I simulated ground coupled to heat exchanger with Ansys fluent and I want to calculate the mean thermal energy (KWh) transferred to the heat exchanger from the soil.
I tried to calculate the heat flux on the interface between the heat exchanger and the soil. I used the coupled wall command between the pipe and soil.but the results give me always 0 W in the interface (Soil/heat exchanger and Heat exchanger/fluid).
But do you see an increase in temperature in the heat exchanger? If so, I guess you're integrating over "both sides" of the interface, so that the ingoing and the outgoing heat flux add up to zero.
If you have a water or gas flow through the heat exchanger, you could also simply calculate the energy input into the fluid via Q=massflow*Cp*deltaT.