An Experimental Investigation of Gaseous Flow Characteristics in Microchannels

Flow Characteristics ◽

Fused Silica ◽

Helium Flow ◽

Gaseous Flow ◽

Compressibility Effect ◽

Circular Tubes ◽

Flow Friction ◽

Friction Factors ◽

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.

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Heat Transfer Equipment; Heat Transfer in Electronic Equipment ◽

Experimental Investigation of Nitrogen Flow in Long Microtubes

10.1115/ht2009-88408 ◽

2009 ◽

Author(s):

Chengwen Li ◽

Li Jia ◽

Tiantian Zhang ◽

Xing Li

Keyword(s):

Experimental Data ◽

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.

Effect of Compressibility on Gaseous Flows in a Micro-Tube

Heat Transfer: Volume 1 ◽

10.1115/ht2003-47166 ◽

2003 ◽

Cited By ~ 2

Author(s):

Yutaka Asako ◽

Kenji Nakayama

Keyword(s):

Reynolds Number ◽

Mach Number ◽

Pressure Distribution ◽

Flow Characteristics ◽

Fused Silica ◽

Two Dimensional ◽

Arbitrary Lagrangian Eulerian ◽

Gaseous Flow ◽

Gaseous Flows ◽

Energy Equations

The product of friction factor and Reynolds number (f·Re) of gaseous flow in the quasi-fully developed region of a micro-tube was obtained experimentally and numerically. The tube cutting method was adopted to obtain the pressure distribution along the tube. The fused silica tubes whose nominal diameters were 100 and 150 μm, were used. Two-dimensional compressible momentum and energy equations were solved to obtain the flow characteristics in micro-tubes. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The both results agree well and it was found that (f·Re) is a function of Mach number.

ASME 2011 9th International Conference on Nanochannels, Microchannels, and Minichannels, Volume 1 ◽

An Experimental Investigation on Heat Transfer Characteristics of Air and CO2 in Microtubes

10.1115/icnmm2011-58102 ◽

2011 ◽

Cited By ~ 2

Author(s):

Chia-Wei Chen ◽

Ting-Yu Lin ◽

Chien-Yuh Yang ◽

Satish G. Kandlikar

Keyword(s):

Heat Transfer ◽

Heat Transfer Performance ◽

Convection Heat Transfer ◽

Transfer Performance ◽

Gaseous Flow ◽

Compressibility Effect ◽

Micro Channels ◽

Significant Difference ◽

Laminar And Turbulent Flow

Several researches dealing with the single-phase forced convection heat transfer inside micro channels have been published in the past decades. The performance of liquid flow has been proved that agree with the conventional correlations very well (Yang and Lin [2007]). However, owing to the low heat transfer coefficient of gaseous flow, it is more difficult to eliminate the effects of thermal shunt and heat loss than water flow while measuring its heat transfer performance. This study provides an experimental investigation on forced convective heat transfer performance of air and gaseous carbon dioxide flowing through two microtube with inner diameter of 920 μm. A non-contacted liquid crystal thermography (LCT) temperature measurement method that proposed by Lin and Yang [2007] was used in this study to measure the surface temperature of microtube. The test results show that the conventional heat transfer correlations for laminar and turbulent flow can be well applied for predicting the fully developed heat transfer performance in microtubes while taking account of the compressibility effect of high pressure gaseous flow in micro tubes. There is no significant difference between CO2 and air in both heat transfer and friction.

AN EXPERIMENTAL INVESTIGATION OF GASEOUS FLOW CHARACTERISTICS IN MICROCHANNELS

Microscale Thermophysical Engineering ◽

10.1080/10893950252901268 ◽

2002 ◽

Vol 6 (2) ◽

pp. 117-130 ◽

Cited By ~ 44

Author(s):

Takuto Araki ◽

Min Soo Kim ◽

Hiroshi Iwai ◽

Kenjiro Suzuki

Keyword(s):

Flow Characteristics ◽

Gaseous Flow

VISCOSITY EFFECTS IN A CHANNEL OF SMALL EXPONENTIAL DIVERGENCE

Canadian Journal of Research ◽

10.1139/cjr35-055 ◽

1935 ◽

Vol 12 (5) ◽

pp. 676-685 ◽

Cited By ~ 6

Author(s):

G. N. Patterson

Keyword(s):

Flow Characteristics ◽

Theoretical Treatment ◽

Photographic Method ◽

General Flow ◽

Viscosity Effects ◽

Diverging Channel ◽

Theoretical Considerations ◽

Theoretical Results ◽

An experimental investigation of a flow form, deduced by Blasius from theoretical considerations, was carried out with air as the medium. A photographic method of measuring velocity distributions was adopted, and a diverging channel was designed from considerations based on the theoretical treatment and on requirements arising out of the experimental method. At a Reynolds number of 35, curves of velocity distribution were measured at various positions along the channel, and comparisons were then made with the corresponding theoretical curves. Good agreement was found over the region of the channel to which the theoretical results could be applied. A study of the experimental curves in that part of the channel to which the theoretical results could not be applied quantitatively showed further that the general flow characteristics described by Blasius are to be found in this region.

Measurement and Prediction of Rough Wall Effects on Friction Factor—Uniform Roughness Results

Journal of Fluids Engineering ◽

10.1115/1.3243568 ◽

1988 ◽

Vol 110 (4) ◽

pp. 385-391 ◽

Cited By ~ 16

Author(s):

W. F. Scaggs ◽

R. P. Taylor ◽

H. W. Coleman

Keyword(s):

Friction Factor ◽

Roughness Element ◽

Discrete Element ◽

Turbulent Pipe Flow ◽

Number Range ◽

Flow Friction ◽

Friction Factors ◽

Roughness Model ◽

Factor Data ◽

The results of an experimental investigation of the effects of surface roughness on turbulent pipe flow friction factors are presented and compared with predictions from a previously published discrete element roughness model. Friction factor data were acquired over a pipe Reynolds number range from 10,000 to 600,000 for nine different uniformly rough surfaces. These surfaces covered a range of roughness element sizes, spacings and shapes. Predictions from the discrete element roughness model were in very good agreement with the data.

Experimental investigation and modelling of light scattering in a-Si:H solar cells deposited on glass/ZnO:Al substrates

MRS Proceedings ◽

10.1557/proc-715-a13.3 ◽

2002 ◽

Vol 715 ◽

Cited By ~ 3

Author(s):

J. Krc ◽

M. Zeman ◽

O. Kluth ◽

F. Smole ◽

M. Topic

Keyword(s):

Surface Roughness ◽

Solar Cells ◽

Angular Distribution ◽

Light Scattering ◽

Optical Model ◽

Distribution Functions ◽

Interface Roughness ◽

Scattering Parameters ◽

AbstractThe descriptive scattering parameters, haze and angular distribution functions of textured ZnO:Al transparent conductive oxides with different surface roughness are measured. An approach to determine the scattering parameters of all internal interfaces in p-i-n a-Si:H solar cells deposited on the glass/ZnO:Al substrates is presented. Using the determined scattering parameters as the input parameters of the optical model, a good agreement between the measured and simulated quantum efficiencies of the p-i-n a-Si:H solar cells with different interface roughness is achieved.