Whenever contact occurs during a non-isothermal simulation, thermal boundary conditions are usually not the same before and after contact. It is possible to impose thermal boundary conditions accordingly on a boundary segment (or face) for which contact detection has been enabled. Whenever contact is taken into account in the energy equation, usually an imposed flux condition before contact changes to an imposed temperature condition in regions where contact has been detected.

In order to alter thermal boundary conditions after contact, a condition of heat transfer by convection is used. This condition is reduced to a penalty formulation when a large value is selected for the transfer coefficient. When contact has been detected at a given location, the flux is expressed as

(17–5)

The parameter has physical dimensions of a convection coefficient. When is large, Equation 17–5 is equivalent to an essential boundary condition in temperature (the temperature of the polymer must be equal to ); it is, however, now imposed by means of a penalty formulation. Whereas, when , the mold acts as an insulated boundary. Very large values of will not make the system excessively stiff, but thin thermal boundary layers can be expected when heat advection dominates the energy equation. A practical way to determine is to use conductivity of the parison material. If Equation 17–5 is equivalent to establishing the mold temperature in a layer thickness , then

(17–6)

where is the heat conductivity of the investigated fluid (polymer or glass), and can be considered as an equivalent thermal thickness that, in general, is lower than the fluid thickness. Very large values of mean that the mold temperature must be established in the polymer over a very small distance.