Turbulent Flow Heat Transfer and Friction in a Rectangular Channel With Varying Numbers of Ribbed Walls

1997 ◽  
Vol 119 (2) ◽  
pp. 374-380 ◽  
Author(s):  
P. R. Chandra ◽  
M. E. Niland ◽  
J. C. Han
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Channel Length ◽  
Diameter Ratio ◽  
Hydraulic Diameter ◽  
Published Data ◽  
Flow Heat ◽  
Turbulent Air Flow

An experimental study of wall heat transfer and friction characteristics of a fully developed turbulent air flow in a rectangular channel with transverse ribs on one, two, and four walls is reported. Tests were performed for Reynolds numbers ranging from 10,000 to 80,000. The pitch-to-rib height ratio, P/e, was kept at 8 and rib height-to-channel hydraulic diameter ratio, e/Dh, was kept at 0.0625. The channel length-to-hydraulic diameter ratio, L/Dh, was 15. The heat transfer coefficient and friction factor values were enhanced with the increase in the number of ribbed walls. The friction roughness function, R(e+), was almost constant over the entire range of tests performed and was within comparable limits of the previously published data. The heat transfer roughness function, G(e+), decreased with additional ribbed walls and compared well with previous work in this area. Friction data obtained experimentally for the case with four ribbed walls compared well with the values predicted by the assumed theoretical relationship used in the present study and past publications. Results of this investigation could be used in various applications of internal channel turbulent flows involving different numbers of roughened walls.

Turbulent Flow Heat Transfer and Friction in a Rectangular Channel With Varying Number of Ribbed Walls

1995 ◽  
Author(s):  
Pankaj R. Chandra ◽  
Michael E. Niland ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Turbulent Flows ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Channel Length ◽  
Diameter Ratio ◽  
Hydraulic Diameter ◽  
Published Data ◽  
Flow Heat ◽  
Turbulent Air Flow

An experimental study of wall heat transfer and friction characteristics of a fully-developed turbulent air flow in a rectangular channel with transverse ribs on one, two, and four walls is reported. Tests were performed for Reynolds numbers ranging from 10,000 to 80,000. The pitch-to-rib height ratio, P/e, was kept at 8 and rib height-to-channel hydraulic diameter ratio, e/Dh, was kept at 0.0625. The channel length-to-hydraulic diameter ratio, L/Dh, was 15. The heat transfer coefficient and friction factor values were enhanced with the increase in the number of ribbed walls. The friction roughness function, R(e+), was almost constant over the entire range of tests performed and was within comparable limits of the previously published data. The heat transfer roughness function, G(e+), decreased with additional ribbed walls and compared well with previous work in this area. Friction data obtained experimentally for the case with four ribbed walls compared well with the values predicted by the assumed theoretical relationship used in the present study and past publications. Results of this investigation could be used in various applications of internal channel turbulent flows involving different number of roughened walls.

Numerical and Experimental Investigation of Heat Transfer Coefficient and Friction Factor in Internal Channels With Fins

2015 ◽  
Author(s):  
Pramesh Regmi ◽  
Pankaj R. Chandra ◽  
Ning Zhang
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Turbulent Flows ◽  
Local Heat ◽  
Industrial Applications ◽  
Channel Length ◽  
Diameter Ratio ◽  
Hydraulic Diameter ◽  
Friction Characteristics ◽  
Wide Range

Surface heat transfer enhancement is widely used in a wide range of industrial applications. The turbulence created by the enhancement has significant effects on increasing the heat transfer. On the other hand, the surface enhancement usually causes a larger friction that leads to a larger pressure drop. In this study, an experimental investigation with computational verification of the wall heat transfer and the friction characteristics of a fully-developed turbulent air flow in a square channel with circular micro-fins was reported. The protuberances of 6.35×10−3 m diameter and 6.35×10−3 m height were placed in three different configurations. Tests were performed for the Reynolds numbers ranging from 27,000 to 96,000. The fin height-to-channel hydraulic diameter ratio, e/Dh, was kept at 0.125. The channel length-to-hydraulic diameter ratio, L/Dh, was 20. The heat transfer was enhanced using micro-fins as turbulence promoters. The computational analysis was also performed and found in close agreement with the experimental results. The simulations can be used in predicting local turbulence characteristics, thus the turbulence-heat transfer relationship. The simulation results can also predict the local heat and friction characteristics and in locating high temperature regions, or “hot spots,” which is beyond the potential of the experimental setup. This investigation could be helpful in applications concerning internal channel turbulent flows and involving micro-fins to boost heat transfer. Heat Exchangers, Air Compressors, Turbines are some of equipment where the results of this study can be utilized.

Augmented Heat Transfer in Square Channels With Parallel, Crossed, and V-Shaped Angled Ribs

1991 ◽  
Vol 113 (3) ◽  
pp. 590-596 ◽  
Author(s):  
J. C. Han ◽  
Y. M. Zhang ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Diameter Ratio ◽  
Hydraulic Diameter ◽  
Square Channel ◽  
Heat Transfer Augmentation ◽  
Better Than

The effect of the rib angle orientation on the local heat transfer distributions and pressure drop in a square channel with two opposite in-line ribbed walls was investigated for Reynolds numbers from 15,000 to 90,000. The square channel composed of ten isolated copper sections has a length-to-hydraulic diameter ratio of 20; the rib height-to-hydraulic diameter ratio is 0.0625; the rib pitch-to-height ratio equals 10. Nine rib configurations were studied: 90 deg rib, 60 and 45 deg parallel ribs, 60 and 45 deg crossed ribs, 60 and 45 deg ∨-shaped ribs, and 60 and 45 deg ∧-shaped ribs. The results show that the 60 deg (or 45 deg) ∨-shaped rib performs better than the 60 deg (or 45 deg) parallel rib and, subsequently, better than the 60 deg (or 45 deg) crossed rib and the 90 deg rib. The ∨-shaped rib produces the highest heat transfer augmentation, while the ∧-shaped rib generates the greatest pressure drop. The crossed rib has the lowest heat transfer enhancement and the smallest pressure drop penalty.

Heat Transfer and Friction Factor in a Square Channel With One, Two, or Four Inclined Ribbed Walls

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Soo Whan Ahn ◽  
Ho Keun Kang ◽  
Sung Taek Bae ◽  
Dae Hee Lee
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Height Ratio ◽  
Square Channel ◽  
Ribbed Channel ◽  
Nusselt Numbers ◽  
Channel Aspect Ratio ◽  
Turbulent Air Flow

An experimental study was carried out to investigate the heat transfer and friction characteristics of a fully developed turbulent air flow in a square channel with 45 deg inclined ribs on one, two, or four walls. Either two opposite walls or all four walls in the channel were heated. Tests were performed for Reynolds numbers (Re) ranging from 7600 to 24,900, the pitch to rib height ratio (P∕e) of 8.0, the rib height to channel hydraulic diameter ratio (e∕Dh) of 0.0667, and the channel aspect ratio of 1.0. The results show that the local Nusselt number and friction factor increase with the number of ribbed walls. With one ribbed wall, the Nusselt numbers on the ribbed side (B) were 50% and 63% greater than those on the adjacent smooth sides (L∕R) and the opposite smooth side (T), respectively. The Nusselt numbers, when the two opposite walls of a four-wall ribbed channel are heated, are found to be 1.49–1.52 times greater than those obtained when all four walls are heated.

Heat Transfer Experiments in High Aspect Ratio Rectangular Channel With Epoxied Short Pin Fins

1983 ◽  
Author(s):  
S. C. Arora ◽  
W. Abdel Messeh
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Temperature Drop ◽  
Diameter Ratio ◽  
Heat Transfer Surface ◽  
Published Data ◽  
Pin Fin ◽  
Pin Fins ◽  
The Cost ◽  
End Wall

In an attempt to reduce the cost of testing many configurations of short pin fins in a rectangular channel, a technique has been identified whereby the pins are epoxied to the end wall and can be easily removed to form a new configuration at the end of a test. Analytical and experimental results indicate that the temperature drop across a thin layer of epoxy (∼.005–.006 cm) (K = 22.5 W/m°C) with copper pin and endwalls was less than 1% of the heat transfer surface temperature. The technique was then used to test 4 pin fin configurations of height to diameter ratio of about unity. The heat transfer results showed excellent agreement with earlier published data, thus confirming the validity of this technique.

Effect of Rib Spacing on Heat Transfer in a Two Pass Rectangular Channel (AR=2:1) at High Rotation Numbers

2011 ◽  
Author(s):  
Jiang Lei ◽  
Je-Chin Han ◽  
Michael Huh
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Orientation Angle ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Transfer Enhancement ◽  
Flow Angle ◽  
Rotation Numbers ◽  
Rotating Channel

In this paper the effect of rib spacing on heat transfer in a rotating two-passage channel (AR=2:1) at orientation angle of 135° was studied. Parallel ribs were applied on leading and trailing walls of the rotating channel at the flow angle of 45°. The rib-height-to-hydraulic diameter ratio (e/Dh) was 0.098. The rib-pitch-to-rib-height (P/e) ratios studied were 5, 7.5, and 10. For each rib-spacing, tests were taken at five Reynolds numbers from 10,000 to 40,000 and for each Reynolds number, experiments were conducted at four rotational speeds up to 400 rpm. Results show that the heat transfer enhancement increases with decreasing P/e from 10 to 5 under non-rotation condition. However, the effect of rotation on the heat transfer enhancement remains about the same for varying P/e from 10 to 5. Heat transfer enhancement due to rotation can be correlated on all surfaces (leading, trailing, inner and outer walls and tip cap region) in the two-passage 2:1 aspect ratio channel.

An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

2006 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
High Reynolds Numbers ◽  
High Reynolds

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e/Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P/e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

Heat Transfer for High Aspect Ratio Rectangular Channels in a Stationary Serpentine Passage With Turbulated and Smooth Surfaces

2013 ◽  
Author(s):  
Matthew A. Smith ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios ◽  
Parallel Configuration

Heat transfer distributions are presented for a stationary three passage serpentine internal cooling channel for a range of engine representative Reynolds numbers. The spacing between the sidewalls of the serpentine passage is fixed and the aspect ratio (AR) is adjusted to 1:1, 1:2, and 1:6 by changing the distance between the top and bottom walls. Data are presented for aspect ratios of 1:1 and 1:6 for smooth passage walls and for aspect ratios of 1:1, 1:2, and 1:6 for passages with two surfaces turbulated. For the turbulated cases, turbulators skewed 45° to the flow are installed on the top and bottom walls. The square turbulators are arranged in an offset parallel configuration with a fixed rib pitch-to-height ratio (P/e) of 10 and a rib height-to-hydraulic diameter ratio (e/Dh) range of 0.100 to 0.058 for AR 1:1 to 1:6, respectively. The experiments span a Reynolds number range of 4,000 to 130,000 based on the passage hydraulic diameter. While this experiment utilizes a basic layout similar to previous research, it is the first to run an aspect ratio as large as 1:6, and it also pushes the Reynolds number to higher values than were previously available for the 1:2 aspect ratio. The results demonstrate that while the normalized Nusselt number for the AR 1:2 configuration changes linearly with Reynolds number up to 130,000, there is a significant change in flow behavior between Re = 25,000 and Re = 50,000 for the aspect ratio 1:6 case. This suggests that while it may be possible to interpolate between points for different flow conditions, each geometric configuration must be investigated independently. The results show the highest heat transfer and the greatest heat transfer enhancement are obtained with the AR 1:6 configuration due to greater secondary flow development for both the smooth and turbulated cases. This enhancement was particularly notable for the AR 1:6 case for Reynolds numbers at or above 50,000.

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.

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