Kinetic Molecular Theory Of Gases Research Articles

Influence of the leakage in air supply networks on the efficiency of application of pneumatic backfill equipment

Purpose. Determining the influence of the degree of pneumatic energy losses in the non-hermetic air supply network on the efficiency of using installed equipment in the pneumatic method of waste utilization from mining and beneficiation of minerals. To achieve this purpose, a tightness control device was developed using the method of fixed volumes. Methods. Using the molecular-kinetic theory of gases, the thermodynamics and hydrodynamics laws, the characteristics of an open thermodynamic system under excess pressure and with a degree of a capillary-type leakage are investigated. Pneumatic energy losses in the pneumatic supply pipeline are determined by the mass of compressed air leaked due to its poor tightness. Findings. The peculiarities of the tightness control of hollow products by the method of fixed volumes have been summarized. The dependences of non-production losses of compressed air and the corresponding pressure drop on the geometric characteristics of the air supply pipeline, the leakage in supply pipeline, and the time of assessing the degree of leakage have been determined. Originality. For the first time, the relationship between the parameters of compressed air in an open thermodynamic system under excess pressure during air leakage and its heat exchange with the environment has been revealed. The influence of compressed air leakage in air supply networks on the efficiency of using vibration-pneumatic machines with an annular ejector in backfill technologies has been determined. Practical implications. The research results can be used to improve the existing or develop the new technological schemes of air supply equipment that use pneumatic energy at mining and metallurgical enterprises. Minimization of energy consumption can significantly expand the scope of application of pneumatic backfilling method.

Ab initio potential energy surfaces for the O2-O2 system and derived thermophysical properties.

New intermolecular potential energy surfaces (PESs) for the quintet, triplet, and singlet states of two rigid oxygen (O2) molecules in their triplet ground electronic states were developed. Quintet interaction energies were obtained for 896 O2-O2 configurations by supermolecular coupled cluster (CC) calculations at levels up to CC with single, double, triple, and perturbative quadruple excitations [CCSDT(Q)] with unrestricted Hartree-Fock (UHF) reference wave functions. Corrections for scalar relativistic effects were calculated as well. Triplet interaction energies were obtained by combining the quintet interaction energies with accurate estimates for the differences between the quintet and triplet energies obtained at the UHF-CCSD(T) level of theory. Here, we exploited the fact that the triplet state is almost identical to the readily accessible "broken-symmetry" state, as shown by Valentin-Rodríguez et al. [J. Chem. Phys. 152, 184304 (2020)]. The singlet interaction energies were estimated from the quintet and triplet interaction energies by employing the Heisenberg Hamiltonian description of the spin splittings. The three PESs are represented analytically by site-site models with five sites per molecule and anisotropic site-site interactions. To validate the PESs, we calculated at temperatures from 55 to 2000K the second virial coefficient using statistical thermodynamics and the shear viscosity, thermal conductivity, and self-diffusion coefficient in the dilute gas phase using the kinetic theory of molecular gases. The calculated property values are in excellent agreement with the most accurate experimental data from the literature. Therefore, we also propose new reference correlations for the investigated properties based solely on the calculated values.

Production of Hydrogen Molecule from Methane Molecule Amplified with Excitation of Anti-Symmetric Modes of Vibration

Some factors, such as pressure and temperature, affect the rate of chemical reactions. In addition, the activation energy barrier must be overcome for the reaction to be initiated. It can be preferred to overcome this barrier by using catalysts and preheating. The catalyst ensures that it obtains the energy to react quickly by transferring it to the reactants. Similarly, the translational, vibrational, and rotational energy levels of reactants can be increased by preheating. According to the kinetic molecular theory of gases, preheating increases the kinetic energies of the gases and the speed of their collision, so the reaction takes place faster. This study theoretically investigates possible reactions of methane that can occur with the effect of only vibrational energy levels. The vibrational excitation of the molecules affects the reaction rates, and the activation barrier is overcome with lower energies. Using laser-based techniques makes the excitation of well-defined vibrational modes possible. This study investigated inelastic collisions of a methane molecule with well-characterized energy levels in infrared spectroscopy with some gases and the vibrational energy transfers that occur in these collisions. The methane molecule is the simplest form of a molecular structure consisting of more than three atoms of hydrogen atoms, which play an essential role in combustion chemistry. It shows that C⸺H stretch excitation increases the reaction rate of methane (CH4) molecules.

Wpływ stanu nierównoważnego gazów rzeczywistych na ich właściwości

"This scientific work presents a study of areas of application and improvement for the Clapeyron–Mendeleev equation to determine the technological parameters of natural and associated petroleum gas under field conditions. As a result of scientific and practical research and laboratory work, the authors, based on the molecular kinetic theory of gases, developed and improved the Clapeyron–Mendeleev equations of state of real gases by adding some genuine parameters for natural and associated petroleum gases produced from oil and gas condensate fields. In this regard, two additional parameters are introduced in the Clapeyron–Mendeleev equation-relative density and relative velocity of gas: and this, as a new scientific result, helps determine any parameter from the seven included in the equation of state of natural and associated petroleum gases developed by the authors. Continuous technological process according to the system of “production, collection, preparation and transportation of products (oil + gas)”, including, separately in non-equilibrium conditions of “collection, preparation and transportation of gas” due to internal energy, causes a natural change in a wide range of basic technological parameters that contribute to frequent changes in the physical and chemical state of the gas. Therefore, this work establishes that one of the main tasks is to show the composition of natural and associated petroleum gas as a result of irreversible transformations of hydrocarbon and acidic components of its internal energy, as a result of which the gas is characterised by a number of patterns in the composition and distribution of components of various hydrocarbon and heterogeneous compositions (i.e., physically and chemically heterogeneous). In these conditions, a practical calculation of gas facilities (gas treatment point, selection of gas separators, field gas pipelines, compressor stations) is carried out to determine process parameters using the Clapeyron–Mendeleev equation of state for real gases, and the results show large errors. This proves once again that many authors have developed equations of state for real gases based on the results of laboratory studies with single-atomic and laboratory gases (hydrogen, nitrogen, oxygen, carbon dioxide, etc.). However, the authors here carried out laboratory studies with products and associated petroleum gas. According to the results of laboratory studies, the authors recommend an improvement of the equation of state of natural and associated petroleum gases.

Определение значений переносных характеристик в многокомпонентных средах на основе анализа микропроцессов

This paper proposes a two-level approach for mathematical modeling of processes in multicomponent gas mixtures. It involves a combination of the description of conservation laws based on macro-equations and the determination of the corresponding transfer coefficients using the analysis of micro-processes. The main purpose of this work is to develop an algorithm for determining transport characteristics in multicomponent media based on the analysis of inner micro-processes. Hence, the kinetic molecular theory of gases and liquids is used, namely, the collision part of the Boltzmann equation. It includes multiple improper integrals taking into account the effect of micro-processes in the medium on the values of transport coefficients. When integrating the Boltzmann equation by the Chapman-Enskog method, the transport coefficients are expressed through integral brackets of the Sonin polynomials, which represent the linear combinations of molecular collision integrals. Their calculations require the use of efficient mathematically sound ways including the elements of parallel computing.

FORECASTING THE AEROIN COMPOSITION OF AIR IN THE PRESENCE OF NATURAL AND ARTIFICIAL SOURCES OF IONIZATION

It is shown that for the design of buildings and individual rooms with normative concentrations of light air ions of both polarities, a preliminary estimated assessment of the dynamics of this indicator in space and time is appropriate. In the general case, it is possible to use the continuity equation for weakly ionized plasma for one direction. This is due to the low concentration of air ions in the air. The ratio of molecular kinetic theory of gases is used to determine the necessary indicators - the average lifetime of air ions, free path length. To determine the average speed - Maxwell's distribution. It is shown that the propagation of air ions due to diffusion processes is insignificant, and the corresponding calculations have large errors. Calculations on the propagation of air ions by directed air movement from the source of artificial ionization are given. The distribution of air ion concentrations can be most accurately calculated taking into account their recombination, deposition on heavy air ions and neutral suspended parts (fine dust and aerosols). Relevant coefficients are mostly issued from reference sources. If there are electrostatic fields in the premises, generated due to the triboelectric effect and other factors, it is necessary to take into account the deposition of air ions on these surfaces. In order to correctly determine the concentrations of air ions, in addition to the values of the mobility of negative and positive air ions, data on electrostatic field strengths are required. The values of such fields are unpredictable, so they are measured by appropriate instruments in similar conditions. Verification of calculated data using electrostatic charge meters and air ion counter proved the reasonable convergence of expected and actual data. It is advisable to develop two- and three-dimensional models of the propagation of air ions of both polarities in rooms of different purposes, configurations of equipment placement, the presence of artificial ionization sources and directional air movement.

First-Principles Diffusivity Ratios for Atmospheric Isotope Fractionation on Mars and Titan.

Recent work used the kinetic theory of molecular gases, along with state-of-the-art intermolecular potentials, to calculate from first principles the diffusivity ratios necessary for modeling kinetic fractionation of water isotopes in air. Here, we extend that work to the Martian atmosphere, employing potential-energy surfaces for the interaction of water with carbon dioxide and with nitrogen. We also derive diffusivity ratios for methane isotopes in the atmosphere of Titan by using a high-quality potential for the methane-nitrogen pair. The Mars calculations cover 100 K to 400 K, while the Titan calculations cover 50 K to 200 K. Surprisingly, the simple hard-sphere theory that is inaccurate for Earth's atmosphere is in good agreement with the rigorous results for the diffusion of water isotopes in the Martian atmosphere. A modest disagreement with the hard-sphere results is observed for the diffusivity ratio of CH3D in the atmosphere of Titan. We present temperature-dependent correlations, as well as estimates of uncertainty, for the diffusivity ratios involving HDO, H2 17O, and H2 18O in the Martian atmosphere, and for CH3D and 13CH4 in the atmosphere of Titan, providing for the first time the necessary data to be able to model kinetic isotope fractionation in these environments.

Understanding of Kinetic Molecular Theory of Gases in Three Modes of Representation among Tenth-Grade Students in Chemistry

An analysis of students’ performance in Kinetic Molecular Theory (KMT) of gases was done to determine the extent of the understanding of these chemistry concepts in three modes of representation, namely macroscopic, microscopic, and symbolic. The study employed one-shot quasi-experimental research where students in Grade 10 at a secondary school in Cebu City were exposed to the Integrated Macro-Micro-Symbolic Approach (IMMSA). A validated post-test tool with macro, micro, and symbolic questions was used in the study. The post-test results revealed that there was a gradual improvement of the students’ understanding from a good understanding of macroscopic and microscopic levels to a very good understanding of the symbolic level. Thus, it was concluded that the use of three modes of chemical representation led to a high extent in the understanding of concepts in chemistry. It is recommended that teachers begin their instruction at the macroscopic level and introduce symbols only after the microscopic level.

First-Principles Diffusivity Ratios for Kinetic Isotope Fractionation of Water in Air.

Kinetic isotope fractionation between water vapor and liquid water or ice depends on the ratio of the diffusivities of the isotopic species in air, but there is disagreement as to the values of these ratios and limited information about their temperature dependence. We use state-of-the-art intermolecular potential-energy surfaces for the water-nitrogen and water-oxygen pairs, along with the kinetic theory of molecular gases, to calculate from first principles the diffusivities of water isotopologues in air. The method has sufficient precision to produce accurate diffusivity ratios. For the HDO/H2O ratio, we find that the often used hard-sphere kinetic theory is significantly in error, and confirm the 1978 experimental result of Merlivat. For the ratios involving 17O and 18O, the simple kinetic theory is relatively close to our more rigorous results. We provide diffusivity ratios from 190 K to 500 K, greatly expanding the range of temperatures for which these ratios are available.

Cross second virial coefficients and dilute gas transport properties of the systems (CH4 + C2H6) and (N2 + C2H6) from accurate intermolecular potential energy surfaces

The cross second virial coefficients and dilute gas shear viscosities, thermal conductivities, and binary diffusion coefficients of the systems (CH4 + C2H6) and (N2 + C2H6) were determined at temperatures from 90 K to 1200 K using statistical thermodynamics and the kinetic theory of molecular gases. The required intermolecular potential energy surfaces (PESs) for CH4–C2H6 and N2–C2H6 interactions are presented in this work, while the like-species interactions were modeled using PESs from our previous studies on the pure gases. All of these PESs are based on high-level quantum-chemical ab initio calculations and were fine-tuned to the most accurate experimental data available for the second virial and cross second virial coefficients. The agreement of the calculated values for all investigated thermophysical properties with the best experimental data is overall very satisfactory and confirms the high accuracy of the calculated values.

Cross second virial coefficient and dilute gas transport properties of the (H2O + CO2) system from first-principles calculations

The cross second virial coefficient and three dilute gas transport properties (shear viscosity, thermal conductivity, and binary diffusion coefficient) of mixtures of water (H2O) and carbon dioxide (CO2) were calculated with high accuracy for temperatures up to 2000 K using statistical thermodynamics and the kinetic theory of molecular gases, respectively. The required intermolecular potential energy surface (PES) for the H2O–CO2 interaction is presented in this work, while the like-species interactions were modeled using PESs from the literature. All three PESs are based on high-level quantum-chemical ab initio computations. The predicted values for the cross second virial coefficient are in satisfying agreement with the best experimental data. In the case of the transport properties, the calculated values should be more accurate than the few available data sets.

The Interaction Potential of Molecules in Multicomponent Gaseous Media

To determine the transport factors in multicomponent gaseous media, the authors used an approach based on the molecular-kinetic theory of gases. A mathematical model of the interaction potential of molecules in multicomponent media is proposed. This model takes into account elastic and geometric parameters of molecules as well as an algorithm for determining the parameters in it.

Thermophysical Properties of Gaseous H2S–N2 Mixtures from First-Principles Calculations

Abstract The cross second virial coefficient and three dilute gas transport properties (shear viscosity, thermal conductivity, and binary diffusion coefficient) of mixtures of hydrogen sulfide (H2S) and nitrogen (N2) were determined with high accuracy at temperatures up to 1200 K using statistical thermodynamics and the kinetic theory of molecular gases, respectively. The required intermolecular potential energy surface (PES) for the H2S–N2 interaction is presented in this work, while the H2S–H2S and N2–N2 PESs were reported previously. All three PESs are based on high-level quantum-chemical ab initio (i.e. first-principles) calculations. There is only very limited experimental information available on the second virial coefficients of H2S–N2 mixtures, and there appear to be no experimental data at all for the transport properties. Thus, the present predictions constitute a substantial increase in our knowledge of the thermophysical properties of this system, which are of practical relevance for modeling sour natural gas.

Cross Second Virial Coefficients and Dilute Gas Transport Properties of the (CH4 + C3H8) and (CO2 + C3H8) Systems from Accurate Intermolecular Potential Energy Surfaces

Accurate values for the cross second virial coefficients and dilute gas shear viscosities, thermal conductivities, and binary diffusion coefficients of the (CH4 + C3H8) and (CO2 + C3H8) systems were determined at temperatures from (150 to 1200) K using state-of-the-art computational approaches. The cross second virial coefficients were calculated semiclassically using the Mayer-sampling Monte Carlo method, while the transport properties were computed by means of the classical trajectory approach in conjunction with the kinetic theory of molecular gases. The required intermolecular potential energy surfaces (PESs) for the CH4–C3H8 and CO2–C3H8 interactions are reported in this work, whereas those for the CH4–CH4, CO2–CO2, and C3H8–C3H8 interactions were taken from our previous work on the pure gases. All PESs are based on high-level quantum-chemical ab initio calculations and were fine-tuned to the best experimental data for the second virial and cross second virial coefficients. Overall, the agreement of ...

Integrated Macro-Micro-Symbolic Approach in Teaching Secondary Chemistry

The purpose of this paper is to investigate the effectiveness of the Integrated Macro-Micro-Symbolic Approach (IMMSA) in teaching Chemistry to 10th graders of a secondary school in Cebu City, Philippines. A pre-post quasi-experimental design with control group was utilized to two groups of students, of which one was exposed to IMMSA and the other to conventional lecture method (CLM). Topics included in the experimentation proper were the five postulates of the Kinetic Molecular Theory of gases. Data gathered from the pre- and post-test tools were analyzed using t-tests, with a level of significance, α=0.01. Study findings revealed that both groups had Below Average performance levels in the pre- and post-test, where the lack of time and spiral progression were seen as reasons for the performances. The study also found out that both groups had significantly increased their performances from the pre- to the post-tests, implying the essence of both lectures and integrated use of modes. Ultimately, the study revealed that IMMSA is more effective than CLM as seen in the students’ enhanced performance, signifying the effective nature of the integration of macroscopic, microscopic and symbolic modes in teaching Chemistry concepts. With this, the Three-tiered model of learning and Chemistry triangle are still valued in the 21st century learning environment.

Development of the kinetic molecular theory of gases concept inventory: Preliminary results on university students’ misconceptions

In this study, we investigated students’ understanding of concepts related to the microscopic model of gas. We thoroughly reviewed the relevant literature and conducted think alouds with students by asking them to answer open-ended questions about the kinetic molecular theory of gases. Thereafter, we transformed the open-ended questions into multiple-choice questions, whereby distractors were based on the results of the think alouds. Thus, we obtained a set of 22 questions, which constitutes our current version of the kinetic molecular theory of gases concept inventory. The inventory has been administered to 250 students from different universities in Croatia, and its content validity has been investigated trough physics teacher surveys. The results of our study not only corroborate the existence of some already known student misconceptions, but also reveal new insights about a great spectrum of students’ misconceptions that had not been reported in earlier research (e.g., misconceptions about intermolecular potential energy and molecular velocity distribution). Moreover, we identified similar distribution of students’ responses across the surveyed student groups, despite the fact that they had been enrolled in different curricular environments.5 MoreReceived 28 June 2016DOI:https://doi.org/10.1103/PhysRevPhysEducRes.12.020139Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAssessmentConcepts & principlesProfessional TopicsFacultyK-12 teachersLower undergraduate studentsPhysics Education Research

The Viscosity of Dilute Water Vapor Revisited: New Reference Values from Experiment and Theory for Temperatures between (250 and 2500) K

Previously reported as well as unpublished experimental data for the viscosity of dilute water vapor in the temperature range from (297 to 528) K, which were obtained using an oscillating-disk viscometer, have been re-evaluated and extrapolated to the limit of zero density. The relative combined expanded (k = 2) uncertainty of the re-evaluated data is 0.2 % at room temperature (297 K to 302 K), 0.4 % at higher temperatures up to 450 K, and 1.0 % at temperatures above 450 K. The classical kinetic theory of molecular gases has been applied to compute the viscosity in the limit of zero density for temperatures between (250 and 2500) K using a highly accurate ab initio potential for the H2O molecule pair. In the temperature range from (311 to 438) K, the experimental zero-density data differ by only about +0.1 % from the calculated values. A new correlation for the zero-density limit, based on both the experimental data and the theoretically calculated values, is proposed. The relative combined expanded (k = ...

Spin Isotope Separation Under Incomplete Carbon Oxidation in a Low-Temperature Plasma in an External Magnetic Field

A theory of spin phenomena that takes the molecular-kinetic theory of gases into account is considered for the first time and the mechanism of paramagnetic separation of carbon isotopes under plasma oxidation in a magnetic field is confirmed experimentally.

Eulerian–Eulerian solid–liquid two-phase flow of sandstone wastewater in a hydropower station rectangular sedimentation tank

The treatment of high-turbidity sandstone wastewater in hydropower projects is a major concern for environment assessment. In this paper, an Eulerian–Eulerian solid–liquid two-phase model for describing water flow and sedimentation in a two-stage rectangular tank was presented. Relative to the Eulerian–Lagrangian approach, the Eulerian–Eulerian two-phase model can investigate the concentration distribution behaviour of particles with specific characteristics in greater detail. The molecular kinetic theory of gases was used to determine the microcosmic flow characteristics, and the collision force between the particles during two-phase solid–liquid flow was obtained. The flow pattern and the distribution of solids in the rectangular clarifiers were investigated. The simulated results were in good agreement with the measured results obtained from the removal efficiency of the first and second tanks. Furthermore, the sensitivity of the suspended solids distribution for the collision force and the effect on particle settling of the baffle position in the rectangular sedimentation tank were evaluated.

New Physical Ideas and Method of Description and Calculation of Resistance to Motion of Small Particles in a Gaseous Medium

New ideas and a new approach to the motion of small–including nanosized–particles are presented, resting on basic concepts of the molecular kinetic theory of gases, statistical physics, and classical mechanics. Two new concepts are introduced: the λ-layer and “counter-moving” pairs of molecules. The first makes it possible to limit the number of molecules under consideration and ignore their collisions with each other. The second makes it possible to exclude Brownian motion of the molecules. It is established that the action of potential van der Waals forces is localized in the vicinity of the small particle in such a way that it is possible in the statistical calculations to assume that the trajectories of the molecules consist of line segments and that impact of a molecule is perfectly elastic and equivalent to impact on an “effective particle” with linear dimension 40% higher than the actual diameter of the particle. Good agreement is obtained with the experimental Cunningham–Millikan–Davies (CMD) approximation, and also with extrapolated values of this approximation.