# What is the fuel temperature in the tanks during a flight?

I'm trying to estimate the temperature of fuel stored in wing tanks during the flight. In my situation, I'm considering two wing tanks of 2000 liters each, one on each wing, at 20°C before the flight

I've run some calculations (I can provide additional numbers if necessary), and I end up with a temperature of 17°C after more than two hours of cruise (Mach 0.5, FL250)

Does this number sound correct to you? I was expecting a much lower temperature. I took a constant mass of fuel, which is not the reality, but even 15°C for instance seems rather hot. What are the usual temperatures of fuel in airliners tanks?

• I'd be curious to see exactly how you got to 17. – Notts90 supports Monica Sep 8 '16 at 11:28
• I used a mutliphysics simulation software (amesim), to model the convective exchanges. I assumed a tank outside surface of 5m² on each side of the wing – tintindu34 Sep 8 '16 at 11:33
• This is related aviation.stackexchange.com/questions/2185/… "For example, at an actual temperature of -56.5 C (SAT) and Mach 0.72 the TAT is -34 C, but at Mach 0.80 the TAT is -29 C." so I guess something is wrong with your calculations. – Mark Sep 8 '16 at 12:03
• Yes I saw that, thank you. It confirms that fuel stays above -40 °C at least. But it does not tell if it is more 10, 0 or -20°C. For my calculations, I took the r – tintindu34 Sep 8 '16 at 12:07
• For my calculations, I accounted for the ram effect: at 25'000 ft, the outside temperature is around -35°C, but at mach 0.5, the stagnation temperature is -22°C. Thus the cooling is not that strong – tintindu34 Sep 8 '16 at 12:17