The 2016 Kigali Amendment to the 1987 Montreal Protocol aims to reduce the emissions from high-global warming potential (GWP) hydrofluorocarbon (HFC) refrigerants by 80-85% by 2045. It is estimated that this may prevent 0.5C of global temperature rise. R134a is a commonly used HFC, often found in air conditioning units. While it grew in popularity following the banning of high ozone depletion potential (ODP) chlorofluorocarbons (CFCs), its high GWP renders its continued use incompatible with the requirements of the Kigali Amendment. Therefore, it is necessary to design new refrigerants to replace it.
Computer-aided molecular design (CAMD) has attracted significant attention in the literature for its potential to quickly design suitable molecules to a specific goal. In this study, group contribution methods are employed for property estimation and the BARON algorithm is utilised to solve an MINLP problem, minimising the ratio of heat capacity to heat of vapourisation. Bromomethane is identified as the most suitable molecule with an objective function value of 3.176, though this is already banned under the Montreal protocol. Trifluoromethanamine is identified as the second best, with an objective function value of 3.342. Additional constraints to limit the inclusion of banned molecules, high GWP molecules and highly flammable molecules would improve this fomrulation to yield more suitable molecules.
The .gms file should run out of the box in GAMS IDE with a valid license.