Exergy Performance Optimization of an Irreversible Closed Intercooled Regenerative Brayton Cogeneration Plant

Abstract

An irreversible closed intercooled regenerative Brayton heat and power cogeneration plant model coupled to constant-temperature heat reservoirs is established using finite time thermodynamics. On the basis of exergy analysis, the performance of the plant is investigated and optimized. Analytical formulae about dimensionless exergy output rate and exergy efficiency are deduced. The two cases with fixed and variable total pressure ratio are studied, and the intercooling pressure ratio and the total pressure ratio are optimized. Meanwhile, the influences of the irreversible compression and expansion losses, the effectivenesses of the intercooler, regenerator, and consumer-side heat exchanger and the consumer-side temperature on the dimensionless exergy output rate and corresponding exergy efficiency, the optimal intercooling pressure ratio and the optimal total pressure ratio are analyzed by detailed numerical examples. Then, the optimization is carried out further by searching for the optimal intercooling pressure ratio, optimal total pressure ratio and optimal heat conductance distributions among the hot-, cold- and consumer-side heat exchangers, the regenerator and the intercooler together for the fixed total heat conductance. The characteristics of the optimal heat conductance distributions versus irreversible losses and consumer-side temperature are researched. In the analysis and optimization, it is both found that there exists optimal consumer-side temperature.