Heat Nodal Sink/Source Boundary Condition

Unit [E/T]

 

A nodal sink/source boundary condition for heat transport applies a predefined extraction or injection of thermal energy to a node.

Nodal sink/source boundary conditions are applied in cases where the injection/abstraction of energy at a certain location is known. A typical example is the simulation of heat extraction by borehole heat exchangers in regional models.

 

For defining boundary conditions, inflows are considered as negative, outflows as positive. Thus a sink/source boundary condition with a positive sign means extraction of thermal energy from the ground, a negative sign is used for injecting energy.

The meaning of a heat nodal sink/source BC depends on whether the convective or divergence form of the transport equation is used. In most practical cases, the usage of this type of boundary condition is to be avoided in combination with the (default) convective form if there is a flow boundary condition on the same node. A temperature boundary condition is to be preferred in these cases.