scholarly journals Mass flow rate measurement of thermal creep flow from transitional to slip flow regime

2016 ◽  
Vol 795 ◽  
pp. 690-707 ◽  
Author(s):  
Hiroki Yamaguchi ◽  
Pierre Perrier ◽  
Minh Tuan Ho ◽  
J. Gilbert Méolans ◽  
Tomohide Niimi ◽  
...  
Keyword(s):  
Flow Regime ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Slip Flow ◽  
Thermal Creep ◽  
Creep Flow ◽  
Slip Flow Regime ◽  
Thermal Creep Flow ◽  
Good Agreement

Measurements of the thermal creep flow through a single rectangular microchannel connected to two tanks maintained initially at the same pressure, but at different temperatures, are carried out for five noble gas species, over a large range of pressure and for two temperature differences between the tanks. The time-dependent pressure variations in both cold and hot tanks are investigated, and the temperature-driven (thermal creep) mass flow rate between two tanks is calculated from these data for the rarefaction parameter ranging from the transitional to slip flow regime. The measured mass flow rate is compared with the numerical solution of the S-model kinetic equation, and they show good agreement. A novel approximate expression to calculate the temperature-driven mass flow rate in the transitional and slip flow regimes is proposed. This expression provides results in good agreement with the measured values of the mass flow rate. In the slip flow regime, the thermal slip coefficient is calculated by employing the previously reported methodology, and the influence of the nature of the gas on this coefficient is investigated. The measured values of the thermal slip coefficient agree well with the values available in the literature, indicating that this coefficient is independent of the shape of a channel.

Gas Mass Flow Rate Measurement in T-Shaped Microchannels in Slip Flow Regime

2011 ◽  
Author(s):  
Yongli Li ◽  
Christine Barrot ◽  
Lucien Baldas ◽  
Ste´phane Colin ◽  
Ju¨rgen J. Brandner ◽  
...  
Keyword(s):  
Flow Regime ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Slip Flow ◽  
Rate Measurement ◽  
Gas Mixing ◽  
Flow Rate Measurement ◽  
Slip Flow Regime ◽  
Good Agreement

A new setup was developed for gas mixing analysis in T-shaped microchannels. The principle of the flow rate measurement was based on the Constant Volume (CV) method [1]. The mass flow rate measurements of two gases N2 / CO2 mixing in a T mixer were carried out in the slip flow regime and followed by a simulation work for comparison. The mass flow rate has a magnitude of 10−8 or 10−7 kg/s and has good agreement with simulation for the lowest inlet over outlet pressures ratios and moderate agreement for the highest inlet over outlet pressures ratios.

Numerical Simulation of Thermal Transpiration in the Slip Flow Regime With Curved Walls

2012 ◽  
Author(s):  
Vlasios Leontidis ◽  
Lucien Baldas ◽  
Stéphane Colin
Keyword(s):  
Boundary Condition ◽  
Boundary Conditions ◽  
Flow Regime ◽  
Stokes Equations ◽  
Slip Flow ◽  
Velocity Slip ◽  
Operating Conditions ◽  
Thermal Creep ◽  
Geometrical Parameters ◽  
Slip Flow Regime

Nowadays, modeling gas flows in the slip flow regime through microchannels can be achieved using commercial Computational Fluid Dynamics codes. In this regime the Navier-Stokes equations with appropriate boundary conditions are still valid. A simulation procedure has been developed for the modeling of thermal creep flow using ANSYS Fluent®. The implementation of the boundary conditions is achieved by developing User Defined Functions (UDFs) by means of C++ routines. The complete first order velocity slip boundary condition, including the thermal creep effects due to an axial temperature gradient and the effect of the wall curvature, and the temperature jump boundary condition are applied. Motivation of the present work is the development of a simulation tool which will help in the pre-calculations and the preliminary design of a Knudsen micropump consisting of successively connected curved and straight channels and in a second step in the numerical optimization of the pump, in terms of geometrical parameters and operating conditions of the system.

scholarly journals Non-equilibrium dynamics of dense gas under tight confinement

2016 ◽  
Vol 794 ◽  
pp. 252-266 ◽  
Author(s):  
Lei Wu ◽  
Haihu Liu ◽  
Jason M. Reese ◽  
Yonghao Zhang
Keyword(s):  
Boltzmann Equation ◽  
Flow Regime ◽  
Mass Flow Rate ◽  
Knudsen Number ◽  
Mass Flow ◽  
Flow Rate ◽  
Transitional Flow ◽  
Molecular Flow ◽  
Parallel Plates ◽  
The Boltzmann Equation

The force-driven Poiseuille flow of dense gases between two parallel plates is investigated through the numerical solution of the generalized Enskog equation for two-dimensional hard discs. We focus on the competing effects of the mean free path ${\it\lambda}$, the channel width $L$ and the disc diameter ${\it\sigma}$. For elastic collisions between hard discs, the normalized mass flow rate in the hydrodynamic limit increases with $L/{\it\sigma}$ for a fixed Knudsen number (defined as $Kn={\it\lambda}/L$), but is always smaller than that predicted by the Boltzmann equation. Also, for a fixed $L/{\it\sigma}$, the mass flow rate in the hydrodynamic flow regime is not a monotonically decreasing function of $Kn$ but has a maximum when the solid fraction is approximately 0.3. Under ultra-tight confinement, the famous Knudsen minimum disappears, and the mass flow rate increases with $Kn$, and is larger than that predicted by the Boltzmann equation in the free-molecular flow regime; for a fixed $Kn$, the smaller $L/{\it\sigma}$ is, the larger the mass flow rate. In the transitional flow regime, however, the variation of the mass flow rate with $L/{\it\sigma}$ is not monotonic for a fixed $Kn$: the minimum mass flow rate occurs at $L/{\it\sigma}\approx 2{-}3$. For inelastic collisions, the energy dissipation between the hard discs always enhances the mass flow rate. Anomalous slip velocity is also found, which decreases with increasing Knudsen number. The mechanism for these exotic behaviours is analysed.

DSMC Simulation: Validation and Application to Low Speed Gas Flows in Microchannels

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
T. Ewart ◽  
J. L. Firpo ◽  
I. A. Graur ◽  
P. Perrier ◽  
J. G. Méolans
Keyword(s):  
Flow Regime ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Streamwise Velocity ◽  
Accommodation Coefficient ◽  
Transitional Flow ◽  
Linearized Boltzmann Equation

A direct simulation Monte Carlo method (DSMC) solver, adapted to the subsonic microflow, is developed under the object-conception language (C++). Some technical details critical in these DSMC computations are provided. The numerical simulations of gas flow in a microchannel are carried out using the developed DSMC solver. Streamwise velocity distributions in the slip flow regime are compared with the analytical solution based on the Navier–Stokes equations with the velocity slip boundary condition. Satisfactory agreements have been achieved. Furthermore, the domain of the validity of this continuum approach is discussed. Simulations are then extended to the transitional flow regime. Streamwise velocity distributions are also compared with the results of the numerical solutions of the linearized Boltzmann equation. We emphasize the influence of the accommodation coefficient on the velocity profiles and on the mass flow rate. The simulation results on the mass flow rate are compared with the experimental data, which allow us to validate the “experimental” technique of the determination of the accommodation coefficient.

Analytical Modeling of Gaseous Slip Flow in Parabolic Microchannels

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Farzad Tahmouresi ◽  
Samir K. Das
Keyword(s):  
Pressure Distribution ◽  
Friction Factor ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Analytical Modeling ◽  
Separation Of Variables ◽  
Slip Flow ◽  
Aspect Ratios ◽  
Gaseous Slip Flow

The paper presents an analytical solution of velocity, mass flow rate, and pressure distribution for fully developed gaseous slip flow in nonsymmetric and symmetric parabolic microchannels. The flow is considered to be steady, laminar, and incompressible with constant fluid properties. Fully developed gaseous slip flow in microchannels of parabolic cross section is solved analytically for various aspect ratios using a parabolic cylindrical coordinate system on applying the method of separation of variables. Prior to apply separation of variables, Arfken transform [Arfken, 1970, Mathematical Methods for Physicists, Academic Press, Orlando, FL, Ch. 2] was used on momentum equations and first-order slip boundary conditions at each channel wall were imposed. A simple model is proposed to predict the friction factor and Reynolds number product fRe for slip flow in parabolic microchannels. Through the selection of a characteristic length scale, the square root of cross-sectional area and the effect of duct shape have been minimized. The results of a normalized Poiseuille number for symmetric parabolic microchannels (ɛ=1) shows good agreement with the previous results [Morini et al., 2004, “The Rarefaction Effect on the Friction Factor of Gas Flow in Micro/Nano-Channels,” Superlattices Microstruct., 35(3–6), pp. 587–599; Khan and Yovanovich, 2008, “Analytical Modeling of Fluid Flow and Heat Transfer in Microchannel/Nanochannel Heat Sinks,” J. Thermophys. Heat Transf., 22(3), pp. 352–359] for rectangular microchannels. The developed model can be used to predict mass flow rate and pressure distribution of slip flow in parabolic microchannels.

scholarly journals Modified Electromechanical Modeling and Parameters Analysis of Magnetoplasmadynamic Thruster

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2428
Author(s):  
Yu Zhang ◽  
Jianjun Wu ◽  
Yang Ou ◽  
Jian Li ◽  
Sheng Tan
Keyword(s):  
Magnetic Field ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Applied Magnetic Field ◽  
Electromechanical Model ◽  
Electromechanical Modeling ◽  
Low Mass ◽  
Thrust Performance ◽  
Good Agreement

To predict the thrust of magnetoplasmadynamic thrusters (MPDTs), a modified electromechanical model was proposed and a comparison with experimental results is presented in this paper. The motion of propellant in the thruster was divided into two portions: the axial motion which was accelerated by the interaction of current and induced self-field, and the swirling motion which was accelerated by the interaction of current and applied magnetic field. The electromechanical model was in good agreement with the experimental data, and the fitting degrees of the model were greater than 0.93. Furthermore, the influence of parameters on the performance of MPDT were investigated by utilizing the electromechanical model. The results indicate that the thrust performance of the thruster improved with the increase of discharge current, anode radius, applied magnetic field strength, and the decrease of mass flow rate. However, the large anode radius and low mass flow rate readily led to the failure of thruster function. Therefore, the model can not only predict the thrust performance of MPDTs, but also guide the design and operation optimization of the thruster.

scholarly journals MASS FLOW RATE INDUCED BY COMBINED ROOF SOLAR COLLECTOR AND VERTICAL STACK IN A HOT HUMID CLIMATE

2014 ◽  
Vol 9 (1) ◽  
pp. 166-177
Author(s):  
Wardah Fatimah Mohammad Yusoff ◽  
Abdul Razak Sapian ◽  
Elias Salleh ◽  
Nor Mariah Adam ◽  
Zabidi Hamzah
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Solar Collector ◽  
Simulation Modelling ◽  
Prevailing Wind ◽  
Local Wind ◽  
Humid Climate ◽  
Hot Humid Climate ◽  
Good Agreement

This paper presents the investigation of solar induced ventilation that utilizes roof solar collector and vertical stack. Three prototypes, namely A, B and C, were developed based on preliminary experimental work. They were then used in simulation study with the objective of determining the prototype that was able to induce the highest mass flow rate. The validation of simulation modelling against experiment indicated a good agreement between these two results. The findings showed that prototype A induced the highest mass flow rate. However, prototype C, which had obstructions at the stack outlets, was more appropriate for application in Malaysia due to various prevailing wind directions. In addition, the findings also indicated that besides solar radiation, the mass flow rate induced by the prototypes was also influenced by the local wind direction, the inlet and outlet positions as well as the outlet design. In summary, the findings highlighted the potential application of the proposed solar induced ventilation in a hot and humid climate.

Computational method for simultaneous inertial measuring of fluid mass flow rate and density

2020 ◽  
Vol 20 (3) ◽  
pp. 869-877
Author(s):  
O.V. Zhilyaev ◽  
V.N. Kovalnogov
Keyword(s):  
Flow Regime ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Difference ◽  
Stationary Flow ◽  
Computational Method ◽  
Fluid Mass ◽  
Mechanical Oscillations ◽  
New Instrument

This work represents the decision of the problem of nonstationary one-dimensioned flow of fluid in a straight pipeline. It shows the method to generate non-stationary flow regime based on utilizing additional pipeline in which mechanical oscillations of fluid are being excited. Pressure difference along the length of oscillating fluid appears to be a measure for the density of the fluid and for its mass flow rate. The possibility of creating a new instrument for measuring the density and mass flow rate of a fluid based on results obtained is shown.

The Use of Dehumidifiers in Desiccant Cooling and Dehumidification Systems

1986 ◽  
Vol 108 (3) ◽  
pp. 684-692 ◽  
Author(s):  
E. Van den Bulck ◽  
J. W. Mitchell ◽  
S. A. Klein
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Inlet Temperature ◽  
Cooling Load ◽  
Humidity Ratio ◽  
Air Mass ◽  
Air Inlet ◽  
Additional Control ◽  
Good Agreement

The use of rotary dehumidifiers in gas-fired open-cycle desiccant cooling systems is investigated by analyzing the performance of the rotary heat exchanger–rotary dehumidifier subsystem. For a given cooling load, the required regeneration heat supply can be minimized by choosing appropriate values for the regeneration air mass flow rate and the wheel rotation speed. A map is presented showing optimal values for rotational speed and regeneration flow rate as functions of the regeneration air inlet temperature and the process air inlet humidity ratio. This regeneration temperature is further optimized as a function of the process humidity ratio. In the analysis, the control strategy adjusts the process air mass flow rate to provide the required cooling load. Additional control options are considered and the sensitivity of the regeneration heat required to the wheel speed, regeneration air mass flow rate, and inlet temperature is discussed. Experimental data reported in the literature are compared with the analytical results and indicate good agreement.

DSMC Simalation of the Pressure and Temperature Driven Flows: Comparison With the Measurements

2009 ◽  
Author(s):  
Timothe´e Ewart ◽  
Irina A. Graur ◽  
Jean-Luc Firpo ◽  
Alexey Polikarpov ◽  
Pierre Perrier ◽  
...  
Keyword(s):  
Flow Regime ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Streamwise Velocity ◽  
Accommodation Coefficient ◽  
Transitional Flow ◽  
Linearized Boltzmann Equation

A DSMC solver, adapted to the subsonic micro flow, is developed under the object-conception language (C++). Some technical details critical in these DSMC computations are provided. The numerical simulations of gas flow in micro channel are carried out using developed DSMC solver. Streamwise velocity distributions in the slip flow regime are compared with the analytical solution based on the Navier-Stokes equations with the velocity slip boundary condition. Satisfactory agreements have been achieved. Furthermore, the domain of the validity of this continuum approach is discussed. Simulations are then extended to transitional flow regime. Streamwise velocity distributions are also compared with the results of the numerical solutions of the linearized Boltzmann equation. We emphasize the influence of the accommodation coefficient on the velocity profiles and on the mass flow rate. The simulation results on the mass flow rate are compared with the experimental data, that allow us to validate the “experimental” technique of the determination of the accommodation coefficient.

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