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Introduction to Thermodynamics
Published in Caroline Desgranges, Jerome Delhommelle, A Mole of Chemistry, 2020
Caroline Desgranges, Jerome Delhommelle
Let us add that if we look at the total sum of work and heat, we end up with the contour integral ∫CWtot + Qtot = 0, meaning that the system goes over a cycle, and thus comes back to exactly the point it started from. It also uncovers something that is crucial for thermodynamics, the concept of state functions. Such functions only depend on the point the system is at and not the path it takes to get there.
Processing Principles
Published in Arthur J. Kidnay, William R. Parrish, Daniel G. McCartney, Fundamentals of Natural Gas Processing, 2019
Arthur J. Kidnay, William R. Parrish, Daniel G. McCartney
Thermodynamic functions are either “State Functions” or “Path Functions.” State functions require knowing only the initial and final states of a system to determine the change in the function. All energy forms, excluding heat and work, mentioned in Section 1.5.3 are state functions. Potential energy provides a simple example. Moving a block from the floor to a table changes the potential energy, and thus the total energy, of the block. This change in potential energy depends only upon the change in elevation. The route taken by the block in going to the table is not relevant. State functions are extremely useful; being independent of path permits state functions to be displayed in charts and tables. An important example is given in the next section.
Chemical Reaction Thermodynamics, Kinetics, and Reactor Analysis
Published in Debabrata Das, Debayan Das, Biochemical Engineering, 2019
In the field of thermodynamics, parameters such as pressure, volume, and temperature are extremely important in order to specify the system conditions. These variables or parameters depict the state of a particular system, and hence they are known as the state functions. Hence, pressure, volume, and temperature may be referred to as state functions. On the other hand, many properties such as work and heat are totally independent of the final and initial states of the system. However, these properties are dependent on the path via which the transformation or change has occurred. Such properties may be termed as path functions.
Thermomechanical response of nonlinear viscoelastic materials
Published in Journal of Thermal Stresses, 2023
A. Khoeini, A. Imam, M. Najafi
In the present study, existence of the entropy function for the nonclassical thermo-viscoelastic materials is established. In addition, an internal rate of production of entropy is defined as a state function for the thermo-viscoelastic materials. Having established existence of the entropy and the internal rate of production of entropy, a balance law for the entropy is derived which is identical to the balance of entropy proposed earlier by Green and Naghdi [19, 20]. The balance of entropy has previously been derived for thermoelastic materials with no viscosity in [24]. The balance of entropy proposed by Green and Naghdi was postulated whereas in the present work it is obtained using the entropy and the internal rate of production of entropy for thermo-viscoelastic materials so that it is not necessary for it to be postulated. Finally, utilizing the balance of entropy, after linearization, a coupled system of differential equations is obtained which describe the thermomechanical response of the classical as well as nonclassical viscoelastic materials.
Pyrolysis of ionic liquid pretreated lignite: Effect of 1-butyl-3-methylimidazolium methyl sulfate pretreatment on kinetic and thermodynamic parameters of lignite
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2021
Saad Saeed, Sana Saeed, Muzaffar Riaz, Muhammad Zahoor, Nabisab Mujawar Mubarak, Sabzoi Nizamuddin, Pranta Barua
Gibbs free energy change (ΔG) is an important thermodynamic state function which gives information about the spontaneity of a reaction and the constant energy production during the process. It is a function of kinetic parameters and peak temperature. In the 1st devolatilization zone, the range of ΔG for untreated lignite was 148.22–159.64 kJ/mol, while for IL-treated lignite, it was 136.78–147.46 kJ/mol (Figure 6(c)). In the 2nd zone, ΔG values increased slightly due to an increase in average temperature, reporting ranges of 149.78–163.63 kJ/mol, and 138.32–151.96 kJ/mol for untreated and IL-treated lignite, respectively (Figure 6(d)). Lower values were obtained for [Bmim][MeSO4] as compared to [Bmim][Cl] and [Emim][Cl] in a previous study (Saeed, Saleem, and Durrani 2020), which is caused by a lower peak temperature. This indicates lower energy production in the case of [Bmim][MeSO4]-pretreated lignite as compared to [Bmim][Cl] and [Emim][Cl].
Effect of doping Zn atom on the structural stability, mechanical and thermodynamic properties of AlLi phase in Mg–Li alloys from first-principles calculations
Published in Philosophical Magazine, 2020
Yuhao Guo, Weicheng Wang, Hanqing Huang, HanHan Zhao, Yuhai Jing, Guangbin Yi, Lan Luo, Yong Liu
The calculated H(T), F(T), S(T) and CV(T) as a thermodynamic state function of temperature for four phases are depicted in Figure 8. In Figure 8(b–d), H(T) and S(T) for four phases gradually increase with an increase in temperature, as well as F(T) decreases as temperature increase. The change in H(T) of the four compounds is consistent with the kBT behaviour and increases almost linearly with temperature [69]. The S(T) describes the dispersal of energy and matter. Figure 8(d) elucidates the change in computed S(T) of the four phases with temperature in consideration of the vibrational contribution. As the temperature gets higher, the difference between the S(T) values of four compounds is increasing. It can be shown that (Al6/8, Zn2/8)Li has the lowest S(T) in the Al–Li–Zn compounds. In addition, H(T), F(T), and S(T) of (Al7/8, Zn1/8)Li, (Al6/8, Zn2/8)Li exhibit a more quickly variety than the other two phases, which may be explained by the difference of phonon frequency.