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The purpose of the study is to optimize the initial conditions of the molding process of a multicomponent mixture into a refrigerator cabinet. Polyurethane foaming has been studied with different starting compositions and temperatures of the initial mixture. The kinetic mechanism has involved four reactions and species species. Using a standard recipe, the chemical kinetics and the numerical implementation have been first validated against the experimental values of the filling time and the density of the final foam. Thereafter, 11,763 different initial conditions are calculated. The results put in evidence that the filling time can be reduced without any significant change in the precursors of the rigidity of the foam. The final temperature of the foam has always remained lower than the limiting temperature so that thermal material deformations in the walls of the cabinet can be avoided. Increasing the physical blowing agent mass fraction beyond the standard recipe does not appear to be a useful option.

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The local dynamics of chemical kinetics at different phases of the nitriding process have been studied. The calculations are performed under the conditions where the temperature and composition data are provided experimentally from an in-service furnace. Results are presented in temporal variations of gas concentrations and the nitrogen coverage on the surface. It is shown that if it is available in the furnace, the adsorption of the N 2 gas can seemingly start at temperatures as low as 200°C. However, at such low temperatures, as the diffusion into the material is very unlikely, this results in the surface poisoning. It becomes clear that, contrary to common knowledge, the nitriding heat treatment with ammonia as a nitrogen-providing medium is possible at temperatures like 400°C. Under these conditions, however, the presence of excess amounts of product gas N 2 in the furnace atmosphere suppresses the forward kinetics in the nitriding process. It seems that the best operating point in the nitriding heat treatment is achieved with a mixture of 6% N 2 . When the major nitriding species NH 3 is substituted by N 2 and the N 2 fraction increases above 30%, the rate of the forward reaction decreases drastically, so that there is no point to continue the furnace operation any further. Hence, during the initial heating phase, the N 2 gas must be purged from the furnace to keep its fraction less than 30% before the furnace reaches the temperature where the reaction starts.