Estimation of Leak Flow Rates Through Narrow Cracks

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Jae-Heon Lee
Keyword(s):  
Friction Factor ◽  
Gas Flow ◽  
Slip Flow ◽  
Nonlinear Ordinary Differential Equation ◽  
Opening Displacement ◽  
Flow Rates ◽  
Choked Flow ◽  
Runge Kutta Method ◽  
Wide Range ◽  
Leak Before Break

The estimation of the gaseous leak flow rates through a narrow crack is important for a leak-before-break analysis as a method of nondestructive testing. Therefore, the methodology to estimate the gaseous leak flow rates in a narrow crack for a wide range of flow conditions, from no-slip to slip flow and from unchoked to choked flow, by using f⋅Re (the product of friction factor and Reynolds number) correlations obtained for a microchannel, was developed and presented. The correlations applied here were proposed by the previous study (Hong, et al., 2007, “Friction Factor Correlations for Gas Flow in Slip Flow Regime,” ASME J. Fluids Eng., 129, pp. 1268–1276). The detail of the calculation procedure was appropriately documented. The fourth-order Runge–Kutta method was employed to integrate the nonlinear ordinary differential equation for the pressure, and the regular-Falsi method was employed to find the inlet Mach number. An idealized crack, whose opening displacement ranges from 2 μm to 50 μm, with the crack aspect ratio of 200, 1000, and 2000, was chosen for sample estimation. The present results were compared with both numerical simulations and available experimental measurements. The results were in excellent agreement. Therefore, the gaseous leak flow rates can be correctly predicted by using the proposed methodology.

scholarly journals KPIM of Gas Transportation: Robust Modification of Gas Pipeline Equations

2008 ◽  
Vol 45 (5) ◽  
pp. 39-47
Author(s):  
A. Falade ◽  
A. Olaberinjo ◽  
M. Oyewola ◽  
F. Babalola ◽  
S. Adaramola
Keyword(s):  
Friction Factor ◽  
Gas Flow ◽  
Research Work ◽  
Flow Equation ◽  
Gas Pipeline ◽  
Flow Rates ◽  
Modified Equations ◽  
Wide Range ◽  
High Degree ◽  
Turbulent Gas Flow

KPIM of Gas Transportation: Robust Modification of Gas Pipeline Equations Studies of the flow conditions of natural gases in pipelines have led to the development of complex equations for relating the volume transmitted through a gas pipeline to the various factors involved, thus deciding the optimum pressures and pipeline dimensions to be used. From equations of this type, various combinations of pipe diameter and wall thickness for a desired rate of gas throughput can be calculated. This research work presents modified forms of the basic gas flow equation for horizontal flow developed by Weymouth and the basic gas flow equation for inclined flow developed by Ferguson. The modified equations incorporate non-iterative forms of the Colebrook-White friction factor into the original forms of the Weymouth's and Ferguson's equations. These modified equations thus eliminate the need for iteration in predicting the flow rate of gas through pipelines as is the case with their original forms when the Colebrook-White friction factor is used. The modified equations also have a wider range of application since the Colebrook-White friction factor is valid for turbulent gas flow as well as for gas flow in a transition zone. On comparing the results it can be seen that the modified Ferguson's equation gives a more accurate prediction of gas flow rates because it takes the pipeline elevation into account. Lower deviations from measured gas flow rates were observed with the modified Ferguson's equation than with the modified basic gas flow equation. The deviations observed using the modified Ferguson equation were found to range from -0.16% to +3.21%. Conclusively, these less cumbersome newly developed equations with high degree reliability will be useful in predicting the rates of gas flow for a wide range of its conditions, pipeline elevation and pipeline lengths.

Friction Factor Correlations for Gas Flow in Slip Flow Regime

2007 ◽  
Vol 129 (10) ◽  
pp. 1268-1276 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Stephen E. Turner ◽  
Mohammad Faghri
Keyword(s):  
Friction Factor ◽  
Flow Regime ◽  
Gas Flow ◽  
Slip Flow ◽  
Channel Height ◽  
Inlet Temperature ◽  
Arbitrary Lagrangian Eulerian ◽  
Knudsen Numbers ◽  
Wide Range ◽  
Slip Flow Regime

Poiseuille number, the product of friction factor and Reynolds number (fRe) for quasi-fully-developed gas microchannel flow in the slip flow regime, was obtained numerically based on the arbitrary-Lagrangian-Eulerian method. Two-dimensional compressible momentum and energy equations were solved for a wide range of Reynolds and Mach numbers for constant wall temperatures that are lower or higher than the inlet temperature. The channel height ranges from 2 μm to 10 μm and the channel aspect ratio is 200. The stagnation pressure pstg is chosen such that the exit Mach number ranges from 0.1 to 1.0. The outlet pressure is fixed at atmospheric conditon. Mach and Knudsen numbers are systematically varied to determine their effects on fRe. The correlation for fRe for the slip flow is obtained from that of fRe of no-slip flow and incompressible theory as a function of Mach and Knudsen numbers. The results are in excellent agreement with the available experimental measurements. It was found that fRe is a function of Mach and Knudsen numbers and is different from the values by 96/(1+12Kn) obtained from the incompressible flow theory.

Experimental Investigations on Friction Factors of Gaseous Flow Through a Micro-Tube With Smooth Surface

2017 ◽  
Author(s):  
Takayuki Shigeishi ◽  
Chungpyo Hong ◽  
Yutaka Asako
Keyword(s):  
Friction Factor ◽  
Smooth Surface ◽  
Gas Flow ◽  
Experimental Investigations ◽  
Adiabatic Wall ◽  
Choked Flow ◽  
Friction Factors ◽  
Wide Range ◽  
Flow Through ◽  
Local Pressures

The purpose of the present study is to experimentally investigate flow characteristics on semi-local friction factors of nitrogen gas flow through a micro-tube with a smooth surface. The experiments were performed using a glass micro-tube with 266 μm in diameter and 120 mm in length. Three static pressure holes are drilled on the wall near the micro-tube outlet at intervals of 5 mm, and the local pressures were measured with the outlet discharged into the atmosphere. The local values of Mach number, temperature and friction factor were obtained from the measured local pressures. The result in the wide range of Reynolds number was also obtained, including the choked flow. Darcy friction factor and Fanning friction factor obtained under the assumptions of both a Fanno flow (adiabatic wall) and an Isothermal flow were compared with empirical correlations in the literature and numerical results.

Poiseuille Number Correlations of Gas Flow in Concentric Micro Annular Tubes

2008 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Boundary Conditions ◽  
Gas Flow ◽  
Slip Flow ◽  
Tube Length ◽  
Slip Boundary Conditions ◽  
Slip Boundary ◽  
Rarefaction Effect ◽  
Wide Range ◽  
Poiseuille Number ◽  
Fast Flow

Poiseuille number, the product of friction factor and Reynolds number (f · Re) for quasi-fully developed concentric micro annular tube flow was obtained for both no-slip and slip boundary conditions. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The compressible momentum and energy equations were solved for a wide range of Reynolds and Mach numbers for both isothermal flow and no heat conduction flow conditions. The detail of the incompressible slip Poiseuille number is kindly documented and its value defined as a function of r* and Kn is represented. The outer tube radius ranges from 50 to 150μm with the radius ratios of 0.2, 0.5 and 0.8 and selected tube length is 0.02m. The stagnation pressure, pstg is chosen in such away that the exit Mach number ranges from 0.1 to 0.7. The outlet pressure is fixed at the atmospheric pressure. In the case of fast flow, the value of f · Re is higher than that of incompressible slip flow theory due to the compressibility effect. However in the case of slow flow the value of f · Re is slightly lower than that of incompressible slip flow due to the rarefaction effect, even the flow is accelerated. The value of f · Re obtained for no-slip boundary conditions is compared with that of obtained for slip boundary conditions. The values of f · Re obtained for slip boundary conditions are predicted by f · Re correlations obtained for no-slip boundary conditions since rarefaction effect is relatively small for the fast flow.

Experimental Study on Single-Phase Gas Flow in Microtubes

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
T. T. Zhang ◽  
L. Jia ◽  
C. W. Li ◽  
L. X. Yang ◽  
Y. Jaluria
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Single Phase ◽  
Slip Flow ◽  
Experimental System ◽  
Flow Region ◽  
Flow And Heat Transfer ◽  
Wide Range ◽  
Physical Insight ◽  
Insight Into

An experimental system for single-phase gas flow in microtubes has been developed. The effects of viscous heating and compressibility on the flow and temperature field were studied for a wide range of governing parameters. Also, an analytical/numerical model of the flow was developed. Numerical results for the flow and heat transfer in the slip flow region were found to agree quite well with the experimental data, lending support to the model. The study provides greater physical insight into and understanding the effects of viscous dissipation and compressibility in microtube flow and the associated heat transfer. In addition, the combined experimental and numerical simulation approaches of the process can be used for control and optimization of systems based on microtube heat transfer.

A Friction Factor Correlation for Gas Flow in Parallel Plate Microchannels by Considering Combined Effects of Compressibility and Rarefaction

2008 ◽  
Author(s):  
Xiaohong Yan ◽  
Qiuwang Wang
Keyword(s):  
Friction Factor ◽  
Velocity Gradient ◽  
Parallel Plate ◽  
Gas Flow ◽  
Stokes Equations ◽  
Control Volume ◽  
Slip Flow ◽  
Slip Boundary Condition ◽  
Combined Effects ◽  
Slip Boundary

The effects of compressibility and rarefaction for gas flow in microchannels have been extensively studied separately. However, these two effects are always combined for gas flow in microchannels. In this paper, the two-dimensional compressible Navier-Stokes equations are solved for gas flow in parallel plate channels with a slip boundary condition to study the combined effects of compressibility and rarefaction on the friction factor. The numerical methodology is based on the control volume finite difference scheme. It is found that the effect of compressibility increases the velocity gradient near the wall which then increases the friction factor. On the other hand, increasing the velocity gradient near the wall leads to a much larger slip velocity and implies a stronger rarefaction effect and a corresponding decrease in the friction factor. These two opposite effects make the effect of compressibility on friction factor for slip flow weaker than that for no-slip compressible flow. A correlation among fRe, Kn and Ma is presented. The correlation is validated with available experimental and analytical results.

Axial and Radial Investigation of Hydrodynamics in a Bubble Column; Influence of Fluids Flow Rates and Sparger Type

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Hélène Chaumat ◽  
Anne-Marie Billet ◽  
Henri Delmas
Keyword(s):  
Liquid Flow ◽  
Gas Flow ◽  
Bubble Column ◽  
Bubble Diameter ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Batch Mode ◽  
Flow Rates ◽  
Wide Range ◽  
Injection Zone

A detailed investigation of local hydrodynamics in a pilot plant bubble column has been performed using various techniques, exploring both axial and radial variations of the gas hold-up, bubble average diameter and frequency, surface area. A wide range of operating conditions has been explored up to large gas and liquid flow rates, with two sparger types. Two main complementary techniques were used: a quasi local measurement of gas hold-up via series of differential pressure sensors to get the axial variation and a double optic probe giving radial variations of gad hold-up, bubble average size and frequency and surface area.According to axial evolutions, three zones, where radial evolutions have been detailed, have been separated: at the bottom the gas injection zone, the large central region or column bulk and the disengagement zone at the column top. It was found that significant axial and radial variations of the two phase flow characteristics do exist even in the so called homogeneous regime. The normalized profiles of bubble frequency appear sparger and gas velocity independent contrary to bubble diameter, gas hold-up and interfacial area normalized profiles. In any case bubbles are larger in the sparger zone than elsewhere.The main result of this work is the very strong effect of liquid flow on bubble column hydrodynamics at low gas flow rate. First the flow regime map observed in batch mode is dramatically modified with a drastic reduction of the homogeneous regime region, up to a complete heterogeneous regime in the working conditions (uG> 0.02 m/s). On the contrary, liquid flow has limited effects at very high gas flow rates.A large data bank is provided to be used for example in detailed comparison with CFD calculations.

Development of a Unique, Passive, Microgravity Vortex Separator

2005 ◽  
Author(s):  
M. Ellis ◽  
C. Kurwitz ◽  
F. Best
Keyword(s):  
Waste Water ◽  
Phase Separation ◽  
Power Systems ◽  
Gas Flow ◽  
Full Range ◽  
Operating Conditions ◽  
Microgravity Environment ◽  
Flow Rates ◽  
Wide Range ◽  
Vortex Separator

In the microgravity environment experienced by space vehicles, liquid and gas do not naturally separate as on Earth. This behavior presents a problem for two-phase space systems, such as environment conditioning, waste water processing, and power systems. Furthermore, with recent renewed interest in space nuclear power systems, a microgravity Rankine cycle is attractive for thermal to electric energy conversion and would require a phase separation device. Responding to this need, researchers have conceived various methods of producing phase separation in low gravity environments. These separator types have included wicking, elbow, hydrophobic/hydrophilic, vortex, rotary fan separators, and combinations thereof. Each class of separator achieved acceptable performance for particular applications and most performed in some capacity for the space program. However, increased integration of multiphase systems requires a separator design adaptable to a variety of system operating conditions. To this end, researchers at Texas A&M University (TAMU) have developed a Microgravity Vortex Separator (MVS) capable of handling both a wide range of inlet conditions as well as changes in these conditions with a single, passive design. Currently, rotary separators are recognized as the most versatile microgravity separation technology. However, compared with passive designs, rotary separators suffer from higher power consumption, more complicated mechanical design, and higher maintenance requirements than passive separators. Furthermore, research completed over the past decade has shown the MVS more resistant to inlet flow variations and versatile in application. Most investigations were conducted as part of system integration experiments including, among others, propellant transfer, waste water processing, and fuel cell systems. Testing involved determination of hydrodynamic conditions relating to vortex stability, inlet quality effects, accumulation volume potential, and dynamic volume monitoring. In most cases, a 1.2 liter separator was found to accommodate system flow conditions. This size produced reliable phase separation for liquid flow rates from 1.8 to 9.8 liters per minute, for gas flow rates of 0.5 to 180 standard liters per minute, over the full range of quality, and with fluid inventory changes up to 0.35 liters. Moreover, an acoustic sensor, integrated into the wall of the separation chamber, allows liquid film thickness monitoring with an accuracy of 0.1 inches. Currently, application of the MVS is being extended to cabin air dehumidification and a Rankine power cycle system. Both of these projects will allow further development of the TAMU separator.

Experimental Study of Low Concentration Sand Transport in Multiphase Air–Water Horizontal Pipelines

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Kamyar Najmi ◽  
Alan L. Hill ◽  
Brenton S. McLaury ◽  
Siamack A. Shirazi ◽  
Selen Cremaschi
Keyword(s):  
Experimental Study ◽  
Gas Flow ◽  
Intermittent Flow ◽  
Sand Transport ◽  
Physical Parameters ◽  
Internal Diameter ◽  
Flow Rates ◽  
Minimum Flow ◽  
Wide Range ◽  
Sand Size

The ultimate goal of this work is to determine the minimum flow rates necessary for effective transport of sand in a pipeline carrying multiphase flow. In order to achieve this goal, an experimental study is performed in a horizontal pipeline using water and air as carrier fluids. In this study, successful transport of sand is defined as the minimum flow rates of water and air at which all sand grains continue to move along in the pipe. The obtained data cover a wide range of liquid and gas flow rates including stratified and intermittent flow regimes. The effect of physical parameters such as sand size, sand shape, and sand concentration is experimentally investigated in 0.05 and 0.1 m internal diameter pipes. The comparisons of the obtained data with previous studies show good agreement. It is concluded that the minimum flow rates required to continuously move the sand increases with increasing sand size in the range examined and particle shape does not significantly affect sand transport. Additionally, the data show the minimum required flow rates increase by increasing sand concentration for the low concentrations considered, and this effect should be taken into account in the modeling of multiphase sand transport.

Friction Factor Correlations of Slip Flow in Micro-Tubes

2007 ◽  
Author(s):  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Mohammad Faghri
Keyword(s):  
Mach Number ◽  
Friction Factor ◽  
Slip Flow ◽  
Constant Heat Flux ◽  
Arbitrary Lagrangian Eulerian ◽  
Constant Wall Temperature ◽  
Wide Range ◽  
Exit Mach Number ◽  
Poiseuille Number ◽  
Energy Equations

Poiseuille number, the product of friction factor and Reynolds number (f·Re) for quasi-fully developed flow in a micro-tube was obtained in slip flow regime. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. Two-dimensional compressible momentum and energy equations were solved for a wide range of Reynolds and Mach numbers with two thermal boundary conditions: CWT (constant wall temperature) and CHF (constant heat flux), respectively. The tube diameter ranges from 3 to 10μm and the tube aspect ratio is 200. The stagnation pressure, pstg is chosen in such away that the exit Mach number ranges from 0.1 to 1.0. The outlet pressure is fixed at the atmospheric pressure. In slip flow, Mach and Knudsen numbers are systematically varied to determine their effects on f·Re. The correlation for f·Re is obtained from numerical results. It was found that f·Re is mainly a function of Mach number and Knudsen number and is different from the values obtained by 64/(1+8Kn) for slow flow. The obtained f·Re correlations are applicable to both no-slip and slip flow regimes.

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