Experimental evaluation of a low-power direct air-cooled double-effect LiBr–H2O absorption prototype

This paper describes a new small air-cooled double-effect LiBr–H2O absorption prototype directly powered by fuel and discusses the experimental findings for some tests carried out in Madrid in 2007, with natural gas as energy source. The prototype, which has been designed to supply 7kW of cooling power, was able to chill water up to 7–18°C under extreme outdoor temperatures. A new flat-sheet adiabatic absorber was used allowing it to operate at outdoor temperatures about 45°C without any sign of crystallization. A mean daily coefficient of performance (COP) of about 1.05 was obtained. Since this absorption machine does not need cooling tower, there is neither water consumption nor Legionella pollution. Moreover, it is a quite compact unit. The ratio of cooling power over volume is about 6.0kW/m3, while for the only air-cooled absorption chiller, Rotartica 045v, in the marked until 2009 this ratio is 4kW/m3. When comparing with electric chillers presently on the market, this prototype was found to have a cooling cost approximately 15.9% higher and an environmental impact 16.7% lower. The absorption prototype is a more environmentally friendly solution as it does not emit fluorinated refrigerants.