Exergy Analysis of an Industrial Waste Heat Recovery Based Cogeneration Cycle for Combined Production of Power and Refrigeration

Abstract

In this paper, a novel industrial waste heat recovery based cogeneration is proposed for the combined production of power and refrigeration. The system is an integration of Rankine power cycle and absorption refrigeration cycle. A thermodynamic analysis through energy and exergy is employed, and a comprehensive parametric study is performed to investigate the effects of exhaust gas inlet temperature, pinch-point, and gas composition on energy efficiency, power-to-cold ratio, and exergy efficiency of the cogeneration cycle and exergy destruction in each component. The variation in specific heat with exhaust gas composition and temperature is accounted in the analysis for further discussion. The first-law efficiency decreases while power-to-cold ratio and exergy efficiency increase with increasing exhaust gas inlet temperature. The parameters, such as power-to-cold ratio and second-law efficiency, decrease while first-law efficiency increases with increasing pinch-point. Exergy efficiency significantly varies with gas composition and oxygen content of the exhaust gas. Approximating the exhaust gas as air, and the air standard analysis leads to either underestimation or overestimation of cogeneration cycle performance on exergy point of view. Exergy analysis indicates that maximum exergy is destroyed during the steam generation process; which represents around 40% of the total exergy destruction in the overall system. The exergy destruction in each component of the system varies significantly with exhaust gas inlet temperature and pinch-point. The present analysis contributes further information on the role of composition, exhaust gas temperature, and pinch-point influence on the performance of a waste heat recovery based cogeneration system from an exergy point of view.