Linear Approximation of Efficiency for Similar Non- Endoreversible Cycles to the Carnot Cycle

In the present paper the non-endoreversible Curzon-Ahlborn, Stirling and Ericsson cycles as models of thermal engines are discussed from the viewpoint of finite time thermodynamics. That is, it is propose the existence of a finite time of heat transfer for isothermal processes, but the cycles are analyzed assuming they are not endoreversible cycles, through a factor that represents the internal ireversibilities of them, so that the proposed heat engine models have efficiency closer to real engines. Some results of previous papers are used, and from the get expressions for the power output function and ecological function a methodology to obtain a linear approximation of efficiency including adequate parameters are shown, similar to those obtained in that previous paper used. Variable changes are made right, like those used previously

Comparative Performance Analysis of a Simplified Curzon-Ahlborn Engine

This paper presents a finite-time thermodynamic optimization based on three different optimization criteria: Maximum Power Output (MP), Maximum Efficient Power (MEP), and Maximum Power Density (MPD), for a simplified Curzon-Ahlborn engine that was first proposed by Agrawal. The results obtained for the MP are compared with those obtained using MEP and MPD criteria. The results show that when a Newton heat transfer law is used, the efficiency values of the engine working in the MP regime are lower than the efficiency values ( τ ) obtained with the MEP and MPD regimes for all values of the parameter τ = T 2 / T 1 , where T 1 and T 2 are the hot and cold temperatures of the engine reservoirs ( T 2 < T 1 ) , respectively. However, when a Dulong-Petit heat transfer law is used, the efficiency values of the engine working at MEP are larger than those obtained with the MP and the MPD regimes for all values of τ . Notably, when 0 < τ < 0.68 , the efficiency values for the MP regime are larger than those obtained with the MPD regime. Also, when 0.68 < τ < 1 , the efficiency values for the aforementioned regimes are similar. Importantly, the parameter τ plays a crucial role in the engine performance, providing guidance during the design of real power plants

Local Stability Analysis of a Thermo-Economic Model of a Chambadal-Novikov-Curzon-Ahlborn Heat Engine

In this work we present a local stability analysis of the thermo-economic model of an irreversible heat engine working at maximum power conditions. The thermo-economic model is based on the maximization of a benefit function which is defined by the ratio of the power output and the total cost involved in the plant’s performance. Our study shows that, after a small perturbation, the system decays exponentially to the steady state determined by two different relaxation times. In particular, we show that the relaxation times are function of the temperature ratio τ = T2/T1 (T1 > T2), the cost function ƒ and the parameter R (a parameter related to the degree of internal irreversibilities). We observe that the stability of the system improves as τ increases whereas for changes in ƒ and R, the stability properties are characterized by a rapid decay along the fast eigendirection as ƒ increases and R decreases. Finally, we discuss our results in the context of energetic properties

Catálogo de los recursos pesqueros continentales de Colombia

El documento que presentamos al público tiene una importancia tanto para la academia y centros de investigación como para las autoridades, tomadores de decisiones y el público en general, en aras de la generación de una conciencia colectiva sobre la problemática asociada a los recursos pesqueros y la necesidad de tomar medidas urgentes para su aprovechamiento sostenible por el bien común. En este contexto, el “Catalogo de los recursos pesqueros continentales de Colombia” contiene la información científicamente válida que ha llevado a establecer que las especies de peces de consumo y en consecuencia con alto valor comercial en aguas continentales son 173, cifra que probablemente se ampliará con futuros estudios y nuevos datos. De las especies listadas, 31 se encuentran categorizadas con algún grado de amenaza, siendo precisamente la causa el aprovechamiento derivado de su valor comercial, y que de continuar el aprovechamiento descontrolado, a la brevedad estaremos presenciando su extinción.Bogotá, D. C