Polytropic Carnot heat engine

2019 ◽  
Vol 34 (24) ◽  
pp. 1950197 ◽  
Author(s):  
M. Askin ◽  
M. Salti ◽  
O. Aydogdu
Keyword(s):  
Equation Of State ◽  
Heat Engine ◽  
Point Of View ◽  
Carnot Cycle ◽  
Interesting Point ◽  
Thermal Equation ◽  
Expansion Phase ◽  
Polytropic Gas ◽  
Free Parameters ◽  
The Universe

Recent astrophysical datasets have implied that the universe has entered a speedy expansion phase. The Polytropic gas model, which describes a unified formulation of dark contents (matter plus energy), is one of the most reasonable definitions of this mysterious phenomenon. This interesting formulation allows to simulate the dark contents in the cosmic form of the perfect fluid and gives an interesting point of view in the discussion of fundamental theories of physics. In the first step of our investigation, we discuss the thermal equation-of-state (EoS henceforth) and obtain the EoS and deceleration parameters as explicit functions of temperature. Subsequently, we obtain a relation for the thermal efficiency of the Carnot heat engine which depends on free parameters given in the cosmological Polytropic gas description and the limits of maximal and minimal temperatures imposed on the Carnot cycle.

scholarly journals Action and Entropy in Heat Engines: An Action Revision of the Carnot Cycle

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 860
Author(s):  
Ivan R. Kennedy ◽  
Migdat Hodzic
Keyword(s):  
Heat Engine ◽  
Working Fluid ◽  
Field Energy ◽  
Carnot Cycle ◽  
Gibbs Potential ◽  
Atmospheric Gases ◽  
Temperature Dependent ◽  
Expansion Phase ◽  
Heat Engines ◽  
The Difference

Despite the remarkable success of Carnot’s heat engine cycle in founding the discipline of thermodynamics two centuries ago, false viewpoints of his use of the caloric theory in the cycle linger, limiting his legacy. An action revision of the Carnot cycle can correct this, showing that the heat flow powering external mechanical work is compensated internally with configurational changes in the thermodynamic or Gibbs potential of the working fluid, differing in each stage of the cycle quantified by Carnot as caloric. Action (@) is a property of state having the same physical dimensions as angular momentum (mrv = mr2ω). However, this property is scalar rather than vectorial, including a dimensionless phase angle (@ = mr2ωδφ). We have recently confirmed with atmospheric gases that their entropy is a logarithmic function of the relative vibrational, rotational, and translational action ratios with Planck’s quantum of action ħ. The Carnot principle shows that the maximum rate of work (puissance motrice) possible from the reversible cycle is controlled by the difference in temperature of the hot source and the cold sink: the colder the better. This temperature difference between the source and the sink also controls the isothermal variations of the Gibbs potential of the working fluid, which Carnot identified as reversible temperature-dependent but unequal caloric exchanges. Importantly, the engine’s inertia ensures that heat from work performed adiabatically in the expansion phase is all restored to the working fluid during the adiabatic recompression, less the net work performed. This allows both the energy and the thermodynamic potential to return to the same values at the beginning of each cycle, which is a point strongly emphasized by Carnot. Our action revision equates Carnot’s calorique, or the non-sensible heat later described by Clausius as ‘work-heat’, exclusively to negative Gibbs energy (−G) or quantum field energy. This action field complements the sensible energy or vis-viva heat as molecular kinetic motion, and its recognition should have significance for designing more efficient heat engines or better understanding of the heat engine powering the Earth’s climates.

THERMODYNAMIC STABILITY OF A FLUID WITH VARIABLE EQUATION OF STATE

2010 ◽  
Vol 25 (27) ◽  
pp. 2333-2348 ◽  
Author(s):  
NAIRWITA MAZUMDER ◽  
RITABRATA BISWAS ◽  
SUBENOY CHAKRABORTY
Keyword(s):  
Equation Of State ◽  
Thermodynamic Stability ◽  
State Parameter ◽  
Expansion Process ◽  
Thermal Equation ◽  
Third Law Of Thermodynamics ◽  
Variable Equation ◽  
Third Law ◽  
The Universe ◽  
General Thermodynamics

This paper deals with general thermodynamics for the universe filled with a perfect fluid, obeying an equation of state p = ω(z)ρ where the varying equation of the state parameter is chosen as two-index parametrization models namely: (a) linear redshift parametrization: ω(z) = ω0 + ω1z or (b) Jassal–Bagla–Padmanabhan (JBP) parametrization: [Formula: see text] where ω0, ω1 are constants. The behavior of temperature and the thermodynamic stability have been discussed. The thermal equation of state depends on both temperature and volume. As the universe evolves the fluid cools down obeying third law of thermodynamics and there will be thermodynamic stability during the expansion process without any phase transition or passing through any critical point.

Viscous effects in the dark sector of the Universe

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040041
Author(s):  
J. C. Fabris ◽  
T. R. P. Caramês ◽  
A. Wojnar ◽  
H. E. S. Velten
Keyword(s):  
Short Review ◽  
Point Of View ◽  
Accelerated Expansion ◽  
Viscous Effects ◽  
Dark Sector ◽  
Expansion Phase ◽  
Observational Point ◽  
Small Scales ◽  
Viscous Models ◽  
The Universe

Viscous properties are attributed to the dark sector of the Universe. They contribute to the accelerated expansion phase of the Universe and can alleviate existing tensions in the [Formula: see text]CDM model at small scales. We provide a short review of recent efforts on this topic. Different viscous models for the dark sector are analysed both from theoretical and observational point of view.

scholarly journals Cosmological test on viscous bulk models using Hubble parameter measurements and type Ia supernovae data

2019 ◽  
Vol 79 (9) ◽  
Author(s):  
A. Hernández-Almada
Keyword(s):  
Hubble Parameter ◽  
Point Of View ◽  
Type Ia Supernovae ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Type Ia ◽  
Free Parameters ◽  
Ia Supernovae ◽  
The Universe ◽  
Phenomenological Point

Abstract From a phenomenological point of view, we analyze the dynamics of the Universe at late times by introducing a polynomial and hyperbolic bulk viscosity into the Einstein field equations respectively. We constrain their free parameters using the observational Hubble parameter data and the Type Ia Supernovae dataset to reconstruct the deceleration q and the jerk j parameters within the redshift region $$0<z<2.5$$0<z<2.5. At current epochs, we obtain $$q_0 = -\,0.680^{+0.085}_{-0.102}$$q0=-0.680-0.102+0.085 and $$j_0 = 2.782^{+1.198}_{-0.741}$$j0=2.782-0.741+1.198 for the polynomial model and $$q_0 = -\,0.539^{+0.040}_{-0.038}$$q0=-0.539-0.038+0.040 ($$-\,0.594^{+0.056}_{-0.056}$$-0.594-0.056+0.056) and $$j_0 = 0.297^{+0.051}_{-0.050}$$j0=0.297-0.050+0.051 ($$1.124^{+0.196}_{-0.178}$$1.124-0.178+0.196) for the tanh (cosh) model. Furthermore, we explore the statefinder diagnostic that gives us evident differences with respect to the concordance model (LCDM). According to our results this kind of models is not supported by the data over LCDM.

scholarly journals Holographic description of the early universe

2020 ◽  
pp. 26-29
Author(s):  
A.N. Makarenko ◽  
◽  
A.V. Timoshkin ◽  
Keyword(s):  
Equation Of State ◽  
Cosmological Model ◽  
Viscous Fluid ◽  
Energy Conservation ◽  
Early Universe ◽  
Early Stage ◽  
Generalized Equation ◽  
Point Of View ◽  
Holographic Description ◽  
The Universe

The holographic principle is applied to the description of the Universe at an early stage of its evolution. As an example, we study a cosmological model with a bounce followed by a transition to the early stage of inflation. We study cosmological models of a viscous fluid with a generalized equation of state in terms of holographic cutoff proposed by Nojiri and Odintsov. Within these models, the infrared radius is calculated in terms of the particle horizon or event horizon. The laws of energy conservation are obtained from a holographic point of view. A viscous fluid describing bounce and early inflation is presented as generalized holographic energy

THE LAWS OF THERMODYNAMICS AND THERMODYNAMIC STABILITY OF THE MODIFIED CHAPLYGIN GAS

2010 ◽  
Vol 25 (32) ◽  
pp. 2779-2793 ◽  
Author(s):  
TANWI BANDYOPADHYAY ◽  
SUBENOY CHAKRABORTY
Keyword(s):  
Equation Of State ◽  
Thermodynamic Stability ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
Expansion Process ◽  
Thermal Equation ◽  
Laws Of Thermodynamics ◽  
Thermodynamic Pressure ◽  
The Universe ◽  
General Thermodynamics

Laws of thermodynamics have been examined for the universe filled with a perfect fluid, obeying an adiabatic equation of state p = γρ-A/ρα (called modified Chaplygin gas), where γ, A and α are positive constants and ρ and p are energy density and thermodynamic pressure respectively. Using general thermodynamics, the behavior of temperature and the thermodynamic stability has been discussed for modified Chaplygin gas. A scenario is obtained such that the thermal equation of state depends on both temperature and volume and there will be thermodynamic stability during the expansion process so that the fluid cools down through the expansion without any phase transition (or passing through any critical point).

scholarly journals The universe dominated by the extended Chaplygin gas

2015 ◽  
Vol 30 (13) ◽  
pp. 1550070 ◽  
Author(s):  
E. O. Kahya ◽  
B. Pourhassan
Keyword(s):  
Phase Transition ◽  
Equation Of State ◽  
Critical Point ◽  
Order Term ◽  
Chaplygin Gas ◽  
Point Of View ◽  
Fluid Equation ◽  
Barotropic Fluid ◽  
Density Perturbations ◽  
The Universe

In this paper, we consider a universe dominated by the extended Chaplygin gas which was recently proposed as the last version of Chaplygin gas models. Here, we only consider the second-order term which recovers quadratic barotropic fluid equation of state. The density perturbations are analyzed in both relativistic and Newtonian regimes and show that the model is stable without any phase transition and critical point. We confirmed stability of the model using thermodynamics point of view.

scholarly journals Action and Entropy in Heat Engines: An Action Revision of the Carnot Cycle

2021 ◽  
Author(s):  
Ivan Robert Kennedy ◽  
Migdat Hodzic
Keyword(s):  
Heat Engine ◽  
Working Fluid ◽  
Field Energy ◽  
Carnot Cycle ◽  
Gibbs Potential ◽  
Atmospheric Gases ◽  
Temperature Dependent ◽  
Expansion Phase ◽  
Heat Engines ◽  
The Difference

Despite the remarkable success of Carnot’s heat engine cycle in founding the discipline of thermodynamics two centuries ago, false viewpoints of his use of the caloric theory in the cycle still linger, limiting his legacy. An action revision of the Carnot cycle can correct this, showing that the heat flow powering external mechanical work is compensated internally with configurational changes in the thermodynamic or Gibbs potential of the working fluid, differing in each stage of the cycle quantified by Carnot as caloric. Action (@) is a property of state having the same physical dimensions as angular momentum (mrv=mr2ω). However, this property is scalar rather than vectorial, including a dimensionless phase angle (@=mr2ωδφ). We have recently confirmed with atmospheric gases that their entropy is a logarithmic function of the relative vibrational, rotational and translational action ratios with Planck’s quantum of action ħ. The Carnot principle shows that the maximum rate of work (puissance motrice) possible from the reversible cycle is controlled by the difference in temperature of the hot source and the cold sink, the colder the better. This temperature difference between the source and the sink also controls the isothermal variations of the Gibbs potential of the working fluid, that Carnot identified as reversible temperature-dependent but unequal exchanges in caloric. Importantly, the engine’s inertia ensures that heat from work performed adiabatically in the expansion phase is all restored to the working fluid during the adiabatic recompression, less the net work performed. This allows both the energy and the thermodynamic potential to return to the same values at the beginning of each cycle, a point strongly emphasized by Carnot. Our action revision equates Carnot’s calorique, or the non-sensible heat later described by Clausius as ‘work-heat’ exclusively to negative Gibbs energy (-G) or quantum field energy. This action field complements the sensible energy or vis-viva heat as molecular kinetic motion and its recognition should have significance for designing more efficient heat engines or better understanding of the heat engine powering the Earth’s climates.

scholarly journals Dynamical system analysis of FLRW models with Modified Chaplygin gas

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ali Osman Yılmaz ◽  
Ertan Güdekli
Keyword(s):  
Dynamical System ◽  
Equation Of State ◽  
Energy Density ◽  
System Analysis ◽  
Chaplygin Gas ◽  
Modified Chaplygin Gas ◽  
State Spaces ◽  
The Universe ◽  
Matter Energy ◽  
Far Future

AbstractWe investigate Friedmann–Lamaitre–Robertson–Walker (FLRW) models with modified Chaplygin gas and cosmological constant, using dynamical system methods. We assume $$p=(\gamma -1)\mu -\dfrac{A}{\mu ^\alpha }$$ p = ( γ - 1 ) μ - A μ α as equation of state where $$\mu$$ μ is the matter-energy density, p is the pressure, $$\alpha$$ α is a parameter which can take on values $$0<\alpha \le 1$$ 0 < α ≤ 1 as well as A and $$\gamma$$ γ are positive constants. We draw the state spaces and analyze the nature of the singularity at the beginning, as well as the fate of the universe in the far future. In particular, we address the question whether there is a solution which is stable for all the cases.

scholarly journals Can Quantum Correlations Lead to Violation of the Second Law of Thermodynamics?

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 573
Author(s):  
Alexey V. Melkikh
Keyword(s):  
Quantum Entanglement ◽  
Local Equilibrium ◽  
Heat Engine ◽  
Thermodynamic Quantity ◽  
Second Law Of Thermodynamics ◽  
Quantum Correlations ◽  
Von Neumann Entropy ◽  
Second Law ◽  
Carnot Cycle ◽  
Technical Discussion

Quantum entanglement can cause the efficiency of a heat engine to be greater than the efficiency of the Carnot cycle. However, this does not mean a violation of the second law of thermodynamics, since there is no local equilibrium for pure quantum states, and, in the absence of local equilibrium, thermodynamics cannot be formulated correctly. Von Neumann entropy is not a thermodynamic quantity, although it can characterize the ordering of a system. In the case of the entanglement of the particles of the system with the environment, the concept of an isolated system should be refined. In any case, quantum correlations cannot lead to a violation of the second law of thermodynamics in any of its formulations. This article is devoted to a technical discussion of the expected results on the role of quantum entanglement in thermodynamics.

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