Power optimization of an irreversible regenerative Brayton cycle with isothermal heat addition

Year 2015, Volume: 1 Issue: 4, 279 - 286, 01.04.2015

Rajesh Kumar S C Kaushik Raj Kumar

https://doi.org/10.18186/jte.44164

Cited By: 11

Abstract

An irreversible regenerative Brayton cycle model with two heat additions is analyzed here. The external irreversibilities due to finite temperature difference and internal irreversibilities due to fluid friction losses in compressor / turbine, regenerative heat loss, pressure loss are included in the analysis. Power output of the model is obtained and thermodynamically optimized. A detailed analysis shows that with judicious selection of parameters viz. efficiency of turbine and compressor, effectiveness of various heat exchangers, isothermal pressure drop ratio, pressure drop recovery coefficients and heat capacitance rate of the working fluid, the power output of the model can be made to reach its highest possible value. It is well proven with the obtained results that induction of two heat additions significantly enhances model efficiency above 20% as compared to conventional gas power plants. The power output remains constant while the corresponding thermal efficiency increases as regenerator side effectiveness is increased. This meticulous result is different from those obtained by previous researchers. The model analyzed in this paper gives lower values of power output and corresponding thermal efficiency as expected and replicates the results of an irreversible regenerative Brayton cycle model discussed in the literature at pressure recovery coefficients of α=α2=1. regenerative Brayton cycle based on endoreversible and irreversible configuration with the application of isothermal heat additions in the view of finite time thermodynamic approach. Wang et al. [14] applied the hypothesis of finite time thermodynamics to analyze an irreversible closed intercooled regenerated Brayton cycle and optimized the intercooler pressure ratio for optimum power and corresponding efficiency. Kaushik et al. [15] performed a thermodynamic analysis of an irreversible regenerative Brayton cycle with isothermal heat addition and optimized the power output in context with working medium temperature. They observed an improvement of 15% in the thermal efficiency of Brayton cycle with heat addition at constant temperature. Chen et al. [16] analyzed power and efficiency of an endoreversible closed intercooled regenerated Brayton cycle in the view of finite time thermodynamics. Wang et al. [17-19] performed power optimization by altering effectiveness of various heat exchangers for intercooled and regenerated Brayton cycles coupled to fixed [17] and finite temperature [18-19] heat reservoirs based on endoreversible [17,18] and irreversible [19] mode.. Jubeh [20] performed exergy analysis of a regenerative Brayton cycle and found appreciable increase in second law efficiency at lesser pressure ratio, small environment temperature and elevated entrance temperature of expander with the introduction of two heat additions. Further, Wang et al. [21] investigated power and power density of externally irreversible Brayton cycle with two heat additions in the view of finite time thermodynamics and found the range of isothermal heat addition on various performance parameters of endoreversible Brayton cycle. On the basis of recent literature, a model of an irreversible regenerative Brayton cycle with pressure drop as supplementary irreversibility is considered in this paper and expressions for maximum power output and corresponding thermal efficiency of an irreversible regenerative Brayton cycle are obtained. The effect of effectiveness of various heat exchangers, efficiency of turbine and compressor, heat capacitance rates, isothermal pressure drop ratio and pressure recovery coefficients have been studied in detail and the results are presented on graphs. The model analyzed in this paper gives lower values of power output and corresponding thermal efficiency as expected. as

Keywords

Thermodynamic Optimization, Irreversible Brayton cycle, Regenerator, Power and Efficiency

Power optimization of an irreversible regenerative Brayton cycle with isothermal heat addition

Abstract

Keywords

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