(247n) Molecular Dynamics Simulations of Mixtures of Refrigerants and Deep Eutectic Solvents

Molecular dynamics simulations of mixtures
of refrigerants and deep eutectic solvents

Rubaiyet Abedin, John C. Flake and Francisco R. Hung

Cain Department of Chemical Engineering, Louisiana
State University, Baton Rouge, LA 70803

Heating
and cooling buildings in the U.S. consumes an enormous amount of energy (>10
quadrillion BTU), and is responsible for adding ~1 billion metric tons of CO₂
in the earth's atmosphere every year. Much of this energy is used as
electricity in vapor-compression systems; however, this technology is mature
and only evolutionary improvements are expected in the near future. Remarkably,
a few studies have shown that several common ionic liquids (ILs) can be
combined with standard fluorocarbon refrigerants for use in absorption refrigeration
systems that use waste heat at relatively low temperatures (~ 100 °C).
Nevertheless, there is limited understanding (and data) on the VLE behavior of
these systems, and only one working example of an absorption system using this
type of mixture. Furthermore, deep eutectic solvents (DESs), a relatively new
class of solvents, share many of the properties of ILs while being considerable
cheaper and mostly nontoxic. A fundamental understanding of how the chemical
structure of the different species affects the solubility of fluorocarbons in a
DES is crucial to design mixtures suitable for use in absorption refrigeration
systems that use solar energy or waste heat. In this study, we used molecular
dynamics (MD) simulations to study mixtures of a conventional fluorocarbon
refrigerant, 1,1,1,2-tetrafluoroethane (R134a) with two conventional DESs (1:2
choline chloride/urea and 1:2 choline chloride/glycerol). Results for the
Henry's law constant of R134a in the two DESs as a function of temperature are
reported and analyzed in terms of molecular level properties (radial
distribution functions, relevant interaction energies).