Thermal Insulation

The Thermal Insulation node is the default boundary condition for all heat transfer interfaces. This boundary condition means that there is no heat flux across the boundary:

n k T = 0

This condition specifies where the domain is well insulated. Intuitively this equation says that the temperature gradient across the boundary must be zero. For this to be true, the temperature on one side of the boundary must equal the temperature on the other side. Because there is no temperature difference across the boundary, heat cannot transfer across it.

An interesting numerical check for convergence is the numerical evaluation of the thermal insulation condition along the boundary. Another check is to plot the temperature field as a contour plot. Ideally the contour lines are perpendicular to any insulated boundary.

B O U N D A R Y S E L E C T I O N

Outflow

The Outflow node provides a suitable boundary condition for convection-dominated heat transfer at outlet boundaries. In a model with convective heat transfer, this condition states that the only heat transfer over a boundary is by convection. The temperature gradient in the normal direction is zero, and there is no radiation. This is usually a good approximation of the conditions at an outlet boundary in a heat transfer model with fluid flow.

B O U N D A R Y S E L E C T I O N

The Outflow node does not usually require any user input. If required, select the boundaries that are convection-dominated outlet boundaries.

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