22 May 2008

THERMODYNAMIC COMPARISON OF WATER BASED WORKING FLUID COMBINATIONS FOR VAPOUR ABSORPTION HEAT TRANSFORMERS


Vapour absorption heat transformer (VAHT) is a promising alternative, among
various methods used for waste heat up gradation. The performance and cost of the VAHT
are strongly dependent on the refrigerant, absorbent and their mixtures. In this paper,
thermodynamic comparisons of fifteen water-based working fluids have been made based on
both energy and exergy efficiencies. Simulation is carried out with constant waste heat input.
It is found that H2O-(LiCl+LiNO3) system produces the highest absorber heat output for given
waste heat input than other working fluid combinations followed by H2O-LiBr system with a
gross temperature lift of 30oC. The Coefficient of performance and Exergetic efficiency are
higher for these combinations compared to other water based combinations. The selection of
best working fluid considering various operating conditions has been outlined and
conclusions drawn based on performance are presented.