The Inflow condition is available at boundaries that are exterior to a fluid domain and is equivalent to having a virtual channel “upstream”. It is used to define a heat flux at the inlet boundary that brings the same energy to the fluid domain as if you had modeled the virtual channel as a real CFD domain. The virtual channel can be seen as a long insulated channel with given thermal properties at the inlet, and with the same velocity profile as defined in the settings for the
Inflow boundary condition.
![](images/heat_ug_modeling.06.53.1.png)
where the enthalpy variation ΔH depends on temperature and pressure difference:
Equation 3-1 expresses the fact that the normal conductive heat flux at the inflow boundary is proportional to the flow rate and enthalpy variation between the upstream conditions and inlet conditions.