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Highlights

Thermodynamic properties of LiNO3-[MMIM][DMP]/H2O were measured systematically.

Thermodynamic performance of an AHP cycle using LiNO3-[MMIM][DMP]/H2O was analyzed.

LiNO3-[MMIM][DMP]/H2O has potentials used as an alternative working pair.

Abstract

In this work, LiNO3-[MMIM][DMP] (1,3-dimethylimidazolium dimethylphosphate)/H2O was suggested as a potential working pair for a vacuum boiler driven waste water-source absorption heat pump (AHP) cycle. The crystallization temperature, vapor pressure, density, viscosity, specific heat capacity, and specific enthalpy for this ternary system were measured systematically and correlated by the least-squares method. Based on the experimental data, the performance of an AHP cycle was calculated at condensation temperatures from 48 °C to 58 °C and compared with that using LiNO3/H2O and LiBr/H2O under the same operation conditions. The results show that LiNO3-[MMIM][DMP]/H2O has a larger temperature operating range compared to LiNO3/H2O and has a lower generation temperature compared to LiBr/H2O. The coefficient of performance (COP) is slightly less than that for LiNO3/H2O and LiBr/H2O, but it is still above 1.77. The exergetic coefficient of performance (ECOP) for LiNO3-[MMIM][DMP]/H2O varies from 0.57 to 0.62, which is located between that for LiNO3/H2O and LiBr/H2O. LiNO3-[MMIM][DMP]/H2O shows some potentials as an alternative work pair for an AHP cycle using a low temperature driving heat source such as vacuum boiler or solar collector.

Keywords

Absorption heat pump

Working pair

Ionic liquid

Thermodynamic properties

COP and ECOP

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