scholarly journals CARNOT AND PHILIPS HEAT ENGINES IN VIEW OF THE THEORY OF THERMODYNAMIC POTENTIALS

2019 ◽  
Vol 20 (9-10) ◽  
pp. 154-165 ◽  
Author(s):  
V. G. Kiselev
Keyword(s):  
Traditional Approach ◽  
Potential Method ◽  
Ideal Gas ◽  
Absolute Temperature ◽  
Chemical Thermodynamics ◽  
Heat Engines ◽  
Thermodynamic Potentials ◽  
Cyclic Processes ◽  
New Research ◽  
Direct Use

A study has been made of the Philips and Carnot cycles based on the modernized physicochemical model of "ideal gas", which utilizes the theory of thermodynamic potentials and assumes the presence of chemical energy. The feasibility study of the Phillips and Carnot heat engines using the thermodynamic potential method is substantiated by plotting the diagrams of the dependence of the internal energy and Helmholtz energy on the absolute temperature and their comparison with the usual pressure-volume diagrams. This method is compared with traditional approach to analysis of cyclic processes. Based on the analysis carried out, the results are similar to those obtained in the study of these processes in the traditional way. On the other hand, the use of new research methods has a significant advantage, since it allows direct use of the activity of the substance (gas) and the entire arsenal of chemical thermodynamics for the analysis of cyclic processes, for example, in the thermal machines of Philips and Carnot.

scholarly journals On the ambiguity of an ideal gas entropy concept

2020 ◽  
Vol 22 (4) ◽  
pp. 32-42
Author(s):  
V. G. Kiselev
Keyword(s):  
Critical Analysis ◽  
Ideal Gas ◽  
Absolute Temperature ◽  
Carnot Cycle ◽  
Perfect Gas ◽  
Reversible Process ◽  
Thermodynamic Potentials ◽  
Adiabatic Processes ◽  
Isothermal Processes

Based on a critical analysis of the existing characteristics of an ideal gas and the theory of thermodynamic potentials, the article considers its new model, which includes the presence of an ideal gas in addition to kinetic energy of potential (chemical) energy, in the framework of which the isothermal and adiabatic processes in it are studied both reversible and irreversible, in terms of changes in the entropy of the system in question, observed in case. In addition, a critical analysis was made of the process of introducing the concept of entropy by R. Clausius, as a result of which the main requirements for entropy were established, the changes of which are observed in isothermal and adiabatic quasistatic processes, in particular, it was revealed that if in isothermal processes involving one in a perfect gas, the entropy ST is uniquely characterized by the value , regardless of whether the process is reversible or not, then when the adiabatic processes occur, the only requirement made of them is the condition of mutual destruction adiabats in this Carnot cycle. As a result of this circumstance, in fact, in thermodynamics various “adiabatic” entropies are used, namely; const SA = const R ln V  и  C V ln T , and in addition, as established in this paper, CV, which leads, despite the mathematically perfect introduction of the concept of entropy for the Carnot cycle, to the impossibility of its unambiguous interpretation and, therefore, the determination of its physicochemical meaning even for perfect gas. A new concept is introduced in the work: “total” entropy of an ideal gas SS = R ln V + C V , satisfying the criteria of R. Clausius, on the basis of which it was established that this type of entropy multiplied by the absolute temperature characterizes a certain level of potential energy of the system, which can besuccessively converted to work in an isothermal reversible process, with the supply of an appropriate amount of heat, and in the adiabatic reversible process under consideration.

Solar Thermal Energy

2018 ◽  
Author(s):  
E. L. Wolf
Keyword(s):  
Solar Cells ◽  
Thermal Energy ◽  
Fossil Fuel ◽  
Rankine Cycle ◽  
Carnot Cycle ◽  
The Sun ◽  
Solar Thermal Energy ◽  
Heat Engines ◽  
Direct Use ◽  
Fossil Fuel Energy

The Sun’s spectrum on Earth is modified by the atmosphere, and is harvested either by generating heat for direct use or for running heat engines, or by quantum absorption in solar cells, to be discussed later. Focusing of sunlight requires tracking of the Sun and is defeated on cloudy days. Heat engines have efficiency limits similar to the Carnot cycle limit. The steam turbine follows the Rankine cycle and is well developed in technology, optimally using a re-heat cycle of higher efficiency. Having learned quite a bit about how the Sun’s energy is created, and how that process might be reproduced on Earth, we turn now to methods for harvesting the energy from the Sun as a sustainable replacement for fossil fuel energy.

Processes and Responses

2017 ◽  
Author(s):  
Jochen Rau
Keyword(s):  
Heat Engine ◽  
Cyclic Process ◽  
Free Enthalpy ◽  
Initial State ◽  
Thermodynamic Potentials ◽  
Grand Potential ◽  
Laws Of Thermodynamics ◽  
Cyclic Processes ◽  
Energy Exchanges ◽  
Thermodynamic Processes

Thermodynamic processes involve energy exchanges in the forms of work, heat, or particles. Such exchanges might be reversible or irreversible, and they might be controlled by barriers or reservoirs. A cyclic process takes a system through several states and eventually back to its initial state; it may convert heat into work (engine) or vice versa (heat pump). This chapter defines work and heat mathematically and investigates their respective properties, in particular their impact on entropy. It discusses the roles of barriers and reservoirs and introduces cyclic processes. Basic constraints imposed by the laws of thermodynamics are considered, in particular on the efficiency of a heat engine. The chapter also introduces the thermodynamic potentials: free energy, enthalpy, free enthalpy, and grand potential. These are used to describe energy exchanges and equilibrium in the presence of reservoirs. Finally, this chapter considers thermodynamic coefficients which characterize the response of a system to heating, compression, and other external actions.

scholarly journals Chemical and biochemical thermodynamics reunification (IUPAC Technical Report)

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Antonio Sabatini ◽  
Marco Borsari ◽  
Gerard P. Moss ◽  
Stefano Iotti
Keyword(s):  
Chemical Reactions ◽  
Atp Hydrolysis ◽  
Joint Commission ◽  
Chemical Thermodynamics ◽  
Thermodynamic Quantities ◽  
Biochemical Reactions ◽  
Mathematical Transformation ◽  
Biochemical Nomenclature ◽  
Thermodynamic Potentials ◽  
Technical Report

AbstractAccording to the 1994 IUBMB-IUPAC Joint Commission on Biochemical Nomenclature (JCBN) on chemical and biochemical reactions, two categories of thermodynamics, based on different concepts and different formalisms, are established: (i) chemical thermodynamics, which employ conventional thermodynamic potentials to deal with chemical reactions [1], [2], [3]; and (ii) biochemical thermodynamics, which employ transformed thermodynamic quantities to deal with biochemical reactions based on the formalism proposed by Alberty [4], [5], [6], [7]. We showed that the two worlds of chemical and biochemical thermodynamics, which so far have been treated separately, can be reunified within the same thermodynamic framework. The thermodynamics of chemical reactions, in which all species are explicitly considered with their atoms and charge balanced, are compared with the transformed thermodynamics generally used to treat biochemical reactions where atoms and charges are not balanced. The transformed thermodynamic quantities suggested by Alberty are obtained by a mathematical transformation of the usual thermodynamic quantities. The present analysis demonstrates that the transformed values for ΔrG′0 and ΔrH′0 can be obtained directly, without performing any transformation, by simply writing the chemical reactions with all the pseudoisomers explicitly included and the elements and charges balanced. The appropriate procedures for computing the stoichiometric coefficients for the pseudoisomers are fully explained by means of an example calculation for the biochemical ATP hydrolysis reaction. It is concluded that the analysis reunifies the “two separate worlds” of conventional thermodynamics and transformed thermodynamics.

Thermoelasticity

1997 ◽  
Author(s):  
Burak Erman ◽  
James E. Mark
Keyword(s):  
Equation Of State ◽  
Elastic Deformation ◽  
Additional Assumption ◽  
Polymer Network ◽  
Ideal Gas ◽  
Absolute Temperature ◽  
Constant Volume ◽  
Conformational Energy ◽  
Network Chain ◽  
Constant Deformation

The important postulate that intermolecular interactions are independent of extent of deformation leads directly to the conclusion that such interactions cannot contribute to an energy of elastic deformation ΔEel at constant volume. In the earliest theories of rubberlike elasticity, it was additionally assumed that, intramolecular contributions to ΔEel were likewise nil. In this idealization that the total ΔEel is zero, the elastic retractive force exhibited by a deformed polymer network would be entirely entropic in origin. At the molecular level, this would correspond, of course, to assuming all configurations of a network chain to be of exactly the same conformational energy and thus the average configuration to be independent of temperature. Under these circumstances, the dependence of stress on temperature is strikingly simple, as shown, for example, by the equation . . . f* = υkT/V (〈r2〉i/〈r2〉0)(α – α-2) . . . . . . (9.1) . . . that characterizes a polymer network in elongation where, it should be recalled, 〈r2〉i3/2 is proportional to the volume of the network. This additional assumption that 〈r2〉0 is independent of temperature would lead to the prediction that the elastic stress determined at constant volume and elongation α is directly proportional to the absolute temperature. Such network chains would be akin to the particles of an ideal gas, which would obey the equation of state p = nRT(1/V) and thus exhibit a pressure at constant deformation (1/V) likewise directly proportional to the temperature.

scholarly journals Time–energy uncertainty principle for irreversible heat engines

2020 ◽  
Vol 378 (2170) ◽  
pp. 20190171 ◽  
Author(s):  
Rudolf Hanel ◽  
Petr Jizba
Keyword(s):  
Uncertainty Principle ◽  
Nonequilibrium Thermodynamics ◽  
Real Life ◽  
Ideal Gas ◽  
Irreversible Processes ◽  
Bohr Radius ◽  
Heat Engines ◽  
Working Medium ◽  
Semi Empirical ◽  
The Ideal

Even though irreversibility is one of the major hallmarks of any real-life process, an actual understanding of irreversible processes remains still mostly semi-empirical. In this paper, we formulate a thermodynamic uncertainty principle for irreversible heat engines operating with an ideal gas as a working medium. In particular, we show that the time needed to run through such an irreversible cycle multiplied by the irreversible work lost in the cycle is bounded from below by an irreducible and process-dependent constant that has the dimension of an action. The constant in question depends on a typical scale of the process and becomes comparable to Planck’s constant at the length scale of the order Bohr radius, i.e. the scale that corresponds to the smallest distance on which the ideal gas paradigm realistically applies. This article is part of the theme issue ‘Fundamental aspects of nonequilibrium thermodynamics’.

scholarly journals Ubiquitous presence of paracetamol in human urine: sources and implications

Reproduction ◽  
2014 ◽  
Vol 147 (4) ◽  
pp. R105-R117 ◽  
Author(s):  
Hendrik Modick ◽  
Tobias Weiss ◽  
Georg Dierkes ◽  
Thomas Brüning ◽  
Holger M Koch
Keyword(s):  
General Population ◽  
Human Biomonitoring ◽  
Oral Exposure ◽  
Over The Counter ◽  
Occupational Setting ◽  
Wide Range ◽  
New Research ◽  
Occupational Settings ◽  
Direct Use

N-acetyl-4-aminophenol (acetaminophen/paracetamol, NA4AP) is one of the most commonly used over-the-counter analgesic and antipyretic drugs. Recent studies have reported anti-androgenic effects of NA4AP in vitro and possible associations between intrauterine exposure to NA4AP and the development of male reproductive disorders in humans. NA4AP is also a major metabolite of aniline (phenylamine), representing 75–86% of the aniline dose excreted in urine. Aniline is an important large-volume intermediate in several industrial processes. Besides individuals in various occupational settings with aniline exposure, the general population is also known to be ubiquitously exposed to aniline. In this article, we provide an overview of the recent literature concerning the intake of NA4AP during pregnancy and the possible anti-androgenic effects of NA4AP as well as literature concerning its known metabolic precursor aniline. We also present new research data, including the first human biomonitoring data on NA4AP excretion in urine, showing ubiquitous NA4AP body burdens in the general population at a wide range of concentrations. We found a small but significant impact of smoking on urinary NA4AP concentrations. We further present preliminary data on NA4AP excretion after therapeutic acetaminophen use, after aniline exposure in an occupational setting, and during a controlled fasting study (excluding oral exposure to both aniline and acetaminophen). Our findings indicate exposure to aniline (or aniline-releasing substances) as well as nutrition (next to the direct use of acetaminophen as medication) as possible sources of internal body burdens of NA4AP.

scholarly journals Holographic heat engines and static black holes: A general efficiency formula

2019 ◽  
Vol 28 (02) ◽  
pp. 1950030 ◽  
Author(s):  
Felipe Rosso
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Upper Bound ◽  
Heat Engine ◽  
Thermodynamic System ◽  
Ideal Gas ◽  
Heat Flows ◽  
Heat Engines ◽  
Static Black Hole

Starting from simple observations regarding heat flows for static black holes (or any thermodynamic system with [Formula: see text]), we get inequalities which restrict their change in energy and adiabatic curves in the [Formula: see text] plane. From these observations, we then derive an exact efficiency formula for virtually any holographic heat engine defined by a cycle in the [Formula: see text] plane, whose working substance is a static black hole. Moreover, we get an upper bound for its efficiency and show that for a certain class of black holes, this bound is universal and achieved by an “ideal gas” hole. Finally, we compute exact efficiencies for some particular and new engines.

Molecular Processes during Deformation of Rubberlike Elastic Bodies

1946 ◽  
Vol 19 (3) ◽  
pp. 525-533
Author(s):  
Kurt H. Meter ◽  
A. J. A. Van Der Wyk
Keyword(s):  
Structural Data ◽  
Ideal Gas ◽  
Absolute Temperature ◽  
Chain Molecule ◽  
Molecular Processes ◽  
Chain Molecules ◽  
Elastic Bodies ◽  
Vulcanized Rubber ◽  
Chain Links ◽  
Made In

Abstract It has been demonstrated that the elastic force of a moderately vulcanized rubber kept at a constant stress is proportional to the absolute temperature, T, in the region of medium elongations. In this respect, rubber behaves somewhat like an ideal gas, the pressure of which at constant volume is also proportional to T. By applying the first and second laws of thermodynamics, it can be shown that the internal energy of isothermally stretched rubber changes as little as that of an ideal gas if its volume is increased or decreased isothermally. In both cases, however, the entropy of the system changes. Meyer, Susich, and Valkó, Karrer, and Busse explain this behavior in the following way. All rubberlike substances consist of long, flexible, chain molecules whose links are thermally mobile. In the undeformed amorphous rubber, the molecules represent randomly coiled chains ; as a result of the deformation their shape is changed, e.g., partly stretched by elongation. Thus a thermo-dynamically less probable shape is forced on them ; the thermal agitation tends to eliminate it ; because of the reciprocal felting and intertwining of the molecules, a return to the thermodynamically more probable state is possible only if the deformation can be reversed. The thermally mobile chain links are referred to as kinetic units or chain segments. In the present paper, we shall discuss the molecular processes taking place in the course of deformation, in particular such questions as: “How is the deforming force transferred to an individual chain molecule and its segment?” “How does the molecule react to this force?” After having discussed these questions, we shall examine how far the requirements are complied with for a quantitative theory such as the derivation of an equation to calculate the modulus of elasticity from structural data. We shall also discuss the attempts known to have been made in this direction so far.

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