Analysis of an integrated absorption/liquid desiccant air conditioning system

Abstract

This paper presents an analysis of an integrated absorption cooling machine with a water heat-driven liquid desiccant dehumidifier for air conditioning systems. The waste heat recovery unit operates between the condenser of the absorption machine and the liquid absorbent regenerator. A mathematic model for the liquid desiccant unit is described and the governing equations are solved. The model is applied to the dehumidifying chamber (DHC) and the regeneration chamber (RGC) in a coupled mode. Results showed that the cooling water temperature and the transfer potentials are the controlling factors affecting the DHC while the mass transfer potential and the absorbent air mass ratio are dominant in the RGC. For a 42°C/31°C DBT/WBT outside air, the integrated system has an estimated overall COP of 1.21 for a supply of hot water at 140°C fed to the generator and a cooling water supply at 30°C. This COP is 50% higher than the COP for the absorption chiller alone (0.81). The overall COP is higher than that for a double effect absorption machine if the outside air conditions and the cooling water effects are taken into consideration. Moreover, a LiBr-H 2O solution is used at both ends of the system, which would reflect some savings in both capital and running cost of the air conditioning unit.