Heat pump working fluid selection—economic and thermodynamic comparison of criteria and boundary conditions

The study analyzes approaches for the selection of working fluids for the design of heat pump cycles based on numerical modeling. Different approaches for defining economically reasonable assumptions for the heat exchanger dimensioning were compared with respect to the identification of thermodynamically and economically promising working fluids.

It was revealed that comparisons based on fixed heat exchanger investment do not exploit the performance of potentially high performing fluids. The approach of defining the pinch point temperature differences in the heat exchangers was found to provide results that were closest to the economic optimum, while being readily applicable in screening procedures.

The method was demonstrated by two examples using excess heat from data centers for district heating supply. For the two cases, zeotropic mixtures were identified that could improve the thermodynamic performance by 30%–35% while achieving a reduction of levelized cost of heat of 8% to 10%.