a ship, that cools the super-heated fluid, not a shell-and-tube model, nor a plate-configured heat exchanger. The seawater is obviously too cold and too corrosive to directly interact with marine equipment. But, configured as a heat exchanger, indirect contact engineering places the sea water in a separate fluid circuit, a system that again transfers energy via an energy transferring interface. Only, this time the energy is cooling the fluid, not imparting heat.

Arguably still a two-phase heat exchanger solution, there are two different liquids, and they’re kept separate. The big difference, though, is that the water comes from outside the vessel, from the sea water. Furthermore, that water cools a ship’s stored medium, it doesn’t function as a heat imbuing system. It’s strictly a heat exchanging cooler, if that term makes sense. Interestingly, there’s another group of heat exchanging solutions available for marine applications. Again, they use available energy sources. They scavenge heat. Engine exhaust marine heat exchangers fit into this latter category.


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