We develop a mathematical model of nonisothermal flow of non-Newtonian media with a power reological law in a plane channel in accounting for the energy dissipation, the effect of constant sliding at walls, and the dependence of viscosity on temperature, pressure, and character of transformation. The model developed is applied to description of the influence of different factors on kinetics and heat exchange during the flow of thermosetting plastics and rubber mixtures in pouring channels of molds for pressure-die casting. Based on a solution obtained for the profiles of temperature and speed, as well as for the pressure difference and the Nusselt criterion, the calculations are made in order to estimate the influence of different factors on the main characteristics of flow and heat exchange in reologically complicated reacting media. In the case when the temperature of the channel walls is much higher than that of the flowing out polymer, the processes of heat conductivity and heat dissipation contribute to the mixture heating in the channel.