11-05-2016, 01:35 AM
AzBob is right; it's fluid dynamics and thermodynamics working together. The contact of the water with the various surfaces of the engine is what cools to to a specified temperature. The water is then cooled by its movement through, and contact with, the radiator. The engine is directly cooled by liquid. The liquid is directly cooled by air. They are two separate systems.
Clearances in direct air-cooled engines are greater than in liquid-cooled engines because the range of temperature over which they operate is greater, so there must be additional room for pistons and cylinders to expand and contract. Piston and ring design can be different, as well.
Air-cooled aircraft engines consume a lot of oil, especially the big round ones. Gallons per flight.
If we take the "all engines are air-cooled" suggestion to its conclusion we would have to acknowledge that everything on Earth is cooled by the vacuum of outer space, which has no temperature, and is "as cold as you can get" with the lowest possible temperature being about -270 C.
Clearances in direct air-cooled engines are greater than in liquid-cooled engines because the range of temperature over which they operate is greater, so there must be additional room for pistons and cylinders to expand and contract. Piston and ring design can be different, as well.
Air-cooled aircraft engines consume a lot of oil, especially the big round ones. Gallons per flight.
If we take the "all engines are air-cooled" suggestion to its conclusion we would have to acknowledge that everything on Earth is cooled by the vacuum of outer space, which has no temperature, and is "as cold as you can get" with the lowest possible temperature being about -270 C.