New Experimental Vapor-Liquid Equilibria Data and Thermodynamic Modelling for R1234yf/propane/R32 as low-GWP Mixtures in Heat Pump Applications

This paper presents new experimental results for the Vapor – Liquid Equilibria of binary mixtures of R1234yf and propane at 277 and 313 K. The newly collected data are then used, in combination with other existing data retrieved from the literature, to calibrate the Peng-Robinson Equation of State with suitable accuracy for domestic vapour compression heat pump cycles simulations. After calibration, the Equation of State is applied to numerical simulations, in Aspen Plus, aimed at finding the optimal refrigerant composition, among ternary mixtures containing R1234yf, propane and R32. Results identify a Pareto curve where the optimal mixtures (with flammability lower or equal to A2L and GWP < 500) are represented in terms of two contrasting objectives: COP and the volumetric heating effect. Ternary mixtures containing propane and R1234yf respectively in the range 0÷12%mass and 18÷30%mass are Pareto optimal: the mixture with the best COP (2.7% lower than R410A one) is the binary pair R32 = 70% + R1234yf = 30%, a composition very close to the one of the commercial refrigerant R454B. On the other hand, the mixture with the largest volumetric effect (6.5% higher than R410A one) is the ternary blend R32 = 70% + R1234yf = 18% + propane = 12%. This study confirms that is quite challenging to find R410A replacements featuring at the same time reasonable heating capacity and a COP not lower than R410A one.