Performance analysis for a real closed regenerated Brayton cycle via methods of finite-time thermodynamics

Abstract

Performance analysis of a real power cycle has been performed using finite-time thermodynamics. The analytical formulae about the relations between power output and pressure ratio, and between efficiency and pressure ratio of a real closed regenerated Brayton cycle coupled to variable-temperature heat reservoirs are derived. In the analysis, the irreversibilities involve the heat resistance losses in the hot- and cold-side heat exchangers and the regenerator, the irreversible (non-isentropic) expansion and compression losses in the turbine and compressor, and the pressure drop loss in the pipe and system. The optimal performance characteristics of the cycle may be obtained by optimising the distribution of heat conductance or heat-transfer surface areas among two heat exchangers and regenerator, and the matching between working fluid and heat reservoirs. For the specified heat reservoir conditions, the power output is dependent on the effectiveness of the regenerator, and there exists an optimal matching among the effectivenesses of the hot- and cold-side heat exchangers and the regenerator. The influences of the effectiveness of the regenerator, the effectiveness of the hot- and cold-side heat exchangers, the efficiencies of the turbine and compressor, the pressure recovery coefficient and the inlet temperature ratio of the heat reservoirs on the power output and efficiency of the cycle are analysed by detailed numerical examples.