>
> Tracy has argued that all your cooling air comes in
> at 200mph, then has to
> slow down to almost 0mph to go through the radiator,
> then accelerate back
> to 200mph again. All that work being done on the air
> costs you -- it's
> drag. So he says that you want to put the minimum
> amount of air through the
> radiator.
>
> I don't know whether its significant or not, but a
> couple of secondary
> effects occur to me...
>
> 1. If the air at the radiator is compressed, it will
> be able to carry more
> heat away per cubic metre. So you want to maximise
> the air pressure at the
> radiator. But compressing air heats it.
>
> 2. Heating the air as it comes through the radiator
> will cause it to
> expand, and therefore produce thrust, which might be
> useful in accelerating
> the air back up to the 200mph exit speed. I vaguely
> recall that the P51's
> cooling system produced some thrust.
>
> Frank.
>
>
Don't forget that as the air is heated it also expands
and becomes less dense and therefore has less capacity
to transfer the heat from the water.
                        John


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