Experimental Investigation of Nitrogen Flow in Long Microtubes

2009 ◽  
Author(s):  
Chengwen Li ◽  
Li Jia ◽  
Tiantian Zhang ◽  
Xing Li
Keyword(s):  
Experimental Data ◽  
Experimental Investigation ◽  
Flow Characteristics ◽  
Nitrogen Flow ◽  
Current Experiment ◽  
Turbulent Region ◽  
Compressibility Effect ◽  
Friction Factors ◽  
Macro Scale ◽  
Predicted Values

Nitrogen flow characteristics in Polyetheretherketone microtubes with inner diameters (D) ranging from 0.255mm to 0.553mm were experimentally investigated. It is indicated that most of the experimental points in laminar region are coincided with the conventional theoretical predicted value, but several plots caused by instrumental errors are lower than predicted values at small Re. In turbulent region, the friction factors for D = 0.255mm microtubes with L = 0.800m and 1.591m are slightly lower than conventional values; the experimental data for D = 0.553mm microtube with L = 0.800m is lower than that in D = 0.255mm pipes. The entrance effect obviously influences friction factor even if the L/D of microtubes is more than 60, where it can always be neglected in macro-scale. Due to the enhancement of compressibility effect as diameter decrease (Kn increase), friction constant is larger in smaller-size microtubes. The transition Reynolds number in current experiment (except for L = 0.200mm and D = 0.553mm) ranges from1600–2000, while a little early transition phenomenon is found in L = 0.200m, D = 0.553mm tube.

An Experimental Investigation of Gaseous Flow Characteristics in Microchannels

2004 ◽  
Author(s):  
G. H. Tang ◽  
Y. L. He
Keyword(s):  
Experimental Investigation ◽  
Flow Characteristics ◽  
Fused Silica ◽  
Helium Flow ◽  
Gaseous Flow ◽  
Compressibility Effect ◽  
Circular Tubes ◽  
Flow Friction ◽  
Friction Factors ◽  
Good Agreement

Gaseous flow characteristics in fused silica microtubes and square microchannels are studied experimentally. The existing works in the literature on experimental gaseous flow are analyzed. The data in fused silica micro circular tubes with diameters ranging from 50 μm to 201 μm and the data in fused silica micro square channels with hydraulic diameter ranging from 52 μm to 100 μm show that the flow friction factors are in good agreement with the theoretical prediction for conventional tubes and no distinguishable deviation is observed. The transition Reynolds number is around 2000 and a slight early transition from laminar to turbulent is observed due to the compressibility effect. For the helium flow in fused silica microtubes with inner diameters ranging from 10 μm to 20 μm, the decrease in friction factor is observed. In addition, factors including roughness, compressibility and rarefaction that may have significant effects on flow characteristics in microchannels are discussed.

Experimental Investigation of Subcooled Flashing Flow in Simulated Cracks

2011 ◽  
Author(s):  
Brian Wolf ◽  
Shripad T. Revankar ◽  
Jovica R. Riznic
Keyword(s):  
Experimental Data ◽  
Experimental Investigation ◽  
Flow Rate ◽  
Test Specimen ◽  
Room Temperature ◽  
Flow Characteristics ◽  
Test Facility ◽  
Experimental Program ◽  
Flow Discharge ◽  
Subcooled Water

In this study an experimental program was developed to measure the choking flow rate of subcooled water through simulated tube crack geometries (L/D<10 L< 5mm) and results are compared with models in literature. A test facility was designed and built to measure leak rates of subcooled water from through-wall simulated tube cracks up to 6.8 MPa. Two types of test specimens were used in the experimental program. One, a round orifice like hole is created to simulate a pitting type flaw. The others are laser cut slits representing axial cracks. Flow discharge tests were carried out with water at room temperature to determine the flow characteristics for each test specimen. Also, subcooled flashing discharge tests with heated water were carried out up to a vessel pressure of 6.8 MPa at various subcoolings. A modified Burnell correlation was developed using upstream saturation and subcooled temperature conditions and the predictions of the correlation agreed well with the present experimental data.

Laminar, Transitional and Turbulent Friction Factors for Gas Flows in Smooth and Rough Microtubes

2008 ◽  
Author(s):  
Marco Lorenzini ◽  
Gian Luca Morini ◽  
Sandro Salvigni
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Turbulent Regime ◽  
Turbulent Friction ◽  
Compressibility Effect ◽  
Flow Acceleration ◽  
Friction Factors ◽  
Macro Scale ◽  
Fully Developed Turbulent Flow ◽  
Microscale Transport

Theoretical and experimental works on microscale transport phenomena have been carried out in the past decade in the attempt to analyse possible new effects and to assess the influence of scaling on the classical correlations which are used in macro-scale heat and fluid flow, following the need to supply engineers with reliable correlations to be used in the design of micro-scale devices. These results were sometimes in mutual contrast, as is the case for the determination of the friction factor, which has been found to be lower, higher or comparable to that for macroscopic channels, depending on the researchers. In this work the compressible flow of nitrogen inside circular microchannels from 26 μm to 508 μm in diameter and with different surface roughness (<1%) is investigated for the whole range of flow conditions: laminar, transitional and turbulence. Over 5000 experimental data have been collected and analysed. The data confirmed that in the laminar regime the agreement with the conventional theory is very good in terms of friction factors both for rough and smooth microtubes. For the smaller microchannels (<100 μm) when Re is greater than 1300 the friction factor tends to deviate from the Poiseuille law because the flow acceleration due to compressibility effect gains in importance. The transitional regime was found to start no earlier than at values of the Reynolds number around 1800–2000. Both smooth and sudden changes in the flow regime have been found, as reported for conventional tubes. Fully developed turbulent flow was attained with both smooth and rough tubes, and the results for smooth tubes seem to confirm Blasius’s relation, while for rough tubes the Colebrook’s correlation is found to be only partially in agreement with the experimental friction factors. In the turbulent regime the dependence of the friction factor on the Reynolds number is less pronounced for microtubes with respect to the prediction of the Colebrook’s correlation and the friction factor tends only to depend on the microtube relative roughness.

Experimental and Numerical Investigations of Air Flow Characteristics Through Microporous Media

2006 ◽  
Author(s):  
Ruina Xu ◽  
Peixue Jiang
Keyword(s):  
Experimental Data ◽  
Porous Media ◽  
Flow Regime ◽  
Air Flow ◽  
Slip Flow ◽  
Particle Diameter ◽  
Flow Characteristics ◽  
Average Particle ◽  
Friction Factors ◽  
Slip Flow Regime

The effect of particle diameter on the air flow characteristics in various micro-porous media test sections was studied experimentally and numerically. The test sections were made of bronze particles with average diameters of 200 μm, 125 μm, 90 μm and 40 μm. The experimentally measured friction factors in the porous media with average diameters of 200 μm and 125 μm agree well with the known correlation. However, the experimental values for the friction factors in the micro-porous media with 90 μm a and 40 μm average diameters are much less than the known correlation. Also, the differences between the experimental results and the known correlation increase with decreasing average particle diameter. Numerical simulations of the air flow in micro-porous media including rarefaction were performed using the CFD code FLUENT 6.1 to predict the pressure drop characteristics in the four test sections. The calculated friction factors for the non-slip flow regime in the micro-porous media agree well with the known correlation and the experimental data. The numerically predicted friction factors for the slip flow regime in the micro-porous media with 90 μm and 40 μm diameter particles were less than the known correlation and close to the experimental data. The results show that rarefaction effects occur in air flows in the micro-porous media with particle diameters less than 90 a and that numerical calculations with velocity slip on the boundary can simulate the slip flows in micro-porous media.

scholarly journals Experimental data for the slug two-phase flow characteristics in horizontal pipeline

Data in Brief ◽  
2018 ◽  
Vol 16 ◽  
pp. 527-530 ◽  
Author(s):  
Abdalellah O. Mohmmed ◽  
Mohammad S. Nasif ◽  
Hussain H. Al-Kayiem
Keyword(s):  
Experimental Data ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Two Phase

Experimental Investigation of Effect of Tip Coolant Ejection on Internal Flow Characteristics Within a Realistic Blade Coolant Channel

2013 ◽  
Author(s):  
Jian Pu ◽  
Zhaoqing Ke ◽  
Jianhua Wang ◽  
Lei Wang ◽  
Hongde You
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Turbine Blade ◽  
Flow Rate ◽  
Flow Characteristics ◽  
Reynolds Numbers ◽  
Flow Ratio ◽  
Lp Turbine ◽  
Mass Flow Ratio

This paper presents an experimental investigation on the characteristics of the fluid flow within an entire coolant channel of a low pressure (LP) turbine blade. The serpentine channel, which keeps realistic blade geometry, consists of three passes connected by a 180° sharp bend and a semi-round bend, 2 tip exits and 25 trailing edge exits. The mean velocity fields within several typical cross sections were captured using a particle image velocimetry (PIV) system. Pressure and flow rate at each exit were determined through the measurements of local static pressure and volume flow rate. To optimize the design of LP turbine blade coolant channels, the effect of tip ejection ratio (ER) from 180° sharp bend on the flow characteristics in the coolant channel were experimentally investigated at a series of inlet Reynolds numbers from 25,000 to 50,000. A complex flow pattern, which is different from the previous investigations conducted by a simplified square or rectangular two-pass U-channel, is exhibited from the PIV results. This experimental investigation indicated that: a) in the main flow direction, the regions of separation bubble and flow impingement increase in size with a decrease of the ER; b) the shape, intensity and position of the secondary vortices are changed by the ER; c) the mass flow ratio of each exit to inlet is not sensitive to the inlet Reynolds number; d) the increase of the ER reduces the mass flow ratio through each trailing edge exit to the extent of about 23–28% of the ER = 0 reference under the condition that the tip exit located at 180° bend is full open; e) the pressure drop through the entire coolant channel decreases with an increase in the ER and inlet Reynolds number, and a reduction about 35–40% of the non-dimensional pressure drop is observed at different inlet Reynolds numbers, under the condition that the tip exit located at 180° bend is full open.

Theoretical and Experimental Investigation of Pipe Wall Thinning Detection Using Guided Waves

2008 ◽  
Author(s):  
Isoharu Nishiguchi ◽  
Fumitoshi Sakata ◽  
Seiichi Hamada
Keyword(s):  
Experimental Data ◽  
Power Generation ◽  
Experimental Investigation ◽  
Reflection Coefficient ◽  
Guided Waves ◽  
Pipe Wall ◽  
Thermal Power ◽  
Wall Thinning ◽  
Torsional Waves ◽  
Simplified Method

A method to investigate pipe wall thinning using guided waves has been developed for pipes in thermal power generation facilities. In this paper, the reflection coefficient and the transmission coefficient are derived for the torsional waves which propagate along a pipe and a simplified method to predict the waveform is proposed. The predictions of the waveforms by the FEM and a simplified method based on the reflection of torsional waves are also examined by comparing with experimental data.

Separation in oscillating laminar boundary-layer flows

1971 ◽  
Vol 47 (1) ◽  
pp. 21-31 ◽  
Author(s):  
R. A. Despard ◽  
J. A. Miller
Keyword(s):  
Experimental Data ◽  
Boundary Layer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Reverse Flow ◽  
Oscillation Amplitude ◽  
Hot Wire ◽  
Boundary Layer Flows ◽  
Laminar Boundary Layers ◽  
History Of

The results of an experimental investigation of separation in oscillating laminar boundary layers is reported. Instantaneous velocity profiles obtained with multiple hot-wire anemometer arrays reveal that the onset of wake formation is preceded by the initial vanishing of shear at the wall, or reverse flow, throughout the entire cycle of oscillation. Correlation of the experimental data indicates that the frequency, Reynolds number and dynamic history of the boundary layer are the dominant parameters and oscillation amplitude has a negligible effect on separation-point displacement.

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