An Experimental and Analytical Investigation of Friction Factors for Fully Developed Flow in Internally Finned Triangular Ducts

1986 ◽  
Vol 108 (3) ◽  
pp. 507-512 ◽  
Author(s):  
H. Chegini ◽  
S. K. Chaturvedi
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Analytical Investigation ◽  
Momentum Equation ◽  
Fully Developed Flow ◽  
Finite Difference Technique ◽  
Friction Factors ◽  
Experimental Values ◽  
Good Agreement

Friction factors for fully developed flow in triangular ducts with fins of various height and width are investigated for Reynolds numbers ranging from 150 to 90,000. Two triangular ducts having apex angles of 60 and 38.8 deg are studied. Results are presented in the form of standard plots of friction factor as a function of Reynolds number. Friction factor values for the smooth triangular duct cases are in good agreement with the existing results. For the finned-duct cases, the fully developed axial velocity profiles in laminar flow are determined by solving the x-momentum equation iteratively by the Gauss–Seidel finite-difference technique. The theoretically determined friction factors for these cases are in good agreement with the experimental values of friction factors based on pressure drop measurements.

Numerical and Experimental Analysis of Turbulent Flow in Corrugated Pipes

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
Henrique Stel ◽  
Rigoberto E. M. Morales ◽  
Admilson T. Franco ◽  
Silvio L. M. Junqueira ◽  
Raul H. Erthal ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Velocity Magnitude ◽  
Geometric Configurations ◽  
Corrugated Surfaces ◽  
Friction Factors

This article describes a numerical and experimental investigation of turbulent flow in pipes with periodic “d-type” corrugations. Four geometric configurations of d-type corrugated surfaces with different groove heights and lengths are evaluated, and calculations for Reynolds numbers ranging from 5000 to 100,000 are performed. The numerical analysis is carried out using computational fluid dynamics, and two turbulence models are considered: the two-equation, low-Reynolds-number Chen–Kim k-ε turbulence model, for which several flow properties such as friction factor, Reynolds stress, and turbulence kinetic energy are computed, and the algebraic LVEL model, used only to compute the friction factors and a velocity magnitude profile for comparison. An experimental loop is designed to perform pressure-drop measurements of turbulent water flow in corrugated pipes for the different geometric configurations. Pressure-drop values are correlated with the friction factor to validate the numerical results. These show that, in general, the magnitudes of all the flow quantities analyzed increase near the corrugated wall and that this increase tends to be more significant for higher Reynolds numbers as well as for larger grooves. According to previous studies, these results may be related to enhanced momentum transfer between the groove and core flow as the Reynolds number and groove length increase. Numerical friction factors for both the Chen–Kim k-ε and LVEL turbulence models show good agreement with the experimental measurements.

Turbulence Model Investigation of Water Flow in Rough Micro Channels

2009 ◽  
Author(s):  
Shobeir Aliasghar Zadeh ◽  
Rolf Radespiel
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Rectangular Cross Section ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Micro Channel ◽  
Conventional Theory ◽  
Roughness Elements ◽  
Micro Channels ◽  
Experimental Values

Three-dimensional laminar and turbulent water flows in smooth and rough micro channels with rectangular cross-section were numerically simulated. The hydraulic diameter of the smooth micro channel is 190 μm and 191 μm for the rough one. The roughness inducing surfaces, which were modelled by three rectangular elements placed on the sidewall of the micro channel, are 50 μm high and 50 μm wide. The simulations were conducted for Reynolds numbers between 100 and 4000. The effects on the friction factor and flow characteristics due to the roughness elements, varying Reynolds numbers and low-Reynolds number turbulence models were investigated and compared with the experimental values reported by Hao et al. [1]. Furthermore, the velocity profiles in various Reynolds number and flow regimes have been compared with μPIV measurements. At Reynolds numbers less than 2100 the computed friction factors in the smooth micro channel agree well with the measurements and the values of the conventional theory. For the micro channel with roughness elements, the friction factor approaches the value of measurements and conventional theory, when Re < 900. Transition from laminar to turbulent flow occurs at about Reynolds numbers of 2100 and 900 in smooth and rough micro channel, respectively. Comparison of simulated results using the Spalart-Allmaras and SST K-ω turbulence models with experimental values show good agreement. By contrast, the K-ε model overestimates the pressure loss in micro channels.

Experimental Determination of Friction Factors for Straight and Curved Microchannels

2010 ◽  
Vol 5 (3) ◽  
pp. 63-70
Author(s):  
Vladimir М. Aniskin ◽  
Kseniya V. Adamenko ◽  
Anatoliy A. Maslov
Keyword(s):  
Friction Factor ◽  
Software Package ◽  
Reference Value ◽  
Reynolds Numbers ◽  
Experimental Results ◽  
Friction Factors ◽  
Inner Diameter ◽  
Curved Section ◽  
Good Agreement

This article presents experimental results of determining the friction factors for two microchannels with circular crosssection: rectilinear and curvilinear. The inner diameter of channels in both cases was 100 microns. The Reynolds numbers ranged from 110 to 2216. Pressure measurement was carried out simultaneously in four locations along the channel. Friction factor for the straight microchannel was in good agreement with the theoretical value for the round smooth tubes. For the curved microchannel, the value of friction factor of the curved section was 17 percent less than the reference value for smoothly curved tubes. The experimental results are compared with calculations which were made using the software package Fluent

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.

Friction-Factor Characteristics for Narrow Channels With Honeycomb Surfaces

1992 ◽  
Vol 114 (4) ◽  
pp. 714-721 ◽  
Author(s):  
T. W. Ha ◽  
G. L. Morrison ◽  
D. W. Childs
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Narrow Channel ◽  
Test Results ◽  
Jump Phenomenon ◽  
Narrow Channels ◽  
Friction Factors ◽  
Factor Data

The experimental determination of friction-factors for the flow of air in a narrow channel lined with various honeycomb geometries has been carried out. Test results show that, generally, the friction-factor is nearly constant or slightly decreases as the Reynolds number increases, a characteristic common to turbulent flow in pipes. However, in some test geometries this trend is remarkably different. The friction factor dramatically drops and then rises as the Reynolds number increases. This phenomenon can be characterized as a “friction-factor jump.” Further investigations of the acoustic spectrum and friction-factor measurements for a broad range of Reynolds numbers indicate that the “friction-factor jump” phenomenon is accompanied by an onset of a normal mode resonance excited coherent flow fluctuation structure, which occurs at Reynolds number of the order of 104. The purpose of this paper is not to present the friction-factor data but to explain the friction-factor-jump phenomenon and friction-factor characteristics.

Heat Transfer And Pressure Drop Of An Angled Discrete Turbulator At Elevated Reynolds Numbers Up To 900,000

2021 ◽  
pp. 1-29
Author(s):  
Sam Ghazi-Hesami ◽  
Dylan Wise ◽  
Keith Taylor ◽  
Peter Ireland ◽  
Étienne Robert
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Friction Factor ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Enhance Heat Transfer ◽  
Near Surface ◽  
Number Range ◽  
Smooth Channel

Abstract Turbulators are a promising avenue to enhance heat transfer in a wide variety of applications. An experimental and numerical investigation of heat transfer and pressure drop of a broken V (chevron) turbulator is presented at Reynolds numbers ranging from approximately 300,000 to 900,000 in a rectangular channel with an aspect ratio (width/height) of 1.29. The rib height is 3% of the channel hydraulic diameter while the rib spacing to rib height ratio is fixed at 10. Heat transfer measurements are performed on the flat surface between ribs using transient liquid crystal thermography. The experimental results reveal a significant increase of the heat transfer and friction factor of the ribbed surface compared to a smooth channel. Both parameters increase with Reynolds number, with a heat transfer enhancement ratio of up to 2.15 (relative to a smooth channel) and a friction factor ratio of up to 6.32 over the investigated Reynolds number range. Complementary CFD RANS (Reynolds-Averaged Navier-Stokes) simulations are performed with the κ-ω SST turbulence model in ANSYS Fluent® 17.1, and the numerical estimates are compared against the experimental data. The results reveal that the discrepancy between the experimentally measured area averaged Nusselt number and the numerical estimates increases from approximately 3% to 13% with increasing Reynolds number from 339,000 to 917,000. The numerical estimates indicate turbulators enhance heat transfer by interrupting the boundary layer as well as increasing near surface turbulent kinetic energy and mixing.

Effect of Surface Roughness on Gaseous Flow Through Microchannels

2000 ◽  
Author(s):  
Stephen E. Turner ◽  
Hongwei Sun ◽  
Mohammad Faghri ◽  
Otto J. Gregory
Keyword(s):  
Surface Roughness ◽  
Reynolds Number ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Helium Flow ◽  
Local Pressure ◽  
Aspect Ratios ◽  
Corrugated Surfaces ◽  
Flow Through ◽  
Effect Of Surface

Abstract This paper presents an experimental investigation on nitrogen and helium flow through microchannels etched in silicon with hydraulic diameters between 10 and 40 microns, and Reynolds numbers ranging from 0.3 to 600. The objectives of this research are (1) to fabricate microchannels with uniform surface roughness and local pressure measurement; (2) to determine the friction factor within the locally fully developed region of the microchannel; and (3) to evaluate the effect of surface roughness on momentum transfer by comparison with smooth microchannels. The friction factor results are presented as the product of friction factor and Reynolds number plotted against Reynolds number. The following conclusions have been reached in the present investigation: (1) microchannels with uniform corrugated surfaces can be fabricated using standard photolithographic processes; and (2) surface features with low aspect ratios of height to width have little effect on the friction factor for laminar flow in microchannels.

Friction factor analysis for a nanofluid circulating in a microchannel filled with a homogeneous porous medium

2022 ◽  
Author(s):  
Francisco Fernando Hernandez ◽  
Federico Mendez ◽  
Jose Joaquin Lizardi ◽  
Ian Guillermo Monsivais
Keyword(s):  
Porous Medium ◽  
Friction Factor ◽  
Porous Matrix ◽  
Velocity Profiles ◽  
Momentum Equation ◽  
Volumetric Concentration ◽  
Forchheimer Equation ◽  
Viscosity Models ◽  
Friction Factors ◽  
Homogeneous Porous Medium

Abstract This work presents the numerical solution for different velocity profiles and friction factors on a rectangular porous microchannel fully saturated by the flow of a nanofluid introducing different viscosity models, including one nanofluid density model. The Darcy-Brinkman-Forchheimer equation was used to solve the momentum equation in the porous medium. The results show that the relative density of the fluid, the nanoparticle diameters and their volumetric concentration have a direct influence on the velocity profiles only when the inertial effects caused by the presence of the porous matrix are important. Finally, it was found that only viscosity models that depend on temperature and nanoparticle diameter reduce the friction factor by seventy percent compared to a base fluid without nanoparticles; furthermore, these models show a velocity reduction of even ten percent along the symmetry axis of the microchannel.

Friction Factor Behavior From Flat-Plate Tests of 12.15 mm Diameter Hole-Pattern Roughened Surfaces

2011 ◽  
Author(s):  
Thanesh Deva Asirvatham ◽  
Dara W. Childs ◽  
Stephen Phillips
Keyword(s):  
Reynolds Number ◽  
Flat Plate ◽  
Friction Factor ◽  
Dynamic Pressure ◽  
Reynolds Numbers ◽  
Stagnation Temperature ◽  
Flat Plates ◽  
Number Range ◽  
Current Test ◽  
Rough Plate

A flat-plate tester is used to measure the friction-factor behavior for a hole-pattern-roughened surface facing a smooth surface with compressed air as the medium. Measurements of mass flow rate, static pressure drop and stagnation temperature are carried out and used to find a combined (stator + rotor) Fanning friction factor value. In addition, dynamic pressure measurements are made at four axial locations at the bottom of individual holes of the rough plate and at facing locations in the smooth plate. The description of the test rig and instrumentation, and the procedure of testing and calculation are explained in detail in Kheireddin in 2009 and Childs et al. in 2010. Three hole-pattern flat-plates with a hole-pattern diameter of 12.15 mm were tested having depths of 0.9, 1.9, and 2.9 mm. Tests were done with clearances at 0.254, 0.381, and 0.653 mm, and inlet pressures of 56, 70 and 84 bar for a range of pressure ratios, yielding a Reynolds-number range of 100,000 to 800,000. The effects of Reynolds number, clearance, inlet pressure, and hole depth on friction factor are studied. The data are compared to friction factor values of three hole-pattern flat-plates with 3.175 mm diameter holes with hole depths of 1.9, 2.6, and 3.302 mm tested in the same rig described by Kheireddin in 2009. The test program was initiated mainly to investigate a “friction-factor jump” phenomenon cited by Ha et al. in 1992 in test results from a flat-plate tester using facing hole-pattern plates where, at elevated values of Reynolds numbers, the friction factor began to increase steadily with increasing Reynolds numbers. Friction-factor jump was not observed in any of the current test cases.

Analyses of Liquid Flow in Micro-Conduits

2004 ◽  
Author(s):  
Junemo Koo ◽  
Clement Kleinstreuer
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Friction Factor ◽  
Viscous Dissipation ◽  
Wall Slip ◽  
Reynolds Numbers ◽  
Darcy Number ◽  
Low Reynolds Numbers ◽  
Dissipation Effect ◽  
Liquid Flows

Experimental observations of liquid microchannel flow are reviewed and results of computer experiments concerning channel entrance, wall slip, non-Newtonian fluid, surface roughness, viscous dissipation and flow instability effects on the friction factor are discussed Specifically, based on numerical friction factor analyses, the entrance effect should be taken into account for any microfluidic system. It is a function of channel length, aspect ratio and the Reynolds number. Non-Newtonian fluid flow effects are expected to be important for polymeric liquids and dense particle suspension flows. The wall-slip effect is negligible for liquid flows. For relatively low Reynolds numbers, i.e., Re > 1,200, onset to instabilities may have to be considered because of possible geometric non-uniformities, including a contraction and/or bend at the microchannel inlet as well as substantial surface roughness. Significant roughness effects, described with a new porous medium layer (PML) model, are a function of the Darcy number, the Reynolds number and cross-sectional configurations. This model was applied to micro-scale liquid flows in straight channels, tubes and rotating cylinders, and validated with experimental data sets. In contrast to published models, PML model simulations yield both an increase and decrease of the friction factor depending on the Darcy number. Viscous dissipation in microchannels is a strong function of the channel aspect ratio, Reynolds number, Eckert number, Prandtl number, and conduit hydraulic diameter. Specifically, viscous dissipation effects are quite important for fluids with low specific heat capacities and high viscosities, even for very low Reynolds numbers, i.e., ReD < 1. The viscous dissipation effect was found to decrease as the fluid temperature increases. As the aspect ratio deviates from unity, the viscous dissipation effect increases. It was found that ignoring the viscous dissipation effect could ultimately affect friction factor measurements for flows in micro-conduits. This could imply a significant amount of viscous heat generation and, for example, may diminish a projected micro-heat-exchanger performance.

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