{"title":"Calculation of the Thermodynamic Properties of Methane up to 30 MPa Using a New Equation of State with Regular and Scale Parts and Few Constants","authors":"P. P. Bezverkhii, O. S. Dutova","doi":"10.1134/s0018151x23020037","DOIUrl":null,"url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The heat capacities <span>\\({{C}_{v}}\\)</span>, <i>C</i><sub><i>p</i></sub> and speed of sound <i>W</i> of methane were calculated by a new equation of state with few adjustable constants. The equation includes a new regular part with 13 coefficients and a scale part with 6 coefficients with a regular crossover function containing two fitting parameters. The constants in the equation of state were determined using only (<i>p</i>, ρ, <i>T</i>) data for СH<sub>4</sub>; no data on <span>\\({{C}_{v}}\\)</span>, <i>C</i><sub><i>p</i></sub>, and <i>W</i> were employed, except for the data on isochoric heat capacity <span>\\({{C}_{v}}\\)</span> in the ideal-gas state and value of <span>\\({{C}_{v}}\\)</span> at 100 K on the liquid branch on the liquid–vapor equilibrium curve. The calculated values of <span>\\({{C}_{v}}\\)</span>, <i>C</i><sub><i>p</i></sub>, and <i>W</i> are close to the experimental and tabulated values in the regular region. Calculations in the critical region uses universal critical indices α, β, γ according to the three-dimensional Ising model. A discrepancy with the tabulated data is caused by application of the scaling equation of state. The calculated values are compared with the predictions by the known crossover equations of state for СH<sub>4</sub>. The root-mean-square error in the description of СH<sub>4</sub> pressure is σ<sub><i>р</i></sub> = 0.5%, the mean absolute deviation is 0.3%, the uncertainty in <span>\\({{C}_{v}}\\)</span> does not exceed 5%.</p>","PeriodicalId":13163,"journal":{"name":"High Temperature","volume":"75 1","pages":""},"PeriodicalIF":1.0000,"publicationDate":"2024-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"High Temperature","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1134/s0018151x23020037","RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"PHYSICS, APPLIED","Score":null,"Total":0}
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Abstract
The heat capacities \({{C}_{v}}\), Cp and speed of sound W of methane were calculated by a new equation of state with few adjustable constants. The equation includes a new regular part with 13 coefficients and a scale part with 6 coefficients with a regular crossover function containing two fitting parameters. The constants in the equation of state were determined using only (p, ρ, T) data for СH4; no data on \({{C}_{v}}\), Cp, and W were employed, except for the data on isochoric heat capacity \({{C}_{v}}\) in the ideal-gas state and value of \({{C}_{v}}\) at 100 K on the liquid branch on the liquid–vapor equilibrium curve. The calculated values of \({{C}_{v}}\), Cp, and W are close to the experimental and tabulated values in the regular region. Calculations in the critical region uses universal critical indices α, β, γ according to the three-dimensional Ising model. A discrepancy with the tabulated data is caused by application of the scaling equation of state. The calculated values are compared with the predictions by the known crossover equations of state for СH4. The root-mean-square error in the description of СH4 pressure is σр = 0.5%, the mean absolute deviation is 0.3%, the uncertainty in \({{C}_{v}}\) does not exceed 5%.
期刊介绍：
High Temperature is an international peer reviewed journal that publishes original papers and reviews written by theoretical and experimental researchers. The journal deals with properties and processes in low-temperature plasma; thermophysical properties of substances including pure materials, mixtures and alloys; the properties in the vicinity of the critical point, equations of state; phase equilibrium; heat and mass transfer phenomena, in particular, by forced and free convections; processes of boiling and condensation, radiation, and complex heat transfer; experimental methods and apparatuses; high-temperature facilities for power engineering applications, etc. The journal reflects the current trends in thermophysical research. It presents the results of present-day experimental and theoretical studies in the processes of complex heat transfer, thermal, gas dynamic processes, and processes of heat and mass transfer, as well as the latest advances in the theoretical description of the properties of high-temperature media.
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