Optimal refrigerant mixture in single-stage high-temperature heat pumps based on a multiparameter evaluation
Adrián Fernández-Moreno, Adrián Mota-Babiloni, Pau Giménez-Prades, Joaquín Navarro-Esbrí
Abstract
High-temperature heat pumps (HTHPs) are compression systems that convert residual heat to high-grade heat used in several industrial applications. Refrigerants for HTHPs are still not explored, and most studies consider only pure refrigerants. This study carries out a general screening of binary and ternary mixtures for HTHPs through a multiparameter optimization based on low global warming potential (GWP) refrigerants that are feasible for operating at higher temperatures. The proposed methodology considers several parameters such as coefficient of performance, volumetric heating capacity, flammability, GWP, and perfect glide matching. The blends were required to have a critical temperature above 150 °C and to provide high energy performance to diminish the indirect carbon footprint. No ideal mixture was found for every parameter, so a trade-off solution was required. The most critical variable was flammability, reducing the coefficient of performance significantly if the ASHRAE Std 34 A1 restriction had to be fulfilled. Finally, different mixtures are given as the bests based on the main optimizable parameter. The most promising ones which comply with the environmental restriction were R-1233zd(E) and R-1336mzz(Z) based mixtures.