thermodynamic properties

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Evaluation of irreversibility in an ammonia-water absorption refrigeration system using three different mathematical models to calculate the thermodynamic properties

Evaluation of irreversibility in an ammonia-water absorption refrigeration system using three different mathematical models to calculate the thermodynamic properties

Second Law or Exergy Analyses of Absorption Refrigeration Systems (ARS) are very important for optimisations based on available work; these analyses are derived from the operating conditions and property calculations. There are several methods available for calculating the thermodynamic properties used in modelling these systems. A thermodynamic study on an ARS with the ammonia-water mixture (base case) was carried out with the objective of analysing the sensitivity of the overall and individual component irreversibility to the thermodynamic property. To this end, three existing methods were used: (M1), a model proposed by Ibrahim and Klein (1993) and used in the Engineering Equation Solver (EES) commercial software; (M2), a model proposed by Tillner-Roth and Friend (1998) and embodied in REFPROP v.8.0 developed by the National Institute of Standards and Technology (NIST); and (M3), a method proposed by Xu and Goswami (1999) that was programmed for this analysis. The obtained differences in the properties and the first law performance of the ARS are insignificant in the determination of the coefficient of performance (COP) (base case: 0.595, M1: 0.596, M2: 0.594, M3: 0.599). For the second law analysis, the overall irreversibility was the same (123.339kW) despite the irreversibilities per component had important differences: the solution heat exchanger (M1: 5.783kW, M2: 6.122kW, M3: 8.701kW), the desorber (generator) (M1: 51.302kW, M2: 45.713kW, M3: 49.098kW) and the rectifier (M1: 0.766kW, M2: 3.565kW, M3: 0.427kW). The components that destroy exergy the most are the desorber, the absorber and the condenser. Keywords: ammonia-water properties; absorption refrigeration; coefficient of performance; irreversibility.
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12 Lee mas

Excess Thermodynamic Properties of Chainlike Mixtures. 1. Predictions from the Soft−SAFT Equation of State and Molecular Simulation

Excess Thermodynamic Properties of Chainlike Mixtures. 1. Predictions from the Soft−SAFT Equation of State and Molecular Simulation

Monte Carlo simulation and theory are used to calculate excess thermodynamic properties of binary mixtures of Lennard-Jones chains. Chainlike molecules are formed by Lennard-Jones spherical sites that are tangentially bonded. This molecular model accounts explictly for the most important microscopic features of real chainlike molecules, such as n-alkanes: repulsive and attractive forces between chemical groups and the connectivity of segments to make up the chain. A version of the statistical associating fluid theory, the so-called Soft - SAFT equation of state, is used to check the theory’s ability to predict this kind of property. Predictions from the theory are directly compared to NPT Monte Carlo simulation results obtained in the present work. The influence of segment size, dispersive energy, and chain length on excess properties is studied using simulation and theory, and results are analyzed and discussed. The equation of state is then used to predict the general trends of some excess thermodynamic properties of real n-alkane binary mixtures, such as excess volumes and heats. In particular, the temperature and chain-length dependence of these properties is studied. The Soft - SAFT theory is found to be able to correctly describe the most important features of excess thermodynamic properties of n-alkane models.
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10 Lee mas

Steam transport simulation in a geothermal pipeline network constrained by internally consistent thermodynamic properties of water

Steam transport simulation in a geothermal pipeline network constrained by internally consistent thermodynamic properties of water

An ActiveX control, SteamTablesGrid, is used to calculate the thermodynamic properties of water. A study of the interrelationship among thermodynamic state variables like temperature, pressure, volume, internal energy, etc. indicates the internal consistency in the thermodynamic properties of steam only. The application of GeoSteamNet is demonstrated in the management and optimization of steam flow in a hypothetical geothermal power plant with two wells and one production unit. GeoSteamNet calculates all the parameters like fluid velocity, different types of energies such as heat loss, mechanical (kinetic and potential) energy, thermal energy, frictional energy, and total energy. Thus, the mass, linear momentum and energy balances at each nodal point in the pipeline network are used to validate the algorithm. Additionally, the computer program can also be used efficiently in the design and construction of geothermal pipeline network.
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12 Lee mas

Thermodynamic properties and phase equilibria of branched chain fluids using first- and second-order Wertheim’s thermodynamic perturbation theory

Thermodynamic properties and phase equilibria of branched chain fluids using first- and second-order Wertheim’s thermodynamic perturbation theory

The theoretical predictions could be improved by intro- ducing some modifications in the model and theory. It is possible to consider a more realistic model in which branched chains are represented by heteronuclear chains, i.e., the segments modeling the chemical groups of alkane mol- ecules can have different molecular parameters. This modi- fication in the model, which introduces different molecular volumes in the description of linear and branched chains, has proven to be important in previous studies of isomeric molecules. 48 A further modification in the model consists of including a more accurate description of the dispersive 共 at- tractive 兲 intermolecular forces. As discussed by Yethiraj and Hall 14 and Escobedo and de Pablo, 15 the effect of branching on the thermodynamic properties of the system will be more pronounced for molecules with attractive interactions, such as the Lennard-Jones intermolecular potential. Unfortunately, there is no analytical expression available at present for the three-body correlation function of the reference fluid 共 as a function of the reduced temperature and density 兲 .
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10 Lee mas

Thermodynamic properties of CO2 during controlled decompression of supercritical extraction vessels

Thermodynamic properties of CO2 during controlled decompression of supercritical extraction vessels

A Supercritical (Sc) Fluid (ScF) is defined as a substance whose pressure and temperature are above its corresponding supercritical conditions. Under these conditions, no condensation takes place either under an isotermic compression or an isobaric cooling. Thermophysical and transport properties of supercritical fluids can vary strongly with changes in pressure and temperature. ScFs have two distinguishable regions, with gas-like properties and liquid-like properties, respectively. The boundary between both regions is defined as the pseudocritical line; which coincides with the local maxima of the specific heat (Pioro et al. 2011). This pseudocritical line nears the isochoric line that passes through the critical point. For the specific case of carbon dioxide (CO 2 ), the critical point is at 30.7 ºC and 7.3 MPa. Saturation and solidification
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66 Lee mas

Association of polymers and small solute molecules with phospholipid membranes

Association of polymers and small solute molecules with phospholipid membranes

Althrough the capability and popularity of MD and MC are growing fast„ Addi- tional there are many hybrid techniques which integrate the features from both MD and MC, many other method, have been developed and used for a more specific task and mission, can also look into the detail of the physical system perspectively. One of a recent work is called Single Chain Mean Field (SCMF) theory, has been applied to study the equilibrium composition of lipid membranes. Different types of coarse- grained model ( 3 -bead-type, 10 -bead-type, 44 -bead-type) of the cell membrane lipid (DMPC) were introduced. Based on the result, essential equilibrium properties of the phospholipid bilayer such as compressibility constant, volume fraction, the free energy and the area per lipid can be obtained with good precision and in accordance with experimental data. The best results are shown for 3 -bead model, which is good enough to reproduce the essential mechanic and thermodynamic properties of lipid membranes. However, such model is too coarse-grained to describe the difference between different types of lipids and more detailed, more beads model is necessary to describe their mixtures. With more beads and more detailed structure, we can gain access to more detailed microscopic information.
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132 Lee mas

Synthesis, microstructural, optical and mechanical properties of yttria stabilized zirconia thin films

Synthesis, microstructural, optical and mechanical properties of yttria stabilized zirconia thin films

Yttria-stabilized zirconia (YSZ) thin films are a technologically important material. It exhibits exceptional properties, such as high chemical and thermal stability, good mechanical properties, high electrical resistivity and magnetic permittivity, low thermal conductivity, good corrosion resistance, high ionic conductivity, and high refractive index [1]. Some of the applications include thin films optics [2–4], as electrolyte material in solid oxide fuel cells [5,6], switchable mirrors [7], and oxygen sensors [5]. On the other hand, multilayers films have been extensively used in soft X-ray optics, such as mirrors [8], optical devices [9], band pass filters, beam splitters, etc. [10]. It is worthwhile to mention that despite the wide range of applications of YSZ thin films, there is a lack of data related to its optical properties, and particularly in the band structure of this important material. A number of techniques have been employed to produce YSZ
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20 Lee mas

Nutritional Properties of Bamboo

Nutritional Properties of Bamboo

Increasing scientific evidence has indicated that consumption of certain foods may lead to reduce risk of certain diseases such as CVD, cancer, and other age-related conditions. Many investi- gations have led to the identification of certain food constituents belonging to the group “bioactive compounds” that can influence metabolism, gene expression, cellular signaling, and interact with disease precursors and disease-developing mechanisms (Rostagno and others 2010). Bioactive compounds are essential and nonessen- tial compounds that occur in nature, are part of the food chain, and have an effect on human health (Kris-Etherton and others 2004; Biesalski and others 2009). Plant food contains many bioac- tive compounds in addition to those that are traditionally consid- ered nutrients. These physiologically active compounds, referred to as “phytochemicals,” are produced via secondary metabolism in relatively small amounts (Rodriguez and others 2006). They are being intensively studied to evaluate their effects on health. Some groups of phytochemicals that have significant health po- tentials are carotenoids, phenolic compounds (flavonoids, phytoe- strogens, phenolic acids), phytosterols and phytostanols, saponins, tocotrienols, organosulfur compounds (allium compounds and glucosinolates), and nondigestible carbohydrates (dietary fiber and prebiotics). These compounds vary widely in chemical structure and function and are grouped accordingly. Because of the many plant-based bioactive compounds that have been identified, there have been numerous epidemiological, clinical, and experimental studies conducted to evaluate their health effects. Phenolic com- pounds, including their subcategory flavonoids, are present in all plants and have antioxidant properties. Plant sterol or phytosterol is a bioactive compound of all vegetable foods. Bamboo shoots are rich in both phenols and phytosterols.
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17 Lee mas

Thermodynamic coarsening arrested by viscous fingering in partially miscible binary mixtures

Thermodynamic coarsening arrested by viscous fingering in partially miscible binary mixtures

We propose the following mechanism to explain the observed supersaturation in the liquid (Fig. 5, insets; see Video 2 [50]). The viscous instability leads to recurrent pinch off of small bubbles from large patches of vapor. A newly formed small bubble is quickly consumed by surrounding larger bubbles due to Ostwald ripening. This is achieved, as shown in Fig. 2, by small bubbles first dissolving into the liquid. The mass transfer into large bubbles is limited by diffusion, implying that if the rate of bubble shedding is large compared with the rate of diffusive mass transfer through the liquid, this disparity will result in an excess dissolved concentration. Therefore, the interplay between hydrodynamic instability and thermodynamic coarsening results in a liquid phase that is, on average, always supersaturated. In other words, the emergence of flow disorder from viscous fingering drives the mixture out of compositional equilibrium permanently.
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5 Lee mas

CHARACTERISTIC PROPERTIES OF QUASIDISKS

CHARACTERISTIC PROPERTIES OF QUASIDISKS

In this section we shall collect some definitions and properties of plane quasiconformal mappings. The basic reference is the book by Lehto and Virtanen to which we refer for all details. In what follows D and D ′ will denote domains in the extended complex plane C =

97 Lee mas

Elaboración de láminas biodegradables a partir de los residuos del almidón de yuca(Manihot esculenta)

Elaboración de láminas biodegradables a partir de los residuos del almidón de yuca(Manihot esculenta)

This research aimed at developing biodegradable sheets from the residues of cassava (Manihot esculenta) starch as an alternative to reduce contamination caused by non-biodegradable residues, as an alternative to using common plastic. The selection of the raw material to be used and its proportions were stablished; due to its availability, cassava starch was used in the highest proportion (80%, 50%, 30%); in addition, water, glycerin and vinegar were used as plasticizers, because of the additional properties that they provide to the plastic. The materials formed 3 mixtures in w/w ratio; 80% starch + 13% water + 0.3% acetic acid + 6.7 glycerin; 50% starch + 42% water + 0.4% acetic acid + 7.6 glycerin; and 30% starch + 5% acetic acid + 8.5 glycerin, each mixture was blended, heated (between 60°C and 67°C) and poured into molds, 6 experimental units of 100g for each mixture were prepared, forming 18 sheets of 15x10 cm. 9 sheets were buried and 9 were left outdoor for 90 days, monitoring was done twice a week until reaching at least 90% of degradation. Treatment 1 which used the highest proportion of raw material (80%) showed the highest degradation time 90.67 ± 0.58 and 59.67 ± 1.53 days outdoor and buried respectively, with a cost of $ 2.82 per sheet.
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50 Lee mas

Estudio teórico de propiedades termodinámicas y optoelectronicas de nuevos materiales fotovoltaicos de banda intermedia = Theoretical study of thermodynamic and optoelectronic properties of new intermediate band photovoltaic materials

Estudio teórico de propiedades termodinámicas y optoelectronicas de nuevos materiales fotovoltaicos de banda intermedia = Theoretical study of thermodynamic and optoelectronic properties of new intermediate band photovoltaic materials

The experimental characterization of bulk intermediate-band materials should show good optoelectronic properties. Thus, the experimental characterization included not only the analysis of optical absorption through diffuse reflectance UV-Vis-NIR spectra and overall efficiency with photocatalytic degradation [20] but also other properties of the materials (e.g.) magnetic behaviour using Electron Paramagnetic Resonance (EPR) spectra. If in the experimental findings the carrier lifetimes on the heavily doped semiconductors show increased values, therefore it is demonstrated that, in fact, the intermediate-band formation annihilates the Shockley-Read-Hall recombination and instead, the promotion of extra carriers takes place [21]. Materials with high resistivity while also showing high photon absorption with clear enhancement of the absorption below the fundamental optical band-gap is also an indication of an intermediate-band formation [22]. In addition, certain materials [23, 24] show a behaviour that demonstrates that while, at high concentration of the dopants, non-radiative recombination might deteriorate the material, at low dopant concentration an increased photoresponse might be related with the formation of an intermediate-band material.
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236 Lee mas

TítuloSelf compacting recycled concrete: basic mechanical properties, rheology, robustness and thixotropy

TítuloSelf compacting recycled concrete: basic mechanical properties, rheology, robustness and thixotropy

Contrary to increasing cement content, increasing aggregate content (relative to a fixed water to cement ratio) increases viscosity, due to increased particle interactions [ERDO05]. The particle size distribution of aggregates significantly influences workability and rheological properties. It is generally accepted that a well graded aggregate with particles of a wide range of sizes decreases viscosity. Increasing the packing density generally improves the flow. The morphological properties of aggregates also influence the rheology of concrete [QUIR03]. Spherical shapes or rounded aggregates give lower viscosity than angular ones. Rounded and smooth aggregates require less water than angular or flat and/or elongated particles to achieve the same slump. Spherical particles flow more easily around each other and result in reduced viscosity. Size distribution and particle shape can be especially important in the case of the microfines of aggregates. Although these increase the water demand of the mixture due to increased surface area, it has been reported that they can improve flow by improving the grading of the fine aggregates.
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323 Lee mas

THERMODYNAMIC ANALYSIS OF THE ABSORPTION ENHANCED STEAM REFORMING OF BIOFUEL MODEL COMPOUNDS

THERMODYNAMIC ANALYSIS OF THE ABSORPTION ENHANCED STEAM REFORMING OF BIOFUEL MODEL COMPOUNDS

total number of atoms of the j th element in the reaction mixture [28]. All calculations were performed through the use of the equilibrium module of the HSC chemistry software [29]. HSC calculates the equilibrium composition of all possible combination of reactions that are able to take place within the thermodynamic system. These equilibrium calculations make use of the equilibrium composition module of the HSC program that is based on the Gibbs free energy minimization technique. The GIBBS program of this module finds the most stable phase combination and seeks the phase compositions where the Gibbs free energy of the system reaches its minimum (equation 2) at a fixed mass balance (a constraint minimization problem, equation 3), constant pressure and temperature.
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50 Lee mas

Thermodynamic analysis of the solubility of propranolol-HCl in ethanol + water mixtures

Thermodynamic analysis of the solubility of propranolol-HCl in ethanol + water mixtures

SUMMARY. Propranolol-HCl (PPN-HCl) is a non selective β -adrenergic blocker widely used in therapeu- tics. Nevertheless, their physicochemical properties in aqueous media have not been adequately studied. In this context, by using the van’t Hoff and Gibbs equations the thermodynamic functions Gibbs energy, en- thalpy, and entropy of solution for this drug in ethanol (EtOH) + water (W) cosolvent mixtures, were eval- uated from solubility data determined at several temperatures. The solubility was the greatest in the mix- tures with 0.60 or 0.70 in mass fraction of EtOH and the lowest in neat W (or neat EtOH, as well) at al- most all the temperatures studied. This behavior shows the cosolvent effect present for this electrolyte drug in this solvent system. By means of enthalpy-entropy compensation analysis, non-linear ΔH soln 0-app vs.
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1 Lee mas

Cálculo de propiedades termodinámicas para mezclas multicomponente en el entorno de programación Android

Cálculo de propiedades termodinámicas para mezclas multicomponente en el entorno de programación Android

37 El objeto de este proyecto consiste en realizar una aplicación Android (Calculator of Thermodynamic properties) con el fin de proporcionar una herramienta orientada a los estudiantes de ingeniería, o cualquier persona interesada en ello, que realice el cálculo de propiedades y estado físico (líquido o vapor), represente las gráficas correspondientes a las relaciones presión-temperatura de los componentes que se deseen (componentes puros), y permita al usuario acceder a una base de datos con los componentes disponibles, que él mismo puede modificar o actualizar a su antojo. Puesto que la orientación del programa es ser para uso académico se ha hecho en inglés y está sujeto a una licencia libre GNU.
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171 Lee mas

Kinetic and thermodynamic studies on transmetalation reactions

Kinetic and thermodynamic studies on transmetalation reactions

D. Pablo Espinet Rubio, con D.N.I. nº 17176361F y D. Juan Ángel Casares González, con D.N.I. nº 09740156R, Catedráticos de Universidad del Departamento de Química Física y Química Inorgánica de la Facultad de Ciencias, como Directores de la Tesis Doctoral Kinetic and Thermodynamic studies on transmetalation reactions, presentada por Desiré Carrasco Fernández dentro del programa: “Doctorado en Química: Química de síntesis, métodos de separación, catálisis y materiales avanzados” impartido por el Instituto Universitario CINQUIMA, autorizan la presentación de la misma, considerando que cumple todos los requisitos para ello.
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220 Lee mas

Computer simulation of nanoparticles translocation through phospholipid membranes within single chain mean field approach

Computer simulation of nanoparticles translocation through phospholipid membranes within single chain mean field approach

There is a number of different techniques, how the simulation of the membrane with a chosen approximation can be performed. While some properties of the mem- brane can be estimated purely analytically, better approach is to run a computer simulation with the use of Molecular Dynamics (MD) or Monte-Carlo (MC) meth- ods. The Molecular Dynamics is the most “brute-force” approach, dealing with numerical solving of Newton’s equations of motion for the molecules presented in the system. It gives the most detailed information about the evolution of the system in time, and represents its true dynamics behavior. On the other hand this method is the most computationally expensive, and if the equilibrium properties of the sys- tem should be studied, it can take a lot of time to reach the equilibrium with MD method. Unquestionable advantage of the method, emerging from its popularity, is availability of free and commercial program packages for performing the simu- lations, and existing of good models already fitted for description of phospholipid membranes.
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77 Lee mas

MC 2312 Fluid Mechanics – White pdf

MC 2312 Fluid Mechanics – White pdf

The limiting volume * is about 10 9 mm 3 for all liquids and for gases at atmospheric pressure. For example, 10 9 mm 3 of air at standard conditions contains approximately 3 10 7 molecules, which is sufficient to define a nearly constant density according to Eq. (1.1). Most engineering problems are concerned with physical dimensions much larger than this limiting volume, so that density is essentially a point function and fluid proper- ties can be thought of as varying continually in space, as sketched in Fig. 1.2a. Such a fluid is called a continuum, which simply means that its variation in properties is so smooth that the differential calculus can be used to analyze the substance. We shall assume that continuum calculus is valid for all the analyses in this book. Again there are borderline cases for gases at such low pressures that molecular spacing and mean free path 3 are com- parable to, or larger than, the physical size of the system. This requires that the contin- uum approximation be dropped in favor of a molecular theory of rarefied-gas flow [8]. In principle, all fluid-mechanics problems can be attacked from the molecular viewpoint, but no such attempt will be made here. Note that the use of continuum calculus does not pre- clude the possibility of discontinuous jumps in fluid properties across a free surface or fluid interface or across a shock wave in a compressible fluid (Chap. 9). Our calculus in Chap. 4 must be flexible enough to handle discontinuous boundary conditions.
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1023 Lee mas

Application of the Extended Hildebrand solubility approach applied to mitomycin C in ethanol + water mixtures

Application of the Extended Hildebrand solubility approach applied to mitomycin C in ethanol + water mixtures

334.33, IUPAC [6-Amino-8a-methoxy-5-methyl-4,7- dioxo-1,1a,2,4,7,8,8a,8b-octahydroazireno[2',3':3,4] pyrrolo[1,2-a]indol-8-yl]methyl carbamate, CAS Registry No.: 50-07-7) (Gandhi and Murthy, 2012) is an antibiotic and anti-neoplastic material isolated from the broth of Streptomyces caespitosus and is one of the naturally occurring antibiotics that was first discovered in 1956 (Hata, et al., 1956). This drug has been demonstrated to have antifibroblastic activity in vitro and in vivo (Unal, 2004). It is an antineoplastic antibiotic that acts as an alkylating agent by inhibiting DNA and protein synthesis. It can inhibit cell division, protein synthesis, and fibroblast proliferation (Rahbar, et al., 2000). Despite the usefulness of these drugs, their physicochemical properties in aqueous solution have not yet studied completely (Budavari, et al., 2001; Gandhi and Murthy, 2012). In particular, it is well known that their solubilities in neat aqueous media are very low (Jouyban, 2010). It is noteworthy that cosolvency is the best technique used in pharmacy for increasing drugs solubility (Rubino, 1988; Yalkowsky, 1999). On the other hand, it is clear that predictive methods of physicochemical properties of drugs, in particular the ones intended to estimate solubilities, are very important for industrial pharmacists because they allow optimizing several design processes (Budavari, 2001; Martin, et al., 1993; Regosz, et al., 1992; Martínez and Gómez, 2002; Hanaee, et al., 2005).
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10 Lee mas

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