Experimental Investigations of Laminar, Transitional to Turbulent Gas Flow in Rib-Patterned Micro-Channels

2011 ◽  
Author(s):  
Chungpyo Hong ◽  
Toru Yamada ◽  
Yutaka Asako ◽  
Mohammad Faghri ◽  
Ichiro Ueno
Keyword(s):  
Mach Number ◽  
Friction Factor ◽  
Gas Flow ◽  
Flow Direction ◽  
Channel Length ◽  
Experimental Investigations ◽  
Patterned Surfaces ◽  
Micro Channels ◽  
Wide Range ◽  
Turbulent Gas Flow

The effects of rib-patterned surfaces on laminar, transitional to turbulent gas flow in micro-channels were experimentally investigated in the present study. The experiments were performed for two micro-channels having either smooth or rib-patterned surfaces. The micro-channels were etched into silicon wafers and capped with glass substrates. The micro-ribs were patterned on the microchannel surfaces and oriented perpendicular to the flow direction. The pressure was measured at seven locations along the channel length to determine local values of Mach number and friction factor for a wide range of flow regime from laminar to turbulent flow. The friction factors with the hydraulic diameter based on the rib-to-upper-wall height were compared with that for incompressible theory on Moody chart. The values of the product of friction factor and Reynolds number (f·Re) as a function of Mach number were also compared with those of smooth micro-channels and incompressible theory.

Experimental Investigations of Laminar, Transitional to Turbulent Gas Flow in a Micro-Channel

2010 ◽  
Author(s):  
Chungpyo Hong ◽  
Toru Yamada ◽  
Yutaka Asako ◽  
Mohammad Faghri ◽  
Koichi Suzuki ◽  
...  
Keyword(s):  
Mach Number ◽  
Flow Regime ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Channel Length ◽  
Transitional Flow ◽  
Experimental Investigations ◽  
Compressibility Effect ◽  
Micro Channels ◽  
Wide Range

This paper presents experimental results on flow characteristics of laminar, transitional to turbulent gas flows through micro-channels. The experiments were performed for three micro-channels. The micro-channels were etched into silicon wafers, capped with glass, and their hydraulic diameter are 69.48, 99.36 and 147.76 μm. The pressure was measured at seven locations along the channel length to determine local values of Mach number and friction factor for a wide range of flow regime from laminar to turbulent flow. Flow characteristics in transitional flow regime to turbulence were obtained. The result shows that f·Re is a function of Mach number and higher than incompressible value due to the compressibility effect. The values of f·Re were compared with f·Re correlations in available literature.

Experimental Investigations of Turbulent Gas Flow in a Micro-Channel

2011 ◽  
Author(s):  
Shinichi Matsushita ◽  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Ichiro Ueno
Keyword(s):  
Mach Number ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Gas Flow ◽  
Experimental Investigations ◽  
Micro Channel ◽  
Pressure Transducers ◽  
Friction Factors ◽  
Turbulent Flow Regime ◽  
Turbulent Gas Flow

This paper presents experimental investigations on turbulent gas flow characteristics of nitrogen gas through a micro-channel. The micro-channels were etched into silicon wafers, capped with glass, and their hydraulic diameter is 147.76 micro meters. The micro-channel was designed with a main flow channel and seven side channels, which lead to the pressure transducers. The stagnation pressure was designated in such a way that the flow is in turbulent flow regime. The outlet of the channel faced to the atmosphere. The pressures of the main channel at seven locations were measured by gauge pressure transducers to determine local values of Mach number. And the pressure differences of each pressure ports were measured by differential pressure transducers to obtain the pressure losses precisely. The pressure distribution of turbulent gas flow through a micro-channel falls steeply and Mach number increases near the outlet with increasing the inlet pressure due to flow acceleration. Both Darcy friction factor and Fanning friction factor were obtained for turbulent flow. The result shows that the obtained both friction factors were evaluated as a function of Reynolds number on the Moody chart. The values of Darcy friction factors differ from Blasius correlation for turbulent flow regime due to the compressibility effects, however the values of Fanning friction factors coincide with Blasius correlation.

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.

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.

Experimental Investigation of Gas Flow in Microchannels

2004 ◽  
Vol 126 (5) ◽  
pp. 753-763 ◽  
Author(s):  
Stephen E. Turner ◽  
Lok C. Lam ◽  
Mohammad Faghri ◽  
Otto J. Gregory
Keyword(s):  
Surface Roughness ◽  
Experimental Investigation ◽  
Mach Number ◽  
Friction Factor ◽  
Knudsen Number ◽  
Gas Flow ◽  
Slip Flow ◽  
Reynolds Numbers ◽  
Channel Length ◽  
Limiting Case

This paper presents an experimental investigation of laminar gas flow through microchannels. The independent variables: relative surface roughness, Knudsen number and Mach number were systematically varied to determine their influence on the friction factor. The microchannels were etched into silicon wafers, capped with glass, and have hydraulic diameters between 5 and 96 μm. The pressure was measured at seven locations along the channel length to determine local values of Knudsen number, Mach number and friction factor. All measurements were made in the laminar flow regime with Reynolds numbers ranging from 0.1 to 1000. The results show close agreement for the friction factor in the limiting case of low Ma and low Kn with the incompressible continuum flow theory. The effect of compressibility is observed to have a mild (8 percent) increase in the friction factor as the Mach number approaches 0.35. A 50 percent decrease in the friction factor was seen as the Knudsen number was increased to 0.15. Finally, the influence of surface roughness on the friction factor was shown to be insignificant for both continuum and slip flow regimes.

Gas flow in micro-channels

1995 ◽  
Vol 284 ◽  
pp. 257-274 ◽  
Author(s):  
John C. Harley ◽  
Yufeng Huang ◽  
Haim H. Bau ◽  
Jay N. Zemel
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Friction Factor ◽  
Theoretical Investigation ◽  
Gas Flow ◽  
Slip Flow ◽  
First Order ◽  
Micro Channels ◽  
Theoretical Predictions ◽  
Good Agreement

An experimental and theoretical investigation of low Reynolds number, high subsonic Mach number, compressible gas flow in channels is presented. Nitrogen, helium, and argon gases were used. The channels were microfabricated on silicon wafers and were typically 100 μm wide, 104 μm long, and ranged in depth from 0.5 to 20 μm. The Knudsen number ranged from 10-3 to 0.4. The measured friction factor was in good agreement with theoretical predictions assuming isothermal, locally fully developed, first-order, slip flow.

Effect of Internal Coolant Crossflow Orientation on the Discharge Coefficient of Shaped Film Cooling Holes

1999 ◽  
Author(s):  
Michael Gritsch ◽  
Christian Saumweber ◽  
Achmed Schulz ◽  
Sigmar Wittig ◽  
Edwin Sharp
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Strong Impact ◽  
Hot Gas ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Cooling Hole

Discharge coefficients of three film-cooling hole geometries are presented over a wide range of engine like conditions. The hole geometries comprise a cylindrical hole and two holes with a diffuser shaped exit portion (a fanshaped and a laidback fanshaped hole). For all three hole geometries the hole axis was inclined 30° with respect to the direction of the external (hot gas) flow. The flow conditions considered were the hot gas crossflow Mach number (up to 0.6), the coolant crossflow Mach number (up to 0.6) and the pressure ratio across the hole (up to 2). The effect of internal crossflow approach direction, perpendicular or parallel to the main flow direction, is particularly addressed in the present study. Comparison is made of the results for a parallel and perpendicular orientation, showing that the coolant crossflow orientation has a strong impact on the discharge behavior of the different hole geometries. The discharge coefficients were found to strongly depend on both hole geometry and crossflow conditions. Furthermore, the effects of internal and external crossflow on the discharge coefficients were described by means of correlations used to derive a predicting scheme for discharge coefficients. A comparison between predictions and measurements reveals the capability of the method proposed.

Experimental Investigation of Gaseous Flow in a Micro-Tube

2009 ◽  
Author(s):  
Yasuhiro Yoshida ◽  
Chungpyo Hong ◽  
Yutaka Asako ◽  
Koichi Suzuki
Keyword(s):  
Mach Number ◽  
Gas Flow ◽  
Electrical Discharge Machining ◽  
Tube Length ◽  
Experimental Investigations ◽  
Arbitrary Lagrangian Eulerian ◽  
Atmospheric Conditions ◽  
Compressibility Effect ◽  
Wide Range ◽  
Tube Exit

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.

Effect of Internal Coolant Crossflow Orientation on the Discharge Coefficient of Shaped Film-Cooling Holes

1999 ◽  
Vol 122 (1) ◽  
pp. 146-152 ◽  
Author(s):  
M. Gritsch ◽  
C. Saumweber ◽  
A. Schulz ◽  
S. Wittig ◽  
E. Sharp
Keyword(s):  
Mach Number ◽  
Film Cooling ◽  
Gas Flow ◽  
Flow Direction ◽  
Pressure Ratio ◽  
Strong Impact ◽  
Hot Gas ◽  
Discharge Coefficients ◽  
Wide Range ◽  
Cooling Hole

Discharge coefficients of three film-cooling hole geometries are presented over a wide range of engine like conditions. The hole geometries comprise a cylindrical hole and two holes with a diffuser-shaped exit portion (a fanshaped and a laidback fanshaped hole). For all three hole geometries the hole axis was inclined 30 deg with respect to the direction of the external (hot gas) flow. The flow conditions considered were the hot gas crossflow Mach number (up to 0.6), the coolant crossflow Mach number (up to 0.6) and the pressure ratio across the hole (up to 2). The effect of internal crossflow approach direction, perpendicular or parallel to the main flow direction, is particularly addressed in the present study. Comparison is made of the results for a parallel and perpendicular orientation, showing that the coolant crossflow orientation has a strong impact on the discharge behavior of the different hole geometries. The discharge coefficients were found to strongly depend on both hole geometry and crossflow conditions. Furthermore, the effects of internal and external crossflow on the discharge coefficients were described by means of correlations used to derive a predicting scheme for discharge coefficients. A comparison between predictions and measurements reveals the capability of the method proposed. [S0889-504X(00)01601-9]

Experimental Study on Roughness Effect for Laminar Micro-Channel Gas Flow

2001 ◽  
Author(s):  
Jih-Hsing Tu ◽  
Fangang Tseng ◽  
Ching-Chang Chieng
Keyword(s):  
Experimental Study ◽  
Surface Roughness ◽  
Friction Factor ◽  
Gas Flow ◽  
Micro Channel ◽  
Micro Machining ◽  
Roughness Effect ◽  
Relative Roughness ◽  
Smooth Channel ◽  
Micro Channels

Abstract Present study investigates the roughness effect on laminar gas flow for microchannels ranging from 40 to 600 μm with various roughness heights (40–82 nm) by systematical experiments. The micro-channels are manufactured by micro-machining technology and KOH anisotropic etching is employed to achieve various roughness patterns. Experimental results shows that higher product levels of Reynolds number (Reh) and friction factor (f) are obtained for microchannels of larger size and smaller relative roughness and friction factor f approaches to laminar flow theory value f0 for very smooth channel but the ratio of (f/f0) decreases as the surface roughness increases.

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