Theory Of Heat Engines Research Articles

Characteristics of Dust Devils in Two Pre-Selected Landing Regions of the Tianwen-1 Mission—Comparing Observations and Predictions Using Numerical Model

The spatial and temporal distribution of dust devils (DDs) in the two pre-selected landing regions (ZA and ZB) of the Tianwen-1 mission in southern Utopia Planitia have been investigated by using images from the Context Camera (CTX) of the Mars Reconnaissance Orbiter (MRO). From the images of the regions in 8 Martian years, no DD was found in ZA, while 77 DDs were found in ZB. The observed DDs are mainly distributed in the northeastern part of ZB. The temporal variation in the observed DDs shows a prominent two-peak pattern in their local early spring and late summer. The size and height of the observed DDs have also been evaluated from the images, and they show a similar temporal variation as the occurrence. To investigate the possible conditions pertinent to these observed patterns of DD distribution, some analysis based on the thermodynamic theory of heat engines was performed using the output of the Mars climate model, MarsWRF. The spatial and temporal distribution of the simulated DDs are generally consistent with the observation, with significantly more DDs in ZB. Analysis of the model results suggests that the spatial distributions of the predicted DDs are mainly related to the distribution of sensible heat flux, which, in turn, is mainly determined by the surface-to-air temperature difference. The difference in DDs between ZA and ZB (more DDs in ZB) is dominated by the difference in sensible heat flux, which, in turn, is mainly related to the spatial variation of surface albedo.

Speed and efficiency limits of multilevel incoherent heat engines.

We present a comprehensive theory of heat engines (HE) based on a quantum-mechanical "working fluid" (WF) with periodically modulated energy levels. The theory is valid for any periodicity of driving Hamiltonians that commute with themselves at all times and do not induce coherence in the WF. Continuous and stroke cycles arise in opposite limits of this theory, which encompasses hitherto unfamiliar cycle forms, dubbed here hybrid cycles. The theory allows us to discover the speed, power, and efficiency limits attainable by incoherently operating multilevel HE depending on the cycle form and the dynamical regimes.

Thermally Forced Convection over a Mountainous Tropical Island

Abstract Observations from the Dominica Experiment (DOMEX) and cloud-resolving numerical simulations are used to study a thermally forced convection event over the Caribbean island of Dominica on 18 April 2011. A clear diurnal cycle of island thermal forcing and cumulus convection was observed, with cumuli initiating over the southwestern flank of the ridge and deepening as they drifted eastward. Apart from errors in cloud fraction and (notably) precipitation, the simulations verified well against the observations, provided horizontal grid spacings of 500 m or less were used. The simulated flows developed an island-scale solenoidal circulation with an organized and intense updraft over the ridge that focused convective initiation. Sensitivity tests investigated the impacts of topographic forcing, subcloud winds, and cloud–radiative feedbacks on the island-scale horizontal inflow and cloud vertical mass flux. These experiments confirmed that thermal forcing drove the island convection and that the inflow and cloud mass flux were maximized under weak ambient cross-island winds. The simulations also indicated that cloud shading and precipitation each reduced the island inflow by ~20% while cloud latent heat release enhanced it by ~20%. However, precipitation caused a much smaller reduction in cloud mass flux (10%) than did cloud shading (50%) owing to effective secondary convective initiation by subcloud cold pools. Thermodynamic heat-engine theory provided accurate predictions of the simulated solenoidal updraft magnitudes in selected cases. It also provided a simple explanation for the weakening of the simulated thermal circulation in the presence of island orography: a shallower mixed layer reduced the efficiency of the thermal circulation.

Aplicação de uma teoria termodinâmica no estudo de um Vórtice Ciclônico de Altos Níveis sobre o nordeste do Brasil

Este estudo teve como objetivo principal aplicar a teoria da máquina térmica em um evento de Vórtice Ciclônico de Altos Níveis (VCAN), ocorrido sobre o Nordeste do Brasil com o intuito de analisar um dos mecanismos de manutenção desse tipo de sistema. A teoria da máquina térmica, baseada na segunda lei da termodinâmica, foi utilizada para calcular a diferença de pressão existente entre dois pontos localizados no centro e na periferia do VCAN. O modelo Brazilian developments on the Regional Atmospheric Modeling System (BRAMS) conseguiu representar bem o evento ocorrido no período de 10 a 21 de janeiro de 2011, mostrando uma maior intensidade deste evento no período de 16 a 19 de janeiro de 2011. A teoria da máquina térmica apresentou-se como uma ferramenta capaz de ser utilizada no estudo dos VCANs, mostrando boa concordância com as simulações realizadas com o modelo.

Available Potential Energy and Exergy in Stratified Fluids

Lorenz's theory of available potential energy (APE) remains the main framework for studying the atmospheric and oceanic energy cycles. Because the APE generation rate is the volume integral of a thermodynamic efficiency times the local diabatic heating/cooling rate, APE theory is often regarded as an extension of the theory of heat engines. Available energetics in classical thermodynamics, however, usually relies on the concept of exergy and is usually measured relative to a reference-state maximizing entropy at constant energy, whereas APE's reference state minimizes potential energy at constant entropy. This review seeks to shed light on the two concepts; it covers local formulations of available energetics, alternative views of the dynamics/thermodynamics coupling, APE theory and the second law of thermodynamics, APE production/dissipation, extensions to binary fluids, mean/eddy decompositions, APE in incompressible fluids, APE and irreversible turbulent mixing, and the role of mechanical forcing on APE production.

Remarks on Quasi-Equilibrium Theory

Abstract A recent article by J. I. Yano has indicated that there is an inconsistency in the original formulation of the quasi-equilibrium theory of Arakawa and Schubert. He argues that this inconsistency results from a contradiction in the two asymptotic limits of the theory; that is, the fractional area covered by convection, and the ratio of the convective adjustment and large-scale timescales cannot simultaneously go to zero, σ → 0 and τADJ/τLS → 0. Yano cites the heat engine theory proposed by Renno and Ingersoll as “formally establishing” this contradiction. It is demonstrated in this paper that the quasi-equilibrium framework originally developed by Arakawa and Schubert is perfectly consistent with the heat engine theory for steady-state convection, that is, when the timescale associated with the large-scale forcing τLS approximates the effective adjustment timescale of the large-scale ensemble of convective clouds τEFF. Indeed, the quasi-equilibrium framework states that, on the large scale, the at...

A Simple Theory for Waterspouts

Abstract It is shown that the simple thermodynamic theory for dust devils, proposed by Renno et al., also applies to waterspouts. The theory is based on the thermodynamics of heat engines and predicts the central pressure and the wind speed of these convective vortices. Moreover, it provides a simple physical interpretation of their general characteristics. In particular, the heat engine theory shows that convective vortices are more likely to form in the regions where the occurrence of the warmest and moistest updrafts and the coldest and driest downdrafts are supported by the local environment. These are the regions where both the heat input into the convective heat engine is maximum and the solenoidal generation of vorticity is the greatest. This explains why waterspouts are frequently observed near the boundaries between relatively warm and relatively cold waters. Moreover, since the work done by the convective heat engine is equal to the total heat input multiplied by the thermodynamic efficiency, th...

99/02716 Performance characteristic of fluid power converters

The endoreversible thermodynamic theory of heat engines is extended to fluid flow power converters. The useful power can be extracted from the piston and cylinder apparatus. The correlation between power output and efficiency is derived based on a linear flow resistance relationship. The influences of the piston-cylinder friction and nonlinear flow resistance relationships on the performance of the converter are also analyzed in this paper. Performance optimization is undertaken based on the overall size constraints. The paper also develops an analogy among the fluid flow power converters, endoreversible heat engines, endoreversible isothermal chemical engines, classical reversible heat engines, and the ideal motor powered by electrical battery. The results can be applied to the performance analyses and optimization for many steady-flow shaft-powered components.

The influence of nonlinear flow resistance relations on the power and efficiency from fluid flow

The endoreversible thermodynamic theory of heat engines is extended to fluid flow power converters. The relation between power output and efficiency, which involves the maximum (reversible) efficiency (with zero power output) as well as the maximum power and the corresponding efficiency bound, is derived based on the nonlinear flow resistance relations. Some modification to the results from recent literature is performed, and a theory of generalized thermodynamic optimization is provided.

Mathematical formulation of the heat-engine theory of thermodynamics including negative absolute temperatures

Mathematical formulation of the heat-engine theory of thermodynamics including negative absolute temperatures

Mathematical formulation of the heat-engine theory of thermodynamics including negative absolute temperatures

In order to treat negative absolute temperatures in the heat-engine theory of thermodynamics with logical consistency, a mathematical scheme is proposed which consists of three basic concepts, cycles, reservoirs and heats, and three axioms (1) the existence of at least one irreversible cycle, (2) the existence of a reversible cycle operating between any two reservoirs, (3) the scaling of the size of a cycle and the combination of two cycles. The axiom (1) is the weakest form of the second law of thermodynamics. A basic theorem of the heat-engine theory, a stronger version of Carnot's theorem is derived, and based on it the meaning of temperature is clarified and various forms of the second law are investigated to examine the possibility of negative absolute temperatures. The set of cycles is represented as a half-space in a vector space, and the absolute temperatures are related to a normal vector of the hyperplane which supports the half-space.

The Concepts and Logic of Classical Thermodynamics as a Theory of Heat Engines, Rigorously Constructed upon the Foundation Laid by S. Carnot and F. Reech. C. Truesdell , S. Bharatha

Previous articleNext article No AccessBook ReviewsThe Concepts and Logic of Classical Thermodynamics as a Theory of Heat Engines, Rigorously Constructed upon the Foundation Laid by S. Carnot and F. Reech. C. Truesdell , S. Bharatha Edward E. DaubEdward E. Daub Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Isis Volume 70, Number 3Sep., 1979 Publication of the History of Science Society Article DOIhttps://doi.org/10.1086/352333 Views: 5Total views on this site Copyright 1979 History of Science Society, Inc.PDF download Crossref reports no articles citing this article.

Absolute temperatures as a consequence of Carnot's general axiom

1. Program In our book, Concepts and Logic of Classical Thermodynamics,1 Mr. BHARATHA and I developed classical thermodynamics on the basis of Part I of Carnot's General Axiom, namely, the motive power of a Carnot cycle is positive and is determined by its operating temperatures and by the amount of heat it absorbs. For a given body, then, there is a function G such that for any Carnot cycle # L(%) = G(0+,0 ,C + (^j)>0. (1) The domain of G is the set of operating temperatures and heats absorbed that may appertain to Carnot cycles for the body in question. It is part of the definition of a Carnot cycle that 6+>6~ and that C+(^)>0. This definition and 1 C. Truesdell & S. Bharatha, Concepts and Logic of Classical Thermodynamics as a Theory of Heat Engines, Rigorously Constructed upon the Foundation Laid by S. Carnot and F. Reech, N.Y. etc., Springer-Verlag, 1977.

C. Truesdell and S. Bharatha: The Concepts and Logic of Classical Thermodynamics as a Theory of Heat Engines, Rigorously Constructed upon the Foundation Laid by S. Carnot and F. Reech, Springer-Verlag, New York and Berlin, 1977, xxii+154ページ, 24×16.5cm, 8,440円 (Texts and Monographs in Physics).

C. Truesdell and S. Bharatha: The Concepts and Logic of Classical Thermodynamics as a Theory of Heat Engines, Rigorously Constructed upon the Foundation Laid by S. Carnot and F. Reech, Springer-Verlag, New York and Berlin, 1977, xxii+154ページ, 24×16.5cm, 8,440円 (Texts and Monographs in Physics).

Inchley's Theory of Heat Engines. Edited and revised by H. Wright Baker, D.Sc. Published by Longmans, Green and Co., Ltd. Price 14/-.

Inchley's Theory of Heat Engines. Edited and revised by H. Wright Baker, D.Sc. Published by Longmans, Green and Co., Ltd. Price 14/-.