Search of new A2 refrigerant mixtures. Possibilities of reducing hydrocarbons flammability via mixtures.

The latest efforts to search new refrigerant blends have been generally focused on locating A1 refrigerants. However, little research has been done related to the lower (A2) and mild (A2L) flammability refrigerants blends, despite the fact that the use of these mixtures would allow to increase the maximum refrigerant charge from 500 g to 1200 g and, therefore, the cooling capacity of the systems. In this work, the search of A2 low-GWP mixtures is addressed. Concretely, the aim is to know the possibilities of forming A2 blends with a GWP below 150 by mixing hydrocarbons with less flammable refrigerants. To determine the flammability classification, an approach based on Linteris' et al. work is used, updating it to the A3/A2 limit. To determine the limit composition, for each mixture a fractionation analysis was conducted, following ASHRAE 34 requirements. Results show that there are a few possibilities that can meet the requirements. Finally, resulting mixtures were contrasted using energetic criteria. It has been concluded that no blend with an A2 or A2L component with hydrocarbons is of interest, since the use of pure components is preferable to any blend.