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Properties of Gases and Gas Mixtures
Published in Kavati Venkateswarlu, Engineering Thermodynamics, 2020
The real gases do not obey the assumptions made in the kinetic theory of gases. At very low pressures or very high temperatures, real gas obeys the ideal gas equation as intermolecular attraction and volume occupied by molecules compared to the total volume are not considered at this state. When the pressure increases, intermolecular forces increase and the volume of molecules becomes considerable when compared to that of gas. Thus real gases deviate from the ideal gas equation of state appreciably with an increase in pressure. Van der Waals introduced two correction factors ‘a’ and ‘b’ in the ideal gas equation, first one to account for intermolecular attraction and the second one to account for volume of molecules. The Van der Waals equation is (p+aν2)(ν−b)=RT
Introduction
Published in W. Li Kam, Applied Thermodynamics: Availability Method And Energy Conversion, 2018
The equation of state for an ideal gas is satisfactory in modeling many gases and vapors under certain conditions, such as the temperature more than twice the critical temperature or the pressure less than 1 atm. However, this equation of state definitely is not universally valid. When the behavior of a gas cannot be modeled by the ideal gas equation, the gas is generally referred to as a real gas. The P-υ-T relationships of real gases may be presented in several ways. A simple method involves a use of the compressibility factor Z. That is, () Pυ=ZRT
NATURAL GAS PROPERTIES CALCULATIONS FROM COMPOSITION
Published in A. Attari, D.L. Klass, Natural Gas Energy Measurement, 2003
DEFINITIONS The definitions of the pertinent properties are not necessarily totally unambiguous. The reasons are some unfortunate federal regulations and some misguided standard practices. The adopted definitions are consistent with GPA-2172 which is the most recent standard published covering this topic. Compressibility Factor The compressibility factor is the ratio of the ideal gas density to the real gas density when both are at the same temperature and pressure. The primary function of compressibility factor is to indicate the deviation of real gas behavior from that of the ideal gas. Relative Density The relative density is the ratio of the density of the gas at its temperature and pressure to that of dry air at its temperature and pressure. The relative density is primarily a means to establish the molar mass of the gas. Heating Value Heating value refers to the total energy transferred as heat in an ideal combustion reaction at base temperature and pressure. For net heating value, the water formed in the combustion appears as vapor in the products; for gross heating value, the water formed in the combustion appears as liquid in the products. COMPRESSIBILITY FACTOR The compressibility factor is usually the most convenient form in which to express the equation of state P=P (T,p). From the definition, it is (1) where Z is compressibility factor, p is density per mass, M is molar mass, P is pressure, R is the gas constant, T is temperature and super * denotes ideal gas. At conditions of temperature and pressure near ambient, the truncated virial equation of state adequately represents the volumetric behavior of natural gas (2) In Equation 2, B is the second virial coefficient for the natural gas mixture and is a function only of temperature and composition
Adsorption of industrial dye onto a zirconium metal-organic framework: synthesis, characterization, kinetics, thermodynamics, and DFT calculations
Published in Journal of Coordination Chemistry, 2022
Gamil A. A. Al-Hazmi, Adel A. El-Zahhar, Mohamed G. El-Desouky, Mohamed A. El-Bindary, Ashraf A. El-Bindary
Zr-MOF resulted in a high-efficiency adsorbent. SEM pictures of Zr-MOF show a large number of pores where dyes could be adsorbed. Zr-MOF possesses a huge surface area of 1498 m2/g which IUPAC classifies as microporous materials and can be utilized for the adsorption of dyes and purification of polluted water. The initial dye concentration and pH of the starting material, the effects of temperature, contact time, and MB adsorption were all substantial. Langmuir isotherm for MB was superior according to the adsorption equilibrium. The adsorption energy (Ea) of MB is 15 kJmol−1 on average, suggesting chemisorption. The adsorption kinetics follow a pseudo-second-order kinetic model (R2). The adsorption of MB on Zr-MOF adsorbents was characterized using the MMRG model, which requires sideways interrelations between adsorbate molecules. A monolayer model based on the real gas law (MMRG) and a monolayer model based on the ideal gas law (MMIG) were both explored. Under the experimental conditions, the computed (ΔH°, ΔS°, and ΔG°) demonstrated adsorption of MB on Zr-MOF is spontaneous and endothermic. Because of its performance, Zr-MOF offers good reusability, consistently greater than 90% after the third cycle. Zr-MOF offers potential in many applications due to standard mesopores, huge surface area, and crystalline frameworks.
Numerical analysis of the Sodium–Water Reaction in a minichannel to evaluate the safety of a Printed Circuit Steam Generator
Published in Journal of Nuclear Science and Technology, 2022
is the stagnation pressure, is the hydraulic diameter of the leak passage, and is the stagnation enthalpy of steam in . This correlation was comparable with the Moody’s model [36] under the saturated steam condition and used in the SELPSTA code that analyzed the system response of a SWR in the KALIMER to determine the steam leak rate [37]. The results of the leak rate calculated using the CFD and the correlation are summarized in Table 3. The CFD tends to underpredict the steam critical flow rate compared to the correlation. In the present CFD model, the ideal gas law determines the choking condition when the ratio of pressure in the crack to stagnation pressure becomes 0.53. Although it is recommended to use the real gas model or a property table of steam to predict the critical flow rate, the ideal gas law is used in this case to ensure the convergence of analysis.
Effect Chain Analysis of Supercritical Fuel Disintegration Processes Using an LES-based Entropy Generation Analysis
Published in Combustion Science and Technology, 2020
Florian Ries, Dennis Kütemeier, Yongxiang Li, Kaushal Nishad, Amsini Sadiki
By examining the density distribution within the supercritical injection process, it can be clearly seen that the liquid-like core of the jet remains nearly unchanged up to . Then, instabilities occur and pockets of liquid-like nitrogen are separated from the potential core of the jet. These pockets are carried away by the flow and dissolve further downstream while pseudo-boiling and turbulent mixing take place. Regarding real gas effects, values of the compressibility factor are small at the inner core of the jet and close to one away from it. This suggests that only the inner core is dominated by real gas effects, while the fluid in the outer region behaves similar to an ideal gas. Similar dynamics and thermodynamic effects were also observed in experimental investigations (Oschwald et al., 2006; Chehroudi, Talley, and Coy, 2002) and DNS studies (Ries, Janicka, and Sadiki, 2017; Battista, Picano, and Casciola 2014) of supercritical fuel injection processes.