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![Comparison between thermal expansion coefficient of water which has been calculated from different EOS, Redlich-Kwong [25] and reference values [29] at P = 20 MPa.](profile/Mohammad-Raveshi/publication/282633397/figure/fig16/AS:734834175537152@1552209528733/Comparison-between-thermal-expansion-coefficient-of-water-which-has-been-calculated-from.jpg)
Comparison between thermal expansion coefficient of water which has been calculated from different EOS, Redlich-Kwong [25] and reference values [29] at P = 20 MPa.
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... Overall, the impact of gas temperature on k L a i manifests through several mechanisms: (a) kinetic energy and motion of CO 2 molecules at the gasliquid interface, (b) solubility of CO 2 in water in the mass concentration boundary, (c) void fraction variations, and (d) interfacial structures behavior. The cumulative effect of these factors creates a complex interplay that ultimately shapes the net influence of gas temperature on 15) , where M is the molar mass of CO 2 and R is the universal gas constant) [74,75]. ...
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Present numerical study examines the free convection heat transfer characteristics of supercritical water flow past a stretching sheet. A suitable equation for thermal expansion coefficient in supercritical fluid region is derived based on the equation of state approach (EOS) in terms of compressibility factor, pressure and temperature. In the present study Redlich-Kwong equation of state (RK-EOS) is used to calculate the thermal expansion coefficient in supercritical region. The values of thermal expansion coefficient calculated through RK-EOS lies close to the NIST data values when compared to the other equations of state like VW-EOS (Van der Waals equation of state) and Ideal gas-EOS. Also, the behaviour of Nusselt number is studied to characterize the heat transfer characteristics of supercritical water. However, the equations governing the supercritical fluid flow past a stretching sheet are coupled and nonlinear in nature. Hence, Runge-Kutta fourth-order integration scheme with shooting technique (RK-SM) is used to solve these equations. Numerical computations are performed for supercritical water (SCW) under the influence of various control parameters. Similarity solutions are obtained in terms of flow profiles in supercritical fluid region. Present study reports that, the normal velocity profile decreases and temperature field increases for the increasing values of reduced pressure and reduced temperature. Also, axial velocity profile shows the dual behaviour for the increasing values of unsteady parameter, reduced temperature and reduced pressure in the supercritical boundary layer region. Further, the component of normal velocity profile decays for the increasing values of unsteady parameter in supercritical fluid region. The calculated values of thermal expansion coefficient using Redlich-Kwong equation of state lies in the proximity of NIST data values when compared to Van der Waals and Ideal gas equations of state. Also, the local skin-friction coefficient decreases for the increasing values of reduced pressure and reduced temperature.
This study experimentally investigates the mixed-convection heat transfer on a moving vertical flat plate. The setup comprises a hanger–pulley system above a transparent volume in which the experimental model moves; a flywheel-motor assembly, which generates the oscillation movement; a power supply; and a datalogger. The experimental model comprises two copper plates on which the thermocouples are placed and Kapton heaters between the plates. For the study, heat flux was applied to the plate surface (q”) and the Womersley number (Wo) and dimensionless oscillation amplitude (Ao) were varied; the effects of these parameters on mixed-convection heat transfer were analyzed. The experiments were performed for four different values of Ao and five different oscillation frequencies with three different heat fluxes. The results show that heat-transfer performance is significantly affected by Ao, Wo, and heat flux applied to the plate surface. We observed that heat-transfer performance increases with the increase of both the Wo number and the dimensionless oscillation amplitude for all heat fluxes tested. The obtained results are presented as a function of dimensionless numbers. We also compare experimental results with other researchers' prior-published studies.
Supercritical natural convection of Newtonian and couple stress fluids about an isothermal cylinder employing the equation of state (EOS) model is addressed in the current numerical investigation. At first, a suitable equation for heat expansion rate based on Redlich–Kwong EOS (RK-EOS), Soave modification EOS (Soave-EOS), Peng-Robinson EOS (PR-EOS) and Virial EOS (Virial-EOS) is obtained under the supercritical region in terms of compressibility parameter, pressure and temperature. The evaluated heat expansion rate values based on these equations of state and local NuX have been validated with practical values and found that the RK-EOS is an appropriate EOS to predict the natural convection characteristics of supercritical fluid (nitrogen) when compared to other models. The governing couple stress liquid circulation equations over a vertical cylinder are computationally solved by employing the finite difference technique. The current numerical study shows that the steady-state and transient velocity fields of a supercritical Newtonian fluid are considerably higher than couple stress fluid and these velocity profiles increase with an increase in reduced pressure and decrease with an increase in reduced temperature. Further, the thermal field is suppressed with magnifying reduced pressure and enhanced with amplifying reduced temperature. Using the present study, it can be concluded that the RK-EOS is considered to be an appropriate EOS to govern the thermal parameters of supercritical Newtonian and couple stress fluids.
The present paper studies through numerical methods, the thermodynamic heat transfer characteristics of free convection flow of supercritical nitrogen over a vertical cylinder. In the present analysis, the values of volumetric thermal expansion coefficient ( $\beta$ ) are evaluated based on Redlich-Kwong equation of state (RK-EOS) and Van der Waals equation of state (VW-EOS). The calculated analytical thermal expansion coefficient values using RK-EOS are very close to NIST data values in comparison with VW-EOS. A set of coupled nonlinear partial differential equations (PDEs) governing the supercritical fluid (SCF) flow are derived, converted into non-dimensional form with the help of suitable dimensionless quantities and solved using Crank-Nicolson implicit finite difference method. The simulations are carried out for nitrogen in the supercritical region. The obtained numerical data is expressed in terms of graphs and tables for various values of physical parameters. The increasing value of reduced temperature decreases the average Nusselt number and skin-friction coefficient, whereas amplifying value of reduced pressure enhance the heat transfer rate and wall shear stress in the SCF region. Present results are compared with the previous results and the two are found to be in good agreement, i. e. the numerically generated results found to be in agreement with existing results.
A new thermodynamic computational model has been proposed for the current study, which deals with the free convective supercritical Casson fluid flow past a vertical cylinder. In this model, pressure, temperature and compressibility factor are the critical parameters to govern the thermal expansion coefficient. The present model is based on the Redlich–Kwong equation of state. Comparisons with experimental results and determined values of thermal expansion coefficient for the choice of chemical compound (isobutene) from the present study show great similarity. The chemical compound isobutane has many industrial applications. For instance, in geothermal power plant, supercritical isobutane is employed as a working fluid, it is used in the deactivated (USY alkylation) catalyst regeneration, it is used in heat pumps and many other industrial processes. Furthermore, isobutane finds extensive application as a propellant in foam products and aerosol cans, as a refrigerate gas in freezers and refrigerators, as a feedstock in industries of petrochemical importance, for standardisation of gas mixtures and emission monitoring, etc. In addition, the Casson fluid flow model can be used to study the blood flow rheology, slurry flows, etc. The numerical scheme such as Crank–Nicolson type is demonstrated to simplify the governing nonlinear coupled partial differential equations. The transient results of flow-field variables, coefficients of heat and momentum transport for a Casson fluid under supercritical condition for various values of reduced pressure and reduced temperature are computed and discussed through graphs.
