Friction Factor Measurements in an Equally Spaced Triangular Array of Circular Tubes

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Peter Vassallo ◽  
Paul Symolon
Keyword(s):  
Reynolds Number ◽  
Friction Factor ◽  
Test Data ◽  
Tube Bundle ◽  
Cross Flow ◽  
Outer Diameter ◽  
Number Range ◽  
New Correlation ◽  
Reynolds Number Range ◽  
Factor Data

Friction factor data for adiabatic cross flow of water in a staggered tube array were obtained over a Reynolds number range (based on hydraulic diameter and gap velocity) of about 10,000–250,000. The tubes were 12.7mm(0.5in.) outer diameter in a uniformly spaced triangular arrangement with a pitch-to-diameter ratio of 1.5. The friction factor was compared to several literature correlations and was found to be best matched by the Idelchik correlation. Other correlations were found to significantly vary from the test data. Based on the test data, a new correlation is proposed for this tube bundle geometry, which covers the entire Reynolds number range tested.

Study on In-Flow Vibration of Cylinder Arrays Caused by Cross Flow

2011 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Keisuke Nishimura ◽  
Yoshiaki Fujita ◽  
Chihiro Kohara
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Cross Flow ◽  
Thin Plates ◽  
Streamwise Direction ◽  
Number Range ◽  
Direction Transverse ◽  
Drag Forces ◽  
Cylinder Arrays ◽  
Reynolds Number Range

The authors have studied the in-flow vibration phenomena of cylinder arrays caused by cross-flow in the low Reynolds number range around Re=800. This Reynolds number range has been studied because it is the range where symmetric vortex shedding occurs. This report is our first trial to study the in-line fluidelastic vibration of cylinder arrays. In initial tests, the flow velocity was increased up to the maximum achievable level by the test equipment. However, it was found that the array’s cantilever tube supports resulted in large static tube deflections due to static drag forces. The cylinder array tube supports have therefore been replaced by thin plates supported at both ends. The cylinders are set to be flexible both in the streamwise direction and the direction transverse to the flow. The obtained results of these two patterns are also compared with previous cantilevered data. The origin of the observed vibrations whether a self-induced mechanism or vortex shedding is discussed in detail.

Experimental Measurements and Computations of Heat Transfer and Flow Friction Factor in a Staggered Pin Fin Array

2001 ◽  
Author(s):  
Forrest E. Ames ◽  
Christopher S. Solberg ◽  
Michael D. Goman ◽  
Daniel J. Curtis ◽  
Bradley T. Steinbrecker
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Experimental Measurements ◽  
Wall Region ◽  
Number Range ◽  
Flow Friction ◽  
Pin Fin ◽  
Factor Data ◽  
Pin Fin Array

Abstract This paper presents experimental measurements and CFD calculations for heat transfer and flow friction factor in a staggered pin fin array. The heat transfer and flow friction factor data are taken in a constant temperature facility and are acquired over a Reynolds number range of 1500 to 31,000. The array is comprised of eight rows of pins spaced at 2.5 diameters in the streamwise and spanwise directions with a pin height of two diameters. The heat transfer data are presented in terms of both average array data and row resolved data. The data accurately match the recent pin fin correlation of Chyu et at. [1] and extend its range to lower Reynolds numbers. The flow friction factor data accurately match the low and high Reynolds number data of Metzger et al. [2]. The steady state computations for a 2D and 3D representation of the geometry are performed and compared with archival correlations and the present data. The calculations are performed using a general purpose commercial solver (FLUENT 5.3 [3]) and apply the realizable k-ε model of Shih et al. [4] along with a two layer model which solves the k equation in the near wall region. Generally, the calculations perform relatively well with the 2D calculations matching the literature correlations slightly better than the 3D calculations.

scholarly journals Numerical simulation of vortex induced vibration in heat exchanger tube bundle at low Reynolds number

2017 ◽  
Vol 14 (2) ◽  
pp. 77-91
Author(s):  
Asif Khan ◽  
Shahab Khushnood ◽  
Najum Ul Saqib ◽  
Imran Sajid Shahid
Keyword(s):  
Reynolds Number ◽  
Heat Exchanger ◽  
Stokes Equations ◽  
Tube Bundle ◽  
Lift Coefficient ◽  
Flow Analysis ◽  
Cross Flow ◽  
Heat Exchanger Tube ◽  
Number Range ◽  
Exchanger Tube

It is sound recognized that when the tube is forced to vibrate or is naturally excited to sufficient amplitudes by flow-induced forces, cyclones peeling phenomena arises at downstream of a tube which clues to vibration in the tube. Two-dimensional numerical recreation model for the computation of flow induced vibration of heat exchanger tube bundle imperiled to cross- flow is proficient in current research. Computational Fluid Dynamics (CFD) tool, GAMBIT (grid generation) and ANSYS FLUENT (fluid flow analysis) are operated during numerical investigations. k-epsilon model is used to solve the Navier– Stokes equations. Lift coefficient graph derived from analysis is used to predict the vortex shedding frequency using Fast Fourier Transform (FFT). The results of flow rate, Strouhal number, Reduced velocity, Natural frequency of tube as found from the experimental data has been verified numerically for a Reynolds number range of 4.45 × 104<Re <4.65 × 104 . It is concluded that experimental results are well in agreement with the numerical results.

Low Reynolds Number Turbulent Flow in Large Aspect Ratio Rectangular Ducts

1971 ◽  
Vol 93 (2) ◽  
pp. 296-299 ◽  
Author(s):  
G. S. Beavers ◽  
E. M. Sparrow ◽  
J. R. Lloyd
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Equivalent Diameter ◽  
Large Aspect Ratio ◽  
Number Range ◽  
Aspect Ratios ◽  
Reynolds Number Range ◽  
Low Reynolds

Experiments are reported on fully developed turbulent flows at low Reynolds numbers in rectangular ducts of large aspect ratio. Six ducts, with aspect ratios between 15.5:1 and 35.0:1, were employed for the investigation, covering a Reynolds number range from 5,000 to 27,000. A friction factor, Reynolds number relation expressed as f = 0.507 R−0.30 was found to be an excellent representation of the experimental data when the equivalent diameter was used as the characteristic length dimension. The Blasius and Prandtl circular tube friction factor relations, generalized by use of the equivalent diameter, gave results within 5 percent or better of the aforementioned correlation over the Reynolds number range of this investigation.

Vortex shedding from a circular cylinder in moderate-Reynolds-number shear flow

1980 ◽  
Vol 101 (4) ◽  
pp. 721-735 ◽  
Author(s):  
Masaru Kiya ◽  
Hisataka Tamura ◽  
Mikio Arie
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Shear Flow ◽  
Vortex Shedding ◽  
Transverse Velocity ◽  
Number Range ◽  
Uniform Shear ◽  
Reynolds Number Range ◽  
Moderate Reynolds Number ◽  
Shear Parameter

The frequency of vortex shedding from a circular cylinder in a uniform shear flow and the flow patterns around it were experimentally investigated. The Reynolds number Re, which was defined in terms of the cylinder diameter and the approaching velocity at its centre, ranged from 35 to 1500. The shear parameter, which is the transverse velocity gradient of the shear flow non-dimensionalized by the above two quantities, was varied from 0 to 0·25. The critical Reynolds number beyond which vortex shedding from the cylinder occurred was found to be higher than that for a uniform stream and increased approximately linearly with increasing shear parameter when it was larger than about 0·06. In the Reynolds-number range 43 < Re < 220, the vortex shedding disappeared for sufficiently large shear parameters. Moreover, in the Reynolds-number range 100 < Re < 1000, the Strouhal number increased as the shear parameter increased beyond about 0·1.

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.

scholarly journals Asymmetrical Split-and-Recombine Micromixer with Baffles

Micromachines ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 844 ◽  
Author(s):  
Wasim Raza ◽  
Kwang-Yong Kim
Keyword(s):  
Reynolds Number ◽  
Geometrical Parameters ◽  
Mixed Species ◽  
Mixing Index ◽  
Number Range ◽  
Mixing Performance ◽  
Curved Channels ◽  
Advection Diffusion Equation ◽  
Advection Diffusion ◽  
Reynolds Number Range

The present work proposes a planar micromixer design comprising hybrid mixing modules of split-and-recombine units and curved channels with radial baffles. The mixing performance was evaluated numerically by solving the continuity and momentum equations along with the advection-diffusion equation in a Reynolds number range of 0.1–80. The variance of the concentration of the mixed species was considered to quantify the mixing index. The micromixer showed far better mixing performance over whole Reynolds number range than an earlier split-and-recombine micromixer. The mixer achieved mixing indices greater than 90% at Re ≥ 20 and a mixing index of 99.8% at Re = 80. The response of the mixing quality to the change of three geometrical parameters was also studied. A mixing index over 80% was achieved within 63% of the full length at Re = 20.

Performance characteristics of a chilled water spirally coiled finned tube in cross flow for air conditioning applications

2012 ◽  
Vol 227 (2) ◽  
pp. 320-331 ◽  
Author(s):  
Abdalla Gomaa ◽  
Wael IA Aly ◽  
Ashraf Mimi Elsaid ◽  
Eldesuki I Eid
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Friction Factor ◽  
Flow Direction ◽  
Cross Flow ◽  
Finned Tube ◽  
Performance Characteristics ◽  
Curvature Ratio ◽  
Coiled Tube ◽  
Chilled Water

In the present study, the thermo-fluid characteristics of a spirally coiled finned tube in cross flow were experimentally investigated. This investigation covered different design parameters such as curvature ratio, air velocity, flow direction, fin pitch and flow rate of chilled water on performance characteristics of the spirally coiled finned tube. The purpose was to evaluate this kind of the spirally finned-tube cooling coils with particular reference to bare coiled tube. Six test specimens were designed and manufactured with curvature ratios of 0.027, 0.03, 0.04, tube pitches of 18, 20, 30 mm and fin pitches of (33, 22, 11 mm). Experiments were carried out in a pilot wind tunnel with air Reynolds number ranging from 35,500 to 245,000. Two types of chilled water flow directions entering the spiral coil were tested at Reynolds number ranging from 5700 to 25,300, the first was inward flow direction and the other was to outward flow direction. The results revealed that the inward flow direction has significant enhancement effect on the Nusselt number compared with outward flow direction by 37.0% for tube pitch of 18 mm and curvature ratio of 0.027. The decrease of fin pitch enhances the Nusselt number by 21.92% on expense of friction factor by 10.9%. In the case of spirally coiled bare tube, the decreasing of the curvature ratio increases air side Nusselt number by 33.69% on expense of friction factor by 18.36%. General correlations of Nusselt number and air friction factor for bare and finned spirally coiled tube were correlated based on reported experimental data.

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