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Second Law of Thermodynamics
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
The Carnot cycle is the most prominent reversible cycle, which is named after Nicolas Leonard Sadi Carnot, who first proposed it in 1824. The Carnot heat engine is a theoretical heat engine that functions on the Carnot cycle. Figure 6.11 shows the p-v and T-s diagrams of the Carnot cycle. As shown in the figure, the cycle constitutes two reversible adiabatic processes and two reversible isothermal processes. Heat Q1 is added to the working fluid at constant temperature T1 in the process 1-2. The working fluid then expands isentropically in the process 2-3. Heat Q2 is rejected from the working fluid at constant temperature T2 in the process 3-4 and it is then compressed isentropically in the process 4-1.
A new method to optimise finite dimensions thermodynamic models: application to an irreversible Stirling engine
Published in International Journal of Ambient Energy, 2018
F. Lanzetta, A. Vaudrey, P. Baucour
For all of these conditions, the net work (37) and the efficiency (43) can be simplified as And: The resulting efficiency and net work correspond to the reversible Stirling engine (Reader and Hooper 1983; Organ 1992; Walker et al. 1993). One should notice that the efficiency of Equation (45) is equal to the one obtained with a reversible Carnot heat engine (Blank, Davis, and Wu 1994; Chen 1994; Blank and Wu 1996).
Second law analysis of the 160â Wp standalone solar photovoltaic system
Published in International Journal of Sustainable Energy, 2019
Ranjeet Kumar Jha, Avadhesh Yadav, Durgesh Sharma
The maximum work potential of a heat engine can be calculated by applying Carnot heat engine between source and sink, Figure 5 shows a reversible heat engine working between SPV modules and ambient (Sharma and Jha 2016).
Thermodynamic analysis and multi-objective optimisation of endoreversible Lenoir heat engine cycle based on the thermo-economic performance criterion
Published in International Journal of Ambient Energy, 2019
Mohammad H. Ahmadi, Mohammad Alhuyi Nazari, Michel Feidt
There are several approaches in analysing and optimisation of cycles (Ashouri et al. 2015, 2017; Ding, Chen, and Liu 2017). In order to have higher efficiency in cycles, it is necessary to analyse them (Gong, Chen, and Sun 2013; Shen et al. 2013) and find source of irreversibilities (Chen and Xia 2016; Bi and Chen 2017); consequently, better optimisation can be performed. Since the analysis and optimisation of various heat engine cycles for various objectives were made by using the finite-time thermodynamics theory (Curzon and Ahlborn 1975; Bejan 1996; Berry 2000; Chen 2004, 2005; Ge, Chen, and Sun 2008; Andresen 2011; Feidt 2012; Ahmadi, Dehghani, and Mohammadi 2013; Ahmadi, Mohammadi, and Dehghani 2013; Ahmadi, Sayyaadi, Dehghani, et al. 2013; Ahmadi, Sayyaadi, Mohammadi, et al. 2013; Ge, Chen, and Sun 2016), it has made tremendous progress in different periods. The endoreversible model for heat engine cycles, which was originally used by Novikov (1958) and Curzon and Ahlborn (1975), is the basic model of the finite-time thermodynamics. Wenzhen (1989) and Chen, Fengrui, and Lingen (1990) derived the fundamental optimal formulae of power and thermal efficiency for endoreversible Carnot heat engine with the fixed total heat-transfer area of heat exchangers, and made some performance optimisations. Lingen et al. (1997) investigated performances of steady-flow thermodynamic cycles coupled with constant- and variable-temperature heat reservoirs, derived the optimal performance characteristics of endoreversible Carnot and Brayton heat engines with fixed total thermal conductance of the heat exchangers and obtained the optimal power output and the thermal efficiency limit, and made a comparison between the two cycles. Zhang et al. (2007) established a relatively universal endoreversible steady-flow heat engine cycle model, which consisted of two adiabatic branches, two constant thermal-capacity heating branches and a constant thermal-capacity cooling branch, and focused on power, efficiency and their optimal relationship, and the exergy-based ecological performance. Yang et al. (2014) built an endoreversible model of an intercooled regenerated Brayton heat and power cogeneration plant coupled with variable-temperature heat reservoirs, and optimised the heat conductance distributions and the intercooling pressure ratio was selected based on the exergetic analysis. The ecological coefficient of performance (ECOP) is another ecological criterion that introduced by Ust and colleagues (Ust, Sahin, and Sogut 2005; Sogut, Ust, and Sahin 2006; Ust et al. 2006).