The operation and performance of any refrigeration system depends mainly on the choice of the working fluids. Since classical compounds like the chlorofluorocarbons and hydrochlorofluorocarbons are now completely phased out, substitutes are required. In previous works, a method for computer-aided design and test of alternative compounds were presented. Relevance and importance of the group contribution concept for such methods are investigated, considering two model systems, namely, the ejecto-compression and absorption refrigeration machines with specific configurations like insertion of a distillation column and elimination of the condenser, respectively. The obtained results allow extending this approach to model other complex refrigeration systems.