Why 24PSI? Why not the more standard 14 - 16 PSI?

High absolute pressure in the coolant system at altitude?

Here is how I reason it out.
At sea level the ambient air pressure is 15 psi. So the system absolute
pressure is 30 psi with a 15 psi cap. At altitude, where the 
ambient air pressure may only be 7.5 psi, the system absolute 
pressure with a 15 psi cap would drop to 22.5 psi.
I think Tracy Crook was the first to discover this.

Teledyne Continental, in their very excellent SAE paper 871042 "Design 
and Development of the Voyager Liquid Cooled  Aircraft Engine" stated 
on page 9; "With the 250 degree maximum allowably coolant inlet 
temperature to the engine a 30 psi minimum pressure must be maintained  
at the coolant pump inlet to prevent boiling and cavitation."
I think Continental uses a 50 psi system pressure.
Take a peak at this bullet proof pressurized coolant tank
in an aircraft with the Continental liquid cooled engine.

Yes I know about nucleate boiling Jon so I, like you, are
somewhat confused :-)

Altitude.

Paul Lamar
 
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