Exergetic performance optimization of an endoreversible variable-temperature heat reservoirs intercooled regenerated Brayton cogeneration plant

Abstract

An endoreversible intercooled regenerative Brayton cogeneration plant model coupled to variable-temperature heat reservoirs is established. On the basis of the exergetic analysis, the performance of the plant is investigated using finite time thermodynamics. Analytical formulae about dimensionless exergy output rate and exergy efficiency are deduced. By taking the maximum exergy output rate and exergy efficiency as the objectives, the heat conductance allocations among the hot-, cold- and consumer-side heat exchangers, the intercooler and the regenerator, the choice of intercooling pressure ratio are optimized by detailed numerical examples, and the corresponding exergy efficiency and exergy output rate are obtained. When the optimization is performed further with respect to the total pressure ratio of the cogeneration cycle, double-maximum exergy output rate and double-exergy efficiency are obtained. The effects of the total heat conductance, the consumer-side temperature and the thermal capacitance rate matching between the working fluid and the heat reservoirs on the double-maximum dimensionless exergy output rate and the double-maximum exergy efficiency are analyzed, it is found that there exists an optimal consumer-side temperature which leads to a thrice-maximum dimensionless exergy output rate, and there exist optimal thermal capacity rate matchings between the heat reservoirs and the working fluid, respectively, which lead to a thrice-maximum dimensionless exergy output rate and a thrice-maximum exergy efficiency.