Vaporization of JP-8 Jet Fuel in a Simulated Aircraft Fuel Tank ...

In the beginning of the test, the liquid fuel was heated to 30°F above its initial
temperature and allowed to vaporize until quasi-equilibrium is achieved. From figure
6.4, it can be seen that the amount of fuel evaporated was similar to the amount of fuel
stored in the ullage, because at this point there was little condensation. Once dew point
conditions were reached, the condensation rate increased and the mass of fuel stored in
the ullage leveled off even though the mass of fuel evaporated still increased, as it did for
the duration of the test. As the climb to altitude was initiated, the mass of fuel stored in
the ullage began to decrease rapidly as ullage gas was vented due to the pressure
differential between the ullage and the atmosphere. The ambient air temperature was
decreasing quite rapidly at this point due to the increasing altitude, and the fuel tank
temperatures began to decrease, causing an increase in the rate of condensation and a
decrease in the mass of fuel stored in the ullage. Upon descending from cruise, air
entered through the vents due to the pressure differential and diluted the ullage vapor
mixture. When the fuel tank was back to sea level atmospheric pressure, the fuel tank
temperatures were about 15°F cooler than at the beginning of the test, and the mass of
fuel stored in the ullage was about 0.002 kg less than at the beginning.
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