Thermodynamic Analysis Method Research Articles

Temperature dependence and related properties of beta-cyclodextrin inclusion effects on the fluorescence intensities of hydroxycoumarin-based pesticides

The temperature dependence of the enhanced fluorescence intensities of warfarin and coumachlor complexed with β-cyclodextrin was investigated in a temperature range of 15–40°C. From these results, equilibrium constants at six different temperatures (15, 20, 25, 30, 35, 40°C) and the standard-enthalpy and -entropy changes for the complexation of β-cyclodextrin with these pesticides were estimated by means of the stoichiometric and thermodynamic analysis methods. Characterization of the fluorescence-enhancing effect of β-cyclodextrin on these pesticides was done on the basis of equilibrium and thermodynamic properties of the relevant inclusion complexes.

Effect modelling and optimization, a new methodology for combined energy and environment synthesis of industrial processes

Combining mathematical programming and thermodynamic analysis for solving energy integration of industrial processes appears to be a very powerful tool to target minimum energy cost requirements. Defining the role played by thermodynamic analysis and numerical methods allowed us to define a generic method for calculating the energy integration even of complex industrial sites. The method has been adapted to solve combined energy and environments synthesis of industrial processes. In the approach, different alternative process schemes are included in this superstructure, the optimal structure being extracted using MILP optimization that minimizes the cost of energy, including raw materials, fuels and electricity, rather than just thermal energy. This new modelling approach, that allowed us to target process modifications and improvements has been named EMO (effect modelling and optimization). In the paper, we discuss how the approach has been extended to represent the environmental and energy interactions both in terms of objective functions and constraints. Having developed the mathematical tool, we discuss the role that this tool plays in the engineering method developed to reach combined energy and environmental targets in industrial processes. The generic method has been validated on applications in two major industries: one from the pulp and paper industry and one from the brewing industry. The example of the Kraft pulp process is used to illustrate the application of the approach.

Thermogravimetric investigation of the chemical compatibility of graphite and metal oxides

Methods of thermodynamic analysis and gravimetric measurement are used to study graphite and its mixtures with metal oxides heated to 1000°C under nonisothermal conditions. The chemical compatibility of graphite with Al2O3, CaO, SiO2, MgO, Fe2O3, TiO2, Na2O, and K2O is investigated. It is shown experimentally that under the given conditions the loss of mass (Δm /m) in specimens with these additives as reflected by the gravimetric curves does not exceed Δm /m in a purely graphite specimen.

The Influence of the Temperature of Calcination on the Surface Fractal Dimensions of Ca(OH)2-Derived Sorbents

An investigation was carried out on the surface morphological features of two types of mesoporous sorbents derived from fine hydrated lime powder, termed H–CaO and C–CaO. Specifically, the surface fractal dimensions,dSF’s, of the sorbents obtained at various temperatures of calcination have been determined from their respective adsorption–desorption isotherms of nitrogen measured at 77 K, by a recently proposed thermodynamic method of analysis. A definite trend in the variation ofdSFwith the temperature of calcination has been discerned for both sorbents. Moreover, thedSFfor each sorbent attained a maximum at 1273 K. The results of the present work may facilitate our understanding of various phenomena occurring on the irregular interfaces of heterogeneous systems at elevated temperatures.

Characterization of self-affinity in the global regime.

Methods for characterization of self-affine surfaces and measurements of their roughness exponents H are developed. It is shown that for smoothed surfaces, which underwent particular coarse graining or averaging of the small-scale fluctuations, the excess surface area ${\mathit{S}}_{\mathrm{ex}}$ and the mean square root radius of curvature ${\mathit{a}}_{\mathit{c}}$ are related by two distinct asymptotic power laws if ${\mathit{a}}_{\mathit{c}}$ is well below or well above a certain crossover scale ${\mathit{a}}_{\mathrm{cr}}$. In the local regime of self-affinity, when ${\mathit{a}}_{\mathit{c}}$\ensuremath{\ll}${\mathit{a}}_{\mathrm{cr}}$, ${\mathit{S}}_{\mathrm{ex}}$\ensuremath{\propto}(${\mathit{a}}_{\mathit{c}}$/${\mathit{a}}_{\mathrm{cr}}$${)}^{\mathrm{\ensuremath{-}}(1\mathrm{\ensuremath{-}}\mathit{H})}$. In the global regime of self-affinity, when ${\mathit{a}}_{\mathit{c}}$\ensuremath{\gg}${\mathit{a}}_{\mathrm{cr}}$, ${\mathit{S}}_{\mathrm{ex}}$\ensuremath{\propto}(${\mathit{a}}_{\mathit{c}}$/${\mathit{a}}_{\mathrm{cr}}$${)}^{\mathrm{\ensuremath{-}}2(1\mathrm{\ensuremath{-}}\mathit{H})/(2\mathrm{\ensuremath{-}}\mathit{H})}$. The former scaling relationship is consistent with the well known definition of local fractal dimensions ${\mathit{d}}_{\mathrm{loc}}$=${\mathit{d}}_{\mathrm{top}}$+1-H. The latter scaling relationship offers alternatives for characterization of self-affinity over large scales by means of excess dimensions defined as ${\mathit{d}}_{\mathrm{ex}}$=${\mathit{d}}_{\mathrm{top}}$+2(1-H)/(2-H) and can be used for determination of roughness exponents from the measurements provided in the global regime. The thermodynamic method of fractal analysis, proposed earlier for self-similar surfaces (A.V. Neimark, Pis'ma Zh. Eksp. Teor. Fiz. 51, 535 (1990) [JETP Lett. 51, 607 (1990)]; Physica A 191, 258 (1992)), is extended for self-affine surfaces for determination of fractal dimensions and roughness exponents from adsorption and capillary experimental data.

A diverse approach for the solution of the isothermal multiphase flash problem. Application to vapor‐liquid‐liquid systems

AbstractThe paper presents a novel approach for the solution of the isothermal multiphase flash problem with particular application to systems exhibiting liquid‐liquid‐vapor equilibria. The approach includes a rigorous method for thermodynamic stability analysis as a first step and an efficient phase identification procedure. The stability analysis, exercised only once, uses a modification of the Gibbs tangent plane criterion. The identification procedure implements the results of the stability test in a sequence of liquid‐liquid and liquid‐vapor calculations only till the phase configuration with a minimum Gibbs energy is determined.The efficiency and reliability of the proposed new method is illustrated by solving three typical problems encountered in enhanced oil recovery, natural gas processing and petrochemical industry.

Application of a New Algorithm for Prediction and Modelling of Multiphase Behavior: A Case Study of Some Prototype Natural Gas Systems

The prediction and modelling are studied of complex multiphase behavior of four prototype ternary mixtures typically encountered in cryogenic processing of natural gases, with a new approach for solving the isothermal multiphase flash problem. The method includes a rigorous method for thermodynamic stability analysis as the first step and an efficient phase identification procedure as the second. The new algorithm provides an accurate global description of phase behavior of the studied LNG systems, and excellent agreement of the results obtained with experimental data.

Thermochemical properties of some liquid III–V alloys

Heat contents of the Ga-P, In-P, Ga-As and In-As systems were measured by a drop-calorimeter in the respective concentration ranges of X p = 0.02 to 0.1, X p = 0.05 to 0.5, X As = 0.05 to 0.5 and X As = 0.05 to 0.5, and 1n the temperature ranges of 800 to 1550K. The enthalpies of fusion for InP, GaAs and InAs were determined as 44.09 ± 0.09, 53.36 ± 0.10 and 37.92 ± 0.14kJ g-atom −, respectively, at the corresponding melting points of 1340 ± 1, 1514 ± 1 and 1221 ± 1K. A thermodynamic analysis method was applied to calculate thermodynamic quantities such as the Gibbs free energies of mixing in the liquid Ga-P, In-P, Ga-As and In-As systems. An optimization of experimental data for these systems were carried out, and the coefficients for the excess Gibbs free energies of mixing for the liquid phase were derived in this study.

A network thermodynamic method of analysis and simulation of membrane transport during cryopreservation

A network thermodynamic method of analysis and simulation of membrane transport during cryopreservation

Exergy analysis of multi-stage desalination plants

In improving thermal schemes the exergy method of thermodynamic analysis has been used. This allowed optimal distribution of parameters within the elements of the thermal scheme to be made. Such distribution substantially reduces exergy losses during irreversible processes. It was established by the exergy method that the highest exergy losses occurred during the heat exchange, much less losses took place during separation of sea water into brine and fresh water, and the least exergy losses could be observed during hydrodynamic processes.

Thermodynamic Formulations of Excess and Absolute Values of Adsorption on Solid Surfaces: A Comparison of One- and Two-Phase Approaches

The generally used methods of thermodynamic adsorption analysis are summarized in two basic concepts: the two-phase approach (which is an adequate picture of volume phase thermodynamics in adsorption) and the one-phase approach (which uses excess values for the thermodynamic description of adsorption). Differential and integral molar values of adsorption Δ a X̄ and Δ a X in the two-phase approach are not identical with the corresponding excess values Δ a X̄s and Δ a Xs in the one-phase approach. Especially at high temperatures and high pressures they may be entirely different. It is shown that the experimental methods most usually in adsorption thermodynamics (as adsorption volumetry and gravimetry) give excess data which are to be used in the one-phase approach but which can be transformed to the two-phase approach. Using statistical thermodynamic calculations the difference between these basic concepts is shown over a wide temperature range for the first virial coefficient, the internal energy and the heat capacity of adsorption.

Thermodynamic study of the liquid Fe-S system by use of a drop calorimeter

Heat contents of the Fe-S system were measured with a drop calorimeter in the sulfur composition range X s = 0.380–0.500 (FeS) and in the temperature range 942–1506 K to construct an ( H T - H 298.15)-temperature-composition ternary diagram. By use of a thermodynamic analysis method, the mixing free energy, enthalpy and entropy of the liquid Fe-S mixtures were determined at 1473 and 1523 K, based on the measured heat contents. The partial molar free energies (activity of iron and partial pressure of diatomic sulfur) agreed well with the literature values, suggesting the applicability of the thermodynamic analysis method for liquid mixtures with semi-metals or chalcogen.

Thermodynamic investigation of the liquid PbS system by using a drop calorimeter

Heat contents of the PbS system were measured by a drop calorimeter in the composition range of sulfur X s = 0 to 0.5 (PbS) and in the temperature range of 560 to 1500 K, and a heat content-temperature-composition ternary diagram was constructed. By using a quantitative thermodynamic analysis method, free energy, heat and entropy of mixing in the liquid PbS binary and PbPbS pseudo-binary systems were derived from the measured heat contents. The obtained partial molar free energies of mixing (activities) are considerably different from those estimated by the use of a regular solution model.

Exergy concepts for thermal plant: First of two papers on exergy techniques in thermal plant analysis

In this work the concepts applicable to a method of thermodynamic analysis known as exergy analysis are defined and discussed. Expressions are obtained for exergy components of a steady stream of matter and the relationship between the exergy of a steady stream of matter and that of a closed system is derived. The concept of the standard environment is introduced, its relationship to standard chemical exergy is established, and tables of standard chemical exergy of chemical elements are presented. An idealized model of an open system interacting with the standard environment is used to show the relationship between absolute availability function and exergy.

A Study on Combustion Processes in a Direct Injection Diesel Engine : 1st Report, A Method of Thermodynamic Analysis Using Measured Flame Temperature

A Study on Combustion Processes in a Direct Injection Diesel Engine : 1st Report, A Method of Thermodynamic Analysis Using Measured Flame Temperature

Thermodynamic theory of thin-filmHe3-He4solutions

Expectations are presented with regard to the concentration profile and the extent of superfluidity in thin films of /sup 3/He-/sup 4/He in a Van der Waals field. A thermodynamic method of analysis is outlined which, although treating a somewhat idealized configuration, is amenable to experimental confirmation. The connection between this analysis and experiment is discussed in detail. (AIP)

Chemical thermodynamics for optimization of epitaxial film deposition processes

Systems used in epitaxial technology are classified from the point of view of the amount of initial information needed and the appropriate method of thermodynamic analysis to be used. New technological possibilities are revealed by application of the analysis to some typical systems with several depositing elements. The role of thermodynamic analysis in general optimization procedure is outlined.

A thermodynamic method of bearing analysis : A. Nica, Tribology, 4 (4) (1971) 218–226; 13 figs., 24 refs.

A thermodynamic method of bearing analysis : A. Nica, Tribology, 4 (4) (1971) 218–226; 13 figs., 24 refs.

A Thermodynamic Analysis for Detonation-Free Engine Performance

A method of thermodynamic analysis of power cycles incorporating more complete expansion and turbocharging with after-cooling is presented; it predicts the performance of constant volume combustion engines under detonation-free conditions. The analysis involves expressing the detonation limit in terms of the firing pressure and a theoretical adiabatic end-gas temperature. Expressing the detonation limit in this form, the performance map for any constant volume combustion engine can be predicted. The map yields detonation-free operation over a wide range of bmep and bsfc by identifying the required combinations of fuel-air ratio, compression ratio, expansion ratio, and blower pressure ratio. The analysis requires information on the combustion characteristics of the specific engine, namely, the deviations of the thermal efficiency and the firing pressure from those derived from the equivalent fuel-air cycle. Analysis showed that a significant gain of engine output can be realized without detonation occurring by employing higher blower pressure ratio and firing pressure. The lower limit of fuel consumption is determined directly by the performance of the turbocharger and indirectly by the heating of the inlet air and the detonation limit. Tests performed on a 17-in-bore single cylinder gas engine at two different expansion ratios verified the analytical prediction of detonation-free operation over a wide range of bmep, from 135 to 346 psi. The type of performance map resulting from this analysis is useful in the selection of engine performance and engine parameters for the development of new engines.