Convective heat transfer coefficients of fuel oil?

[Downtown84]

I'm setting up a thermal resistance network to determine the heat loss through the insulated wall of a heated fuel/crude oil tank but i can't seem to find values for the convective heat transfer coefficient of the fuel oil (kerosene) or the crude oil at elevated temperatures. I have only found values at room temperature (20 degrees C). I would try to determine the values using Rayleigh and Nusselt numbers, but the problem does not give the temperature of the inner wall, only the fluid temperature. Does anyone know of a resource where i can find these convective heat transfer coefficients, or of a way to calculate/estimate them without knowing the inner surface temperature? Thanks in advance.

 

[BvU]

Perhaps it helps to post the complete problem statement ?

 

[Mech_Engineer]

To calculate free convection parameters you'll need the fluid temperature and the wall temperature. If you haven't been provided the wall temperature, can you assume it is the same as environmental temp?