Exergy analysis of multi-effect water–LiBr absorption systems: From half to triple effect

Abstract

An exergy analysis, which only considers the unavoidable exergy destruction, is conducted for single, double, triple and half effect Water–Lithium bromide absorption cycles. Thus, the obtained performances represent the maximum achievable performance under the given operation conditions. The coefficient of performance (COP), the exergetic efficiencies and the exergy destruction rates are determined and the effect of the heat source temperature is evaluated. As expected, the COP increases significantly from double lift to triple effect cycles. The exergetic efficiency varies less among the different configurations. In all cycles the effect of the heat source temperature on the exergy destruction rates is similar for the same type of components, while the quantitative contributions depend on cycle type and flow configuration. Largest exergy destruction occurs in the absorbers and generators, especially at higher heat source temperatures.

The authors also wish to acknowledge support of this research work from the Spanish Ministry of Education and Science (projects DPI2002- 00706, DPI2008-04099, PHB2008-0090-PC and BFU2008-863 00196) and the Spanish Ministry of External Affairs (projects A/ 8502/07, HS2007-864 0006 and A/020104/08).