Solar Fired, Compressor Assisted Absorption Chillers

This paper presents the results of a thermodynamic and heat transfer analysis of solar fired, compressor assisted absorption chillers. The objectives are to determine and evaluate the feasibility of using vapor compressors to lower the operating temperature of the primary generator, simplify the maintenance and reduce the cost of solar/waste heat powered absorption HVAC systems. The nominal generator temperature in a single effect absorption chiller is 88°C and the coefficient of performance is approximately 0.8. A standard double effect chiller requires the high temperature generator to operate at about 150°C. The nominal COP of a double effect cycle is 1.2 to 1.4. Various modifications have been proposed to lower the operating temperature of the primary generator. One such modification is to add a vapor compressor to the basic cycle. Computer models that simulate the effect of vapor compressors at selected locations in single and double effect LiBr/H₂O absorption chillers have been developed. Two locations were modeled for single effect chillers and three locations for double effect chillers. The best results were obtained for a double effect chiller with the compressor located between the high and low temperature generators.