What is the difference between "water-to-air intercooler" and "air-to-air intercooler" in diesel engines ?

What is the difference between "water-to-air intercooler" and "air-to-air intercooler" in diesel engines ?

Intercoolers can be categorized by cooling medium as follows: water-to-air intercoolers, which use water to cool the boosted air; and air-to-air intercoolers, which use ambient air to cool the boosted air, with the air supplied by an independent fan. Due to the limitation of coolant temperature, water-to-air intercoolers struggle to achieve lower intake air temperatures (such as below 80°C). Additionally, the heat carried away by the coolant must ultimately be dissipated into the atmosphere through the radiator, which inadvertently places an additional load on the cooling system's water radiator. Moreover, from a heat transfer perspective, this involves a two-stage process, resulting in relatively low overall heat transfer efficiency. Furthermore, since coolant circulates in the water-to-air intercooling system, there is a risk of coolant leaking into the cylinders due to intercooler failure, potentially causing water hammer incidents.

Therefore, air-to-air intercoolers are increasingly being adopted in power plant engines. This design is compact and completely prevents coolant from entering the engine in case of intercooler leakage. Additionally, air-to-air intercoolers can be arranged in series with radiators, reducing the number of components in the cooling system, simplifying the overall structure, and lowering manufacturing costs. As a result, they are widely used in engines for generator sets.