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William A Ducker - One of the best experts on this subject based on the ideXlab platform.
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lubrication forces in air and Accommodation Coefficient measured by a thermal damping method using an atomic force microscope
Physical Review E, 2010Co-Authors: Christopher D F Honig, John E Sader, Paul Mulvaney, William A DuckerAbstract:By analysis of the thermally driven oscillation of an atomic force microscope (AFM) cantilever, we have measured both the damping and static forces acting on a sphere near a flat plate immersed in gas. By varying the proximity of the sphere to the plate, we can continuously vary the Knudsen number (Kn) at constant pressure, thereby accessing the slip flow, transition, and molecular regimes at a single pressure. We use measurements in the slip-flow regime to determine the combined slip length (on both sphere and plate) and the tangential momentum Accommodation Coefficient, σ . For ambient air at 1 atm between two methylated glass solids, the inverse damping is linear with separation and the combined slip length on both surfaces is 250 nm ± 100 nm , which corresponds to σ=0.77 ± 0.24 . At small separations (Kn>0.4) the measured inverse damping is no longer linear with separation, and is observed to exhibit reasonable agreement with the Vinogradova formula.
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lubrication forces in air and Accommodation Coefficient measured by a thermal damping method using an atomic force microscope
Physical Review E, 2010Co-Authors: Christopher D F Honig, John E Sader, Paul Mulvaney, William A DuckerAbstract:By analysis of the thermally driven oscillation of an atomic force microscope (AFM) cantilever, we have measured both the damping and static forces acting on a sphere near a flat plate immersed in gas. By varying the proximity of the sphere to the plate, we can continuously vary the Knudsen number (Kn) at constant pressure, thereby accessing the slip flow, transition, and molecular regimes at a single pressure. We use measurements in the slip-flow regime to determine the combined slip length (on both sphere and plate) and the tangential momentum Accommodation Coefficient, $\ensuremath{\sigma}$. For ambient air at 1 atm between two methylated glass solids, the inverse damping is linear with separation and the combined slip length on both surfaces is $250\text{ }\text{nm}\ifmmode\pm\else\textpm\fi{}100\text{ }\text{nm}$, which corresponds to $\ensuremath{\sigma}=0.77\ifmmode\pm\else\textpm\fi{}0.24$. At small separations $(\text{Kn}g0.4)$ the measured inverse damping is no longer linear with separation, and is observed to exhibit reasonable agreement with the Vinogradova formula.
Tomohide Niimi - One of the best experts on this subject based on the ideXlab platform.
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conductive heat transfer in a gas confined between two concentric spheres from free molecular to continuum flow regime
International Journal of Heat and Mass Transfer, 2017Co-Authors: Hiroki Yamaguchi, Tomohide Niimi, Minh T Ho, Yoichi Matsuda, Irina GraurAbstract:The conductive heat transfer through a gas confined between two concentric spherical shells maintained at different temperatures is investigated from the free-molecular to the continuum flow regime. The heat flux, measured using a recently proposed experimental system to extract the thermal Accommodation Coefficient, is compared with analytical expressions and numerical results. From this comparison it is found that in the free-molecular flow limit, the experimental data are well explained by the analytical expression for the arbitrary radius and temperature ratios of the spherical surfaces. In the continuum limit, the temperature dependence of the thermal conductivity Coefficient should be considered in the analytical expression. In the transitional flow regime, a revised function for the heat flux interpolation is proposed to give better fitting to the numerical results. By employing these knowledge, the thermal Accommodation Coefficient extraction procedure for the system is revised, and it is shown that the re-calculated Accommodation Coefficient allows to reproduce well the measured heat flux.
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investigation on heat transfer between two coaxial cylinders for measurement of thermal Accommodation Coefficient
Physics of Fluids, 2012Co-Authors: Hiroki Yamaguchi, Yu Matsuda, Tomohide Niimi, Kazuaki Kanazawa, Alexey Polikarpov, Irina GraurAbstract:The heat flux between two coaxial cylinders was measured in the range from the free molecular to the early transitional flow regimes for extraction of the thermal Accommodation Coefficient using an approximate relation on the pressure dependence of the heat flux. The experimental coaxial cylinders' geometry has been traditionally implemented for the measurement of the thermal Accommodation Coefficient using the low-pressure method; however, the actual experimental setup was characterized by large temperature difference and large cylinders' radius ratio. Compared to the original low-pressure method, much higher pressure range was applied. In order to verify assumptions in the Accommodation Coefficient extraction, the heat flux under measurement conditions was simulated numerically by the nonlinear S-model kinetic equation. Very good agreement was found between the measured and the simulated heat flux. The proposed procedure of the thermal Accommodation Coefficient extraction was discussed in detail and verified. The temperature dependence of the thermal Accommodation Coefficient was also found.
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tangential momentum Accommodation Coefficient measurements for various materials and gas species
1st European Conference on Gas Micro Flows GasMems 2012, 2012Co-Authors: Hiroki Yamaguchi, Yu Matsuda, Tomohide NiimiAbstract:The tangential momentum Accommodation Coefficient was measured from the gaseous flow through a single microtube. The mass flow rate was measured by the constant volume technique, where the rate is related to time rate of pressure variation in a fixed volume tank. The measured mass flow rate was fitted by the theoretical mass flow rate expressed by the slip velocity at the surface to deduce the slip Coefficient, which can be related to the tangential Accommodation Coefficient. The mean Knudsen number, which is determined as the mean pressure of the inlet and the outlet, was set to be below 0.32, where the second-order slip boundary condition was suggested to be valid. The measurement system was designed to allow using a microtube with large diameter of several hundred micrometers. Since low pressure environment was essential for large Knudsen number condition for the flow through such large microtube, a low leakage measurement system realized by applying the UHV technology is needed. Applicability of sub millimeters size microtubes allowed us to measure the tangential momentum Accommodation Coefficients on various materials. In this study, we measured the tangential momentum Accommodation Coefficients on an engineering metal surface for various gas species.
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Experimental measurement on tangential momentum Accommodation Coefficient in a single microtube
Microfluidics and Nanofluidics, 2011Co-Authors: Hiroki Yamaguchi, Tsuneo Hanawa, Oto Yamamoto, Yu Matsuda, Yasuhiro Egami, Tomohide NiimiAbstract:The tangential momentum Accommodation Coefficient (TMAC) was investigated experimentally from the mass flow rate through a single microtube under the slip flow and the early part of the transition regime. The measurements were carried out by the constant-volume method under the mean Knudsen number smaller than 0.3, which is based on the mean pressure of the inlet and the outlet of the microtube, to apply the second-order slip boundary condition. To measure TMACs on various materials, quite large microtube was employed, which require the reduction in leakage. TMAC was obtained from the slip Coefficient determined by the relation of the mass flow rate to the mean Knudsen number. The obtained mass flow rate was well explained by the theoretical equation. TMACs of deactivated-fused silica with argon, nitrogen, and oxygen were measured, showing the tangential momentum was not accommodated completely to the surface, and the values showed good agreement with previous studies. From the comparison between microtubes with different inner diameter, it is showed that TMAC is determined mainly by gas species and surface material.
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experimental study on measurement of tangential momentum Accommodation Coefficient in microtube
ASME 2010 8th International Conference on Nanochannels Microchannels and Minichannels ICNMM2010 Collocated with 3rd Joint US-European Fluids Engineeri, 2010Co-Authors: Hiroki Yamaguchi, Tsuneo Hanawa, Oto Yamamoto, Yu Matsuda, Yasuhiro Egami, Tomohide NiimiAbstract:Along with the progress in micro- and nano-technologies, such as Micro Electro Mechanical Systems (MEMS) and μ-TAS (Micro-Total Analysis Systems), the Knudsen number, which is a non dimensional parameter for rarefaction, of the flow around and inside the systems becomes large. In such high Knudsen number flows, gas-surface interaction has become important for flow field analyses. To illustrate overall gas-surface interaction without any detailed processes, an Accommodation Coefficient, α, is the most widely used as an empirical parameter for a practical purpose. One of Accommodation Coefficients, the tangential momentum Accommodation Coefficient (TMAC) αt , is in closely related to the loss of the pressure through a micro channel. Therefore, TMAC is an important Coefficient for flow inside micro/nano fluidic devices. To obtain TMAC from experiments, the mass flow rate measurements in a microtube were carried out using the constant volume method. The results obtained from the experiments were analyzed in frame of the Navier-Stokes equation associated with the second order velocity slip boundary condition. The mean Knudsen number was less than 0.3, where the velocity slip boundary condition is applicable. From the mass flow rates, the slip Coefficient of the boundary condition was obtained, and then, TMAC was determined. The experimental apparatus showed very low leakage rate, and TMAC was determined with a high degree of accuracy. The TMACs of the same surface material with different dimensional parameters were compared for validation of the system.Copyright © 2010 by ASME
Hiroki Yamaguchi - One of the best experts on this subject based on the ideXlab platform.
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conductive heat transfer in a gas confined between two concentric spheres from free molecular to continuum flow regime
International Journal of Heat and Mass Transfer, 2017Co-Authors: Hiroki Yamaguchi, Tomohide Niimi, Minh T Ho, Yoichi Matsuda, Irina GraurAbstract:The conductive heat transfer through a gas confined between two concentric spherical shells maintained at different temperatures is investigated from the free-molecular to the continuum flow regime. The heat flux, measured using a recently proposed experimental system to extract the thermal Accommodation Coefficient, is compared with analytical expressions and numerical results. From this comparison it is found that in the free-molecular flow limit, the experimental data are well explained by the analytical expression for the arbitrary radius and temperature ratios of the spherical surfaces. In the continuum limit, the temperature dependence of the thermal conductivity Coefficient should be considered in the analytical expression. In the transitional flow regime, a revised function for the heat flux interpolation is proposed to give better fitting to the numerical results. By employing these knowledge, the thermal Accommodation Coefficient extraction procedure for the system is revised, and it is shown that the re-calculated Accommodation Coefficient allows to reproduce well the measured heat flux.
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investigation on heat transfer between two coaxial cylinders for measurement of thermal Accommodation Coefficient
Physics of Fluids, 2012Co-Authors: Hiroki Yamaguchi, Yu Matsuda, Tomohide Niimi, Kazuaki Kanazawa, Alexey Polikarpov, Irina GraurAbstract:The heat flux between two coaxial cylinders was measured in the range from the free molecular to the early transitional flow regimes for extraction of the thermal Accommodation Coefficient using an approximate relation on the pressure dependence of the heat flux. The experimental coaxial cylinders' geometry has been traditionally implemented for the measurement of the thermal Accommodation Coefficient using the low-pressure method; however, the actual experimental setup was characterized by large temperature difference and large cylinders' radius ratio. Compared to the original low-pressure method, much higher pressure range was applied. In order to verify assumptions in the Accommodation Coefficient extraction, the heat flux under measurement conditions was simulated numerically by the nonlinear S-model kinetic equation. Very good agreement was found between the measured and the simulated heat flux. The proposed procedure of the thermal Accommodation Coefficient extraction was discussed in detail and verified. The temperature dependence of the thermal Accommodation Coefficient was also found.
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tangential momentum Accommodation Coefficient measurements for various materials and gas species
1st European Conference on Gas Micro Flows GasMems 2012, 2012Co-Authors: Hiroki Yamaguchi, Yu Matsuda, Tomohide NiimiAbstract:The tangential momentum Accommodation Coefficient was measured from the gaseous flow through a single microtube. The mass flow rate was measured by the constant volume technique, where the rate is related to time rate of pressure variation in a fixed volume tank. The measured mass flow rate was fitted by the theoretical mass flow rate expressed by the slip velocity at the surface to deduce the slip Coefficient, which can be related to the tangential Accommodation Coefficient. The mean Knudsen number, which is determined as the mean pressure of the inlet and the outlet, was set to be below 0.32, where the second-order slip boundary condition was suggested to be valid. The measurement system was designed to allow using a microtube with large diameter of several hundred micrometers. Since low pressure environment was essential for large Knudsen number condition for the flow through such large microtube, a low leakage measurement system realized by applying the UHV technology is needed. Applicability of sub millimeters size microtubes allowed us to measure the tangential momentum Accommodation Coefficients on various materials. In this study, we measured the tangential momentum Accommodation Coefficients on an engineering metal surface for various gas species.
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Experimental measurement on tangential momentum Accommodation Coefficient in a single microtube
Microfluidics and Nanofluidics, 2011Co-Authors: Hiroki Yamaguchi, Tsuneo Hanawa, Oto Yamamoto, Yu Matsuda, Yasuhiro Egami, Tomohide NiimiAbstract:The tangential momentum Accommodation Coefficient (TMAC) was investigated experimentally from the mass flow rate through a single microtube under the slip flow and the early part of the transition regime. The measurements were carried out by the constant-volume method under the mean Knudsen number smaller than 0.3, which is based on the mean pressure of the inlet and the outlet of the microtube, to apply the second-order slip boundary condition. To measure TMACs on various materials, quite large microtube was employed, which require the reduction in leakage. TMAC was obtained from the slip Coefficient determined by the relation of the mass flow rate to the mean Knudsen number. The obtained mass flow rate was well explained by the theoretical equation. TMACs of deactivated-fused silica with argon, nitrogen, and oxygen were measured, showing the tangential momentum was not accommodated completely to the surface, and the values showed good agreement with previous studies. From the comparison between microtubes with different inner diameter, it is showed that TMAC is determined mainly by gas species and surface material.
-
experimental study on measurement of tangential momentum Accommodation Coefficient in microtube
ASME 2010 8th International Conference on Nanochannels Microchannels and Minichannels ICNMM2010 Collocated with 3rd Joint US-European Fluids Engineeri, 2010Co-Authors: Hiroki Yamaguchi, Tsuneo Hanawa, Oto Yamamoto, Yu Matsuda, Yasuhiro Egami, Tomohide NiimiAbstract:Along with the progress in micro- and nano-technologies, such as Micro Electro Mechanical Systems (MEMS) and μ-TAS (Micro-Total Analysis Systems), the Knudsen number, which is a non dimensional parameter for rarefaction, of the flow around and inside the systems becomes large. In such high Knudsen number flows, gas-surface interaction has become important for flow field analyses. To illustrate overall gas-surface interaction without any detailed processes, an Accommodation Coefficient, α, is the most widely used as an empirical parameter for a practical purpose. One of Accommodation Coefficients, the tangential momentum Accommodation Coefficient (TMAC) αt , is in closely related to the loss of the pressure through a micro channel. Therefore, TMAC is an important Coefficient for flow inside micro/nano fluidic devices. To obtain TMAC from experiments, the mass flow rate measurements in a microtube were carried out using the constant volume method. The results obtained from the experiments were analyzed in frame of the Navier-Stokes equation associated with the second order velocity slip boundary condition. The mean Knudsen number was less than 0.3, where the velocity slip boundary condition is applicable. From the mass flow rates, the slip Coefficient of the boundary condition was obtained, and then, TMAC was determined. The experimental apparatus showed very low leakage rate, and TMAC was determined with a high degree of accuracy. The TMACs of the same surface material with different dimensional parameters were compared for validation of the system.Copyright © 2010 by ASME
Christopher D F Honig - One of the best experts on this subject based on the ideXlab platform.
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lubrication forces in air and Accommodation Coefficient measured by a thermal damping method using an atomic force microscope
Physical Review E, 2010Co-Authors: Christopher D F Honig, John E Sader, Paul Mulvaney, William A DuckerAbstract:By analysis of the thermally driven oscillation of an atomic force microscope (AFM) cantilever, we have measured both the damping and static forces acting on a sphere near a flat plate immersed in gas. By varying the proximity of the sphere to the plate, we can continuously vary the Knudsen number (Kn) at constant pressure, thereby accessing the slip flow, transition, and molecular regimes at a single pressure. We use measurements in the slip-flow regime to determine the combined slip length (on both sphere and plate) and the tangential momentum Accommodation Coefficient, σ . For ambient air at 1 atm between two methylated glass solids, the inverse damping is linear with separation and the combined slip length on both surfaces is 250 nm ± 100 nm , which corresponds to σ=0.77 ± 0.24 . At small separations (Kn>0.4) the measured inverse damping is no longer linear with separation, and is observed to exhibit reasonable agreement with the Vinogradova formula.
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lubrication forces in air and Accommodation Coefficient measured by a thermal damping method using an atomic force microscope
Physical Review E, 2010Co-Authors: Christopher D F Honig, John E Sader, Paul Mulvaney, William A DuckerAbstract:By analysis of the thermally driven oscillation of an atomic force microscope (AFM) cantilever, we have measured both the damping and static forces acting on a sphere near a flat plate immersed in gas. By varying the proximity of the sphere to the plate, we can continuously vary the Knudsen number (Kn) at constant pressure, thereby accessing the slip flow, transition, and molecular regimes at a single pressure. We use measurements in the slip-flow regime to determine the combined slip length (on both sphere and plate) and the tangential momentum Accommodation Coefficient, $\ensuremath{\sigma}$. For ambient air at 1 atm between two methylated glass solids, the inverse damping is linear with separation and the combined slip length on both surfaces is $250\text{ }\text{nm}\ifmmode\pm\else\textpm\fi{}100\text{ }\text{nm}$, which corresponds to $\ensuremath{\sigma}=0.77\ifmmode\pm\else\textpm\fi{}0.24$. At small separations $(\text{Kn}g0.4)$ the measured inverse damping is no longer linear with separation, and is observed to exhibit reasonable agreement with the Vinogradova formula.
Mohammad Kassemi - One of the best experts on this subject based on the ideXlab platform.
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Effect of interfacial turbulence and Accommodation Coefficient on CFD predictions of pressurization and pressure control in cryogenic storage tank
Cryogenics, 2016Co-Authors: Mohammad Kassemi, Olga KartuzovaAbstract:Pressurization and pressure control in cryogenic storage tanks are to a large extent affected by heat and mass transport across the liquid-vapor interface. These mechanisms are, in turn, controlled by the kinetics of the phase change process and the dynamics of the turbulent recirculating flows in the liquid and vapor phases. In this paper, the effects of Accommodation Coefficient and interfacial turbulence on tank pressurization and pressure control simulations are examined. Comparison between numerical predictions and ground-based measurements in two large liquid hydrogen tank experiments, performed in the K-site facility at NASA Glenn Research Center (GRC) and the Multi-purpose Hydrogen Test Bed (MHTB) facility at NASA Marshall Space Flight Center (MSFC), are used to show the impact of Accommodation Coefficient and interfacial and vapor phase turbulence on evolution of pressure and temperatures in the cryogenic storage tanks. In particular, the self-pressurization comparisons indicate that: (1) numerical predictions are essentially independent of the magnitude of the Accommodation Coefficient; and (2) surprisingly, laminar models sometimes provide results that are in better agreement with experimental self-pressurization rates, even in parametric ranges where the bulk flow is deemed fully turbulent. In this light, shortcomings of the present CFD models, especially, numerical treatments of interfacial mass transfer and turbulence, as coupled to the Volume-of-Fluid (VOF) interface capturing scheme, are underscored and discussed.
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cfd modeling of the multipurpose hydrogen test bed mhtb self pressurization and spray bar mixing experiments in normal gravity effect of the Accommodation Coefficient on the tank pressure
51st AIAA SAE ASEE Joint Propulsion Conference, 2015Co-Authors: Olga Kartuzova, Mohammad KassemiAbstract:A CFD model for simulating the self-pressurization of a large scale liquid hydrogen storage tank is utilized in this paper to model the MHTB self-pressurization experiment. The kinetics-based Schrage equation is used to account for the evaporative and condensi ng interfacial mass flows in this model. The effect of the Accommodation Coefficient for calculating the interfacial mass transfer rate on the tank pressure during tank selfpressurization is studied. The values of the Accommodation Coefficient which were considered in this study vary from 1.0e-3 to 1.0e-1 for the explicit VOF model and from 1.0e-4 to 1.0e-3 for the implicit VOF model. The ullage pressure evolutions are compared against experimental data. A CFD model for controlling pressure in cryogenic storage tanks by spraying cold liquid into the ullage is also presented. The Euler-Lagrange approach is utilized for tracking the spray droplets and for modeling the interaction between the droplets and the continuous phase (ullage). The spray model is coupled with the VOF model by performing particle tracking in the ullage, removing particles from the ullage when they reach the interface, and then adding their contributions to the liquid. Droplet-ullage heat and mass transfer are modeled. The flow, temperature, and interfacial mass flux, as well as droplets trajectories, size distribution and temperatures predicted by the model are presented. The ul lage pressure and vapor temperature evolutions are compared with experimental data obtained from the MHTB spray bar mixing experiment. The effect of the Accommodation Coefficient for calculating the interfacial and droplet mass transfer rates on the tank pressure during mixing of the vapor using spray is studied. The values used for the Accommodation Coefficient at the interface vary from 1.0e-5 to 1.0e-2. The droplet Accommodation Coefficient values vary from 2.0e-6 to 1.0e-4.
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cfd modeling of the multipurpose hydrogen test bed mhtb self pressurization and spray bar mixing experiments in normal gravity effect of the Accommodation Coefficient on the tank pressure
51st AIAA SAE ASEE Joint Propulsion Conference, 2015Co-Authors: Olga Kartuzova, Mohammad KassemiAbstract:In this paper, a computational model that describes pressure control phase of a typical MHTB experiment will be presented. The fidelity of the model will be assessed by comparing the models predictions with MHTB experimental data. In this paper CFD results for MHTB spray bar cooling case with 50 tank fill ratio will be presented and analyzed. Effect of Accommodation Coefficient for calculating droplet-ullage mass transfer will be evaluated.