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Yutaka Asako - One of the best experts on this subject based on the ideXlab platform.
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Flow characteristics of Gaseous Flow through a microtube discharged into the atmosphere
International Journal of Heat and Mass Transfer, 2018Co-Authors: C Hong, Yutaka Asako, Goku Tanaka, Hiroshi KatanodaAbstract:Abstract Flow characteristics for a wide range of Reynolds number up to turbulent gas Flow regime, including Flow choking were numerically investigated with a microtube discharged into the atmosphere. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The LB1 turbulence model was used in the turbulent Flow case. Axis-symmetric compressible momentum and energy equations of an ideal gas are solved to obtain the Flow characteristics. In order to calculate the underexpanded (choked) Flow at the microtube outlet, the computational domain is extended to the downstream region of the hemisphere from the microtube outlet. The back pressure was given to the outside of the downstream region. The computations were performed for adiabatic microtubes whose diameter ranges from 10 to 500 μm and whose aspect ratio is 100 or 200. The stagnation pressure range is chosen in such a way that the Flow becomes a fully underexpanded Flow at the microtube outlet. The results in the wide range of Reynolds number and Mach number were obtained including the choked Flow. With increasing the stagnation pressure, the Flow at the microtube outlet is underexpanded and choked. Although the velocity is limited, the mass Flow rate (Reynolds number) increases. In order to further validate the present numerical model, an experiment was also performed for nitrogen gas through a glass microtube with 397 μm in diameter and 120 mm in length. Three pressure tap holes were drilled on the glass microtube wall. The local pressures were measured to determine local values of Mach numbers and friction factors. Local friction factors were numerically and experimentally obtained and were compared with empirical correlations in the literature on Moody’s chart. The numerical results are also in excellent agreement with the experimental ones.
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Under-Expanded Gaseous Flow at a Straight Micro-Tube Exit
Journal of Fluids Engineering, 2014Co-Authors: Takahiro Yoshimaru, Yutaka Asako, Toru YamadaAbstract:This paper focuses on under-expanded Gaseous Flow at a straight micro-tube exit. The pitot total pressure of gas Flow (jet) in the downstream region from a straight micro-tube exit was measured by a total pressure pitot tube to accumulate data for validation of numerical results. A micro-tube of 495 mu m in diameter and 56.3 mm in length and a total pressure pitot tube of 100 mu m in outer diameter were used. The pitot total pressure was measured at intervals of 0.1 mm in both the Flow and radial directions. The measurement was done for the mass Flow rates of 9.71 x 10(-5) kg/s and 1.46 x 10(-4) kg/s. The data were accumulated for validation of the numerical results to reveal the characteristics of the under-expanded gas Flow at the exit of a micro-tube. Comparisons were conducted for numerical results of corresponding cases and a slight discrepancy can be seen between numerical and experimentally measured pitot total pressures.
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Pressure loss of Gaseous Flow at a micro-tube outlet
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2010Co-Authors: Y. Horii, Yutaka Asako, C HongAbstract:The pressure loss of Gaseous Flow at a micro-tube outlet was investigated numerically. The numerical methodology is based on the arbitrary Lagrangian—Eulerian (ALE) method. Axis-symmetric compressible momentum and energy equations are solved to obtain the pressure loss coefficient of Gaseous Flow at a micro-tube outlet. Computed tube diameters are 50, 100, and 150μm. The stagnation pressure of upper stream of the tube is chosen in such a way that the Mach number at the tube outlet ranges from 0.1 to 1.2. The ambient (back) pressure is fixed at the atmospheric pressure. The pressure loss coefficients are compared with available experimental data for a conventionally sized tube. The effects of the Mach number and the tube diameter on the pressure loss coefficient are discussed and a correlation for the pressure loss coefficient is proposed.
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Total Temperature Measurements of Gaseous Flow at Micro-Tube Outlet
Volume 2: Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Computational Heat Transfer, 2009Co-Authors: Takaharu Yamamoto, C Hong, Yutaka Asako, Koichi SuzukiAbstract:This paper presents experimental results on heat transfer characteristics of Gaseous Flow in a micro-tube with constant wall temperature. The experiment was performed for nitrogen gas Flow through a micro-tube with 166 micro meters in diameter and 50mm in length. The wall temperature was maintained at 305K, 310K, 330K and 350K by circulating water around the micro-tube, respectively. The stagnation pressure is chosen in such a way that the exit Mach number ranges from 0.1 to 1.0. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass Flow rate, and the inlet pressure were measured. The numerical computations based on the Aribitary - Langrangian - Eulerian (ALE) method were also performed for the same cases of the experiment for validation of numerical computation. The both results are in excellent agreement. The total temperatures obtained by the present study are slightly higher than those of the incompressible Flow. This is due to the additional heat transfer near the micro-tube outlet caused by the temperature decrease due to the energy conversion into the kinetic energy. A quantitative correlation for the prediction of the heat transfer rate of the Gaseous Flow in a micro-tube was proposed.Copyright © 2009 by ASME
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Total Temperature Measurements of Gaseous Flow at Micro-Tube Outlet: Cooled From the Wall
Volume 9: Heat Transfer Fluid Flows and Thermal Systems Parts A B and C, 2009Co-Authors: Takaharu Yamamoto, C Hong, Yutaka Asako, Koichi SuzukiAbstract:This paper presents experimental results on heat transfer characteristics of Gaseous Flow in a micro-tube with constant wall temperature whose wall temperature is lower than the inlet temperature (cooled case). The experiment was performed for nitrogen gas Flow through a micro-tube with 163.4 micro meters in diameter and 50 mm in length. The gas was heated at the inlet of the micro-tube to Tin = 315K, 335K and 355K. The wall temperature was maintained at 305K which was lower than the inlet temperature by circulating water around the micro-tube. The stagnation pressure was chosen in such a way that the exit Mach number ranges from 0.1 to 0.9. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass Flow rate, and the inlet pressure were measured. The numerical computations based on the aribitary-Langrangian-Eulerian (ALE) method were also performed for the same conditions of the experiment. The total and bulk temperature obtained by the present study are compared with those of the numerical cases and also compared with temperatures of the incompressible Flow. The results have similar trends.Copyright © 2009 by ASME
Zhaoli Guo - One of the best experts on this subject based on the ideXlab platform.
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Lattice Boltzmann simulation of separation phenomenon in a binary Gaseous Flow through a microchannel
Journal of Applied Physics, 2016Co-Authors: Liang Wang, Zhaoli GuoAbstract:Gas separation of a binary Gaseous mixture is one of characteristic phenomena in the micro-scale Flows that differ from the conventional size Flows. In this work, the separation in a binary gas mixture Flows through a microchannel is investigated by the lattice Boltzmann method with a diffuse-bounce-back (DBB) boundary condition. The separation degree and rate are measured in the He--Ar and Ne--Ar systems for different mole fractions, pressure ratios, and Knudsen numbers. The results show that the separation phenomenon in the He--Ar mixture is more obvious than that in the Ne--Ar mixture at the same mole fraction owing to the larger molecular mass ratio. In addition, the increase in the pressure ratio reduces the difference in the molecular velocities between the two species, and the separation phenomenon becomes weaker. However, the gas separation is enhanced with an increase in the Knudsen number. This is because the resulting rarefaction effect reduces the interactions between the gas molecules of the two species, and thus increases the difference in the molecular velocity.
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lattice boltzmann simulation of separation phenomenon in a binary Gaseous Flow through a microchannel
Journal of Applied Physics, 2016Co-Authors: Liang Wang, Zhaoli GuoAbstract:Gas separation of a binary Gaseous mixture is one of the characteristic phenomena in the micro-scale Flows that differ from the conventional size Flows. In this work, the separation in binary gas mixture Flows through a microchannel is investigated by the lattice Boltzmann method with a diffuse-bounce-back boundary condition, where the wall function approach with effective relaxation time is combined in consideration of the high Knudsen numbers. The separation degree and rate are measured in the He–Ar and Ne–Ar systems for different mole fractions, pressure ratios, and Knudsen numbers. The results show that the separation phenomenon in the He–Ar mixture is more obvious than that in the Ne–Ar mixture at the same mole fraction owing to the larger molecular mass ratio. In addition, the increase in the pressure ratio reduces the difference in the molecular velocities between the two species, and the separation phenomenon becomes weaker. However, the gas separation is reduced with an increase in the Knudsen number. This is because the resulting rarefaction effect reduces the interactions between the gas molecules of the two species and thus increases the difference in the molecular velocity.
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Pressure Distribution of the Gaseous Flow in Microchannel: A Lattice Boltzmann Study
Communications in Computational Physics, 2013Co-Authors: Zhaoli GuoAbstract:In this paper the pressure distribution of the Gaseous Flow in a microchannel is studied via a lattice Boltzmann equation (LBE) method. With effective relaxation times and a generalized second order slip boundary condition, the LBE can be used to simulate rarefied gas Flows from slip to transition regimes. The Knudsen minimum phenomena of mass Flow rate in the pressure driven Flow is also investigated. The effects of Knudsen number (rarefaction effect), pressure ratio and aspect ratio (compression effect) on the pressure distribution are analyzed. It is found the rarefaction effect tends to the curvature of the nonlinear pressure distribution, while the compression effect tends to enhance its nonlinearity. The combined effects lead to a local minimum of the pressure deviation. Furthermore, it is also found that the relationship between the pressure deviation and the aspect ratio follows a pow-law.
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Lattice Boltzmann simulation of surface roughness effect on Gaseous Flow in a microchannel
Journal of Applied Physics, 2008Co-Authors: Zhenhua Chai, Zhaoli Guo, Lin Zheng, Baochang ShiAbstract:At the microscale level, it is impossible to obtain a completely smooth wall surface, and the effect of surface roughness may be a main factor responsible for some different characteristics between fluid Flow in the microchannels and that in conventional size channels. In the present work, the lattice Boltzmann method is applied to investigate the Gaseous Flow in a microchannel with surface roughness which is modeled by an array of rectangular modules. The effects of relative surface roughness, roughness distribution, and rarefaction on Gaseous Flow are studied, but the compressibility effect is neglected since the Mach number is less than 0.2. It was shown that the surface roughness had an important influence on friction factor and mass Flow rate. In particular, this effect becomes more significant with the decrease of the Knudsen number. This is because the rarefaction reduces the interaction between the gas molecules and the channel walls, which results in reduction of the surface roughness effect.
Liang Wang - One of the best experts on this subject based on the ideXlab platform.
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Lattice Boltzmann simulation of separation phenomenon in a binary Gaseous Flow through a microchannel
Journal of Applied Physics, 2016Co-Authors: Liang Wang, Zhaoli GuoAbstract:Gas separation of a binary Gaseous mixture is one of characteristic phenomena in the micro-scale Flows that differ from the conventional size Flows. In this work, the separation in a binary gas mixture Flows through a microchannel is investigated by the lattice Boltzmann method with a diffuse-bounce-back (DBB) boundary condition. The separation degree and rate are measured in the He--Ar and Ne--Ar systems for different mole fractions, pressure ratios, and Knudsen numbers. The results show that the separation phenomenon in the He--Ar mixture is more obvious than that in the Ne--Ar mixture at the same mole fraction owing to the larger molecular mass ratio. In addition, the increase in the pressure ratio reduces the difference in the molecular velocities between the two species, and the separation phenomenon becomes weaker. However, the gas separation is enhanced with an increase in the Knudsen number. This is because the resulting rarefaction effect reduces the interactions between the gas molecules of the two species, and thus increases the difference in the molecular velocity.
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Lattice Boltzmann simulation of separation phenomenon in a binary Gaseous Flow through a microchannel
Journal of Applied Physics, 2016Co-Authors: Liang Wang, Zimian XuAbstract:Gas separation of a binary Gaseous mixture is one of the characteristic phenomena in the micro-scale Flows that differ from the conventional size Flows. In this work, the separation in binary gas mixture Flows through a microchannel is investigated by the lattice Boltzmann method with a diffuse-bounce-back boundary condition, where the wall function approach with effective relaxation time is combined in consideration of the high Knudsen numbers. The separation degree and rate are measured in the He–Ar and Ne–Ar systems for different mole fractions, pressure ratios, and Knudsen numbers. The results show that the separation phenomenon in the He–Ar mixture is more obvious than that in the Ne–Ar mixture at the same mole fraction owing to the larger molecular mass ratio. In addition, the increase in the pressure ratio reduces the difference in the molecular velocities between the two species, and the separation phenomenon becomes weaker. However, the gas separation is reduced with an increase in the Knudsen nu...
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lattice boltzmann simulation of separation phenomenon in a binary Gaseous Flow through a microchannel
Journal of Applied Physics, 2016Co-Authors: Liang Wang, Zhaoli GuoAbstract:Gas separation of a binary Gaseous mixture is one of the characteristic phenomena in the micro-scale Flows that differ from the conventional size Flows. In this work, the separation in binary gas mixture Flows through a microchannel is investigated by the lattice Boltzmann method with a diffuse-bounce-back boundary condition, where the wall function approach with effective relaxation time is combined in consideration of the high Knudsen numbers. The separation degree and rate are measured in the He–Ar and Ne–Ar systems for different mole fractions, pressure ratios, and Knudsen numbers. The results show that the separation phenomenon in the He–Ar mixture is more obvious than that in the Ne–Ar mixture at the same mole fraction owing to the larger molecular mass ratio. In addition, the increase in the pressure ratio reduces the difference in the molecular velocities between the two species, and the separation phenomenon becomes weaker. However, the gas separation is reduced with an increase in the Knudsen number. This is because the resulting rarefaction effect reduces the interactions between the gas molecules of the two species and thus increases the difference in the molecular velocity.
C Hong - One of the best experts on this subject based on the ideXlab platform.
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Flow characteristics of Gaseous Flow through a microtube discharged into the atmosphere
International Journal of Heat and Mass Transfer, 2018Co-Authors: C Hong, Yutaka Asako, Goku Tanaka, Hiroshi KatanodaAbstract:Abstract Flow characteristics for a wide range of Reynolds number up to turbulent gas Flow regime, including Flow choking were numerically investigated with a microtube discharged into the atmosphere. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The LB1 turbulence model was used in the turbulent Flow case. Axis-symmetric compressible momentum and energy equations of an ideal gas are solved to obtain the Flow characteristics. In order to calculate the underexpanded (choked) Flow at the microtube outlet, the computational domain is extended to the downstream region of the hemisphere from the microtube outlet. The back pressure was given to the outside of the downstream region. The computations were performed for adiabatic microtubes whose diameter ranges from 10 to 500 μm and whose aspect ratio is 100 or 200. The stagnation pressure range is chosen in such a way that the Flow becomes a fully underexpanded Flow at the microtube outlet. The results in the wide range of Reynolds number and Mach number were obtained including the choked Flow. With increasing the stagnation pressure, the Flow at the microtube outlet is underexpanded and choked. Although the velocity is limited, the mass Flow rate (Reynolds number) increases. In order to further validate the present numerical model, an experiment was also performed for nitrogen gas through a glass microtube with 397 μm in diameter and 120 mm in length. Three pressure tap holes were drilled on the glass microtube wall. The local pressures were measured to determine local values of Mach numbers and friction factors. Local friction factors were numerically and experimentally obtained and were compared with empirical correlations in the literature on Moody’s chart. The numerical results are also in excellent agreement with the experimental ones.
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Pressure loss of Gaseous Flow at a micro-tube outlet
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science, 2010Co-Authors: Y. Horii, Yutaka Asako, C HongAbstract:The pressure loss of Gaseous Flow at a micro-tube outlet was investigated numerically. The numerical methodology is based on the arbitrary Lagrangian—Eulerian (ALE) method. Axis-symmetric compressible momentum and energy equations are solved to obtain the pressure loss coefficient of Gaseous Flow at a micro-tube outlet. Computed tube diameters are 50, 100, and 150μm. The stagnation pressure of upper stream of the tube is chosen in such a way that the Mach number at the tube outlet ranges from 0.1 to 1.2. The ambient (back) pressure is fixed at the atmospheric pressure. The pressure loss coefficients are compared with available experimental data for a conventionally sized tube. The effects of the Mach number and the tube diameter on the pressure loss coefficient are discussed and a correlation for the pressure loss coefficient is proposed.
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Total Temperature Measurements of Gaseous Flow at Micro-Tube Outlet
Volume 2: Theory and Fundamental Research; Aerospace Heat Transfer; Gas Turbine Heat Transfer; Computational Heat Transfer, 2009Co-Authors: Takaharu Yamamoto, C Hong, Yutaka Asako, Koichi SuzukiAbstract:This paper presents experimental results on heat transfer characteristics of Gaseous Flow in a micro-tube with constant wall temperature. The experiment was performed for nitrogen gas Flow through a micro-tube with 166 micro meters in diameter and 50mm in length. The wall temperature was maintained at 305K, 310K, 330K and 350K by circulating water around the micro-tube, respectively. The stagnation pressure is chosen in such a way that the exit Mach number ranges from 0.1 to 1.0. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass Flow rate, and the inlet pressure were measured. The numerical computations based on the Aribitary - Langrangian - Eulerian (ALE) method were also performed for the same cases of the experiment for validation of numerical computation. The both results are in excellent agreement. The total temperatures obtained by the present study are slightly higher than those of the incompressible Flow. This is due to the additional heat transfer near the micro-tube outlet caused by the temperature decrease due to the energy conversion into the kinetic energy. A quantitative correlation for the prediction of the heat transfer rate of the Gaseous Flow in a micro-tube was proposed.Copyright © 2009 by ASME
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Total Temperature Measurements of Gaseous Flow at Micro-Tube Outlet: Cooled From the Wall
Volume 9: Heat Transfer Fluid Flows and Thermal Systems Parts A B and C, 2009Co-Authors: Takaharu Yamamoto, C Hong, Yutaka Asako, Koichi SuzukiAbstract:This paper presents experimental results on heat transfer characteristics of Gaseous Flow in a micro-tube with constant wall temperature whose wall temperature is lower than the inlet temperature (cooled case). The experiment was performed for nitrogen gas Flow through a micro-tube with 163.4 micro meters in diameter and 50 mm in length. The gas was heated at the inlet of the micro-tube to Tin = 315K, 335K and 355K. The wall temperature was maintained at 305K which was lower than the inlet temperature by circulating water around the micro-tube. The stagnation pressure was chosen in such a way that the exit Mach number ranges from 0.1 to 0.9. The outlet pressure was fixed at the atmospheric condition. The total temperature at the outlet, the inlet stagnation temperature, the mass Flow rate, and the inlet pressure were measured. The numerical computations based on the aribitary-Langrangian-Eulerian (ALE) method were also performed for the same conditions of the experiment. The total and bulk temperature obtained by the present study are compared with those of the numerical cases and also compared with temperatures of the incompressible Flow. The results have similar trends.Copyright © 2009 by ASME
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Experimental Investigation of Gaseous Flow in a Micro-Tube
ASME 2009 7th International Conference on Nanochannels Microchannels and Minichannels, 2009Co-Authors: Yasuhiro Yoshida, C Hong, Yutaka Asako, Koichi SuzukiAbstract:Experimental investigations on nitrogen gas Flow characteristics were performed for a micro-tube. The micro-tube was fabricated in a stainless steel block by electrical discharge machining (EDM). The tube diameter was 326 μm and the ratio of length to diameter was 200. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1 to 1.4. The outlet pressure was fixed at atmospheric conditions. The pressure was locally measured at five locations along tube length to determine local values of Mach number and friction factor for a wide range of Flow regime from laminar to turbulent Flow. The result shows that f·Re is a function of Mach number and higher than incompressible value, 64 due to the compressibility effect. The values of f·Re were compared with f·Re correlation in literature. In additional experiments, Mach number at the micro-tube exit was measured by using a Shadowgraph system which visualizes the shock wave of the gas. The micro-tube with 400 μm in diameter was used for the experiment. The super sonic Flow was observed since Mach number at the micro-tube exit was beyond unity. The experimental results for laminar Flow were compared with the numerical results obtained by the arbitrary-Lagrangian-Eulerian method. The both results are in excellent agreement.Copyright © 2009 by ASME
M Famouri - One of the best experts on this subject based on the ideXlab platform.
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scaling effects for Flow in micro channels variable property viscous heating velocity slip and temperature jump
International Communications in Heat and Mass Transfer, 2009Co-Authors: Kamel Hooman, F Hooman, M FamouriAbstract:This paper reports closed form solutions, based on perturbation techniques, for fully developed, both hydrodynamically and thermally, slip-Flow forced convection in both parallel plate and circular microchannels subject to isothermal wall boundary condition. Scaling effects, including variable property, viscous dissipation, velocity slip, and temperature jump are studied in detail. The results are not only applicable to Gaseous Flow in the slip-Flow regime but also can be used for no-slip liquid Flow in microchannels.