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Experiments on determination of the sorption isotherms of the heart of a palm at different temperatures have been performed. Some mathematical models, available in the literature, were used to predict the hygroscopic behavior of the palm heart. The thermodynamic properties of the palm heart, such as its isosteric heat of sorption, were determined using the Clausius–Clapeyron equation, and the shelf life of the palm heart was calculated using the Heiss–Eichner prediction model equations with regard for the storage conditions of this product and the requirements for its packaging. The results obtained can be used for optimization of the methods of drying and preservation of palm hearts, which is essential for the enhancement of their quality and the successful promotion of them in the international market. [ABSTRACT FROM AUTHOR]

The present study summarizes various findings such as equilibrium moisture contents, effect of temperature and relative humidity, better fitted model for wood sorption, heat transfer characteristic and influence of the wood structure. For this purpose, three African tropical medium-heavy woods were used: Sapelli (Entandrophragma cylindricum (Sprague) Sprague), Sipo (Entandrophragma utile (Dawe & Sprague) Sprague), Kosipo (Entandrophragma candollei Harms). Adsorption and desorption isotherms were measured using the static gravimetric method at 30, 40, 50, 60 °C within the range of 5.5 – 83.6% relative humidity. Thermodynamic properties were calculated from the Clausius-Clapeyron and Avramidis equations. Quantitative anatomical parameters of the woods were determined from the SEM images. Results showed that the highest mean values of the measured anatomical parameters were obtained with Sipo and the lowest with Sapelli. The equilibrium moisture content obtained is relatively lower for Kosipo and higher for Sipo at low temperatures (T < 50 °C) and Sapelli at high temperatures (T ≥ 50 °C). The highest values of thermodynamic properties were obtained with Kosipo and the lowest with Sipo. Results of sorption characteristics are correlated with the anatomical structure of the woods studied. Sipo, with lower density (0.64) and higher vessel diameter, vessel proportion and ray size, has higher moisture content and lower thermodynamic properties. However, this trend is not respected between Kosipo and Sapelli. Kosipo, with a higher density and anatomical parameters, has lower moisture content and higher thermodynamic properties than Sapelli. This could be explained by a lower content of amorphous polymers and the presence of silica in some anatomical elements of Kosipo. [ABSTRACT FROM AUTHOR]

The efficiency of activated carbons prepared from corncob, to remove asphaltenes from toluene modeled solutions, has been studied in this work. The activating agent effect over carbonaceous solid preparation , and also temperature effect on the asphaltenes adsorption on the prepared activated carbons, was studied. The asphaltene adsorption isotherms were determined, and the experimental data were analyzed applying the Langmuir, Freundlich, Redlich–Peterson, Toth and Radke–Prausnitz and Sips models. Redlich–Peterson model described the asphaltenes isotherm on the activated carbons better. The asphaltenes adsorption capacities at 25° for activated carbons were: 1305 mg g−1, 1654 mg g−1 and 559.1 mg g−1 for GACKOH, GACKP and GACH3PO4, respectively. Thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were also evaluated from the adsorption isotherms in asphaltene solutions from toluene solutions, and it was found that the adsorption process was spontaneous and exothermic in nature. Kinetic parameters, reaction rate constant and equilibrium adsorption capacities were evaluated and correlated for each kinetic model. The results show that asphaltene adsorption is described by pseudo-second-order kinetics, suggesting that the adsorption process is chemisorption. The adsorption calorimetry was used to analyze the type of interaction between the asphaltenes and the activated carbons prepared in this work, and their values were compared with the enthalpic values obtained from the Clausius–Clapeyron equation. [ABSTRACT FROM AUTHOR]

The phenomenon of galaxy clustering was studied from the perspective of the gravitational phase transition, which is somewhat different from a phase transition in materials science. There is evidence that the phase transition describing galaxy clustering in an expanding universe is a first‐order phase transition exhibiting a mixed phase. As such, the Clausius–Clapeyron equation is relevant for studying such a system. In this work, we derive a general analog of the Clausius–Clapeyron equation that applies not only toward the coexistence curve in pressure–temperature space, but to a more general parameter space. One key finding is that a cusp exists at the critical point in this mixed phase when viewed in this more general parameter space. We extend this formalism to derive an equation for the curvature of the phase coexistence curve in pressure–temperature space and a more general parameter space. We also verify previous findings of hysteresis in the system via an independent free energy analysis. [ABSTRACT FROM AUTHOR]

An integrated thermodynamic approach for selecting a suitable hydrate former for desalination prior to process design is presented. From amongst the various formers reported in literature, methane, carbon dioxide (CO 2 ), ethane, propane and iso-butane were chosen for this investigation. Simulation studies related to formation of hydrates in pure and saline water (2–8 wt% salt) for the 5 chosen formers have been conducted to predict phase equilibria along with gas solubility in the aqueous phase. A commercial software HydraFLASH was used for this purpose. In addition, the hydration number and phase change enthalpy associated with hydrate formation/dissociation has been calculated, the latter determined using the Clapeyron equation. Simulation results wherever appropriate were validated with experimental data and good agreement was observed. The implications of the thermodynamic data obtained on desalination process design have been discussed to arrive at a suitable choice of former. The results favor propane and ethane as preferred candidates for hydrate based desalination. [ABSTRACT FROM AUTHOR]

The highest rainfall totals (912.2 mm) and the largest number of raindays (133 days), since 1958, were recorded in Thessaloniki during the year of 2014. Extreme precipitation heights were also observed on a seasonal, monthly and daily basis. The examined year presented the highest daily rainfall intensity, the maximum daily precipitation and the largest number of heavy precipitation days (greater than 10 mm), and it also exceeded the previous amounts of precipitation of very wet (95th percentile) and extremely wet (99th percentile) days. According to the automatic circulation type classification scheme that was used, it was found that during this exceptionally wet year, the frequency of occurrence of cyclonic types at the near surface geopotential level increases, while the same types decreased at a higher atmospheric level (500 hPa). The prevailing type was type C which is located at the centre of the study area (Greece), but several other cyclonic types changed during this year not only their frequency but also their percentage of rainfall as well as their daily precipitation intensity. It should be highlighted that these findings differentiated on the seasonal-scale analysis. Moreover, out of the three teleconnection patterns that were examined (Scandinavian Pattern, Eastern Mediterranean Teleconnection Pattern and North Sea-Caspian Pattern), the Scandinavian one (SCAND) was detected during the most of the months of 2014 meaning that it was highly associated with intense precipitation over Greece. [ABSTRACT FROM AUTHOR]

To obtain the equation of state of liquid bismuth and its melting curve, ultrasonic velocity measurements were performed in a multi-anvil apparatus. Using a series of thermodynamic relationships, we extract the volume of liquid bismuth as functions of pressure and temperature up to 973 K and 4.3 GPa. We also introduce a calculation process to build the thermal equations of state of each phase of solid bismuth based on their phase transition boundaries. Combining the thermodynamic parameters of liquid and solid bismuth, we employ the Gibbs equation and the Clausius-Clapeyron equation and finally derive the melting curve up to 8 GPa, which shows excellent consistency with most previous theoretical and experimental results. These results not only demonstrate the accuracy of our experimental and theoretical methods, but also demonstrate the feasibility of the thermodynamic method for obtaining unknown melting curves. [ABSTRACT FROM AUTHOR]

A thermodynamic constraint on convective available potential energy (CAPE) in continental environments is established using an idealized one-dimensional model. This theoretical model simplifies the synoptic-scale preconditioning framework for continental severe convection by considering a dry adiabatic column that comes into contact with a moist land surface. A system of equations is derived to describe the evolution of the ensuing surface boundary layer. From these, the maximum value of transient CAPE in the column can be found for any particular combination of surface temperature and moisture. It is demonstrated that, for a given range of surface temperatures, the value of peak CAPE scales with the Clausius-Clapeyron relation. [ABSTRACT FROM AUTHOR]

We use calorimetry and dilatometry under hydrostatic pressure, X-ray powder diffraction and available literature data in a series of composition-related orientationally disordered (plastic) crystals to characterize both the plastic and melting transitions and investigate relationships between associated thermodynamic properties. First, general common trends are identified: (i) The temperature range of stability of the plastic phase T - T (where T and T are the plastic and melting transition temperatures, respectively) increases with increasing pressure and (ii) both the rate of this increase, d( T - T )/ dp, and the entropy change across the plastic transition analyzed as function of the ratio T / T are quite independent of the particular compound. However, the dependence of the entropy change at the melting transition on T / T at high pressures deviates from the behavior observed at normal pressure for these and other plastic crystals. Second, we find that the usual errors associated with the estimations of second-order contributions in the Clausius-Clapeyron equation are high and thus these terms can be disregarded in practice. Instead, we successfully test the validity of the Clausius-Clapeyron equation at high pressure from direct measurements. [ABSTRACT FROM AUTHOR]

Accurate estimation of the isosteric heat of adsorption is mandatory for a good modeling of adsorption processes. In this paper a thermodynamic formalism on adsorbed phase volume which is a function of adsorption pressure and temperature has been proposed for the precise estimation of the isosteric heat of adsorption. The estimated isosteric heat of adsorption using the new correlation has been compared with measured values of prudently selected several adsorbent-refrigerant pairs from open literature. Results showed that the proposed isosteric heat of adsorption correlation fits the experimentally measured values better than the Clausius-Clapeyron equation. [ABSTRACT FROM AUTHOR]

The production of plasmas during hypervelocity meteoroid and space debris impact has been proposed to explain the presence of paleomagnetic fields on the lunar surface, and also the electromagnetic damage to spacecraft electronic devices. Based on Gibbs' ensemble theory, we deduce Saha equation of state and figure out the ionization degree; further, by using the derivation of Clausius-Clapeyron equation, we obtain the entropy increase and latent heat of plasma transition after vaporization; finally, we analyze the conversion efficiency of kinetic energy into internal energy, present two key contradictions, and revise them with the entropy increase, latent heat, and conversion efficiency. We analyze the aluminum plasma transition from multiple perspectives of the equation of state, latent heat of phase transition, and conversion efficiency and propose the internal energy and impact velocity criterion, based on the laws of thermodynamics. [ABSTRACT FROM AUTHOR]

Thermodynamic properties were obtained from desorption isotherm data for papaya at 40, 50, 60 and 70C. The specific objectives were to model desorption isotherms by GAB and BET models and to apply the enthalpy-entropy compensation theory to desorption isotherm. The GAB model fitted well the data with monolayer moisture content varying from 0.086 to 0.103 g water/g solids. Equilibrium moisture content decreased with increasing temperature. The net isosteric heat of desorption was determined using Clausius-Clapeyron equation and decreased with increasing moisture content varying from 2.52 to 14.26 kJ/mol. The differential entropy values decreased with moisture content from 0.037 to 0.007 J/mol K. The enthalpy-entropy theory proved to be valid since the relationship between enthalpy and entropy was linear and the harmonic temperature (327.6 K) differed from the sample isokinetic temperature (383.4 K). Through the entropy-enthalpy theory, it could be concluded that the water desorption isotherm of papaya is a nonspontaneous process and enthalpy controlled. [ABSTRACT FROM AUTHOR]

The theoretical description of water properties continues to be a challenge. Using quantum cluster equilibrium (QCE) theory, we combine state-of-the-art quantum chemistry and statistical thermodynamic methods with the almost historical Clausius–Clapeyron relation to study water self-dissociation and the thermodynamics of vaporization. We pay particular attention to the treatment of internal rotations and their impact on the investigated properties by employing the modified rigid-rotor–harmonic-oscillator (mRRHO) approach. We also study a novel QCE parameter-optimization procedure. Both the ionic product and the vaporization enthalpy yield an astonishing agreement with experimental reference data. A significant influence of the mRRHO approach is observed for cluster populations and, consequently, for the ionic product. Thermodynamic properties are less affected by the treatment of these low-frequency modes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solid-vapor equilibrium of Lennard-Jones fluid in cylindrical nanopore was examined. • Molecular dynamics (MD) determined solid-vapor equilibrium curves. • Prediction by thermodynamic model was consistent with the MD results. • The thermodynamic model does not contain any tuneable parameters. • The entire phase equilibrium of the three states can be calculated thermodynamically. Molecular dynamics (MD) simulations were used to study the coexistence of solids and vapors of Lennard–Jones methane condensed within cylindrical carbon nanopores. The simulated unit cell includes both the inside and outside of the pores. This allowed us to observe the solid-vapor coexistence within the pores while simulating the pressure depression of the bulk vapor outside the pores. The condensates in the pores were cooled in stages, and the equilibrium vapor pressures were determined at each temperature. The obtained vapor–solid coexistence curves showed significantly lower shifts in pressure than those in the bulk phase. The results of the MD simulations were compared with the Clausius–Clapeyron equation starting from the triple point in the nanopores. The thermodynamic model successfully predicted the simulation results without introducing tunable parameters, demonstrating this concept's validity. Thus, a whole Lennard-Jones phase diagram in cylindrical nanopores can now be predicted. [ABSTRACT FROM AUTHOR]

The moisture sorption isotherms of potato and sweet potato flakes were determined using a gravimetric method at 15, 20, 25 and 30°C for water activity ranging from 0.1 to 0.9. The GAB was found to be the most suitable for describing the relationship between equilibrium moisture content and water activity for the whole range of temperatures and relative humidities. The differential and integral thermodynamic functions of enthalpy and entropy were estimated from the sorption data for potato and sweet potato flakes. The differential enthalpy was determined using the Clausius-Clapeyron equation and decreased with increase in moisture content, the same behavior as found for differential entropy. From the values obtained for differential enthalpy and entropy, it was verified that the compensation theory could be applied, the process being carried out by enthalpy (Tβ>Thm) and non-spontaneous (ΔG>0). The spreading pressures increased with increasing water activity for all the temperatures studied. With respect to the integral properties, it was observed that the enthalpy increased with moisture content, but the entropy decreased. It was also shown that for the moisture range evaluated, the values for integral entropy were negative. [ABSTRACT FROM AUTHOR]

The thermodynamic potentials and Clausius–Clapeyron equation are generalized to the solids with arbitrary homogeneous elastic deformations accompanied by change of the solid volume, in particular, to the solids strained by a uniaxial, biaxial, or triaxial pressure. The concept of an ‘effective’ volumeV* = AVof the strained solid is introduced. The proportionality coefficientAdoes not depend on the strain value and is determined by the elastic compliances of the solid and by the stresses ratios. For hydrostatic pressureA = 1. The thermodynamic potentials, the Clausius–Clapeyron equation, and other thermodynamic equations for the strained solids are obtained from the usual ones only by replacingVwithV*. [ABSTRACT FROM AUTHOR]

Abstract: We give a modified derivation of the Einstein equation of state by considering the Clausius relation on a null hypersurface with a non-vanishing expansion (), i.e. not in the equilibrium. The derivation corresponds to choosing a specific observer to the hypersurface, and such a generalization gives a hint how we can improve the original derivation by Jacobson. We also give an interpretation of the thermodynamic relation based on the Noether charge method. [Copyright &y& Elsevier]

Experimental and field observations evidence the effects of capillarity in narrow pores on inhibiting the thermodynamic stability of gas hydrates and controlling their saturation. Thus, precise estimates of the gas hydrate global inventory require models that accurately describe gas hydrate stability in sediments. Here, an equilibrium model for hydrate formation in sediments that accounts for capillary inhibition effects is developed and validated against experimental data. Analogous to water freezing in pores, the model assumes that hydrate formation is controlled by the sediment pore size distribution and the balance of capillary forces at the hydrate–liquid interface. To build the formulation, we first derive the Clausius–Clapeyron equation for the thermodynamic equilibrium of methane and water chemical potentials. Then, this equation is combined with the van Genuchten's capillary pressure to relate the thermodynamic properties of the system to the sediment pore size distribution and hydrate saturation. The model examines the influence of the sediment pore size distribution on hydrate saturation through the simulation of hydrate formation in sand, silt, and clays, under equilibrium conditions and without mass transfer limitations. The results show that at pressure–temperature conditions typically found in the seabed, capillary effects in very fine-grained clays can limit the maximum hydrate saturation below 20% of the host sediment porosity. [ABSTRACT FROM AUTHOR]

The temperature dependence of the saturated vapour pressure of the antifungal drugs – tioconazole (TCZ), miconazole (MCZ) and climbazole (CLZ) – was determined by the inert gas carrier transfer method. The standard molar enthalpies of sublimation at T = 298.15 K calculated from these data were 117.2 ± 0.5 kJ·mol-1 for TCZ ± 0.9, 106.2 ± 1.0 kJ·mol-1 for MCZ and 113.3 kJ·mol-1for CLZ. The vaporization and sublimation enthalpies of the compounds were found by the Langmuir and Clausius-Clapeyron equations without determining the vapour pressures of the drugs. Sublimation enthalpies derived by both these methods were in good agreement. It was shown that it was possible to estimate the thermodynamic sublimation functions by applying the space clusterization approach to the studied and structurally related compounds. In addition, the temperature and enthalpy of fusion of the compounds were measured by differential scanning calorimetry. [ABSTRACT FROM AUTHOR]

• Heat and entropy of vaporization. • A correction to Clausius-Clapeyron equation. • Method to measure Molecular-Weight of a pure compound. • Equations to estimate the Heat of Vaporization of a compound. In this paper we try to survey in depth a well-known "Rule" in the discipline of Thermodynamics the "Trouton's Rule". This empirical Rule is very useful to get a quick estimate to the heat of vaporization of a compound, but in here we think it is challenging to try to understand why this happens. First, why the vaporization entropy is almost constant for clusters of homologous compounds and second to try to estimate this value just with the help of Classical Thermodynamics. There are many empirical or semiempirical attempts to estimate the heat of vaporization with better success then the straight "Trouton's Rule". For instance, the "Everett" equation although provides in some cases better fit, fails on the polar compounds and at extremely low temperature boiling gasses. On the other hand, there is the famous "Clausius-Clapeyron" equation that comes directly from the heart of thermodynamics but requires more data than the previous ones. Practically requires two pairs of pressure to temperature values with the highest possible precision to provide the heat of vaporization but as we will see later the fit to the experimental values unexpectedly fails. In this paper we tried to approach the problem in a theoretical way in order not only to get a deeper understanding but also to a better tuning of the final formulae. We propose here a correction to the "Clausius-Clapeyron" equation that gives excellent fit with either Polar or non-Polar compounds. Consequently, a method to measure the "Molecular Weight" of a substance is proposed. Moreover, we propose some equations (a modification to the "Everett" equation and a theoretical explanation) to calculate the heat o vaporization to polar and non-polar compounds. [ABSTRACT FROM AUTHOR]

We have proposed a consistent thermodynamic scheme for evaluation of enthalpy changes of hydrate phase transitions based on residual thermodynamics. This entails obtaining every hydrate property such as gas hydrate pressure-temperature equilibrium curves, change in free energy which is the thermodynamic driving force in kinetic theories, and of course, enthalpy changes of hydrate dissociation and formation. Enthalpy change of a hydrate phase transition is a vital property of gas hydrate. However, experimental data in literature lacks vital information required for proper understanding and interpretation, and indirect methods of obtaining this important hydrate property based on the Clapeyron and Clausius-Clapeyron equations also have some limitations. The Clausius-Clapeyron approach for example involves oversimplifications that make results obtained from it to be inconsistent and unreliable. We have used our proposed approach to evaluate consistent enthalpy changes of hydrate phase transitions as a function of temperature and pressure, and hydration number for CH4 and CO2. Several results in the literature of enthalpy changes of hydrate dissociation and formation from experiment, and Clapeyron and Clausius-Clapeyron approaches have been studied which show a considerable disagreement. We also present the implication of these enthalpy changes of hydrate phase transitions to environmentally friendly production of energy from naturally existing CH4 hydrate and simultaneously storing CO2 on a long-term basis as CO2 hydrate. We estimated enthalpy changes of hydrate phase transition for CO2 to be 10–11 kJ/mol of guest molecule greater than that of CH4 within a temperature range of 273–280 K. Therefore, the exothermic heat liberated when a CO2 hydrate is formed is greater or more than the endothermic heat needed for dissociation of the in-situ methane hydrate. [ABSTRACT FROM AUTHOR]