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Suguru Masuzaki - One of the best experts on this subject based on the ideXlab platform.
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conductive and viscous sub layers on forced convection and mechanism of critical heat flux during flow boiling of subcooled water in a circular tube at high Liquid Reynolds Number
Heat and Mass Transfer, 2019Co-Authors: Koichi Hata, Suguru MasuzakiAbstract:The turbulent heat transfer, the subcooled boiling heat transfer and the steady state CHF for a Pt-circular test tube of a 3 mm inner diameter and a 100 mm heated length are measured with a wide range of inlet subcooling and flow velocity at high Liquid Reynolds Number, i.e. Red = 3.01×104 to 1.43×105. The inner surface temperature of the Pt-circular test tube calculated by the steady one-dimensional heat conduction equation is compared with the values derived from authors’ turbulent heat transfer correlation and with the numerical solutions of the RANS equations (Reynolds Averaged Navier-Stokes Simulation) of k-e turbulence model for the flow velocities ranging from 4 to 21 m/s. The thicknesses of conductive sub-layer from non-boiling regime to CHF are measured by numerically analyzing the heat transfers with conductive sub-layer on forced convection and with thinner one dissipated by the evaporation on nucleate boiling. The thicknesses of viscous sub-layer on forced convection are estimated from the thicknesses of the conductive sub-layer and Prandtl Numbers of the surface temperature on the heated surface. Furthermore, the thicknesses of conductive sub-layer at the CHF point are extrapolated from the measured values at various flow velocities. The experimental values of the CHF are also compared with authors’ widely and precisely predictable correlations of critical heat flux during flow boiling of subcooled water and the corresponding theoretical values of the Liquid sub-layer dry-out models suggested by other researchers, respectively. The authors’ correlations and other researchers’ theoretical values can represent the subcooled boiling CHFs obtained in this study within the ranges of −13.27 to 6.76% difference and − 32.51 to 13.16% one, respectively. A suggestion based on the experimental data as to what the dominant mechanism is for critical heat flux during flow boiling of subcooled water on a vertical circular tube is confirmed again at high Liquid Reynolds Number. The transitions to film boiling at the subcooled water flow boiling on the Pt test tube of d = 3 mm and L = 100 mm would occur due to the Liquid sub-layer dry-out model at the steady-state CHF as well as those on the Pt test tube of d = 3 mm and L = 66.5 mm, but not due to the heterogeneous spontaneous nucleation and the hydro-dynamic instability.
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influence of boiling initiation surface superheat on subcooled water flow boiling critical heat flux in a sus304 circular tube at high Liquid Reynolds Number
International Journal of Heat and Mass Transfer, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:Abstract The subcooled boiling heat transfer and the steady-state critical heat flux (CHF) in a vertical circular tube for the Liquid Reynolds Numbers ( Re d = 3.65 × 10 4 –3.08 × 10 5 ) and the flow velocities ( u = 3.95–30.80 m/s) were systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test tube of inner diameter ( d = 6 mm) and heated length ( L = 59.5 mm) was used in this work. The boiling initiation noise of outer surface of the test tube in the open air was simultaneously measured up to CHF point by the sound level meter (SLM) and the microphone of a video camera (MP). The outer surface temperatures of the SUS304 test tube with heating were also observed by an infrared thermal imaging camera (ITIC) and the color temperatures of outer surface of the test tube in the open air were observed by a video camera (VC). The subcooled boiling heat transfer and CHF for SUS304 circular tube were compared with the values calculated by authors’ and other researchers’ correlations for the subcooled flow boiling heat transfer. The influences of flow velocity on the boiling initiation surface heat flux, the boiling initiation surface superheat, the subcooled boiling heat transfer and the CHF were investigated into details based on the experimental data. At the flow velocities higher than 13.3 m/s, boiling initiation surface heat fluxes were close to the CHFs and surface superheats at the CHF were over to the homogeneous spontaneous nucleation temperature as well as the lower limit of the heterogeneous spontaneous nucleation temperature. The dominant mechanism of the subcooled water flow boiling CHF on the SUS304 circular tube was discussed at high Liquid Reynolds Number.
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mechanism of critical heat flux during flow boiling of subcooled water in a circular tube at high Liquid Reynolds Number
Experimental Thermal and Fluid Science, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:The subcooled boiling heat transfer and the steady state critical heat flux (CHF) in a vertical circular tube for the Liquid Reynolds Numbers (Red = 2.77 × 104–3.08 × 105) and the flow velocities (u = 3.95–30.80 m/s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test tube of inner diameter (d = 6 mm) and heated length (L = 59.5 mm) is used in this work. The outer surface temperatures of the SUS304 test tube with heating are observed by an infrared thermal imaging camera and a video camera. The subcooled boiling heat transfers for SUS304 test tube are compared with the values calculated from correlations due to other researchers for the subcooled boiling heat transfer. The influence of flow velocity on the subcooled boiling heat transfer and the CHF is investigated in detail based on the experimental data. Nucleate boiling surface superheats at the CHF are close to the lower limit of the heterogeneous spontaneous nucleation temperature and the homogeneous spontaneous nucleation temperature. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the SUS304 circular tube is made at high Liquid Reynolds Number. On the other hand, the RANS equations (Reynolds Averaged Navier–Stokes Simulation) with k–e turbulent model in a circular tube of a 3 mm in diameter and a 526 mm long are numerically solved for heating of water on heated section of a 3 mm in diameter and a 67 mm long with various thicknesses of conductive sub-layer by using PHOENICS code under the same conditions as the experimental ones previously obtained and with temperature dependent thermo-physical fluid properties. The Platinum (Pt) test tube of inner diameter (d = 3 mm) and heated length (L = 66.5 mm) was used in this experiment. The thicknesses of conductive sub-layer from non-boiling regime to CHF are measured. The thicknesses of conductive sub-layer at the CHF point are predicted for various flow velocities. The experimental values of the CHF are also compared with the corresponding theoretical values of the Liquid sub-layer dry-out models suggested by other researchers, respectively. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the Pt circular tube is made at high Liquid Reynolds Number.
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critical heat fluxes of subcooled water flow boiling in a short vertical tube at high Liquid Reynolds Number
Nuclear Engineering and Design, 2010Co-Authors: Koichi Hata, Suguru MasuzakiAbstract:Abstract The steady state critical heat fluxes (CHFs) and the heat transfer of the subcooled water flow boiling for the flow velocities ( u = 17.2–42.4 m/s), the inlet subcoolings (Δ T sub , in = 80.9–147.6 K), the inlet pressures ( P in = 812.1–1181.5 kPa) and the exponentially increasing heat input ( Q 0 exp( t / τ ), τ = 8.5 s) are systematically measured by the experimental water loop comprised of a new multi-stage canned-type circulation pump with high pump head. The SUS304 test tube of inner diameter ( d = 6 mm), heated length ( L = 59.5 mm), L / d = 9.92 and wall thickness ( δ = 0.5 mm) with surface roughness ( Ra = 3.18 μm) is used in this work. The steady state CHFs of the subcooled water flow boiling for the flow velocities ranging from 17.2 to 42.4 m/s are clarified. The steady state CHFs are compared with the values calculated by our transient CHF correlations against outlet and inlet subcoolings based on the experimental data for the flow velocities ranging from 4.0 to 13.3 m/s. The influence of flow velocity at high Liquid Reynolds Number on the subcooled flow boiling CHF is investigated in detail and the widely and precisely predictable correlations of the transient CHF correlations against outlet and inlet subcoolings in a short vertical tube are derived based on the experimental data at high Liquid Reynolds Number. The transient CHF correlations can describe the subcooled flow boiling CHFs for the wide range of flow velocities at high Liquid Reynolds Number obtained in this work within ±15% difference.
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subcooled boiling heat transfer in a short vertical sus304 tube at Liquid Reynolds Number range 5 19 104 to 7 43 105
Nuclear Engineering and Design, 2009Co-Authors: Koichi Hata, Suguru MasuzakiAbstract:Abstract The subcooled boiling heat transfer and the steady-state critical heat fluxes (CHFs) in a short vertical SUS304-tube for the flow velocities ( u = 17.28–40.20 m/s), the inlet Liquid temperatures ( T in = 293.30–362.49 K), the inlet pressures ( P in = 842.90–1467.93 kPa) and the exponentially increasing heat input ( Q = Q 0 exp ( t / τ ), τ = 8.5 s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test tubes of inner diameters ( d = 3 and 6 mm), heated lengths ( L = 33 and 59.5 mm), effective lengths ( L eff = 23.3 and 49.1 mm), L / d (=11 and 9.92), L eff / d (=7.77 and 8.18), and wall thickness ( δ = 0.5 mm) with average surface roughness ( Ra = 3.18 μm) are used in this work. The inner surface temperature and the heat flux from non-boiling to CHF are clarified. The subcooled boiling heat transfer for SUS304 test tube is compared with our Platinum test tube data and the values calculated by other workers’ correlations for the subcooled boiling heat transfer. The influence of flow velocity on the subcooled boiling heat transfer and the CHF is investigated into details and the widely and precisely predictable correlation of the subcooled boiling heat transfer for turbulent flow of water in a short vertical SUS304-tube is given based on the experimental data. The correlation can describe the subcooled boiling heat transfer obtained in this work within 15% difference. Nucleate boiling surface superheats for the SUS304 test tube become very high. Those at the high flow velocity are close to the lower limit of Heterogeneous Spontaneous Nucleation Temperature. The dominant mechanisms of the flow boiling CHF in a short vertical SUS304-tube are discussed.
Koichi Hata - One of the best experts on this subject based on the ideXlab platform.
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Conductive and viscous sub-layers on forced convection and mechanism of critical heat flux during flow boiling of subcooled water in a platinum circular tube with 3 mm inner diameter and 32.7 mm heated length at high Liquid Reynolds Number
International Journal of Heat and Mass Transfer, 2020Co-Authors: Koichi Hata, Qiusheng LiuAbstract:Abstract The turbulent heat transfer, the subcooled boiling heat transfer and the steady state CHF for a Pt-circular test tube of a 3 mm inner diameter and a 32.7 mm heated length are measured with a wide range of inlet subcooling and flow velocity at high Liquid Reynolds Number, i.e. Red = 2.35 × 104 to 1.12 × 105. For flow velocities ranging from 4.103 to 21.446 m/s, the inner surface temperature of the Pt circular test tube calculated by the steady one-dimensional heat conduction equation is compared with the value obtained from our turbulent heat transfer correlation equation and the numerical solution of the RANS equation (Reynolds mean Navier–Stokes simulation) of the k-e turbulence model. The conduction sub-layer thicknesses from the non-boiling region to CHF are measured in the conduction sub-layer itself in the forced convection region and the thinner sub-layer dissipated by boiling evaporation in the nucleate boiling region. The nondimensional thicknesses of local and average conductive sub-layers and, the thicknesses and nondimensional thicknesses of local and average viscous sub-layers on forced convection are estimated from the thicknesses of local and average conductive sub-layers and Prandtl Numbers evaluated at the calculated temperature of the first control volume on the heated surface. In addition, the thickness of the conductive sublayer at the CHF point is estimated from measurements at various flow velocities. The experimental values of the CHF are also compared with authors’ widely and precisely predictable correlations of critical heat flux during flow boiling of subcooled water and the corresponding theoretical values of the Liquid sub-layer dry-out models suggested by other researchers, respectively. The authors’ correlations and other researchers’ theoretical values can represent the subcooled boiling CHFs obtained in this study within the ranges of −22.74 to −6.21% difference and −22.17 to 6.16% one, respectively. Proposals for the main mechanism of critical heat flux during flow boiling of subcooled water on vertical tubes are confirmed again at high Liquid Reynolds Numbers based on experimental data. The boiling transitions to film boiling at the subcooled water flow boiling in the Pt test tube of d = 3 mm and L = 32.7 mm is not due to heterogeneous spontaneous nucleation or hydro-dynamic instability, but to Liquid sub-layer dry-out model at the steady-state CHF. It is similar to those for the Pt test tubes with d = 3 mm and L = 66.5 mm, and d = 3 mm and L = 100 mm.
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conductive and viscous sub layers on forced convection and mechanism of critical heat flux during flow boiling of subcooled water in a circular tube at high Liquid Reynolds Number
Heat and Mass Transfer, 2019Co-Authors: Koichi Hata, Suguru MasuzakiAbstract:The turbulent heat transfer, the subcooled boiling heat transfer and the steady state CHF for a Pt-circular test tube of a 3 mm inner diameter and a 100 mm heated length are measured with a wide range of inlet subcooling and flow velocity at high Liquid Reynolds Number, i.e. Red = 3.01×104 to 1.43×105. The inner surface temperature of the Pt-circular test tube calculated by the steady one-dimensional heat conduction equation is compared with the values derived from authors’ turbulent heat transfer correlation and with the numerical solutions of the RANS equations (Reynolds Averaged Navier-Stokes Simulation) of k-e turbulence model for the flow velocities ranging from 4 to 21 m/s. The thicknesses of conductive sub-layer from non-boiling regime to CHF are measured by numerically analyzing the heat transfers with conductive sub-layer on forced convection and with thinner one dissipated by the evaporation on nucleate boiling. The thicknesses of viscous sub-layer on forced convection are estimated from the thicknesses of the conductive sub-layer and Prandtl Numbers of the surface temperature on the heated surface. Furthermore, the thicknesses of conductive sub-layer at the CHF point are extrapolated from the measured values at various flow velocities. The experimental values of the CHF are also compared with authors’ widely and precisely predictable correlations of critical heat flux during flow boiling of subcooled water and the corresponding theoretical values of the Liquid sub-layer dry-out models suggested by other researchers, respectively. The authors’ correlations and other researchers’ theoretical values can represent the subcooled boiling CHFs obtained in this study within the ranges of −13.27 to 6.76% difference and − 32.51 to 13.16% one, respectively. A suggestion based on the experimental data as to what the dominant mechanism is for critical heat flux during flow boiling of subcooled water on a vertical circular tube is confirmed again at high Liquid Reynolds Number. The transitions to film boiling at the subcooled water flow boiling on the Pt test tube of d = 3 mm and L = 100 mm would occur due to the Liquid sub-layer dry-out model at the steady-state CHF as well as those on the Pt test tube of d = 3 mm and L = 66.5 mm, but not due to the heterogeneous spontaneous nucleation and the hydro-dynamic instability.
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influence of boiling initiation surface superheat on subcooled water flow boiling critical heat flux in a sus304 circular tube at high Liquid Reynolds Number
International Journal of Heat and Mass Transfer, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:Abstract The subcooled boiling heat transfer and the steady-state critical heat flux (CHF) in a vertical circular tube for the Liquid Reynolds Numbers ( Re d = 3.65 × 10 4 –3.08 × 10 5 ) and the flow velocities ( u = 3.95–30.80 m/s) were systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test tube of inner diameter ( d = 6 mm) and heated length ( L = 59.5 mm) was used in this work. The boiling initiation noise of outer surface of the test tube in the open air was simultaneously measured up to CHF point by the sound level meter (SLM) and the microphone of a video camera (MP). The outer surface temperatures of the SUS304 test tube with heating were also observed by an infrared thermal imaging camera (ITIC) and the color temperatures of outer surface of the test tube in the open air were observed by a video camera (VC). The subcooled boiling heat transfer and CHF for SUS304 circular tube were compared with the values calculated by authors’ and other researchers’ correlations for the subcooled flow boiling heat transfer. The influences of flow velocity on the boiling initiation surface heat flux, the boiling initiation surface superheat, the subcooled boiling heat transfer and the CHF were investigated into details based on the experimental data. At the flow velocities higher than 13.3 m/s, boiling initiation surface heat fluxes were close to the CHFs and surface superheats at the CHF were over to the homogeneous spontaneous nucleation temperature as well as the lower limit of the heterogeneous spontaneous nucleation temperature. The dominant mechanism of the subcooled water flow boiling CHF on the SUS304 circular tube was discussed at high Liquid Reynolds Number.
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mechanism of critical heat flux during flow boiling of subcooled water in a circular tube at high Liquid Reynolds Number
Experimental Thermal and Fluid Science, 2016Co-Authors: Koichi Hata, Katsuya Fukuda, Suguru MasuzakiAbstract:The subcooled boiling heat transfer and the steady state critical heat flux (CHF) in a vertical circular tube for the Liquid Reynolds Numbers (Red = 2.77 × 104–3.08 × 105) and the flow velocities (u = 3.95–30.80 m/s) are systematically measured by the experimental water loop comprised of a multistage canned-type circulation pump with high pump head. The SUS304 test tube of inner diameter (d = 6 mm) and heated length (L = 59.5 mm) is used in this work. The outer surface temperatures of the SUS304 test tube with heating are observed by an infrared thermal imaging camera and a video camera. The subcooled boiling heat transfers for SUS304 test tube are compared with the values calculated from correlations due to other researchers for the subcooled boiling heat transfer. The influence of flow velocity on the subcooled boiling heat transfer and the CHF is investigated in detail based on the experimental data. Nucleate boiling surface superheats at the CHF are close to the lower limit of the heterogeneous spontaneous nucleation temperature and the homogeneous spontaneous nucleation temperature. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the SUS304 circular tube is made at high Liquid Reynolds Number. On the other hand, the RANS equations (Reynolds Averaged Navier–Stokes Simulation) with k–e turbulent model in a circular tube of a 3 mm in diameter and a 526 mm long are numerically solved for heating of water on heated section of a 3 mm in diameter and a 67 mm long with various thicknesses of conductive sub-layer by using PHOENICS code under the same conditions as the experimental ones previously obtained and with temperature dependent thermo-physical fluid properties. The Platinum (Pt) test tube of inner diameter (d = 3 mm) and heated length (L = 66.5 mm) was used in this experiment. The thicknesses of conductive sub-layer from non-boiling regime to CHF are measured. The thicknesses of conductive sub-layer at the CHF point are predicted for various flow velocities. The experimental values of the CHF are also compared with the corresponding theoretical values of the Liquid sub-layer dry-out models suggested by other researchers, respectively. A suggestion as to what the dominant mechanism is for the subcooled flow boiling CHF on the Pt circular tube is made at high Liquid Reynolds Number.
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critical heat fluxes of subcooled water flow boiling in a short vertical tube at high Liquid Reynolds Number
Nuclear Engineering and Design, 2010Co-Authors: Koichi Hata, Suguru MasuzakiAbstract:Abstract The steady state critical heat fluxes (CHFs) and the heat transfer of the subcooled water flow boiling for the flow velocities ( u = 17.2–42.4 m/s), the inlet subcoolings (Δ T sub , in = 80.9–147.6 K), the inlet pressures ( P in = 812.1–1181.5 kPa) and the exponentially increasing heat input ( Q 0 exp( t / τ ), τ = 8.5 s) are systematically measured by the experimental water loop comprised of a new multi-stage canned-type circulation pump with high pump head. The SUS304 test tube of inner diameter ( d = 6 mm), heated length ( L = 59.5 mm), L / d = 9.92 and wall thickness ( δ = 0.5 mm) with surface roughness ( Ra = 3.18 μm) is used in this work. The steady state CHFs of the subcooled water flow boiling for the flow velocities ranging from 17.2 to 42.4 m/s are clarified. The steady state CHFs are compared with the values calculated by our transient CHF correlations against outlet and inlet subcoolings based on the experimental data for the flow velocities ranging from 4.0 to 13.3 m/s. The influence of flow velocity at high Liquid Reynolds Number on the subcooled flow boiling CHF is investigated in detail and the widely and precisely predictable correlations of the transient CHF correlations against outlet and inlet subcoolings in a short vertical tube are derived based on the experimental data at high Liquid Reynolds Number. The transient CHF correlations can describe the subcooled flow boiling CHFs for the wide range of flow velocities at high Liquid Reynolds Number obtained in this work within ±15% difference.
Yu. Ya. Trifonov - One of the best experts on this subject based on the ideXlab platform.
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Linear and nonlinear instabilities of a co-current gas-Liquid flow between two inclined plates analyzed using the Navier–Stokes equations
International Journal of Multiphase Flow, 2020Co-Authors: Yu. Ya. TrifonovAbstract:Abstract The paper is devoted to a theoretical analysis of a co-current gas-Liquid flow between two inclined plates. As a first step, we linearized the Navier-Stokes equations in both phases and carried out a linear stability analysis of the basic steady-state solution over a wide variation of the Liquid Reynolds Number and the gas superficial velocity. We obtained two modes of the unstable disturbances and computed the wavelength and phase velocity of their neutral and the fastest growing disturbances varying the Liquid and gas Reynolds Number. The first mode corresponds to the Kapitza's waves at small values of the gas superficial velocity. The second mode of the unstable disturbances corresponds to the transition to a turbulent flow in the gas phase. We found that the co-current gas velocity destabilize the film flow at all values of the inclination angle and distance between the plates considered in the paper. The range of the wavelength of the unstable disturbances essentially increases with the gas velocity increasing. As a second step, we have performed the systematic study of nonlinear wave regimes. We found that the gas flow affects significantly the wave characteristics decreasing the amplitude and increasing the phase velocity. The complex multi-fold and multi-sheet surface, found on the plane of parameters (wavelength and the Liquid Reynolds Number) for the gravitational film flow, exists at all velocities of the co-current gas flow. We carried out investigation of the “optimal” waves for several folders and presented comparison with the regimes observed in experiments. Using of the strict equations without any additional assumptions is an important feature of this paper.
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Nonlinear wavy regimes of a gas-Liquid flow between two inclined plates analyzed using the Navier–Stokes equations
International Journal of Multiphase Flow, 2019Co-Authors: Yu. Ya. TrifonovAbstract:Abstract The paper is devoted to a theoretical analysis of a counter-current gas-Liquid flow between two inclined plates. We used the Navier-Stokes equations for both Liquid and gas to compute the nonlinear wavy regimes of the flow over a wide variation of the Liquid Reynolds Number and the gas superficial velocity. The main interest is to analyze the variation of the free surface shape, u-velocities and phase velocity of the waves as the superficial gas velocity is increased. We do our investigation for relatively small values of the distance between the plates where the shear modes of the linear disturbances are stable and the gas flow is laminar. We found that with the superficial gas velocity increasing and starting from some critical value of this velocity, the dependences of the main characteristics of the waves demonstrate a qualitative modification. For example, at small values of the plate’s inclination angle the dependences of the gas friction coefficient and the averaged film thickness have a local minimum for different values of the Liquid Reynolds Number at this critical value of the gas superficial velocity. We observe an essential increasing of the portion of the wavy profile with negative values of the u-velocity on the interface starting with this critical velocity. The obtained critical velocities are in reasonable agreement with the onset of flooding observed in experiments and their values have a correct trend with the increasing of the Liquid Reynolds Number.
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Instabilities of a gas-Liquid flow between two inclined plates analyzed using the Navier–Stokes equations
International Journal of Multiphase Flow, 2017Co-Authors: Yu. Ya. TrifonovAbstract:Abstract The paper is devoted to a theoretical analysis of a counter-current gas-Liquid flow between two inclined plates. We linearized the Navier–Stokes equations and carried out a stability analysis of the basic steady-state solution over a wide variation of the Liquid Reynolds Number and the gas superficial velocity. As a result, we found two modes of the unstable disturbances and computed the wavelength and phase velocity of their neutral disturbances varying the Liquid and gas Reynolds Number. The first mode is a “surface mode” that corresponds to the Kapitza's waves at small values of the gas superficial velocity. We found that the dependence of the neutral disturbance wavelength on the Liquid Reynolds Number strongly depends on the gas superficial velocity, the distance between the plates and the channel inclination angle for this mode. The second mode of the unstable disturbances corresponds to the transition to a turbulent flow in the gas phase and there is a critical value of the gas Reynolds Number for this mode. We obtained that this critical Reynolds Number weakly depends on both the channel inclination angle, the distance between the plates and the Liquid flow parameters for the conditions considered in the paper. Despite a thorough search, we did not find the unstable modes that may correspond to the instability in frame of the viscous (or inviscid) Kelvin–Helmholtz heuristic analysis.
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Wavy flow of a Liquid film in the presence of a cocurrent turbulent gas flow
Journal of Applied Mechanics and Technical Physics, 2013Co-Authors: Yu. Ya. TrifonovAbstract:Wavy downflow of viscous Liquid films in the presence of a cocurrent turbulent gas flow is analyzed theoretically. The parameters of two-dimensional steady-state traveling waves are calculated for wide ranges of Liquid Reynolds Number and gas flow velocity. The hydrodynamic characteristics of the Liquid flow are computed using the full Navier-Stokes equations. The wavy interface is regarded as a small perturbation, and the equations for the gas are linearized in the vicinity of the main turbulent flow. Various optimal film flow regimes are obtained for the calculated nonlinear waves branching from the plane-parallel flow. It is shown that for high velocities of the cocurrent gas flow, the calculated wave characteristics correspond to those of ripple waves observed in experiments.
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Flooding in two-phase counter-current flows: Numerical investigation of the gas–Liquid wavy interface using the Navier–Stokes equations
International Journal of Multiphase Flow, 2010Co-Authors: Yu. Ya. TrifonovAbstract:Abstract This paper is devoted to a theoretical analysis of counter-current gas–Liquid wavy film flow between vertical plates. We consider two-dimensional nonlinear waves on the interface over a wide variation of parameters. We use the Navier–Stokes equations in their full statement to describe the Liquid phase hydrodynamics. For the gas phase equations, we use the Benjamin-Miles approach where the Liquid phase is a small disturbance for the turbulent gas flow. We find a region of the superficial velocity where we have two solutions at one set of the problem parameters and where the flooding takes place. We calculate the flooding dependences on the gas/Liquid physical properties, on the Liquid Reynolds Number and on the distance between the plates. These computations allow us to present the correlation for the onset of flooding that based on the fundamental equations and principles.
T. Bauer - One of the best experts on this subject based on the ideXlab platform.
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Liquid Holdup in Trickle-Bed Reactors at Very Low Liquid Reynolds Numbers
Industrial & Engineering Chemistry Research, 2005Co-Authors: Rüdiger Lange, Markus Schubert, T. BauerAbstract:The paper presents experimental results concerning hydrodynamic aspects in a trickle-bed reactor, in which both fluid phases (gas and Liquid) are fed concurrently downward. The static and dynamic Liquid holdup fractions were measured in a trickle-bed reactor (inner reactor diameter 0.034 m) packed with different porous and nonporous particles at very low Liquid mass flow rates using the drainage technique. The Liquid Reynolds Number ReL was in the range of 0.08−1.2 and the gas Reynolds Number ReG in the range of 0.13−2.9. The measurements were performed with organic Liquids and hydrogen and nitrogen as gas phases. The results are presented graphically. It was shown that the ratio of the reactor diameter to the particle diameter and Liquid Reynolds Number affect on the Liquid holdup. The dynamic Liquid holdup increases with an increase in the Liquid Reynolds Numbers and with a decrease in the particle diameter. The effect of the gas flow rate on the Liquid holdup can be neglected. Correlations are derived ...
Osvaldo Miguel Martínez - One of the best experts on this subject based on the ideXlab platform.
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Estimation of overall heat transfer coefficients in packed beds with cocurrent downflow of gas and Liquid
Fuel, 2014Co-Authors: María José Taulamet, Nestor Javier Mariani, Guillermo Fernando Barreto, Osvaldo Miguel MartínezAbstract:Abstract This contribution undertakes the analysis of heat transfer between a packed bed with cocurrent downflow of gas and Liquid, widely known as trickle bed reactor, and an external heating or cooling fluid. Experiments were carried out in a bench scale reactor with water and air, covering trickle and pulsing regimes, in beds presenting aspect ratios (tube to particle diameter ratio) from 4.7 to 34. Four sizes of glass spheres, two of glass cylinders, a mixture of spheres and a commercial trilobe pellet were employed as particles. With the purpose of estimating the overall heat transfer rates, a 1D pseudo-homogeneous model with a single parameter (overall bed heat transfer coefficient, h T ) was employed to analyze the experimental results. An expression to estimate h T (expressed as Nusselt Number) for the low interaction regime in terms of Liquid Reynolds Number, a pellet shape factor and bed to particle diameter ratio is proposed. This expression approximates the experimental values with an average deviation of around 10%.
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On the Influence of Liquid Distribution on Heat Transfer Parameters in Trickle Bed Systems
The Canadian Journal of Chemical Engineering, 2008Co-Authors: Nestor Javier Mariani, Osvaldo Miguel Martínez, Ana Lea Cukierman, Germán Mazza, Guillermo Fernando BarretoAbstract:The aim of this work is to analyse experimental results on radial heat transfer in a packed bed column with cocurrent downflow of Liquid and gas, focused on the influence of radial Liquid distribution and column to particle diameter ratio. For this purpose, two kinds of measurements were carried out: radial Liquid distribution and radial temperature profiles. Heat transfer data as analysed with a model consisting of two regions: a lumped wall region up to a distance of a particle radius from the tube wall, and a distributed core region covering the rest of the bed. Three parameters arose: the radial effective thermal conductivity of the core region (k er,c ), the heat transfer coefficient between both zones (h I ), and the heat transfer coefficient from the wall region to the tube wall (h w,w ). Suitable correlations for the mentioned parameters as a function of gas and Liquid Reynolds Number and particle diameter were developed.
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Liquid hold-up and backmixing in cocurrent upflow three-phase fixed-bed reactors
Chemical Engineering Science, 1998Co-Authors: Miryan Cassanello, Osvaldo Miguel Martínez, Ana Lea CukiermanAbstract:Liquid-phase hydrodynamics is studied in a three-phase fixed bed with cocurrent upflow of gas and Liquid. Residence-time distributions are measured to determine Liquid hold-up and backmixing using different Liquids and glass beads of two sizes. Two types of correlations are tested for Liquid saturation. Correlations based on the drift flux concept are found to account for experimental results. Liquid mixing is described in terms of the axial dispersion model. A close relation between the axial dispersion coefficient and the bubbles sizes estimated using the theory of fluid emulsions is found. Hence, a new type of correlation is proposed to estimate axial dispersion coefficients in this type of reactors. This correlation considers the influences on the Peclet Number of the Liquid Reynolds Number and the two-phase flow dissipation power rate, which would determine bubbles sizes.