Hybrid Compression-Absorption Chiller Driven by low Temperature Waste Heat: Modelling and Analysis (Pages: 11-22)

Romain Loeb1, Mikhail Sorin1 and Brice Le Lostec2

1Université de Sherbrooke, Géniemécanique, Sherbrooke, QC, Canada J1K 2R1 and 2LTE-Hydro-Québec, 600 av. de la Montagne, Shawinigan, QC, Canada G9N 7N5



Abstract: The aim of this study is to model and investigate the concept of a hybrid ammonia-water absorption chiller. Its particularity is having a compressor that creates an intermediate pressure at the desorber. This modification should increase the flexibility of the machine, allowing the recovery of lower temperature waste heat. A preliminary simulation was based on a single stage commercial 10 kW ammonia-water absorption chiller. An experimental study was completed to validate the numerical model of a traditional single stage absorption chiller. The comparative energy and exergy analysis of the hybrid and traditional absorption chillers was undertaken. Due to the reduction of the waste heat temperature for the hybrid chiller, the exergy efficiency increases by 34%. A 38% reduction of the UA coefficient (the product of overall heat transfer coefficient and heat exchanger area), for the same waste heat temperature and refrigeration power, is shown for the hybrid system compared with the traditional one. The theoretical lower bound of the waste heat temperature to be used to drive a hybrid cycle is 42 °C. An economic analysis shows that a hybrid cycle is initially more expensive but quickly becomes profitable compared to a gas-fired absorption machine.

Keywords: Ammonia-water Refrigeration, Hybrid Cycle, Modelling, Experimental Validation, Exergy Analysis, Economic Analysis.