error with experimental values
 

I am working on a heat exchanger which is cylindrical in shape(tube) and have flat fins outside. Inside the tube, some fluid is running and these fluid exchanges heat with the air. I am trying to find out the heat transfer coefficient on the air side and comparing with the experimental value. My CFD data is not correlated with Experimental data. As there are two factors on which heat transfer coefficient is depended (i) velocity of air (ii) wall temperature of the heat exchanger. I think, fluent is not taking the temperature in the account. As I am new in fluent so need assistance for the beginner. Kindly help me out. Thanks