HITTING THE BOUNDS OF CHEMISTRY: LIMITS AND TRADEOFFS FOR LOW-GWP REFRIGERANTS

摘要

We explore the possibilities for low-GWP refrigerants through two approaches. First, we explore theperformance of hypothetical refrigerants to define the limits of what is allowed by thermodynamics. In thesecond approach, we apply property estimation methods and screening parameters to identify best candidatesfrom a database of 100 million chemicals. We find that the optimal thermodynamic characteristics are quiterare; additional fluids are eliminated because they are unstable or highly toxic. We then estimate the cycleperformance (considering the basic cycle, economizer cycle, and a cycle with a liquid-line/suction-line heatexchanger) of the remaining candidates and apply efficiency as an additional screening criterion. The endresult is not thousands of low-GWP candidates, but a handful, and even these present tradeoffs. We arguethat these represent all the viable candidates for single-component, medium- and high-pressurerefrigerants—in other words, we have hit the limits of what chemistry allows.