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From energy conservation, we can show that the mixed mean temperature is constant in the flow development and mixing sections and varies linearly in the heated section. This is shown schematically in the following figure from the MAE 4272 lab manual.

The slope of Tm in the heated section can be obtained from the following equation which is derived from energy balance in the heated section:

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Using the above equation, calculate the mixed mean temperature Tm at x=2.67 m. In the Verification & Validation section, you'll check that this value matches the Tm value calculated by integrating the temperature profile. This should be the case if the FLUENT solver is imposing energy conservation correctly.   energy is conserved in the simulation.

The following video show you the procedure for extracting the wall temperature at x=2.67 m. To repeat the calculation at a different axial location, you can right-click on appropriate items in the tree, duplicate and modify as necessary. You need to double-click on an item in the tree to modify it; this is easy to overlook.

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One can also calculate the mixed mean temperature variation from using energy balance which predicts that the mixed mean temperature should grow linearly in the heated section while being constant in the other two sections. If energy is conserved in the simulation, the two methods should yield the same mixed mean temperature. 

Nusselt No.

The following video shows you the procedure for calculating the Nusselt no. at x=2.67 m from the mixed mean and wall temperatures obtained above. To repeat the calculation at a different axial location, you can right-click on appropriate items in the tree, duplicate and modify as necessary.

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