Academic literature on the topic 'Isentropic compressibility'

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Journal articles on the topic "Isentropic compressibility"

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Firoozabadi, Abbas, and Huanquan Pan. "Two-Phase Isentropic Compressibility and Two-Phase Sonic Velocity for Multicomponent-Hydrocarbon Mixtures." SPE Reservoir Evaluation & Engineering 3, no. 04 (2000): 335–41. http://dx.doi.org/10.2118/65403-pa.

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Summary Two-phase compressibility and two-phase sonic velocity of hydrocarbon mixtures are needed for a variety of applications in well testing, metering, and seismic exploration. In this work, a thermodynamic model is presented to estimate the two-phase isentropic compressibility and two-phase sonic velocity. The model accounts for the mass transfer between the equilibrium phases and the effect of capillary pressure. The results reveal that isothermal and isentropic compressibilities can be different by a factor of 20 in the two-phase near the retrograde dewpoint. With the exception of the retrograde dewpoint, the difference between the isentropic compressibility in the single phase and two phase is less than the corresponding difference for the isothermal compressibility. The sonic velocity in the two phase can be either less or more than the single phase. For the hydrocarbon mixtures that the sonic velocity decreases in the two phase, the decrease is much less pronounced than in nonhydrocarbon systems such as water-steam and water-air. Introduction Fluid compressibility and sonic velocity are used for a wide range of problems in the production and exploration of hydrocarbon reservoirs. These include well testing, metering, and seismic exploration. Various methods are available for the estimation of compressibility and sonic velocity in the single phase—both gas and liquid states.1 For hydrocarbon mixtures in the two-phase state, the available methods are unreliable. Compressibility is often defined on the basis of the thermodynamic path. For an isothermal process, the compressibility relates volume change to pressure change at constant temperature. In an isentropic path, the volume and pressure changes are given by isentropic compressibility. These two compressibilities in the single-phase state are related by2 c T = ( c P / c V ) c S , ( 1 ) where c T is the isothermal compressibility and cS is the isentropic compressibility; cP and cV are the heat capacity at constant pressure and volume, respectively. Since cP≥cV, then cT≥cS. The difference between cT and cS depends on pressure, temperature, and composition, and may vary from 10 to 300% in the single phase for pure hydrocarbons. Available techniques are adequate for the reliable estimation of cT and cS for hydrocarbon mixtures in the single-phase state. For reservoir engineering applications, cT represents the fluid compressibility in the reservoir away from the wellbore. In the wellbore, due to expansion, the fluid may undergo heating or cooling and the process may become nonisothermal. If the heat loss can be neglected, the isentropic compressibility may better represent the pressure and volume changes. In many real applications, the compressibility is perhaps between the two limits. Fluid compressibility in the two-phase gas-liquid state can be very different from the single-phase gas and liquid states. While the gas-phase compressibility is higher than the liquid phase, the two-phase gas-liquid compressibility can be higher than the gas-phase compressibility. The procedure for the calculation of the isothermal two-phase compressibility of hydrocarbon mixtures is presented in Ref. 3. It is clear from the work of Ref. 3 that any averaging technique based on individual phase compressibilities is unacceptable, and may lead to an order of magnitude error. The results presented in Ref. 3 are based on the assumption that the interface between the gas and liquid phases is flat. In porous media, the interface is curved and, therefore, capillary pressure may affect the two-phase compressibility. One purpose of this work is to account for the effect of capillary pressure on two-phase compressibility. Similar to the single phase, where two types of compressibility—isentropic and isothermal—are defined, in the two phase, one can also define isothermal and isentropic compressibilities. To our knowledge, there is no rigorous procedure in the literature for the estimation of two-phase isentropic compressibility of hydrocarbon mixtures. In the two phase for a constant entropy path, mass transfer between phases becomes important. A main objective of this work is to propose the methodology for the calculation of the two-phase isentropic compressibility using a cubic equation of state to describe all the physical parameters. Two-phase isentropic compressibility may be more appropriate than two-phase isothermal compressibility for well-testing applications in two-phase flowing conditions; around the welbore due to expansion, temperature may rise or may fall.2 Closely related to compressibility is the sonic velocity, which is an important parameter in seismic and well-logging technologies. The sonic velocity and the compressibility are related by a=v/cS, where a is the sonic velocity, v is the fluid molar volume, and cS is the isentropic compressibility.
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Prasad, V. Siva. "Thermodynamic studies in ternary mixtures containing water, formamide and t- butanol at 298.15 K." International Journal of Science and Social Science Research 1, no. 4 (2024): 147–56. https://doi.org/10.5281/zenodo.13367131.

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At 298.15 K, ultrasonic speeds and the isentropic compressibilities of aqueous solutions containing formamide (F) + t-butanol have been measured. As the concentration of formamide in the cosolvent (aqueous formamide) increases, it is observed that the concentrations of t-butanol at which isentropic compressibility becomes minimum and ultrasonic speed becomes maximum decrease. This behavior suggests that compared to aqueous t-butanol, aqueous ternary solutions are less structured. The concentration dependence of excess isentropic compressibility and excess ultrasonic speed very nicely reflects this behavior. This behavior is explained by the fact that the presence of formamide reduces t-butanol's capacity to form clathrate hydrates. Isentropic compressibility rises with concentration and ultrasonic speed falls when formamide concentration in the cosolvent (xF) > 0.2. 
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Bhatt, Bishan Datt. "Computation of excess isentropic compressibility via Flory's statistical theory to investigate molecular interactions in n-alcohol–benzylamine mixtures." African Journal of Empirical Research 5, no. 4 (2025): 2043–49. https://doi.org/10.51867/ajernet.5.4.170.

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Excess isentropic compressibility is a key thermodynamic property that offers valuable insight into molecular interactions within liquid mixtures. Understanding these interactions is crucial for characterizing solution structure, designing chemical processes, and developing predictive thermodynamic models. Statistical models play a vital role in interpreting thermodynamic behavior by connecting macroscopic properties with molecular-level interactions. They allow for the prediction and analysis of complex mixture behavior while minimizing the need for extensive experimental data. In this study, the excess isentropic compressibility of n-alcohol–benzylamine mixtures across various compositions was computed using the Flory statistical model. This model requires only minimal input data, specifically, the thermal expansion and isothermal compressibility of the pure components. The computed values were used to assess molecular interactions within the mixtures. A negative deviation in isentropic compressibility was observed, indicating stronger interactions between unlike molecules (i.e., α-alcohol and benzylamine) than between like molecules. The close agreement between experimental and calculated values confirms the effectiveness of this theoretical approach for analyzing molecular interactions. Overall, the method provides a reliable and efficient means to compute excess isentropic compressibility and investigate liquid mixture behavior.
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Marczak, Wojciech. "Is Passynski’s Approach to Hydration Numbers Consistent with Thermodynamics?" Molecules 29, no. 17 (2024): 4214. http://dx.doi.org/10.3390/molecules29174214.

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Hydrophilic and hydrophobic phenomena occur in aqueous solutions. Despite the complex nature of the molecular interactions, the propensity of molecules and ions to hydration is sometimes characterized by a single “hydration number”. Passynski’s method for determining the hydration numbers in dilute aqueous solutions belongs to the group of methods based on the analysis of the isentropic compressibility of a mixture. Isentropic compressibility is a thermodynamic material constant; thus, the paper deals with Passynski’s approach discussed in terms of thermodynamics. First, Passynski’s assumptions were applied to the volume of the mixture. Subsequent strict thermodynamic derivation led to a formula for the hydration number which resembled that of Onori rather than the original one. Passynski’s number turned out to be inconsistent with the thermodynamics and mechanics of fluids. This is a rather purely empirical measure of the slope of the dependence of isentropic compressibility on the solute mole fraction in a dilute aqueous solution. Being the quotient of the slope and the isentropic compressibility of pure water, Pasynski’s numbers are more convenient to analyze and discuss than the slopes themselves. Conclusions about molecular interactions based on these numbers must be treated with considerable caution.
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Harun-Al-Rashid, Md, Tania Tofaz, M. Islam, and T. Biswas. "Sound Velocities and Micellar Behaviour Studies of Dodecyltrimethylammonium Bromide in Aqueous Solutions at 295.15, 302.15 and 309.15 K." International Journal of Chemistry 7, no. 2 (2015): 213. http://dx.doi.org/10.5539/ijc.v7n2p213.

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Speed of sound, u, of dodecyltrimethylammonium bromide (DTAB) aqueous solutions has been determined at 295.15, 302.15 and 309.15 K. The speeds of sound, u, data have been used to estimate isentropic compressibility, Ks, apparent molal isentropic compressibility, φk(s), acoustic impedance, Z, molal sound of speed, Rm, and relative association, RA, of DTAB in aqueous solution. These parameters have been interpreted in terms of solute-solute and solute-solvent interactions and micellar behavior of DTAB.
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Boriskov, G. V., A. I. Bykov, N. I. Egorov, et al. "Isentropic compressibility of VNM-3-2 alloy in area of ultra-high pressures." Doklady Rossijskoj akademii nauk. Fizika, tehničeskie nauki 516, no. 1 (2024): 5–9. https://doi.org/10.31857/s2686740024030018.

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The authors provide the performance and experiment results of the isentropic compression of the tungsten VNM-3-2 alloy up to ultra-high (1 Mbar) pressures in a device based on the magneto-cumulative generator. The points obtained on the diagram “compression-pressure” are compared with a normal isentrope constructed based on the data of shock-wave experiments.
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Wahab, Abdul, and Sekh Mahiuddin. "Isentropic compressibility and viscosity of aqueous and methanolic lithium chloride solutions." Canadian Journal of Chemistry 80, no. 2 (2002): 175–82. http://dx.doi.org/10.1139/v02-007.

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Densities, speeds of sound, and viscosities of aqueous and methanolic lithium chloride solutions were measured as functions of concentration, m (mol kg–1) (0.3911 [Formula: see text] m [Formula: see text] 19.47) and temperature (273.15 [Formula: see text] T [Formula: see text] 323.15 K). Measured values of the density, speeds of sound, and viscosity agree well with previously reported data. The isentropic compressibility isotherms for the aqueous solutions converge at a particular concentration, in the temperature range of the study, providing crucial information regarding the solvation behaviour of the ions. However, for the methanol solutions, the isentropic compressibility isotherms decrease smoothly with concentration and converge on extrapolation. Anion solvation controls the viscosity processes at low temperatures whereas cation solvation controls the same at high temperatures. Total primary solvation numbers of lithium chloride in water and methanol were estimated to be 6.0 and 1.9, respectively.Key words: lithium chloride, speeds of sound, viscosity, isentropic compressibility, solvation number.
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Elangovan, Sampandam. "Density, Ultrasonic Velocity, Isentropic Compressibility, Molar Volumes and Related Excess Parameters Studies on Ethyl Acetate with 1-Ethanol at 303K, 308K, and 313K." Material Science Research India 18, no. 2 (2021): 171–78. http://dx.doi.org/10.13005/msri/180205.

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A binary liquid mixture that consists of ethyl acetate and 1-ethanol has been prepared at various concentrations by the mole fraction method. The ultrasonic velocity and density have been determined at 303K, 308K and 313K. From the experimental data, the excess isentropic compressibility, excess molar volumes, excess internal pressures, and excess molar enthalpy have been computed. The variations were observed as polynomial and fitted to the Redlich-Kister polynomial functions. By using this function, adjustable parameters and the standard deviations have been calculated. The experimental and theoretical data reveal that the existence of the intermolecular interactions between the selected liquid system. The partial molar compressibility’s and partial molar volume also calculated at infinite dilution of the system. In general, the intermolecular forces have tended to the variations in the magnitude and sign of the excess parameters. The excess molar volume (Vme), excess isentropic compressibility (), excess internal pressure ( ) and the enthalpy ( ) show the negative magnitude at the entire range of concentrations and temperatures. The significant variations of these parameters with the mole fraction of ethyl acetate have been analysed. Furthermore, the strength of the intermolecular interactions decreased with increasing the experimental temperatures as 303K > 308K >313K.
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Zhang, X. P., Z. W. Gu, Z. Q. Xiao, et al. "Quasi-isentropic compression of LiH above 400 GPa using magnetocumulative generator." Review of Scientific Instruments 93, no. 4 (2022): 043906. http://dx.doi.org/10.1063/5.0078422.

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The knowledge of high-pressure behavior of LiH is significant for the validation of fundamental theoretical models and applications in thermonuclear materials and potential energy supplies. The compressibility of 7LiH under isentropic compression at high pressure was investigated experimentally and theoretically. The experimental technique for quasi-isentropic compression with low-density materials was developed using the magnetocumulative generator CJ-100 and x-ray flash radiography. The x-ray images and extracted interface of the sample target in dynamic flash radiography experiments were obtained. According to each interface size of the target both before and after compression, the compression ratio of 7LiH and reference material aluminum was obtained. The density of the reference and using its known isentropic curve provide the pressure in the reference. The pressure in 7LiH was deduced from the pressure in the reference and using the calculated gradient correction factor. The quasi-isentropic data point at 438 GPa was obtained experimentally. A semiempirical three-term complete equation of state was constructed and validated for 7LiH using the theory of Mie–Grüneisen–Debye with experimental data from the literature. The quasi-isentrope data point is reasonably consistent with the theoretical results. The quasi-isentropic experimental techniques and results broaden the existing research scope and are practical and helpful to further validate theoretical models in the future.
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Kohar, Kirti, Marvi Gupta, and Hariti Mehta. "Review of Density and Ultrasonic Velocity of Various Complexes and Its Applications." International Journal of Research and Review 11, no. 1 (2024): 431–37. http://dx.doi.org/10.52403/ijrr.20240147.

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This review paper delves into the fundamental principles, measurement techniques, and diverse applications of ultrasonic velocity and density. Ultrasonic velocity serves as a crucial parameter in various fields such as materials science, acoustics, and medical diagnostics whereas density is used for identifying substances, quality control, analyzing mixtures, assessing purity, explaining buoyancy, determining concentrations, calibrating instruments, monitoring pollution, and understanding reactivity. This paper provides an in-depth exploration of the underlying concepts, different measurement methods, and the wide-ranging applications of ultrasonic velocity and density. The ultrasonic velocity and density data have also been used to evaluate various acoustic parameters such as isentropic compressibility, apparent isentropic molar compressibility, solvation number of the solute and relative association. Ultrasonic velocity measurements are found to be useful for on-line assessment of the extent of degradation of mechanical properties associated with precipitation of intermetallics. Keywords: Density, Ultrasonic velocityThis review paper delves into the fundamental principles, measurement techniques, and diverse applications of ultrasonic velocity and density. Ultrasonic velocity serves as a crucial parameter in various fields such as materials science, acoustics, and medical diagnostics whereas density is used for identifying substances, quality control, analyzing mixtures, assessing purity, explaining buoyancy, determining concentrations, calibrating instruments, monitoring pollution, and understanding reactivity. This paper provides an in-depth exploration of the underlying concepts, different measurement methods, and the wide-ranging applications of ultrasonic velocity and density. The ultrasonic velocity and density data have also been used to evaluate various acoustic parameters such as isentropic compressibility, apparent isentropic molar compressibility, solvation number of the solute and relative association. Ultrasonic velocity measurements are found to be useful for on-line assessment of the extent of degradation of mechanical properties associated with precipitation of intermetallics. Keywords: Density, Ultrasonic velocity
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Dissertations / Theses on the topic "Isentropic compressibility"

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Bahadur, Indra. "Excess molar volume and isentropic compressibility for binary or ternary ionic liquid systems." Thesis, 2010. http://hdl.handle.net/10321/559.

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Submitted in fulfillment of the requirements of the Degree of Doctor of Technology: Chemistry, Durban University of Technology, 2010.<br>The thermodynamic properties of mixtures involving ionic liquids (ILs) with alcohols or alkyl acetate or nitromethane at different temperatures were determined. The ILs used were methyl trioctylammonium bis(trifluoromethylsulfonyl)imide ([MOA]+[Tf2N]-) and 1-butyl-3- methylimidazolium methyl sulphate [BMIM]+[MeSO4]-. The ternary excess molar volumes (􀜸􀬵􀬶􀬷 E ) for the mixtures {methyl trioctylammonium bis (trifluoromethylsulfonyl)imide + methanol or ethanol + methyl acetate or ethyl acetate}and (1- butyl-3-methylimidazolium methylsulfate + methanol or ethanol or 1-propanol + nitromethane) were calculated from experimental density values, at T = (298.15, 303.15 and 313.15) K and T = 298.15, respectively. The Cibulka equation was used to correlate the ternary excess molar volume data using binary data from literature. The 􀜸􀬵􀬶􀬷 E values for both IL ternary systems were negative at each temperature. The negative contribution of 􀜸􀬵􀬶􀬷 E values are due to the packing effect and/or strong intermolecular interactions (ion-dipole) between the different molecules. The density and speed of sound of the binary solutions ([MOA]+[Tf2N]- + methyl acetate or ethyl acetate or methanol or ethanol), (methanol + methyl acetate or ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) were also measured at T = ( 298.15, 303.15, 308.15 and 313.15) K and at atmospheric pressure. The apparent molar volume, Vφ , and the apparent molar isentropic compressibility, κφ , were evaluated from the experimental density and speed of sound data. A Redlich-Mayer type equation was fitted to the apparent molar volume and apparent molar isentropic compressibility data. The results are discussed in terms of solute-solute, solute- solvent and solvent-solvent interactions. The apparent molar volume and apparent molar isentropic compressibility at infinite dilution, 􀜸φ 􀬴 and κφ 􀬴, respectively of the binary solutions have been calculated at each temperature. The 􀜸φ 􀬴 values for the binary v systems ([MOA]+[Tf2N]- + methyl acetate or ethyl acetate or methanol or ethanol) and (methanol + methyl acetate or ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) are positive and increase with an increase in temperature. For the (methanol + methyl acetate or ethyl acetate) systems 􀜸φ 􀬴 values indicate that the (ion-solvent) interactions are weaker. The κφ 􀬴 is both positive and negative. Positive κφ 􀬴, for ([MOA] + [Tf2N]- + ethyl acetate or ethanol), (methanol + ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) can be attributed to the predominance of solvent intrinsic compressibility effect over the effect of penetration of ions of IL or methanol or ethanol. The positive κφ 􀬴 values can be interpreted in terms of increase in the compressibility of the solution compared to the pure solvent methyl acetate or ethyl acetate or ethanol. The κφ 􀬴 values increase with an increase in temperature. Negative κφ 􀬴, for ([MOA] + [Tf2N]- + methyl acetate or methanol), and (methanol + methyl acetate) can be attributed to the predominance of penetration effect of solvent molecules into the intra-ionic free space of IL or methanol molecules over the effect of their solvent intrinsic compressibility. Negative κφ 􀬴 indicate that the solvent surrounding the IL or methanol would present greater resistance to compression than the bulk solvent. The κφ 􀬴 values decrease with an increase in the temperature. The infinite dilution apparent molar expansibility, 􀜧φ 􀬴 , values for the binary systems (IL + methyl acetate or ethyl acetate or methanol or ethanol) and (methanol + methyl acetate or ethyl acetate) and (ethanol + methyl acetate or ethyl acetate) are positive and decrease with an increase in temperature due to the solution volume increasing less rapidly than the pure solvent. For (IL + methyl acetate or ethyl acetate or methanol or ethanol) systems 􀜧φ 􀬴 indicates that the interaction between (IL + methyl acetate) is stronger than that of the (IL + ethanol) or (IL + methanol) or (IL + ethyl acetate) solution. For the (methanol + methyl acetate or ethyl acetate) systems 􀜧φ 􀬴 values vi indicate that the interactions are stronger than (ethanol + methyl acetate or ethyl acetate) systems.
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Book chapters on the topic "Isentropic compressibility"

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Kopyshev, V. P., and V. D. Urlin. "Isentropic Compressibility and Equation of State of Hydrogen up to 1 TPa." In High-Pressure Shock Compression of Solids VII. Springer New York, 2004. http://dx.doi.org/10.1007/978-1-4757-4048-6_12.

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LAGOURETTE, Bernard, Pierre LABES, Henri SAINT-GUIRONS, Jacques ALLIEZ, and Suyu YE and Pierre XANS. "Ultrasonic Speed and Isentropic Compressibility of Asymmetric Liquid Ternary Mixtures under High Pressure: a Test for Equations of State and Associated Mixing Rules." In Ultrasonics International 93. Elsevier, 1993. http://dx.doi.org/10.1016/b978-0-7506-1877-9.50116-5.

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Conference papers on the topic "Isentropic compressibility"

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Firoozabadi, Abbas, and Huanquan Pan. "Two-Phase Isentropic Compressibility and Two-Phase Sonic Velocity for Multicomponent-Hydrocarbon Mixtures." In SPE Annual Technical Conference and Exhibition. Society of Petroleum Engineers, 1997. http://dx.doi.org/10.2118/38844-ms.

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Il’kaev, R. I. "Quasi-Isentropic Compressibility of Gaseous Deuterium in Pressure Range up to 300 GPa." In SHOCK COMPRESSION OF CONDENSED MATTER - 2003: Proceedings of the Conference of the American Physical Society Topical Group on Shock Compression of Condensed Matter. AIP, 2004. http://dx.doi.org/10.1063/1.1780187.

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Falcão, António F. O., and João C. C. Henriques. "The Spring-Like Air Compressibility Effect in OWC Wave Energy Converters: Hydro-, Thermo- and Aerodynamic Analyses." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77096.

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The oscillating-water-column (OWC) wave energy converter consists of a hollow (fixed or floating) structure, open to the sea below the water surface. Wave action alternately compresses and decompresses the air trapped above the inner water free-surface, which forces air to flow through a turbine coupled to a generator. The spring-like effect of air compressibility in the chamber is related to the density-pressure relationship. It is known to significantly affect the power performance of the full-sized converter, and is normally not accounted for in model testing at reduced scale. Three theoretical models of increasing complexity are analysed and compared: (i) the incompressible air model; (ii) the isentropic process model; (iii) and the (more difficult and rarely adopted) adiabatic non-isentropic process model in which losses due to the imperfectly efficient turbine are accounted for. The air is assumed as a perfect gas. The hydrodynamic modelling of wave energy absorption is based on linear water wave theory. The validity of the various simplifying assumptions, especially in the aero-thermodynamic domain, is examined and discussed. The validity of the three models is illustrated by a case study with numerical results for a fixed-structure OWC equipped with a Wells turbine subject to irregular waves.
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Sheng, Wanan, Florent Thiebaut, Marie Babuchon, Joseph Brooks, Anthony Lewis, and Raymond Alcorn. "Investigation to Air Compressibility of Oscillating Water Column Wave Energy Converters." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10151.

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It has been suggested that for full scale oscillating water column (OWC) devices, the pressure in and the volume of the air chambers can be large to create air compressibility in the air chamber. Due to compressibility, its density and temperature are different from those in atmosphere. When in exhalation, the pressurized air is driven out of the air chamber and mixes into the atmosphere outside the air chamber; whilst in inhalation, the atmosphere is sucked through the power take-off (PTO) system into the air chamber, and mixes with the de-pressurized air in the chamber. This paper presents a study on air compressibility in OWC air chambers by theoretical analyses and the relevant experimental studies. The theoretical analysis is based on the first-order differential equation for the flowrate and the chamber pressure, which has been derived for the air flow under the assumptions of the isentropic process and the known power take-off characteristics. In the study, an orifice type of PTO and a porous membrane type PTO, which are supposed to represent a typical nonlinear and linear PTO for small models, respectively, are both investigated. The investigation has shown the feasibility of the theoretical method on the air compressibility and the possible power loss due to the air compressibility.
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Giuffre’, Andrea, and Matteo Pini. "Design Guidelines for Axial Turbines Operating With Non-Ideal Compressible Flows." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-14209.

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Abstract The impact of non-ideal compressible flows on the fluid-dynamic design of axial turbine stages is examined. First, the classical similarity equation is revised and extended to account for the effect of flow non-ideality and compressibility. Then, the influence of the most relevant design parameters is investigated through the application of a dimensionless turbine stage model embedding a first-principles loss model. The results show that the selection of optimal duty coefficients is scarcely affected by the molecular complexity of the working fluid, whereas compressibility effects produce an offset in the efficiency trends and in the optimal flow coefficient. Furthermore, flow non-ideality can lead to either an increase or a decrease of stage efficiency of the order of 2–3% relative to turbines designed to operate in dilute gas state. This effect can be predicted at preliminary design phase through the evaluation of the isentropic pressure-volume exponent. 3D RANS simulations of selected test cases corroborate the trends predicted with the reduced-order turbine stage model.
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Bernardini, Chiara, Stuart I. Benton, John D. Lee, Jeffrey P. Bons, Jen-Ping Chen, and Francesco Martelli. "Steady VGJ Flow Control on a Highly Loaded Transonic LPT Cascade: Effects of Compressibility and Roughness." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-27177.

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A new high-speed linear cascade has been developed for low-pressure turbine (LPT) studies at The Ohio State University. A compressible LPT profile is tested in the facility and its baseline performance at different operating conditions is assessed by means of isentropic Mach number distribution and wake total pressure losses. Active flow control is implemented through a spanwise row of vortex-generator jets (VGJs) located at 60% chord on the suction surface. The purpose of the study is to document the effectiveness of VGJ flow control in high-speed compressible flow. The effect on shock-induced separation is assessed by Mach number distribution, wake loss surveys and shadowgraph. Pressure Sensitive Paint is applied to understand the three dimensional flow and shock pattern developing from the interaction of the skewed jets and the main flow. Data show that with increasing blowing ratio the losses are first decreased due to separation reduction, but losses connected to compressibility effects become stronger due to increased passage shock strength and jet orifice choking; therefore the optimum blowing ratio is a tradeoff between these counteracting effects. The effect of added surface roughness on the uncontrolled flow and on flow control behavior is also investigated. At lower Mach number turbulent separation develops on the rough surface and a different flow control performance is observed. Steady VGJs appear to have control authority even on a turbulent separation but higher blowing ratios are required compared to incompressible flow experiments reported elsewhere. Overall, the results show a high sensitivity of steady VGJs control performance and optimum blowing ratio to compressibility and surface roughness.
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Bagwell, Ted G. "CFD Simulation of Flow Tones From Grazing Flow Past a Deep Cavity." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15633.

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Locked-in flow tones due to shear flow over a deep cavity are investigated using Large Eddy Simulation (LES). An isentropic from of the compressible Navier-Stokes equations (pseudo-compressibility) is used to couple the vertical flow over the cavity mouth with the deep cavity resonances (1). Comparisons to published experimental data (2) show that the pseudo-compressible LES formulation is capable of predicting the feedforward excitation of the deep cavity resonator, as well as the feedback process from the resonator to the flow source. By systematically increasing the resonator damping level, it is shown that strong lock-in results in a more organized shear layer than is observed for the locked-out flow state. By comparison, weak interactions (non-locked-in) produce no change in the shear layer characteristics. This supports the 40 dB definition of lock-in defined in the experiment.
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Bassi, F., and M. Savini. "Secondary Flows in a Transonic Cascade: Validation of a 3-D Navier-Stokes Code." In ASME 1992 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1992. http://dx.doi.org/10.1115/92-gt-062.

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In this work is presented a finite volume full 3-D Navier-Stokes solver suitable for turbulent turbomachinery computations. The code is applied to the analysis of the secondary flow patterns in a transonic turbine cascade at three different isentropic outlet Mach numbers; namely 0.50, 1.02, 1.38. Detailed measurements obtained in four planes downstream of the trailing edge allow for comparison of losses, flow angles, vorticity and hence for a deep evaluation of the accuracy of the numerical results. Moreover the code is used to gain insight into the formation and the evolution of secondary flows inside the blade passage, into the generation of losses and into characteristic feature of these flows hard to detect experimentally. All the above mentioned aspects are examined and discussed as well as the influence of compressibility, giving thus a precise picture of secondary flows in the transonic regime.
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Schänzle, Christian, and Peter F. Pelz. "Meaningful and Physically Consistent Efficiency Definition for Positive Displacement Pumps - Continuation of the Critical Review of ISO 4391 and ISO 4409." In ASME/BATH 2021 Symposium on Fluid Power and Motion Control. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/fpmc2021-68739.

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Abstract:
Abstract ISO 4391:1984 gives the common efficiency definition for positive displacement machines. ISO 4409:2019 uses this efficiency definition to specify the procedure for efficiency measurements. If the machine conditions do not correspond with an incompressible flow due to operation at high pressure levels, the compressibility of the fluid and the dead volume of a pump must be taken into account. On this point, ISO 4391:1984 is physically inconsistent. Achten et. al. address this issue in their paper at FPMC 2019 presenting a critical review of ISO 4409:2007. They introduce new definitions of the overall efficiency as well as the mechanical-hydraulic efficiency. At the same time, they question the validity of the volumetric efficiency definition. Li and Barkei continue on this issue in their paper at FPMC 2020 and give a new efficiency definition based on the introduction of a new quantity Φ which describes the volume specific enthalpy of the conveyed fluid. The motivation of this paper is to contribute to the ongoing and fruitful discussion. Our approach starts with the most general efficiency definition, namely the isentropic efficiency. Subsequently, we make assumptions concerning the fluid properties with respect to the compressibility of the conveyed fluid. On the basis of the ideal cycle of a positive displacement pump and the p-v diagram, we derive physically consistent and more meaningful representations of the overall, the mechanical-hydraulic and the volumetric efficiency that address the inconsistency of ISO 4391:1984. Furthermore, we compare our findings with the existing results of Achten et. al. and Li and Barkei.
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10

Utamura, Motoaki, Hiroshi Hasuike, Kiichiro Ogawa, et al. "Demonstration of Supercritical CO2 Closed Regenerative Brayton Cycle in a Bench Scale Experiment." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68697.

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Abstract:
Power generation with a supercritical CO2 closed regenerative Brayton cycle has been successfully demonstrated using a bench scale test facility. A set of a centrifugal compressor and a radial inflow turbine of finger top size is driven by a synchronous motor/generator controlled using a high-speed inverter. A 110 W power generating operation is achieved under the operational condition of rotational speed of 1.15kHz, CO2 flow rate of 1.1 kg/s, and respective thermodynamic states (7.5 MPa, 304.6 K) at compressor and (10.6 MPa, 533 K) at turbine inlet. Compressor work reduction owing to real gas effect is experimentally examined. Compressor to turbine work ratio in supercritical liquid like state is measured to be 28% relative to the case of ideal gas. Major loss of power output is identified as rotor windage. It is found the isentropic efficiency depends little on compressibility coefficient. Off design performance of gas turbine working in supercritical state is well predicted by a Meanline program. The CFD analysis on compressor internal flow indicates that the presence of backward flow around the tip region might create a locally depressurized region leading eventually to the onset of flow instability.
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