Ideal Gas State Research Articles

Thermodynamic Modeling of the Solubility of Quartz in Water up to High Temperatures and Pressures

Available data on speciation of silica in aqueous solutions show that the main forms of silica are the monomer Si(OH)4 and the dimer Si2O(OH)6, with shares of higher polymers growing with an increase of temperature and the total concentration of silica in solution. Thermodynamic properties of the monomer and dimer in the ideal gas state are determined from the quantum-chemical calculations. The fugacity coefficients of these species in water up to water densities of 1200 kg m–3 and temperatures of up to 1350 K are estimated from an empirical correlation based on the stoichiometry of hydroxide species. The fine-tuning of the model is made by comparing calculations with the experimental solubility and speciation data. It was found that to match the speciation results reported as the share of the monomer, it is necessary to consider polymerization of silica beyond the dimer, which can be achieved without increasing the number of fitting parameters. The resulting model reproduces well the experimental results on the solubility of quartz in water, on the distribution of silica between the vapor and liquid phases of water at subcritical temperatures, and on the speciation of silica in water in equilibrium with quartz.

Multi-property evaluation for a gas sample based on the acoustic and electromagnetic resonances measurement in a cylindrical cavity

This study proposes a multi-property evaluation method for a gas sample on the basis of sound speed and relative permittivity measurements by using a cylindrical acoustic-electromagnetic resonator. Validity and reliability of the present apparatus were confirmed from the measurement result for Ar with the relative standard uncertainties of 2 × 10−4 for the sound speed and 4 × 10−6 for the relative permittivity. The sound speed and the relative permittivity measurements for trans-1-chloro-3,3,3-trifluoropropene, which is known as R1233zd(E), were carried out in the wide temperature and pressure ranges to demonstrate the multi-property evaluation for a polar molecular sample. Firstly, specific heat capacity and molar polarization in the ideal-gas state were derived from the sound speed and the relative permittivity data, respectively, based on the acoustic- and the dielectric-virial equations. Secondly, linear regression of the ideal-gas molar polarization and temperature data leaded information of dipole moment and molecular polarizability in accordance with Debye equation. The density-virial coefficients were deduced by use of an empirical correlation with the determined dipole moment on the basis of the corresponding states principle so that the acoustic- and the dielectric-virial coefficients were separately determined from polynomial regression analysis of the sound speed and the relative permittivity data, respectively. Finally, the relative permittivity data in combination with the determined dielectric-virial coefficients yield the value of density. The acquired multi-property data for R1233zd(E) were compared with the existing equation of state or reference model.

Thermodynamic properties of 2-methylfuran

The heat capacity of 2-methylfuranin the temperature range of 8–350 K was determined by vacuum adiabatic calorimetry. The temperature, the enthalpy and the entropy of fusion and purity of investigated sample were determinedbyfractional melting. Thesmoothed thermodynamic functions (changes in enthalpy,entropyand Gibbs energy) in the region of 8–350 K were calculated. The entropies of formation and Gibbs energiesof formationof2-methylfuranat 298.15 K inthe liquid and ideal gas states werefound, using the literature data.

Increase in Axial Compressibility in a Spinning Van der Waals Gas.

We investigated the adiabatic compression along the axial direction of a spinning Van der Waals gas by applying theoretical analysis and molecular dynamics (MD) simulations. Based on the analytical results, the rotation-induced compressibility increase effect is significant in a Van der Waals gas, while the attraction term in the Van der Waals equation of states (EOS) contributes significantly to the compressibility increase in a spinning system. We conducted MD simulations to the axial compression of a spinning gas, whose state is far from the ideal gas state, and further demonstrated that the rotation-induced compressibility increase effect in a dense state is robust, implying that such a phenomenon can be detected in experiments under high-energy-density conditions.

Effect of thermal fluctuation on the thermodynamics of GMGHS black hole

In present paper we discuss the effect of higher order corrections of entropy on the thermodynamic fluctuation of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole (GMGHS), i.,e. charged diatonic black hole. By investigating the thermodynamic property functions, such as the internal energy, the enthalpy, the Helmholtz free energy, the Gibbs free energy and the heat capacity, we find that the correction from the thermodynamic fluctuation is very important for small black hole case and one can neglect the correction for large black hole case. We also find that when there is no thermal fluctuation, this black hole thermodynamic system acts as an ideal gas state. However when we consider the thermal fluctuation, we can see the Van der waals type behavior in GMGHS black hole system. Finally, we discuss the stability of GMGHS black hole by investigating the behaviour of heat capacity under effect of thermal fluctuation, we find that, without any thermal fluctuation, we get the completely unstable black hole. However, with the presence of thermal fluctuation, the black hole becomes stable at smaller value of horizon radius, also there is a stable to unstable phase transition from the corrected specific heat.

Thermal conductivity of R-32/R-125 (40/60 wt. %) mixture in the vapor phase

The gaseous thermal conductivity of binary mixture of R-32/R-125 (40/60) was measured with a coaxial cylinders method in the temperature range of 305–426 K and the pressure range of 0.1–1.8 MPa. The thermal conductivity as a function of pressure and temperature was considered. The correlations for thermal conductivity on dew line and in ideal gas state are presented.

Design and test of porosity testing apparatus for granular materials

In order to improve the accuracy and reliability of porosity measurement of granular materials, on the basis of equation of state of ideal gas and gas displacement method, a rapid measurement apparatus for porosity of granular materials with constant volume was studied and an automatic detection control system was developed. Within measurement range of 0.1∼ 0.4 MPa, the standard stainless-steel spheres, plastic quadrangular prisms, cobblestones and fine gravels with different shapes accurately measurable were adopted, and it was found that the higher the inflation pressure of the system, the smaller the measurement error and the better the repeatability. Using standard stainless-steel sphere and cylinder with porosity of 16.02%, 25.14%, 35.57%, 49.05%, 58.42%, 67.79%, 76.57%, 85.36% and 94.14% respectively, the formula of compensation coefficient was given. The measurement error was 0.3%, which proved the reliability of the measurement results.

Mechanism and numerical model of bubble effect in oil-paper insulation based on microtubule model

In this paper, a numerical model of bubble evolution is established by studying the microstructure of pressboard and the physical process of bubble generation. In the model, the porous structure of fibers is equivalent to microtubules, the gases in the bubbles are classified into two categories, and the ideal gas state equation is used to describe the bubble state. Then the pressure conditions at the bubble boundary and the evaporation rate of water are taken as solution conditions to solve the physical quantities in the state equation. The numerical model provides a new way to calculate the initial temperature of bubble escape (ITBE). And the bubble evolution inside the pressboard is obtained which is hard to be observed in experiment. After that, the influences of moisture content of pressboard and cellulose aging on ITBE in the numerical model are discussed. The model results show that the expansion rate of bubble is not uniform. Bubble growth is slow in the early stage of temperature rise, when the temperature reaches a certain threshold the growth rate of bubble radius increases significantly, which is of great significance to the temperature limit on oil-immersed power transformers.

On the thermodynamics of relativistic ideal gases in the presence of a maximal length

We investigate the thermostatistics of relativistic ideal gases within the recently proposed deformed Heisenberg algebra (Perivolaropoulos, 2017), which includes a maximal length. By using the semiclassical method, the generalized canonical partition function is established and the modified thermodynamic functions are then calculated. It is explicitly shown that the maximal length, unlike the minimal length, modifies the equation of state of relativistic ideal gases. Furthermore, the ultrarelativistic and nonrelativistic regimes are discussed. In contrast to the minimal length corrections, the maximal length corrections do not depend on the considered regime. Such a result confirms that the effects of the maximal length and those of the minimal length are fundamentally different.

The Enthalpy of Formation Of L- α -Amino Acids

The reported values for the enthalpies of formation of α-amino acids in crystalline and ideal gas state are critically examined. Experimental values obtained by means of combustion calorimetry of the solid are compared with values calculated by means of group additivity. The ideal gas enthalpies of formation obtained by combining the solidstate values with the standard sublimation enthalpies are compared with ones calculated both additively and by means of quantum chemistry methods.

The Existence of a Bounded Invariant Region for Compressible Euler Equations in Different Gas States

In this article, by the mean-integral of the conserved quantity, we prove that the one-dimensional non-isentropic gas dynamic equations in an ideal gas state do not possess a bounded invariant region. Moreover, we obtain a necessary condition on the state equations for the existence of an invariant region for a non-isentropic process. Finally, we provide a mathematical example showing that with a special state equation, a bounded invariant region for the non-isentropic process may exist.

Real Gas Models in Coupled Algorithms Numerical Recipes and Thermophysical Relations

In the majority of compressible flow CFD simulations, the standard ideal gas state equation is accurate enough. However, there is a range of applications where the deviations from the ideal gas behaviour is significant enough that performance predictions are no longer valid and more accurate models are needed. While a considerable amount of the literature has been written about the application of real gas state equations in CFD simulations, there is much less information on the numerical issues involved in the actual implementation of such models. The aim of this article is to present a robust implementation of real gas flow physics in an in-house, coupled, pressure-based solver, and highlight the main difference that arises as compared to standard ideal gas model. The consistency of the developed iterative procedures is demonstrated by first comparing against results obtained with a framework using perfect gas simplifications. The generality of the developed framework is tested by using the parameters from two different real gas state equations, namely the IAPWS-97 and the cubic state equations state equations. The highly polynomial IAPWS-97 formulation for water is applied to a transonic nozzle case where steam is expanded at transonic conditions until phase transition occurs. The cubic state equations are applied to a two stage radial compressor setup. Results are compared in terms of accuracy with a commercial code and measurement data. Results are also compared against simulations using the ideal gas model, highlighting the limitations of the later model. Finally, the effects of the real gas formulations on computational time are compared with results obtained using the ideal gas model.

Dipole moment and heat capacity in the ideal gas state derived from relative permittivity and speed of sound measurements for HFO-1123 and HCFO-1224yd(Z)

Abstract The dielectric relative permittivity and speed of sound were simultaneously measured for HFO-1123 and HCFO-1224yd(Z) in the gas phase by using a cylindrical acoustic-electromagnetic cavity resonator. The measurement data for HFO-1123 were obtained in the temperature range of 263 to 333 K and the pressure range of 50 to 520 kPa, and those for HCFO-1224yd(Z) were obtained in the temperature range of 303 to 353 K and the pressure range of 20 to 200 kPa. Both of the fractional standard uncertainties for the relative permittivity and speed of sound measurements were estimated to be typically smaller than 0.02% without taking the sample impurities into account. The dipole moment and density were derived from the relative permittivity data through the dielectric virial equation. Meanwhile, the isobaric heat capacity in the ideal gas state were also derived from the speed of sound data with the acoustic virial equation. The temperature correlations for the ideal gas heat capacities were formulated and compared with the estimated values by the atomic-group contribution methods. It was found from the comparison that the estimated ideal gas heat capacities differed from the present data by more than 2%.

Between supercritical liquids and gases – Reconciling dynamic and thermodynamic state transitions

Experimental, computational, and theoretical results have shown that the notion of a homogeneous supercritical state space has to be replaced with distinct liquid-like and gas-like regions, divided by a cross-over line. Several such cross-over lines have been proposed, such as the Frenkel line, the Fisher-Widom line, and the Widom line. We use thermodynamics arguments, molecular dynamics (MD) simulations, and experimental data to investigate the relation between these lines. This work proposes a new interpretation of the Widom line based on the curvature of the Gibbs free energy, showing that the supercritical cross-over can be evaluated as a projection of the subcritical phase transition from a liquid to an ideal gas state to supercritical conditions. We show that the cross-over across the Widom line should not be regarded as instantaneous, but instead as spreading over a finite temperature interval. The thermodynamic character of the Widom line becomes negligible at reduced pressures p/pcr > 3 and disappears completely at higher pressures p/pcr > 10. We find evidence that measured transitions attributed to the Widom line do in fact match the Frenkel line better. In this way, we suggest a consistent view of the supercritical state space and resolve apparent contradictions.

A combined thermodynamic and crystallographic study of 1,3-diisopropylnaphthalene

The thermodynamic properties and phase behaviour of 1,3-diisopropylnaphthalene were studied for the first time using static vapour pressure measurements, Tian-Calvet calorimetry, and differential scanning calorimetry (DSC). Polymorphic behaviour of the compound was detected and studied in detail by combination of DSC and variable-temperature X-ray powder diffraction. The crystal structure of the disordered metastable phase was obtained using a single-crystal X-ray diffraction for the first time. The experimental study was supplemented by calculating thermodynamic properties in the ideal-gas state using a combination of statistical thermodynamics and quantum-chemical calculations. Recommended vapour pressure equation was derived by simultaneous treatment of vapour pressures, experimental heat capacities of the condensed phases, calculated ideal-gas heat capacities, and temperature and enthalpy of fusion, assuring their mutual thermodynamic consistency.

ЭВОЛЮЦИЯ НЕФТЕГАЗОВОЙ СТРУИ, ИСТЕКАЮЩЕЙ ЧЕРЕЗ РАЗРЫВ МАГИСТРАЛЬНОГО НЕФТЕПРОВОДА (ГАЗОПРОВОДА), РАСПОЛОЖЕННОГО НА ДНЕ ВОДОЕМА

Актуальность исследования связана с растущим интересом к добыче углеводородов на дне Мирового океана. При этом многократно увеличивается опасность аварийного разлива нефтепродуктов в воду. Разливы нефти на платформах Ixtoc-1 и Deepwater Horizon в Мексиканском заливе продемонстрировали неготовность современных методов к быстрой ликвидации аварийных утечек. В связи с этим существует необходимость в исследовании затопленных струй, состоящих из смеси углеводородов (нефти и газа). Кроме этого, при глубоководных разливах многофазной смеси нефти и попутных газов могут образовываться кристаллогидраты, которые могут влиять на динамику распространения этих выбросов. Поэтому изучение динамики распространения струи с учетом гидратообразования позволит сократить время ликвидации возможных утечек. В данной работе рассматривается математическая модель формирования затопленной многофазной струи с учетом гидратообразования при различных начальных условиях. Цель: исследовать формирование затопленной струи в зависимости от начальных условий. Объекты: многофазная струя углеводородов; компоненты струи: нефть, газ, вода; композитные пузырьки, покрытые гидратной оболочкой; характер распространения струйного течения, процесс гидратообразования. Методы. Для описания процесса распространения затопленной струи используется интегральный Лагранжевый метод контрольного объема, согласно которому струя представляется в виде последовательности элементарных объемов, каждый из которых характеризуется линейными размерами и теплофизическими характеристиками. Распространение затопленной струи рассматривается для глубоководных разливов на дне океана, что соответствует случаю, когда на поверхности пузырьков начинают образовываться гидратные оболочки и газовый пузырек превращается в гидратный. Для описания процесса гидратообразования в работе принята предельная схема, согласно которой гидратообразвание лимитируется диффузией газа через гидратную оболочку. Результаты. Дополнена математическая модель течения многофазной затопленной струи с учётом образования гидрата на поверхности пузырьков. Получены зависимости теплофизических характеристик затопленной струи от вертикальной координаты, траектория распространения струи. Для пузырьков метана, которые покрываются гидратной оболочкой, применено уравнение состояния для реальных газов. В результате расчетов получены зависимости радиусов газовой и гидратной составляющих композитного пузырька и его плотности от вертикальной координаты. Установлено, что радиус гидратной составляющей пузырька убывает для случая, когда поведение газа описывается уравнением состояния для идеального газа, и растет для случая применения уравнения состояния для реального газа.

Dispersion and behavior of hydrogen for the safety design of hydrogen production plant attached with nuclear power plant

Development of nuclear energy and hydrogen energy both as renewable energy open up a vast range of prospects. The scheme for hydrogen generation station in nuclear power plant has been carried out in china. However, Nuclear Energy is expected to encourage a safety culture that prevents serious accidents while dispersion of hydrogen from a container produces a risk of combustion. The dispersion and behavior of hydrogen production plant attached with nuclear power plant are still poorly understood. In this paper, a dispersion of hydrogen model is established and is calculated under two typical condition with corrected ideal gas state equation. The flammability of hydrogen after dispersion is studied. The range of flammability of dispersion of hydrogen production plant with different pressures, positions and temperatures is obtained. This work could contribute to the marginal hydrogen safety design for hydrogen production station and lay the foundation for the establishment of a safe distance standard that it's necessary to prevent hydrogen explosion.

Ultrahigh Density of Gas Molecules Confined in Surface Nanobubbles in Ambient Water

To understand the unexpected and puzzling long-term stability of nanoscale gas bubbles, it is crucial to probe their nature and intrinsic properties. We report herein synchrotron-based scanning transmission X-ray microscopy (STXM) evidence of highly condensed oxygen gas molecules trapped as surface nanobubbles. Remarkably, the analysis of absorption spectra of a single nanobubble revealed that the oxygen density inside was 1-2 orders of magnitude higher than that in atmospheric pressure, and these bubbles were found in a highly saturated liquid environment with the estimated oxygen concentration to be hundreds of times higher than the known oxygen solubility in equilibrium. Molecular dynamics simulations were performed to investigate the stability of surface nanobubbles on a heterogeneous substrate in gas-oversaturated water. These results indicated that gas molecules within confinement such as the nanobubbles could maintain a dense state instead of the ideal gas state, as long as their surrounding liquid is supersaturated. Our findings should help explain the surprisingly long lifetime of the nanobubbles and shed light on nanoscale gas aggregation behaviors.

Heat kernel approach for confined quantum gas

In this paper, based on the heat kernel technique, we calculate equations of state and thermodynamic quantities for ideal quantum gases in confined space with external potential. Concretely, we provide expressions for equations of state and thermodynamic quantities by means of heat kernel coefficients for ideal quantum gases. Especially, using an analytic continuation treatment, we discuss the application of the heat kernel technique to Fermi gases in which the expansion diverges when the fugacity [Formula: see text]. In order to calculate the modification of heat kernel coefficients caused by external potentials, we suggest an approach for calculating the expansion of the global heat kernel of the operator [Formula: see text] based on an approximate method of the calculation of spectrum in quantum mechanics. We discuss the properties of quantum gases under the condition of weak and complete degeneration, respectively. Moreover, we give an expansion of the one-loop effective action in D-dimensional space.

Mathematical Model of Small-Volume Air Vessel Based on Real Gas Equation

The gas characteristics of an air vessel is one of the key parameters that determines the protective effect on water hammer pressure. Because of the limitation of the ideal gas state equation applied for a small-volume vessel, the Van der Waals (VDW) equation and Redlich–Kwong (R–K) equation are proposed to numerically simulate the pressure oscillation. The R–K polytropic equation is derived under the assumption that the volume occupied by the air molecules themselves could be ignored. The effects of cohesion pressure under real gas equations are analyzed by using the method of characteristics under different vessel diameters. The results show that cohesion pressure has a significant effect on the small volume vessel. During the first phase of the transient period, the minimum pressure and water depth calculated by a real gas model are obviously lower than that calculated by an ideal gas model. Because VDW cohesion pressure has a stronger influence on the air vessel pressure compared to R–K air cohesion pressure, the amplitude of head oscillation in the vessel calculated by the R–K equation becomes larger. The numerical results of real gas equations can provide a higher safe-depth margin of the water depth required in the small-volume vessel, resulting in the safe operation of the practical pumping pipeline system.