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Efficiency of irreversible Brayton cycles at minimum entropy generation

机译:最小熵产生下不可逆布雷顿循环的效率

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System level optimization of power plants is mainly based on the thermodynamic laws. Various objective functions are proposed that are based on the 1 st and 2nd law of thermodynamics. Given the fast technological advancement of power plants, it is important to understand which optimization objective should be used in practical applications. The objective is to find out whether an entropy-based optimization may be useful when designing gas turbine engines operating on Brayton cycle. The study considers three configurations of open Brayton cycle: a regenerative cycle, a reheat regenerative cycle, and an intercooled regenerative cycle. The operational regimes at maximum thermal efficiency, maximum work output and minimum entropy production of these power cycles are compared. The results reveal that a reduction in cycle entropy production is neither equivalent to an increase in its thermal efficiency; nor to an increase in its work output. Under special circumstances, minimum entropy production design may be identical to maximum thermal efficiency design and/or maximum work output design. The minimum entropy production, the maximum thermal efficiency, and the maximum work output criteria may be equivalent at the condition of fixed heat input. The two first criteria may also lead to an identical design at the condition of fixed work output. It is demonstrated that for practical applications, thermodynamic optimization of gas turbine power plants should continue to be based upon maximum thermal efficiency or maximum work output criteria. An entropy-based design should be avoided.
机译:发电厂的系统级优化主要基于热力学定律。提出了基于热力学第一定律和第二定律的各种目标函数。鉴于发电厂的技术进步日新月异,重要的是要了解在实际应用中应该使用哪个优化目标。目的是找出在设计以布雷顿循环运行的燃气涡轮发动机时,基于熵的优化是否有用。这项研究考虑了开放式布雷顿循环的三种配置:再生循环,再热再生循环和中冷再生循环。比较了这些功率循环在最大热效率,最大功输出和最小熵产生时的运行方式。结果表明,减少循环熵产生既不等同于提高其热效率,也不能降低热效率。也不会增加工作量。在特殊情况下,最小熵产生设计可能与最大热效率设计和/或最大功输出设计相同。在固定热量输入的条件下,最小熵产生,最大热效率和最大功输出标准可以等效。在固定功输出的情况下,这两个第一标准也可能导致相同的设计。结果表明,在实际应用中,燃气轮机发电厂的热力学优化应继续基于最大热效率或最大功输出标准。应避免基于熵的设计。

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