Evaporative Cooling

[langwadt]

Exactly. The only gain is reduced coolant mass.

but that at the cost of much larger radiator area required for steam or a great big compressor

[autogyro]

http://www.youtube.com/watch?v=7bH5F7Sh_MQ

Who needs a radiator anyway.
Water ethanol full loss boil off cooling.

[olefud]

http://www.youtube.com/watch?v=7bH5F7Sh_MQ

Who needs a radiator anyway.
Water ethanol full loss boil off cooling.

Evaporative cooling was used in the thirties on the Schneider Cup planes, but this worked largely because more troublesome low speed operation was on water and the floats incorporated water-immersed condensers/ heat exchangers. For utilitarian use the arrangement TC describes was superior. The Rare Bear Bearcat in the film has an air-cooled engine so the immersed radiator boil off would be from the oil cooler. The unfortunate Galloping Ghost P-51 with a water-cooled Merlin had a similar space shuttle-like arrangement in which a small heat-rejecting radiator was immersed in alcohol that boiled off in a total loss arrangement. However, most of the exotic aircraft arrangements appeared before the Meredith effect was recognized/utilized to offset the drag of a well-designed and positioned radiator, though this is not much useful at car racing speeds.
Generally, evaporative cooling is used to move heat energy from a cooler environment to a hotter one, i.e. a powered heat pump. The ICE is of course flowing heat from the hot engine to the cooler air with a coolant pump about the only power input, and that’s only for enhance efficiency in that the system would operate on its own by thermal siphon.

[riff_raff]

Riff raff I think you misunderstand how evaporative cooling works. The water starts off in a liquid state under pressure in the engine. It flows through and gets heated up. After it leaves the ICE it flows to an expansion chamber. As the pressure drops in the chamber the boiling point goes down. The water boils into steam which converts a fair portion of heat energy. The steam then passes through a condenser where the temperature drops just enough to turn back into liquid state. This liquid is then placed under pressure once raising the boiling point and then sent back through engine.

langwadt, I do understand the principle behind evaporative cooling systems. The benefit of such systems when using water is the relatively large amount of heat absorbed by the fluid when it undergoes a phase change from liquid to gas. But once the fluid (water) transitions from a liquid to a gas state, doesn't the heat transfer process from the metal block/head surfaces to the steam vapor also become far less efficient? The there is also the more practical issue of how do you deal with the problem of cavitation damage in the pump components and coolant jackets surfaces when the water boils? This is a huge consideration when designing engine coolant systems.

While I appreciate that this discussion is mostly academic in nature, I would also like to hear someone propose some creative solutions to these more practical problems.

[langwadt]

Riff raff I think you misunderstand how evaporative cooling works. The water starts off in a liquid state under pressure in the engine. It flows through and gets heated up. After it leaves the ICE it flows to an expansion chamber. As the pressure drops in the chamber the boiling point goes down. The water boils into steam which converts a fair portion of heat energy. The steam then passes through a condenser where the temperature drops just enough to turn back into liquid state. This liquid is then placed under pressure once raising the boiling point and then sent back through engine.

langwadt, I do understand the principle behind evaporative cooling systems. The benefit of such systems when using water is the relatively large amount of heat absorbed by the fluid when it undergoes a phase change from liquid to gas. But once the fluid (water) transitions from a liquid to a gas state, doesn't the heat transfer process from the metal block/head surfaces to the steam vapor also become far less efficient? The there is also the more practical issue of how do you deal with the problem of cavitation damage in the pump components and coolant jackets surfaces when the water boils? This is a huge consideration when designing engine coolant systems.

While I appreciate that this discussion is mostly academic in nature, I would also like to hear someone propose some creative solutions to these more practical problems.

I didn't write the quoted part, I think trinidefender did

[riff_raff]

langwadt- Sorry for the confusion.