Performance analysis of a novel double stage multifunctional open absorption heat pump system: An industrial moist flue gas heat recovery application

Rising industrial energy consumption and waste heat in moist flue gas exhausts are the key scientific issues. A potential hybrid system with efficient heat recovery technology can fulfill the industrial energy demand for dehumidification, heating and cooling applications by utilizing the waste latent heat. The main objective of this study is to present a multifunctional hybrid system for double stage open absorption cycle to recover the latent heat from the exhaust moist flue gas for heating and to dehumidify the ambient humid air for cooling applications by operating at low-grade heat source. The validated thermodynamic models for energy and exergy analysis are developed for its performance optimization and to conduct a comparison with single stage system. The operating inlet parameters are varied to analyze the performance of both systems. The parametric study results showed that the double stage system can operate for a wider moist gas humidity range such as 0.054-0.2 kg/kg at lower regeneration heat source of 96.3celcius with varying thermal performance of 1.24-2.39 as compared to the single stage system which operates for 0.118-0.2 kg/kg and at 112.3-153.8celcius. Furthermore, this hybrid system is capable to provide heating effect of 280.1 kW at thermal performance of 1.73 and 9.85 kW cooling capacity while operating at 113.7celcius heat source temperature. The thermal performance of system is related to the operating pressure in low pressure generator and can be increased 8-11% when pressure is increased from 25 kPa to 35 kPa. However, the cooling capacity is found to be sensitive only to the absorbers and the dew point cooler. The exergy performance results indicate that the exergy efficiency of double stage system is 3-16% higher as compared to single stage with effect of regeneration temperature and varies from 46.2 to 58.63%. Moreover, the highest exergy destruction is found to be in regenerators which accounts for about 49-51% of overall destructed exergy.