The marine heat exchanger operates by circulating engine coolant (freshwater) through a series of tubes or plates, while seawater flows on the opposite side. As heat is transferred from the hot coolant to the cooler seawater, the coolant temperature is reduced before returning to the engine. The heated seawater is then discharged overboard, completing the cooling process. https://www.unitedheatexchangers.com/heat-exchanger/marine-heat-exchanger/