Dave;
Normally efforts are made to cool the gasoline to prevent
vapor lock and improve performance. My old XJS has a fuel cooler that is
cooled by the Freon from a AC pump.
The average vapor pressure of gasoline at room temps is
already fairly high, like 9 psia (absolute), which is below atmospheric
pressure and not much of a problem. You may want to look up somewhere
what it is at higher pressures, but I’d guess two things, one is that as
it increases directly with temp it is likely go increase the pressure in the
tank much more rapidly than the fuel is fed out of the tank, and at temps of
about 190 the pressure could be quite high. I referred to average vapor
pressure because gasoline is a mix of stuff, some of which has much higher VP
than others. They usually refer to the ‘Reid’ vapor pressure
which is computed by some complex formula. So you also run the risk of
altering the compostion; e.g., the n-Pentane coming off much more rapidly than
the iso-octane or some other stuff.
At those temps, anywhere in the line upstream from the pump
a vapor bubble is almost assured.
Not to discourage experimentation, but my opinion would be –
maybe not the best idea.
Al
Subject: [FlyRotary]
Heating the Fuel
In anticipation of the
new turbo, I am considering ways to improve coolant cooling. Besides the
obvious more air, more ducting, more radiator; I have been again toying with
the idea of a heat exchanger. This time coolant to fuel. The plan
would be to use a typical oil/water exchanger but use fuel instead of
oil. I would use the fuel on the way back to the tank, and the coolant
after it has already been cooled by the radiator. The fuel would then go
back to the nice metal tank of the RV.
I am looking for input on
the implications of heating the fuel. I expect it would reach max temps
of about 190 (usually a little cooler) but quickly cool once in the
tank. Can the fuel tolerate that temp without vaporizing? It will
probably expand in the tank but I don't expect that will occur faster than it
is used up. I have no guess as to what temp will become steady state for
the fuel pumped out of the tank. My guess is that it will not be much
warmer than normal, but a slight increase in temp may help with vaporization.
The last question is how
much will it cool the coolant. My hope is about 10 deg but I doubt it
will be quite that much. I know others have considered using the fuel to
cool (Tracy) and I would appreciate your thoughts.