Limits and Optimization of Power Input or Output of Actual Thermal Cycles

Abstract

Abstract:In classical thermodynamic, maximum power obtained from system (or minimum power supplied to system) defined as availability (exergy), but availability term is only used for reversible systems. In reality, there is no reversible system, all systems are irreversible, because reversible cycles doesn't include constrains like time or size and they operates in quasi-equilibrium state. Purpose of this study is to define limits of the all basic thermodynamic cycles and to provide finite-time exergy models for irreversible cycles and to obtain the maximum (or minimum) available power for irreversible (finite-time exergy) cycles. In this study, available power optimization and performance limits were defined all basic irreversible thermodynamic cycles, by using first and second law of thermodynamic. Finally, these results were evaluated in terms of cycles' first and second law efficiency, COP, power output (or input) and exergy destruction.

Optimization performance and thermodynamic analysis of an irreversible nano scale Brayton cycle operating with Maxwell–Boltzmann gas

“…Moreover, Zhu et al [14] performed an exergy based optimization with ecological objective function as E = P À T o r which consists exergy-output rate and exergy-loss rate of a heat pump. Ecological coefficient of performance (ECOP) and exergetic performance coefficient are other criteria that were submitted by Ust et al [15][16][17][18][19][20][21]. Ust et al [15] presented a new thermo-ecological criterion based on coefficient of performance (ECOP) which is defined as the ratio of power output to the loss rate of availability.…”

“…However, COP give information about power needed for cooling load and ECOP give information on entropy generation rate including loss rate of availability which is a great tool for evaluating the system. Açıkkalp and Yamık [21] presented criteria called maximum available work which is defined as MAW ¼ Q H ð1 À T 0 T H Þ À T 0 S gen : Besides, nanotechnology has gained great attention during last decade and in the recent years this is entered through thermodynamic cycles. As a result, it can be said that nano-scale thermal cycles may be of great importance in near future.…”

Exergoeconomic multi objective optimization and sensitivity analysis of a regenerative Brayton cycle

“…They also conducted sensitivity analysis and error analysis in order to improve understanding of the system performance. There are other studies that used, Finite time thermodynamic (FTT), power optimization, thermoenvironmental, and ecological methods in evaluation and comparison of thermal cycles [33][34][35][36][37].…”

Methods used for evaluation of actual power generating thermal cycles and comparing them

“…A number of study were published by the several authors [55][56][57][58][59][60][61][62][63][64][65][66]. A new criteria for assessing actual thermal cycles was submitted by Açıkkalp and Yamık [67]. This method is called as max available work (MAW) and it used for determining limits of real cycles.…”