[izumi11]

Hi everyone I have a simple problem which I hope some of the geniuses on this forum could help me with..
I am simulating a vessel with an internal heat source and autothermal heat exchange between the incoming and outgoing fluid (air). The exchanger is a simple coil with air flowing around it. The walls are meshed with shell elements.
My problem is the following:
The energy balance is not conserved. I have air coming in at 300K and going out at no more than 400K. The inlet flow rate is 2e-6kg/s and internal power source is 5W. That gives a theoretical adiabatic temperature increase of well over 2000K, but it is not realized in my simulation.
I use DO radiation model with 0 absorptivity for air. All walls have an emissivity of 0.14. And external walls are adiabatic.

Any help is greatly appreciated!