Novel multifunctional open absorption heat pump system with compressed air dryer assisted preliminary flash regeneration-An industrial application

Abstract

Industrial exhausts release a tremendous amount of latent heat in form of moist flue gases and at the same time a significant amount of energy is consumed by the industrial process involving compressed dry air of low humidity levels. The open absorption technology can efficiently recover this latent waste heat and is also capable to provide dry air. This study presents a novel multifunctional open absorption system coupled with a compressed air dryer and is characterized by providing a preliminary flash regenerator driven by the heat recovered from the compressed air which can benefit the further regeneration at low heat source temperatures. The validated process and thermodynamic models of this novel multifunctional system are developed and a parametric study is carried out to assess its thermal performance with the effect of important operational parameters. The parametric results indicate that the system is capable to provide compressed dry air for industrial applications at low humidity level of 1.05 g/kg (with dewpoint temperature of −16.3 °C) and also can provide hot water for 184.45 kW heating capacity by operating at a performance coefficient of 1.945 and heat recovery efficiency of 91.95%. The system is also capable to recover the water at the rate of 118.8 kg/h with 92.8% recovery efficiency by operating at 120 °C regeneration heat source and 600 kPa pressure in the dryer. The drying performance of dryer can be enhanced significantly by increasing the operating pressure and by improving the solution inlet parameters. The outlet humidity of air can be decreased up to 0.27 g/kg (with dewpoint temperature of −28.34 °C) by increasing the solution concentration up to 61% at 32 °C temperature and operating pressure of 800 kPa. Moreover, the required heat source temperature in main regenerator can be decreased from 120 °C to 113 °C in effect of the increased air pressure, when the recovered heat from compressed air dryer is capable enough to provide 13.2–42.7% preliminary solution regeneration.