A THERMODYNAMIC ANALYSIS OF REFRIGERANTS. Ⅱ. POSSIBILITIES AND TRADEOFFS FOR LOW-GWP REFRIGERANTS

摘要

We explore the possibilities for refrigerants having low global warming potential (GWP) by use of two distinct approaches. In a companion paper (Domanski et al., 2013), we evaluate the effect of a refrigerant’s fundamental thermodynamic parameters on its performance in the vapor compression cycle; this defines the limits of what is thermodynamically possible for a refrigerant and the optimal thermodynamic parameters needed to approach those limits. In the second approach, presented here, we examine more than 56 000 chemical compounds from a public-domain database. A subset of about 1200 candidate fluids is identified by applying screening criteria to estimates for GWP, flammability, stability, toxicity, and critical temperature. Methodologies for this screening have been presented in earlier works and are summarized here. The fluids with critical temperatures between 300 K and 400 K (i.e., those that could be used in current types of equipment with minor modifications) number 62. The fluids include halogenated olefins; compounds containing oxygen, nitrogen, or sulfur; as well as carbon dioxide. We discuss the tradeoffs presented by these 62 candidates, considering their thermodynamic properties as well as their stability and toxicity characteristics, to the extent that such data are available. No fluid is ideal in all regards-all have one or more negative attributes: poor thermodynamic properties, acute or chronic toxicity, chemical instability, low to moderate flammability, or very high operating pressures.