Screening criteria for ILs used in NH<sub>3</sub> based absorption heat pump systems

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Abstract

This paper describes a properties-optimization work for the working
fluids in NH3 / ionic liquid (ILs) based single-effect absorption heat
pumps. The optimum parameters of the IL can be used as criteria in
screening task-specified ILs, which play the role of absorbents, in
absorption heat pumps. First, a 8-parameter thermodynamic model to
calculate performances of a single-effect absorption heat pump cycle was
proposed, which is based on the non-random two-liquid (NRTL) activity
coefficient model for the vapor pressure and a linear function for the
heat capacity. Then, experimental data on the vapor-liquid equilibrium
(VLE) of solutions and heat capacities of the pure ILs were reviewed and
fitted to obtain ranges of those parameters. Within certain limits, the
values of parameters were optimized in the following step using the
above proposed mode. The objective is a maximum system performance. The
optimized ILs have low molecular weights, low specific heats and have
high absorption capabilities.