Thermodynamic properties of 1,1,1,2-tetrafluoroethane + polyether mixtures up to 60 MPa

2004 ◽  
Vol 82 (8) ◽  
pp. 1271-1279 ◽  
Author(s):  
M JP Comuñas ◽  
C Boned ◽  
A Baylaucq ◽  
E R López ◽  
J Fernández
Keyword(s):  
Thermal Expansion ◽  
Thermodynamic Properties ◽  
Internal Pressure ◽  
Thermal Expansion Coefficient ◽  
Dimethyl Ether ◽  
Expansion Coefficient ◽  
Isothermal Compressibility ◽  
Isobaric Thermal Expansion ◽  
Hfc 134A ◽  
Isobaric Thermal Expansion Coefficient

In this work we report several derived thermodynamic properties, the isothermal compressibility (κT), the isobaric thermal expansion coefficient (αp), and the internal pressure (π), and their excess functions (κTE, αpE, and πE) for the refrigerant + lubricant mixtures HFC-134a + triethylene glycol dimethyl ether and HFC-134a + tetraethylene glycol dimethyl ether. These properties have been determined in wide temperature (293.15–373.15 K) and pressure (10–60 MPa) ranges in an effort to better understand the behaviour of these kinds of mixtures and their thermophysical properties as functions of temperature, pressure, and composition. The analysis of the thermodynamic excess properties (negative values for κTE and αpE, positive values for πE) for both systems shows a high degree of interaction between the refrigerant and the synthetic lubricant molecules. Key words: HFC-134a, high pressure, internal pressure, isobaric thermal expansion coefficient, isothermal compressibility, polyglycol ethers, refrigerant–lubricant mixtures.

scholarly journals Isochoric Specific Heat in the Dual Model of Liquids

2021 ◽  
Author(s):  
Fabio Peluso
Keyword(s):  
Thermal Expansion ◽  
Specific Heat ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Liquid State ◽  
Degrees Of Freedom ◽  
Dual Model ◽  
Isobaric Thermal Expansion ◽  
Isobaric Thermal Expansion Coefficient ◽  
Phonon Theory

We continue in this paper to illustrate the implications of the Dual Model of Liquids (DML) by deriving the expression for the isochoric specific heat as function of the collective degrees of freedom available at a given temperature and analyzing its dependence on temperature. Two main tasks will be accomplished. First, we show that the expression obtained for the isochoric specific heat in the DML is in line with the experimental results. Second, the expression will be compared with the analogous one obtained in another theoretical dual model of the liquid state, the Phonon Theory of Liquid Thermodynamics. This comparison will allow to get interesting insights about the number of collective degrees of freedom available in a liquid and on the value of the isobaric thermal expansion coefficient, two quantities that are related to each other in this framework.

Investigation of the Thermodynamic Properties of Anharmonic Crystals with Defects and Influence of Anharmonicity in Exafs by the Moment Method

1998 ◽  
Vol 12 (02) ◽  
pp. 191-205 ◽  
Author(s):  
Vu Van Hung ◽  
Nguyen Thanh Hai
Keyword(s):  
Thermal Expansion ◽  
Thermodynamic Properties ◽  
Phase Change ◽  
Specific Heat ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Moment Method ◽  
Adiabatic Compressibility ◽  
Relative Displacement ◽  
The Moment

By the moment method established previously on the basis of the statistical mechanics, the thermodynamic properties of a strongly anharmonic face-centered and body-centered cubic crystal with point defect are considered. The thermal expansion coefficient, the specific heat Cv and Cp, the isothermal and adiabatic compressibility, etc. are calculated. Our calculated results of the thermal expansion coefficient, the specific heat Cv and Cp… of W, Nb, Au and Ag metals at various temperatures agrees well with the measured values. The anharmonic effects in extended X-ray absorption fine structure (EXAFS) in the single-shell model are considered. We have obtained a new formula for anharmonic contribution to the mean square relative displacement. The anharmonicity is proportional to the temperature and enters the phase change of EXAFS. Our calculated results of Debye–Waller factor and phase change in EXAFS of Cu at various temperatures agrees well with the measured values.

scholarly journals First-principles investigation of mechanical and thermodynamic properties of nickel silicides at finite temperature -=SUP=-*-=/SUP=-

2018 ◽  
Vol 60 (5) ◽  
pp. 964
Author(s):  
Zhiqin Wen ◽  
Yuhong Zhao ◽  
Hua Hou ◽  
Liwen Chen
Keyword(s):  
Heat Capacity ◽  
Thermal Expansion ◽  
High Temperature ◽  
Thermodynamic Properties ◽  
Thermal Expansion Coefficient ◽  
Debye Temperature ◽  
Expansion Coefficient ◽  
Finite Temperature ◽  
Volumetric Thermal Expansion Coefficient ◽  
Nickel Silicides

AbstractFirst-principles calculations are performed to investigate lattice parameters, elastic constants and 3D directional Young’s modulus E of nickel silicides (i.e., β-Ni_3Si, δ-Ni_2Si, θ-Ni_2Si, ε-NiSi, and θ-Ni_2Si), and thermodynamic properties, such as the Debye temperature, heat capacity, volumetric thermal expansion coefficient, at finite temperature are also explored in combination with the quasi-harmonic Debye model. The calculated results are in a good agreement with available experimental and theoretical values. The five compounds demonstrate elastic anisotropy. The dependence on the direction of stiffness is the greatest for δ-Ni_2Si and θ-Ni_2Si, when the stress is applied, while that for β-Ni_3Si is minimal. The bulk modulus B reduces with increasing temperature, implying that the resistance to volume deformation will weaken with temperature, and the capacity gradually descend for the compound sequence of β-Ni_3Si > δ-Ni_2Si > θ-Ni_2Si > ε-NiSi > θ-Ni_2Si. The temperature dependence of the Debye temperature ΘD is related to the change of lattice parameters, and ΘD gradually decreases for the compound sequence of ε-NiSi > β-Ni_3Si > δ-Ni_2Si > θ-Ni_2Si > θ-Ni_2Si. The volumetric thermal expansion coefficient αV, isochoric heat capacity and isobaric heat capacity C _ p of nickel silicides are proportional to T ^3 at low temperature, subsequently, αV and C _ p show modest linear change at high temperature, whereas C _v obeys the Dulong-Petit limit. In addition, β-Ni_3Si has the largest capability to store or release heat at high temperature. From the perspective of solid state physics, the thermodynamic properties at finite temperature can be used to guide further experimental works and design of novel nickel–silicon alloys.

scholarly journals Isochoric Specific Heat in the Dual Model of Liquids

Liquids ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 77-95
Author(s):  
Fabio Peluso
Keyword(s):  
Thermal Expansion ◽  
Specific Heat ◽  
Thermal Expansion Coefficient ◽  
Liquid State ◽  
Degrees Of Freedom ◽  
Dual Model ◽  
Isobaric Thermal Expansion ◽  
Collective Degree ◽  
Isobaric Thermal Expansion Coefficient ◽  
Phonon Theory

We continue in this paper to illustrate the implications of the dual model of liquids (DML) by deriving the expression for the isochoric specific heat as a function of the collective degree of freedom available at a given temperature and analyzing its dependence on temperature. Two main tasks have been accomplished. First, we show that the expression obtained for the isochoric specific heat in the DML is in line with the experimental results. Second, the expression has been compared with the analogous one obtained in another theoretical dual model of the liquid state, the phonon theory of liquid thermodynamics. This comparison allows providing interesting insights about the number of collective degrees of freedom available in a liquid and the value of the isobaric thermal expansion coefficient, two quantities that are related to each other in this framework.

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