Performance implications of chemical absorption for the carbon-dioxide-cofluid refrigeration cycle

In a CO2-cofluid refrigeration cycle, CO2 condensation and evaporation are replaced by absorption into and out of a non-volatile liquid (“cofluid”). This paper investigates whether the refrigeration performance of such a cycle can be improved in theory by using a cofluid that exhibits chemical affinity for CO2. A Langmuir-like model is used to represent the thermodynamics of CO2 absorption, and steady-state performance metrics are computed by solving a set of physically based equations. Chemically absorbing cofluids having sufficiently strong affinity for CO2 are predicted to have higher specific cooling capacity and higher coefficient of performance (COP) than physical cofluids and also higher COP than transcritical CO2. The useful range of chemical absorption strength is limited by practical considerations like desirable operating pressures.