Analysis of [hmim][PF6] and [hmim][Tf2N] ionic liquids as absorbents for an absorption refrigeration system

• Two ionic liquids were used as absorbents in an absorption refrigeration cycle.
• Redlich–Kwong equation-of-state and two-phase pressure drop used to compute the thermodynamic conditions and performance.
• Anion structure of ionic liquid is important in determining solubility of refrigerant and overall performance.

The performance of ionic liquids, [hmim][PF6] and [hmim][Tf2N], as absorbents in an absorption refrigeration system with 1,1,1,2-tetrafluroethane (R134a) as the refrigerant was modeled. The Redlich–Kwong equation-of-state and two-phase pressure drop model were used to compute the thermodynamic conditions and performance of the working fluid pairs. The effects of the desorber and absorber temperatures, solution heat exchanger, and accessibility of waste heat on the system performance were evaluated. [hmim][Tf2N] showed higher system efficiency compared to [hmim][PF6] except for cases where the solubility difference between the absorber and desorber converged to zero.