scholarly journals A Comparison of Data Reduction Methods for Average Friction Factor Calculation of Adiabatic Gas Flows in Microchannels

Micromachines ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 171 ◽  
Author(s):  
Danish Rehman ◽  
Gian Morini ◽  
Chungpyo Hong
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Numerical Analysis ◽  
Friction Factor ◽  
Data Reduction ◽  
Hydraulic Diameter ◽  
Accurate Estimation ◽  
Gas Flows ◽  
Adiabatic Wall ◽  
Loss Coefficients

In this paper, a combined numerical and experimental approach for the estimation of the average friction factor along adiabatic microchannels with compressible gas flows is presented. Pressure-drop experiments are performed for a rectangular microchannel with a hydraulic diameter of 295 μ m by varying Reynolds number up to 17,000. In parallel, the calculation of friction factor has been repeated numerically and results are compared with the experimental work. The validated numerical model was also used to gain an insight of flow physics by varying the aspect ratio and hydraulic diameter of rectangular microchannels with respect to the channel tested experimentally. This was done with an aim of verifying the role of minor loss coefficients for the estimation of the average friction factor. To have laminar, transitional, and turbulent regimes captured, numerical analysis has been performed by varying Reynolds number from 200 to 20,000. Comparison of numerically and experimentally calculated gas flow characteristics has shown that adiabatic wall treatment (Fanno flow) results in better agreement of average friction factor values with conventional theory than the isothermal treatment of gas along the microchannel. The use of a constant value for minor loss coefficients available in the literature is not recommended for microflows as they change from one assembly to the other and their accurate estimation for compressible flows requires a coupling of numerical analysis with experimental data reduction. Results presented in this work demonstrate how an adiabatic wall treatment along the length of the channel coupled with the assumption of an isentropic flow from manifold to microchannel inlet results in a self-sustained experimental data reduction method for the accurate estimation of friction factor values even in presence of significant compressibility effects. Results also demonstrate that both the assumption of perfect expansion and consequently wrong estimation of average temperature between inlet and outlet of a microchannel can be responsible for an apparent increase in experimental average friction factor in choked flow regime.

Determination of Incompressible Flow Friction in Smooth Circular and Noncircular Passages: A Generalized Approach Including Validation of the Nearly Century Old Hydraulic Diameter Concept

1988 ◽  
Vol 110 (4) ◽  
pp. 431-440 ◽  
Author(s):  
N. T. Obot
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Critical Reynolds Number ◽  
Pressure Coefficient ◽  
Hydraulic Diameter ◽  
Length Scale ◽  
The Difference ◽  
Friction Method ◽  
Reduced Data

It has been demonstrated conclusively that the widely observed differences in data for frictional pressure coefficient between circular and noncircular passages derive from the inseparably connected effects of transition and the choice of a length scale. A relatively simple approach, the critical friction method (CFM), has been developed and when applied to triangular, rectangular, and concentric annular passages, the reduced data lie with remarkable consistency on the circular tube relations. In accordance with the theory of dynamical similarity, it has also been shown that noncircular duct data can be reduced using the hydraulic diameter or any arbitrarily defined length scale. The proposed method is what is needed to reconcile such data with those for circular tubes. With the hydraulic diameter, the critical friction factor almost converges to a universal value for all passages and the correction is simply that required to account for the difference in critical Reynolds number. By contrast, with any other linear parameter, two corrections are needed to compensate for variations in critical friction factor and Reynolds number. Application of the method to roughened passages is discussed.

scholarly journals COMPARISON ANALYSIS OF CORRELATIONS FOR INTERFACIAL FRICTION FACTOR APPLIED IN GAS-LIQUID ANNULAR FLOW IN VERTICAL PIPES

2017 ◽  
Vol 16 (2) ◽  
pp. 54 ◽  
Author(s):  
C. F. de Paula Jr. ◽  
L. E. M. Lima
Keyword(s):  
Experimental Data ◽  
Friction Factor ◽  
Annular Flow ◽  
Interfacial Shear Stress ◽  
Interfacial Friction ◽  
Gas Flows ◽  
Steam Generation ◽  
Definition Of ◽  
Liquid Flows ◽  
Different Characteristics

Gas-liquid flows in pipes can occur in the form of an annular pattern in which the liquid flows as a thin film at pipe wall and the gas flows as a core in pipe center. This flow pattern is often encountered at boiling and condensation processes, for example, in industries of steam generation, cooling or petroleum. In annular flow, the interfacial friction factor is one of the important closing parameters for the definition of the interfacial shear stress and consequently the pressure gradient. In the literature, several correlations are found to estimate the interfacial friction factor. The main objective of this work is to carry out a comparative analysis of some these correlations against experimental data also obtained from the literature. The features and limitations of each correlation were observed, as well as the accuracy of each in relation to experimental data. The results obtained demonstrate that correlations analyzed, present relatively satisfactory results, despite the different characteristics of the correlations, however, it is necessary to carry out more extensive analyses involving others correlations and sets of experimental data.

Frictional Characteristics of Microchannel Gas Flow

2003 ◽  
Author(s):  
Abdullahel Bari ◽  
Jae-Mo Koo ◽  
Linan Jiang ◽  
Jay Paidipati ◽  
Kenneth E. Goodson
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Friction Factor ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Hydraulic Diameter ◽  
Transition To Turbulence ◽  
Gas Flows ◽  
Design And Development ◽  
Predicted Values

The improved rates of heat transfer in microchannel gas flows are promising for the design and development of microfluidic systems. This research focuses on the flow characteristics of air in rectangular micro/minichannels at moderate velocities (∼100 m/sec). The 50.8 mm long channels vary from approximately 266 μm to 1090 μm in hydraulic diameter, and the aspect ratio ranges from 0.1 to 0.75. The value of Re ranged from 250 to 4300, with the intention of studying the transition to turbulence. The friction factor is found to be higher than predicted values for Re < 1400 and lower when Re > 1400 suggesting earlier transition to turbulence.

Investigation of laminar flow frictional losses in a large-hydraulic-diameter pipe and annulus

2005 ◽  
Vol 219 (1) ◽  
pp. 53-60
Author(s):  
P Suresh Kumar
Keyword(s):  
Reynolds Number ◽  
Laminar Flow ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Low Reynolds Numbers ◽  
Friction Factors ◽  
Diameter Pipe ◽  
High Reynolds ◽  
Different Diameters

In the present work an experimental study has been carried out to study the friction factor variation with Reynolds number for laminar flow in a large-hydraulic-diameter pipe and annulus. It is found that for low Reynolds numbers the friction factors are large than those reported in the literature for small-hydraulic-diameter pipe and annulus. Large hydrostatic pressure variation along the circumferential direction causes a different flow pattern in a large-hydraulic-diameter duct and may be why the present results do not match those reported in the literature. A correlation has been proposed in the present paper which is being developed using the present experimental results for both pipe and annulus to correlate the friction factor as a function of Reynolds number and a newly denned Jaga number Jg. An analysis has been carried out using the currently developed friction factor correlations to study how the friction factor will vary for different fluids and different diameters of the pipe and annulus. It is observed that, for high Reynolds numbers ( Re > 100), small-hydraulic-diameter duct and fluids with a large kinematic viscosity, the present correlations show good agreement with the results reported in the literature.

Comments on Compressor Efficiency Scaling With Reynolds Number and Relative Roughness

1989 ◽  
Author(s):  
Terry Wright
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Friction Factor ◽  
Model Test ◽  
Large Scale ◽  
Recent Literature ◽  
Test Results ◽  
Relative Roughness ◽  
Scaling Algorithms ◽  
Compressor Efficiency

The background and literature on scaling of model test results to predict the performance of large scale turbomachines are presented and discussed in the context of both industry restrictions and recent improvements in analytical rigor and accuracy of scaling algorithms. The variety and disparity of methods developed before about 1970 is illustrated and plausible explanation is offered to account for the broad differences. The more recent literature is considered and the older exponential algorithms for scaling are reconciled with the current methods based on friction factor correlations. A simpler form is developed in terms of either exponential or friction factor formulations which includes the influence of Reynolds Number, relative roughness and fixed, friction-independent losses. This method is compared to the recently developed algorithms and to experimental data taken from the literature.

A Novel Explicit Equation for Friction Factor in Smooth and Rough Pipes

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Atakan Avci ◽  
Irfan Karagoz
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Entire Range ◽  
Present Model ◽  
Good Prediction ◽  
Explicit Equation ◽  
Relative Roughness ◽  
Logarithmic Velocity Profile

In this paper, we propose a novel explicit equation for friction factor, which is valid for both smooth and rough wall turbulent flows in pipes and channels. The form of the proposed equation is based on a new logarithmic velocity profile and the model constants are obtained by using the experimental data available in the literature. The proposed equation gives the friction factor explicitly as a function of Reynolds number and relative roughness. The results indicate that the present model gives a very good prediction of the friction factor and can reproduce the Colebrook equation and its Moody plot. Therefore, the new approximation for the friction factor provides a rational, accurate, and practically useful method over the entire range of the Moody chart in terms of Reynolds number and relative roughness.

Experiments on laminar flow in curved channels of square section

1971 ◽  
Vol 48 (3) ◽  
pp. 417-422 ◽  
Author(s):  
J. A. Baylis
Keyword(s):  
Reynolds Number ◽  
Numerical Analysis ◽  
Laminar Flow ◽  
Friction Factor ◽  
Experimental Results ◽  
Radius Of Curvature ◽  
Dean Number ◽  
Rectangular Section ◽  
Curved Channels ◽  
Channel Dimension

Recently Cheng & Akiyama (1970) published a numerical analysis of laminar flow in curved channels of square and rectangular section. Experimental results are presented here for flow in curved channels of square section. The channels were toroidal in shape, and the flow was driven electromagnetically. Various ratios of the channel dimension d to the channel radius of curvature, R, were used to investigate the dependence of friction factor, f, on the Dean number K, and the Reynolds number, Re. For 5 × 102 < K < 7 × 104 the formula (fRe) = 1·51 K½ was found to fit all the results, although R/d was varied from 17·5 down to the low value of 1·75. At lower values of K the analysis of Cheng & Akiyama was approximately validated.

Experiment Study and Numerical Analysis of Flow and Heat Transfer in (110) Silicon Base Microchannel

2008 ◽  
Vol 594 ◽  
pp. 351-356
Author(s):  
Sheng Hong Tsai ◽  
Yu Tang Chen
Keyword(s):  
Reynolds Number ◽  
Numerical Analysis ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Hydraulic Diameter ◽  
Working Fluid ◽  
Surface Geometry ◽  
Micro Scale ◽  
Conductive Surface ◽  
Flow Phenomena

Microchannel heat sink is fabricated on silicon wafer by anisotropic etching, and used Pyrex #7740 as a transparent cover that integrated by anodic bonding. Rectangular microchannel presents the flow phenomena of fluid in micro scale, and this study focus on the boundary conditions which hydraulic diameter (Dh) is from 80m to 350m and Aspect ratio is from 0.24~7.8 of working fluid (DI water). While the size of microchannel is decreasing, laminar flow occurs on the low Reynolds number, which caused by the interaction of viscosity and friction on boundary layer. Sequentially, the influence of dimension decreasing on microchannel that induced transition and turbulent flow in early stage as Reynolds number is still in the range of 600~800. Pressure drop is high (2 bar) when fluid flows through the micro channel, and flux is constrained by the flow resistance during experiment operating. In this study, it takes effect by increasing aspect ratio to reduce pressure drop and enlarge the conductive surface. Geometry of microchannel, hydraulic diameter, and aspect ratio are the key factors in flow phenomena investigation. This research presents the difference between micro scale flow and traditional pipe flow by consideration of Reynolds number. By using computer aided engineering to optimize the aspect ratio of microchannel, which can find the maximum conductive surface under the limitation of pressure drop. The best value of aspect ratio is 0.88~1.22. The simulation result makes good sequence with experiment data. Based on this methodology, numerical analysis can be used to design the optimal microchannel on wafer for cooling hot spot.

scholarly journals Prediction and Measurement of Pressure Drop of Water Flowing in a Rectangular Microchannel

2013 ◽  
Vol 3 (2) ◽  
Author(s):  
M. Mirmanto
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Inlet Temperature ◽  
Mean Velocity ◽  
Rectangular Microchannel ◽  
The Mean ◽  
Poiseuille Number

This paper presents experimental results of pressure drop measurement and prediction of water flowing through a copper rectangular microchannel with a hydraulic diameter of 437 µm. The aim of this work is to identify discrepancies between experimental data and macrochannel theory. An inlet temperature of 60oC was kept constant at the channel entrance and the experiments were performed with Reynolds numbers (based on the mean velocity and hydraulic diameter) ranging up to 4500.  The results show that the pressure drop prediction agrees with the theory. However, the trend of Poiseuille number with the Reynolds number was not constant for laminar flow. This could be due to the entrance effect. Moreover, the friction factor theory could predict the experimental data for turbulent flow. Thus, in this experiment, the theory for flow in macro passages is still applicable.

scholarly journals Theoretical research of friction factor in hydraulically smooth pipes

2021 ◽  
Vol 280 ◽  
pp. 10009
Author(s):  
Mykola Khlapuk ◽  
Olexander Bezusyak ◽  
Liubov Volk ◽  
Zelu Zhang
Keyword(s):  
Experimental Data ◽  
Reynolds Number ◽  
Friction Factor ◽  
Dimensional Analysis ◽  
Research Data ◽  
Geometric Parameters ◽  
Theoretical Research ◽  
Flow Discharge ◽  
Head Losses ◽  
Inner Surface

The paper presents the disclosure of the problem of calculating the friction factor. This problem exists in the calculations of head losses for a given flow discharge and the geometric parameters of the pipes. The analysis of the formulas recommended by known scientists is described. The article also presents the shortcomings of the formulas and the variance of the adequacy of the experimental data. These research data were obtained by J. Nikuradze for smooth pipes. We obtained a formula based on the method of dimensional analysis. This formula characterizes the inner surface of the pipes. Also, this formula describes the change in the friction factor from the Reynolds number. The accuracy of calculating the obtained formula is higher than the accuracy of existing formulas.

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