Thermodynamic and Heat Transfer Characteristics in Single Stage NH3-H2O Absorption Heat Pump

In this paper, the thermodynamic behavior of the ammonia-water mixture at different pressures and range of ammonia concentration, ξ, after rectifier of 0.9000 to 0.9999 has been theoretically studied. At ξ = 0.9000 and saturation pressures of 75 and 0.5 bar, the temperature glides are 64.4 and 81.21°C respectively, while this glides are 0 and 16.1°C at ξ = 0.9999 and the same pressures. This mixture properties affects considerably the absorption system performance and the design of the rectifier as well as other absorption components. The effects of ξ, mass fraction spread, Δξ, specific solution circulation ratio, f, and pressure ratio, Rp, on the heat transfer coefficients during the condensation and the evaporation are investigated. ξ has insignificant effect on the evaporation heat transfer coefficient, but has a little effect on the condensation and the absorber heat transfer coefficients. Δξ and f have considerable effects on the heat transfer coefficient for different absorption heat pump components. Rp has pronounced effect on the evaporation heat transfer coefficient; while has a slight effect on the condensation and the absorber heat transfer coefficients. For Δξ > 0.18, the effect of Rp may be eliminated on the heat transfer coefficient in the absorber.