Exergy Analysis of a Co-generation Cycle for Combined Production of Power and Refrigeration

Authors:

Rajesh Kumar (Amity School of Engineering and Technology, GGSIPU New Delhi)

Abstract:

In this paper, a noval industrial waste heat recovery-based cogeneration is proposed for the combined yielding of power and refrigeration.
The cycle is an integration of Rankine power cycle and absorption refrigeration cycle. Combined first
and second law approach is applied and computational analysis is performed to investigate the
effects of exhaust gas inlet temperature, pinch point, and gas composition on first law efficiency,
power to cold ratio, and second law efficiency of the cogeneration cycle and exergy destruction in
each component. The variation in specific heat with exhaust gas composition and temperature are
accounted in the analysis and results. The first-law efficiency decreases while power to cold ratio
and second law-efficiency increases with increasing exhaust gas inlet temperature. Power to cold
ratio and second law efficiency decreases while first-law efficiency increases with increasing pinch
point. Second law efficiency is significantly varying 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 second law 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 second law point of view.