How the heat fluxes for inlets/outlets in Fluent are calculated
I am simulating in Fluent a heating system in a ventilated room. After achieving quite stable results I checked the heat fluxes through all BCs. All of them make sense to me and are predictable according to hand calculations. All of them except inlet and outlet for which I have no idea how the heat fluxes are calculated. I cannot find any detailed explanation in the manual, except that depending on the models different enthalpy is taken into account and that the reference temperature for all enthalpy calculation is 298.15K. Where can I find any more information about how it is calculated?
When multiplying mass flow rate by weighted-average values of specific heat and temperature difference (the inlet or outlet avg. air temp. minus the reference temp.) I got around the same heat flux for the outlet as calculated by the Fluent, but 3 times higher for the inlet then the one given by the Fluent.