Thermodynamic study of the new working fluid and design/ operation of the advanced cycle for absorption heat pump

Abstract

This study was focused on the absorption heat pump technology, especially on the absorption cooling systems (absorption chiller) which use the lithium bromide-based solutions as working fluids. New working fluid development covering the related thermodynamics, advanced cycle design/ system operation, and the investigation of mass transfer enhancement were included in the study. Conventional absorption heat pumps (cooling/ absorption chillers) which are commonly used for building air-conditionings and industrial applications includes a water cooling tower to efflux the heat to outdoor. In order to lower the size of machine and to use the absorption systems for domestic applications, the water cooling tower have to be removed and a direct air-cooled machine have to be developed. However, the air-cooled absorption cooling machine cannot be easily constructed by using the present working fluid (aqueous lithium bromide solution) due to the crystallization problem. Hence, a new working fluid have to be developed and the work essentially includes various experimental /theoretical and thermodynamic /thermophysical studies on the working fluid. In this study the lithium bromide + lithium iodide + 1,3-propanediol + water (LiBr/LiI mole ratio = 4 and (LiBr + LiI)/$HO(CH_2)_3OH$ mass ratio = 4) solution was selected as a potential working fluid for the air-cooled absorption chiller. The solubilities, vapor pressures, heat capacities, differential heats of dilution, densities, and viscosities of a new working fluid were measured at the extensive concentration and temperature ranges. A new data set of individual property was fitted with a proper regression equation and the Duhring (P-T-X) and enthalpy-concentration (H-T-X) diagrams were constructed by using the measured thermodynamic properties. A cycle simulation for a double-effect series-flow absorption chiller was carried out at several absorber and condenser conditions. The air-cooled absorption chiller using the new w...