Mass Flow Rate Measurements: From Hydrodynamic to Free Molecular Regime

2008 ◽  
Author(s):  
Timothe´e Ewart ◽  
Irina A. Graour ◽  
Pierre Perrier ◽  
J. Gilbert Me´olans
Keyword(s):  
Mass Flow Rate ◽  
Knudsen Number ◽  
Mass Flow ◽  
Flow Rate ◽  
Stationary Flow ◽  
Small Mass ◽  
Accommodation Coefficient ◽  
Navier Stokes ◽  
Number Range ◽  
Free Molecular Regime

An experimental investigation in a single silica microtube in isothermal stationary flow for various gases is made from the hydrodynamic to the near free molecular regime to study the reflection/accommodation process at the wall. This kind of investigation requires, more than other Micro-Electro-Mechanical-Systems (MEMS) experiments, a powerful experimental platform to measure very small mass flow rate. A global analytic expression, based on the Navier-Stokes (NS) equations with second order boundary conditions, is used to yield the Tangential Momentum Accommodation Coefficient (TMAC) in 0.003–0.3 Knudsen number range. Otherwise, the experimental results of the mass flow rate is compared with theoretical values calculated from kinetic approaches using variable TMAC as fitting parameter over the 0.3–30 Knudsen number range. Finally, whatever the theoretical approach the TMAC values obtained from the different gas-surface pairs are rather close one to other, but the TMAC values seem decreasing when the molecular mass increases.

Mass flow rate measurements in a microchannel, from hydrodynamic to near free molecular regimes

2007 ◽  
Vol 584 ◽  
pp. 337-356 ◽  
Author(s):  
TIMOTHÉE EWART ◽  
PIERRE PERRIER ◽  
IRINA A. GRAUR ◽  
J. GILBERT MÉOLANS
Keyword(s):  
Mass Flow Rate ◽  
Knudsen Number ◽  
Mass Flow ◽  
Flow Rate ◽  
Single Channel ◽  
Number Range ◽  
Free Molecular Regime ◽  
First Order ◽  
Slip Regime ◽  
Accommodation Process

Helium mass flow rates in a microchannel were measured, for a wide Knudsen-number range, in isothermal steady conditions. The flow Knudsen numbers, considered here, cover the range from continuum slip regime to the near free molecular regime. We used a single-channel system involved in an experimental platform more powerful than those previously used. The experimental errors and uncertainties were accurately investigated and estimated. In the continuum slip regime, it was found that the first-order approach is pertinent for Knudsen number between 0.03 and 0.3. Moreover, the slip coefficient was deduced by comparing the experiments with the theoretical first-order slip continuum approach. For Knudsen number between 0.03 and 0.7, a polynomial second-power form is proposed for the mass flow rate expression. Otherwise, the experimental results on the mass flow rate were compared with theoretical values calculated from kinetic approaches over the 0.03–50 Knudsen number range, and an overall agreement appears through the comparison. It was also found, when the Knudsen number increased, that the wall influence on measurement occurred first through the accommodation process in the transition regime followed by the wall influence through the aspect ratio in the free molecular regime.

Mass Flow Rate Measurement Through Rectangular Microchannels for Large Knudsen Number Range

2011 ◽  
Author(s):  
M. Hadj Nacer ◽  
Pierre Perrier ◽  
Irina Graur
Keyword(s):  
Boundary Condition ◽  
Mass Flow Rate ◽  
Knudsen Number ◽  
Mass Flow ◽  
Flow Rate ◽  
Stokes Equations ◽  
Rectangular Cross Section ◽  
Velocity Slip ◽  
Bgk Model ◽  
Number Range

The mass flow rate through microchannels with rectangular cross section is measured for the wide Knudsen number range (0.0025–26.2) in isothermal steady conditions. The experimental technique called ‘Constant Volume Method’ is used for the measurements. This method consists of measuring the small pressure variations in the tanks upstream and downstream of the microchannel. The measurements of the mass flow rate are carried out for three gases (Helium, Nitrogen and Argon). The microchannel internal surfaces are covered with a thin layer of gold with mean roughness Ra = 0.87nm (RMS). The continuum approach (Navier-Stokes equations) with first order velocity slip boundary condition was used in the slip regime (Knudsen number varies from 0.0025 to 0.1) to obtain the experimental velocity slip and accommodation coefficients associated to the Maxwell kinetic boundary condition. In the transitional and near free molecular regimes the linearized kinetic BGK model was used to calculate numerically the mass flow rate. From the comparison of the numerical and measured values of the mass flow rate the accommodation coefficient was also deduced.

scholarly journals Development of Hybrid Airlift-Jet Pump with Its Performance Analysis

2018 ◽  
Vol 8 (9) ◽  
pp. 1413 ◽  
Author(s):  
Dan Yao ◽  
Kwongi Lee ◽  
Minho Ha ◽  
Cheolung Cheong ◽  
Inhiug Lee
Keyword(s):  
Boundary Conditions ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Jet Pump ◽  
Two Phase

A new pump, called the hybrid airlift-jet pump, is developed by reinforcing the advantages and minimizing the demerits of airlift and jet pumps. First, a basic design of the hybrid airlift-jet pump is schematically presented. Subsequently, its performance characteristics are numerically investigated by varying the operating conditions of the airlift and jet parts in the hybrid pump. The compressible unsteady Reynolds-averaged Navier-Stokes equations, combined with the homogeneous mixture model for multiphase flow, are used as the governing equations for the two-phase flow in the hybrid pump. The pressure-based methods combined with the Pressure-Implicit with Splitting of Operators (PISO) algorithm are used as the computational fluid dynamics techniques. The validity of the present numerical methods is confirmed by comparing the predicted mass flow rate with the measured ones. In total, 18 simulation cases that are designed to represent the various operating conditions of the hybrid pump are investigated: eight of these cases belong to the operating conditions of only the jet part with different air and water inlet boundary conditions, and the remaining ten cases belong to the operating conditions of both the airlift and jet parts with different air and water inlet boundary conditions. The mass flow rate and the efficiency are compared for each case. For further investigation into the detailed flow characteristics, the pressure and velocity distributions of the mixture in a primary pipe are compared. Furthermore, a periodic fluctuation of the water flow in the mass flow rate is found and analyzed. Our results show that the performance of the jet or airlift pump can be enhanced by combining the operating principles of two pumps into the hybrid airlift-jet pump, newly proposed in the present study.

Experimental and Numerical Investigations on the Aerodynamic Performance of the Three-Stage Turbine With Consideration of the Leakage Flow Effect

2016 ◽  
Author(s):  
Yang Chen ◽  
Jun Li ◽  
Chaoyang Tian ◽  
Gangyun Zhong ◽  
Xiaoping Fan ◽  
...  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Rotor Blade ◽  
Three Dimensional ◽  
Aerodynamic Performance ◽  
Navier Stokes ◽  
Leakage Flow ◽  
Leakage Flows ◽  
Wheel Disk

The aerodynamic performance of three-stage turbine with different types of leakage flows was experimentally and numerically studied in this paper. The leakage flows of three-stage turbine included the shroud seal leakage flow between the rotor blade tip and case, the diaphragm seal leakage flow between the stator blade diaphragm and shaft, as well as the shaft packing leakage flow and the gap leakage flow between the rotor blade curved fir-tree root and wheel disk. The total aerodynamic performance of three-stage turbine including leakage flows was firstly experimentally measured. The detailed flow field and aerodynamic performance were also numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) and S-A turbulence model. The numerical mass flow rate and efficiency showed well agreement with experimental data. The effects of leakage flows between the fir-tree root and the wheel disk were studied. All leakage mass flow fractions, including the mass flow rate in each hole for all sets of root gaps were given for comparison. The effect of leakage flow on the aerodynamic performance of three-stage was illustrated and discussed.

scholarly journals Analysis on Heat Transmission and Fluid Flow Attributes in Solar Air Accumulator Passage with Diverse Faux Jaggedness Silhouettes on Absorber Panel

2019 ◽  
Vol 8 (5S3) ◽  
pp. 32-41 ◽  
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Optimum Shape ◽  
Solar Air Heater ◽  
Artificial Roughness ◽  
Heat Transmission ◽  
Number Range ◽  
Elliptical Shape ◽  
Shape Pattern

There is a necessity to investigate the heat transmission and fluid cascade peculiarities of solar air convectors using varying faux irregular surface and shapes on absorber sheet, so that the solar devices utilize maximum amount of available solar radiated heat energy during day time. These artificial roughness shapes are use for the enhancement of thermal performance. This need arises from the fact that the heat circulation and liquid cascade trait have been investigated by the previous investigators only for the cases that differ considerably from those relevant to solar air brazier having different screen matrix placed in the planes parallel to the flow direction and that the radiant energy being absorbed in depth. In our present research paper we investigating experimentally the behavior of artificial irregularities located over absorber platter of solar air heater vessel of varying shapes like trapezoidal, sin wave, rectangular, alternative elliptical shape pattern etc, with different Reynolds Number range 4000 to 24000, mass flow rate on Nusselt Number and Friction Factor and also find the suitable optimum shape for heat transmission enhancement. The results indicated the best heat transfer enhancement results for the alternative elliptical shape pattern among other artificial roughness with range of 0.0786kg/s – 0.475kg/s mass flow rate with thermal efficiency near about 78%.

Mass Flow Rate Measurements in a MicroChannel: from Hydrodynamic to Free Molecular Regime

2008 ◽  
Author(s):  
I. A. Graur ◽  
P. Perrier ◽  
W. Ghozlani ◽  
J. G. Méolans ◽  
Takashi Abe
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Free Molecular Regime

scholarly journals Performance investigation of a volute porous tongue of a turbocharger turbine

2020 ◽  
Vol 40 (1) ◽  
pp. 59-66
Author(s):  
Abderrahmane Chachoua ◽  
Mohamed Kamal Hamidou ◽  
Mohammed Hamel
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Gas Turbines ◽  
Stokes Equations ◽  
Navier Stokes ◽  
Recirculation Flow ◽  
Recirculating Flow ◽  
Show Evidence ◽  
The Right

The design for better performance of the spiral housing volute used commonly in radial and mixed inflow gas turbines is of prime importance as it affects the machine stage at both design and off design conditions. The tongue of the scroll divides the flow into two streams, and represents a severe source of disturbances, in terms of thermodynamic parameter uniformity, maximum kinetic energy, the right angle of attack to the rotor and minimum losses. Besides, the volute suffers an undesirable effect due to the recirculating mass flow rate in near bottom vicinity of the tongue. The present project is an attempt to design a tongue fitted with cylindrical holes traversing normal to the stream wise direction, where on account of the large pressure difference between the top and the bottom sides of the tongue will force the recirculating flow to go through the rotor inlet. This possibility with its limitations has not yet been explored. A numerical simulation is performed which might provide our suitable objectives. To achieve this goal the ANSYS code is used to build the geometry, generate the mesh, and to simulate the flow by solving numerically the averaged Navier Stokes equations. Apparently, the numerical results show evidence of favorable impact in using porous tongue. The realization of a contact between the main and recirculation flow by drilled holes on the tongue surface leads to a flow field uniformity, a reduction in the magnitude of the loss coefficient, and a 20 % reduction in the recirculating mass flow rate.

scholarly journals Comparison of Swing and Tilting Check Valves Flowing Compressible Fluids

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 758
Author(s):  
Zhi-xin Gao ◽  
Ping Liu ◽  
Yang Yue ◽  
Jun-ye Li ◽  
Hui Wu
Keyword(s):  
Mach Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Check Valve ◽  
Small Mass ◽  
Working Fluid ◽  
Valve Disc ◽  
Valve Opening ◽  
The Difference

Although check valves have attracted a lot of attention, work has rarely been completed done when there is a compressible working fluid. In this paper, the swing check valve and the tilting check valve flowing high-temperature compressible water vapor are compared. The maximum Mach number under small valve openings, the dynamic opening time, and the hydrodynamic moment acting on the valve disc are chosen to evaluate the difference between the two types of check valves. Results show that the maximum Mach number increases with the decrease in the valve opening and the increase in the mass flow rate, and the Mach number and the pressure difference in the tilting check valve are higher. In the swing check valve, the hydrodynamic moment is higher and the valve opening time is shorter. Furthermore, the valve disc is more stable for the swing check valve, and there is a periodical oscillation of the valve disc in the tilting check valve under a small mass flow rate.

Mass flow rate measurements in microtubes: From hydrodynamic to near free molecular regime

2011 ◽  
Vol 23 (4) ◽  
pp. 042004 ◽  
Author(s):  
P. Perrier ◽  
I. A. Graur ◽  
T. Ewart ◽  
J. G. Méolans
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Free Molecular Regime

Mass Flow Rate Measurements in Microchannels

2009 ◽  
Author(s):  
Irina A. Graur ◽  
Pierre Perrier ◽  
J. G. Me´olans
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Accommodation Coefficient ◽  
Steady Flows ◽  
Molecular Weights ◽  
Slip Boundary ◽  
Accommodation Coefficients ◽  
Accommodation Process ◽  
Wall Interaction

Mass flow rate measurements in a single silicon micro channel were carried out for various gases in isothermal steady flows. The results obtained from hydrodynamic to near free molecular regime by using a powerful experimental platform, allowed us to deduce interesting information, notably about the reflection/accommodation process at the wall. In the 0 – 0.3 Knudsen range, a continuum analytic approach was derived from NS equations, associated to first or second order slip boundary conditions. Identifying the experimental mass flow rate curves to the theoretical ones the tangential momentum accommodation coefficient (TMAC) of various gases was extracted. Over all the Knudsen range [0 – 50] the experimental results were compared with theoretical values calculated from the kinetic approaches: using variable accommodation coefficient values as fitting parameter, the theoretical curves were fitted to the experimental ones. Whatever the Knudsen range and whatever the theoretical approach, the TMAC values are found decreasing when the molecular weights of the gas increase (as long as the different gases are compared using the same approach). Moreover, the values of the various accommodation coefficients are rather close one to other but sufficiently smaller than unity to conclude that the full accommodation modelling is not satisfactory to describe the gas/wall interaction.

Sign in / Sign up

Export Citation Format

Share Document