For non-isothermal contact-detection simulations that do not make use of shell elements, it is possible to couple the heat transfer calculation in the parison (or sheet) to the heat transfer in the mold, which undergoes a nonuniform temperature field. This capability—referred to as conjugate heat transfer—models the heat exchange between the mold and the parison, the warmer part heating the cooler one and the usual advection/diffusion mechanism controlling heat exchanges in each zone. Note that the calculation of conjugate heat transfer increases the number of variables in the simulation, since Ansys Polyflow needs to compute a temperature distribution in the mold, rather than assuming it is constant as in Heat Transfer and Contact (Imposed Temperature). Since the elements and nodes in the parison do not correspond to the elements and nodes in the mold, the calculation of conjugate heat transfer will be based on a non-conforming finite-element technique.

The basic idea is that a temperature will be calculated in the mold at each step, using thermal boundary conditions along the wall of the mold. Along the face of the mold that will contact the parison, boundary conditions will vary depending on whether or not there is contact.

In the absence of contact, any usual type of temperature condition can be imposed (most of the time, a zero flux condition applies). At locations where contact has been detected, the heat flux per unit surface that exits the parison is equal (with an opposite sign) to the heat flux per unit surface that enters the mold. Also, the temperature of the parison must match the temperature of the mold at the point of contact. Neither the flux value nor the temperature has been imposed; only the continuity of both quantities is required.

More generally, it is also possible to model a thermal resistance between the parison and the mold to follow Equation 17–5. In this case, both (the parison temperature) and (the mold temperature) are variables of the simulation that vary from point to point, whereas in Heat Transfer and Contact (Imposed Temperature), remains constant.

Imposing continuity of the temperature between the parison and the mold is equivalent to choosing a very high value of the thermal conductivity per unit surface, in Equation 17–5. A lower value will increase the temperature difference between and , and when vanishes the condition is equivalent to insulating both the parison and the mold independently. In this latter case, the parison and the mold are not thermally coupled.

Physical considerations about the equivalent thermal resistance dictate the value of , and that the comments about the value of in Heat Transfer and Contact (Imposed Temperature) also apply to conjugate heat transfer.