Generalization of the Clausius-Clapeyron equation in a coupled thermomechanical model

Knyazeva, A. G.

doi:10.1007/bf02469178

Cited by 7 publications

(3 citation statements)

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“…The mixed gas molecular formula is the sum of the air and LP-EGR molecular formula, each of which uses thermodynamic equations for pressure, temperature, and relative humidity to determine the number of states in the molecules. Based on the Clausius-Clapeyron equation, the partial pressure (P vapor ) of saturated water vapor in the air is calculated using the temperature (T amb ) and relative humidity (Φ) of the ambient air [29].…”

Section: Determination Of Molecular Formula and Condensationmentioning

confidence: 99%

Prediction of Condensation in the Heat Exchangers of Engine Intake Systems according to External Environmental and Operating Conditions

Ju,

Chung,

Lee

et al. 2023

International Journal of Energy Research

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Low-pressure exhaust gas recirculation (LP-EGR) systems are applied to diesel engines because they reduce nitrogen oxide emission by lowering the internal temperature of the cylinder by mixing the oxides with intake air. However, low-temperature ambient conditions include a large amount of vapor in the mixed gas flowing into the intercooler; when heat is exchanged, the water vapor condenses and is adsorbed on the surface of the intercooler fin to form a liquid film. Condensation occurs as the thermal resistance between the vapor and solid surface increases with the thickness of the liquid film and causing a corrosion due to condensation of the surface. In this study, the amount of condensation was predicted through calculations based on thermodynamic studies. Factors that can cause condensation inside the intercooler (fuel, air, and LP-EGR) were selected as variables. A mathematical formula was established to predict the convergence form of condensation or the amount of condensation over time at various temperature and relative humidity conditions. The formula predicted the condensation amount in the intercooler of the diesel engine, compared it to the actual amount of condensation in the test evaluation with an error of less than 4%. Additionally, because the formula can predict the amount of condensation by changing the heat exchange area of the intercooler, the application range of the formula was expanded to predict the condensation in the intercoolers of gasoline vehicles with different heat exchange areas and fuel types. The condensation error was within 2%, indicating a high consistency. Validation of the formula predicts a reliable amount of condensation under various operating and ambient temperature conditions, which means that both the time and cost of the test evaluation require the determination of the cause before solving the actual condensation problem.

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Section: Determination Of Molecular Formula and Condensationmentioning

confidence: 99%

Prediction of Condensation in the Heat Exchangers of Engine Intake Systems according to External Environmental and Operating Conditions

Ju,

Chung,

Lee

et al. 2023

International Journal of Energy Research

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“…Such studies are reviewed, for example, in [Grinfeld, 1990;Ostapenko, 1977], where these problems are also discussed in detail. Investigations in this direction continue presently as well [Knyazeva, 1999].…”

Section: Introductionmentioning

confidence: 96%

Thermomechanics of phase transitions of the first order in solids

Kondaurov¹

2002

Russ. J. Earth Sci.

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Methods of nonequilibrium thermodynamics and continuum mechanics are used for studying phase transitions of the first order in deformable solids with elastic and viscoelastic rheology. A phase transition of the first order is treated as the transition from one branch of the response functional to another as soon as state parameters reach certain threshold values determined by thermodynamic phase potentials and boundary conditions of the problem. Notions of kinematic and rheological characteristics of a phase transition associated with the change of the symmetry group due to the structural transformation and with the difference between thermodynamic potentials in undistorted phase configurations are introduced. In a quasi-thermostatic approximation, when inertia forces and temperature gradients are small, a close system of equations on the interface between deformable solid phases is formulated using laws of conservation. The system of the latter includes, in addition to the traditional balance equations of mass, momentum and energy, the divergence equation ensuring the compatibility of finite strains and velocities. As distinct from the classical case of the liquid (gas) phase equilibrium, the phase transition in solids is supposed to be irreversible due to the presence of singular sources of entropy of the delta function type whose carrier concentrates on the interface between the phases. The relations on the interface including the continuity conditions of the displacement vector, temperature, mass flux and the stress vector, as well as a certain restraint imposed on the jump of the normal component of the chemical potential tensor, are discussed. The latter restraint makes the resulting relations basically distinct from the classical conditions of the phase equilibrium. A generalized Clapeyron-Clausius equation governing the differential dependence of the phase transition temperature on the initial phase deformation is formulated. The paper presents a new relation of the phase transformation theory, namely, the equation describing the differential dependence of the phase transition temperature on the interface orientation relative to the anisotropy axes and the principal axes of the initial phase strain tensor. Based on the relations derived in this study, the phase transformation temperature of an initially isotropic material is shown to assume extreme values if the normal to the interface coincides with the direction of a principal axis of the initial phase strain tensor. The phase transition of the first order in a linear thermoelastic material with small strain values and small deviations of the temperature from its initial value is discussed in detail. A class of materials is distinguished in which an increase in the initial phase strain necessarily changes the character of the phase transformation (a normal phase transition becomes an anomalous one and vice versa). The equilibrium of a compressed viscoelastic layer admitting melting and the effect of stress relaxation in the solid phase on the fluid boun...

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“…Using the condition of equilibrium of the phases, similarly to [16], it is possible to obtain some simple generalizations of the Clausius-Clapeyron equation for phase transitions of the first kind in a deformable solid in the activated state.…”

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confidence: 99%

Thermodynamics of the activated state of materials

Knyazeva

Psakhie

2009

J Appl Mech Tech Phy

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The thermodynamics of irreversible processes is extended to deformable materials whose state and behavior under nonequilibrium conditions are determined by the value and evolution of the additional parameter -the activation parameter. General thermodynamic relations are presented. The concept of the time of existence of a nonequilibrium state is introduced, and the phase coexistence conditions are generalized taking into account the properties of the interface. Methods are described to generalize the relations for irreversible flows, thermodynamic forces, and the equations of state.

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Generalization of the Clausius-Clapeyron equation in a coupled thermomechanical model

Cited by 7 publications

References 1 publication

Prediction of Condensation in the Heat Exchangers of Engine Intake Systems according to External Environmental and Operating Conditions

Prediction of Condensation in the Heat Exchangers of Engine Intake Systems according to External Environmental and Operating Conditions

Thermomechanics of phase transitions of the first order in solids

Thermodynamics of the activated state of materials

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