Efficiency at Maximum Power of the Low-Dissipation Hybrid Electrochemical–Otto Cycle

Abstract

A novel analytical method was developed for analysis of efficiency at maximum power of a hybrid cycle combining electrochemical and Otto engines. The analysis is based on the low-dissipation model, which relates energy dissipation with energy transfer rate. Efficiency at maximum power of a hybrid engine operating between two reservoirs of chemical potentials is evaluated. The engine is composed of an electrochemical device that transforms chemical potential to electrical work of an Otto engine that uses the heat generated in the electrochemical device and its exhaust effluent for mechanical work production. The results show that efficiency at maximum power of the hybrid cycle is identical to the efficiency at maximum power of an electrochemical engine alone; however, the power is the product of the electrochemical engine power and the compression ratio of the Otto engine. Partial mass transition by the electrochemical device from the high to the low chemical potential is also examined. In the latter case, heat is generated both in the electrochemical device and the Otto engine, and the efficiency at maximum power is a function of the compression ratio. An analysis performed using the developed method shows, for the first time, that, in terms of a maximal power, at some conditions, Otto cycle can provide better performance that the hybrid cycle. On the other hand, an efficiency comparison at maximum power with the separate Otto-cycle and chemical engine results in some advantages of the hybrid cycle.

Optimizing Power and Thermal Efficiency of an Irreversible Variable-Temperature Heat Reservoir Lenoir Cycle

“…Compared to the classical thermodynamics, the finite time process of the finite rate heat exchange (HEX) between the system and the environment and the finite size device are considered in the FTT [1][2][3][4][5][6][7][8][9][10][11][56][57][58][59], therefore, the result obtained is closer to the actual HEG performance…”

“…As a further extension of traditional irreversible process thermodynamics, finite-time thermodynamics (FTT) [1][2][3][4][5][6][7][8][9][10][11] has been applied to analyze and optimize performances of actual thermodynamic cycles, and great progress has been made. FTT has been applied in micro-and nano-cycles [12][13][14][15], thermoelectric devices [16,17], thermionic devices [18,19], gas turbine cycles [20][21][22], internal combustion cycles [23,24], cogeneration plants [25,26], thermoradiative cell [27], chemical devices [28,29], and economics [30,31].…”

“…Georgiou [55] first used classical thermodynamics to study the steady flow Lenoir cycle (SFLC) and compared its performance with that of a steady flow Carnot cycle. Compared to the classical thermodynamics, the finite time process of the finite rate heat exchange (HEX) between the system and the environment and the finite size device are considered in the FTT [1][2][3][4][5][6][7][8][9][10][11][56][57][58][59], therefore, the result obtained is closer to the actual HEG performance…”

Power density analysis and multi-objective optimization of an irreversible Otto cycle

“…有限时间热力学 应用于实际热力循环的性能分析和优化，取得了很大的进展。运用 有限时间热力学理论分析 Otto 循环的性能，是改进和优化 Otto 循环热机的新技术，并且发 展了研究 Otto 循环的新方法。在工质比热随温度恒定 [22][23][24][25][26][27][28][29][30][31][32][33][34] 、比热随成分变化 [35,36] 和比热随 温度变化 [37][38][39][40][41][42][43] 时，许多学者在考虑不同损失的条件下，对 Otto 循环的功率、效率和生态学 函数等目标函数的性能进行了研究。 除功率、效率和生态学函数等目标函数外，Sahin 等 [44,45] 引入了一种新的目标函数--功率密度(循环输出功率与最大比容之比)作为新的优化准则， 对可逆 Joule-Brayton 循环进行 了优化，发现了热机在最大功率密度准则下的热效率高于最大功率准则下的热效率，并且前 者设计的热机尺寸更小；陈林根等 [46] 将功率密度这一目标函数引入到可逆 Atkinson 循环最 优性能的分析中；Gumus 等 [47] 将最大功率密度准则应用于可逆 Otto 循环的性能优化中，并 将优化结果与最大功率和最大有效功率准则下得到的优化结果进行了比较；Zhao 和 Xu [48] 考虑了传热和摩擦损失，在工质比热随温度非线性变化时对不可逆 Otto 循环的功率、效率 和功率密度等性能的进行了研究，并将其研究结果与 Atkinson 和 Miller 循环下得到的结果 进行了比较。 以上研究工作均集中在循环性能的单目标优化，但由于各个目标函数之间存在矛盾，为 了协调目标函数间的关系，许多学者开展了循环性能的多目标优化 [49][50][51][52][53][54][55][56][57][58][59] 研究工作。戴东东等 基金项目：国家自然科学基金(51779262)和武汉工程大学研究生教育创新基金项目(CX2020038)资助. 通讯作者：陈林根，Email: lingenchen@hotmail.com, lgchenna@yahoo.com [49]…”

Performance Analysis and Four-Objective Optimization of an Irreversible Rectangular Cycle

“…After decades of development, a series of instructive and practical achievements have been obtained in finite time thermodynamics [1][2][3][4][5][6][7][8], the research objects of which include heat engines [9][10][11][12][13][14][15], refrigerators [16,17], heat pumps [18], chemical cycles [19], and quantum cycles [20,21]. The rectangular cycle (RC) is composed of four thermodynamic processes, its endothermic processes are closed to the endothermic processes of the dual cycle, and its exothermic processes are closed to the exothermic processes of the Miller cycle.…”