Computational Design of New Refrigerant Fluids Based on Environmental, Safety, and Thermodynamic Characteristics

We present a systematic search for new classes of refrigerants
that would possess low values of global warming potential (GWP), along
with low- to moderate flammability and suitable thermodynamic characteristics.
We have developed new methods for estimating, solely from the molecular
structure, the radiative efficiency (RE, a measure of radiative climate
forcing) and atmospheric lifetime; the combination of RE and lifetime
yields an estimate of the GWP. We also developed an estimate of the
lower flammability limit (LFL) based on the enthalpy of formation.
These estimation techniques, along with a previously developed technique
for estimating critical temperature (Tc), are applied to a library of over 56 000 candidate molecules.
We select fluids with GWP < 200; 300 K < Tc < 550 K; and LFL > 0.1 kg·m–3.
Filters for toxicity and chemical stability based on functional groups
are also applied to arrive at 1234 candidates for further study. The
candidates that would be suitable for use in present types of refrigeration
equipment (those having critical temperatures less than 400 K) are
dominated by halogenated alkenes; additional chemical classes, including
halogenated ethers and cyclic compounds, are identified among fluids
with higher critical temperatures.