Holographic Interferometry Study of Spatially Periodic Heat Transfer in a Channel With Ribs Detached From One Wall

1995 ◽  
Vol 117 (1) ◽  
pp. 32-39 ◽  
Author(s):  
Tong-Miin Liou ◽  
Wen-Bin Wang ◽  
Yuan-Jen Chang
Keyword(s):  
Heat Transfer ◽  
Holographic Interferometry ◽  
Hot Spots ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Clearance Ratio ◽  
Heat Transfer Augmentation ◽  
Spatially Periodic ◽  
Periodic Heat ◽  
First Time

The effects of clearance ratio (C/H) and Reynolds number (Re) on the turbulent heat transfer and friction in a rectangular duct with ribs detached from one wall were characterized quantitatively using laser holographic interferometry and pressure measurements. The investigated flow was periodic in space both hydrodynamically and thermally. C/H and Re were varied from 0.25 to 1.5 and 5 × 103 to 5 × 104, respectively. The obtained interferograms, local (Nu) and average (Nu) Nusselt number, and thermal performance (Nup/Nus*) allowed the critical C/H characterizing different mechanisms of heat transfer augmentation to be identified and allowed a comparison of Nu, Nu, and Nup/Nus* among the detached ribbed duct, the attached ribbed duct, and the smooth duct to be made. It was found that the detached ribbed geometry has the advantage of eliminating the hot spots behind the attached ribs. Optimal clearance ratios for heat transfer enhancement between the present periodic detached ribs and previous single detached cylinder were also compared. Furthermore, compact heat transfer and friction correlations were developed for a detached ribbed duct for the first time.

Effect of Rib Height and Pitch on the Thermal Performance of a Passage Disturbed by Detached Solid Ribs

1996 ◽  
Author(s):  
Tong-Miin Liou ◽  
Woei-Jiunn Shuy ◽  
Yu-Houe Tsao
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Pressure Measurements ◽  
Rectangular Duct ◽  
Height Ratio ◽  
Heat Transfer Augmentation ◽  
Spatially Periodic ◽  
The Difference

Laser holographic interferometry and pressure measurements are presented for the effects of rib-to-duct height ratio (H/2B), rib pitch-to-height ratio (Pi/H), and Reynolds number (Re) on the spatially periodic-fully developed turbulent heat transfer and friction in a rectangular duct of width-to-height ratio of 4:1 with an array of ribs detached from one wall at a clearance to rib-height ratio of 0.38. The range of H/2B, Pi/H, and Re examined were 0.13 to 0.26, 7 to 13, and 5×103 to 5×104, respectively. The difference in the H/2B dependence of the thermal performance between the detached and attached solid-rib array is documented. H/2B=0.17 and Pi/H=10 are found to provide the best thermal performance for the range of parameters tested. Compact heat transfer and friction correlations are developed. Additionally, it is found that heat transfer augmentation with a detached solid-rib array is superior to with a detached perforated-rib array, and the mechanism responsible for the difference is revealed by the complementary flow visualization results.

Turbulent Heat Transfer Augmentation and Friction in Periodic Fully Developed Channel Flows

1992 ◽  
Vol 114 (1) ◽  
pp. 56-64 ◽  
Author(s):  
T.-M. Liou ◽  
J.-J. Hwang
Keyword(s):  
Heat Transfer ◽  
Hot Spots ◽  
Channel Flows ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Augmentation ◽  
Relative Contribution ◽  
Friction Factors

Measurements are presented of the distribution of average friction factors (f) as well as local and average (Nu) heat transfer coefficients for fully developed channel flows with two rib-roughened opposite walls. The temperature measurements were made by using both a laser holographic interferometer and thermocouples. In addition, the reattachment length was determined by flow visualization. The Reynolds number (Re) was varied from 5.0 × 103 to 5.4 × 104; the rib pitch-to-height ratios (Pi/H) were 10, 15, and 20; and the rib height-to-hydraulic diameter ratios (H/De) were 0.063, 0.081, and 0.106. The detailed results allowed the peaks of heat transfer augmentation and the regions susceptible to hot spots to be located and allowed the relative contribution of the rib surface and the channel wall to the heat transfer augmentation to be determined. Moreover, relative to a smooth duct, the enhancement of both Nu and f at various Re, Pi/H, and H/De was documented in detail. Furthermore, compact correlations in terms of Re, Pi/H, and H/De were developed for both Nu and f.

Effect of Rib Height and Pitch on the Thermal Performance of a Passage Disturbed by Detached Solid Ribs

1998 ◽  
Vol 120 (3) ◽  
pp. 581-588 ◽  
Author(s):  
Tong-Miin Liou ◽  
Woei-Jiunn Shuy ◽  
Yu-Houe Tsao
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Pressure Measurements ◽  
Rectangular Duct ◽  
Height Ratio ◽  
Heat Transfer Augmentation ◽  
Spatially Periodic ◽  
The Difference

Laser holographic interferometry and pressure measurements are presented for the effects of rib-to-duct height ratio (H/2B), rib pitch-to-height ratio (Pi/H), and Reynolds number (Re) on the spatially periodic-fully developed turbulent heat transfer and friction in a rectangular duct of width-to-height ratio of 4:1 with an array of ribs detached from one wall at a clearance to rib-height ratio of 0.38. The ranges of H/2B, Pi/H, and Re examined were 0.13 to 0.26, 7 to 13, and 5 × 103 to 5 × 104, respectively. The difference in the H/2B dependence of the thermal performance between the detached and attached solid-rib array is documented. H/2B = 0.17 and Pi/H = 10 are found to provide the best thermal performance for the range of parameters tested. Compact heat transfer and friction correlations are developed. Additionally, it is found that heat transfer augmentation with a detached solid-rib array is superior to with a detached perforated-rib array, and the mechanism responsible for the difference is revealed by the complementary flow visualization results.

Turbulent Heat Transfer Augmentation Using Microscale Disturbances Inside the Viscous Sublayer

1992 ◽  
Vol 114 (2) ◽  
pp. 348-353 ◽  
Author(s):  
H. Kozlu ◽  
B. B. Mikic ◽  
A. T. Patera
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Heat Removal ◽  
Channel Flows ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Two Dimensional ◽  
Optimal Position ◽  
Heat Transfer Augmentation ◽  
Near Wall

We report here on an experimental study of heat transfer augmentation in turbulent flow. Enhancement strategies employed in this investigation are based on the near-wall mixing processes induced in the sublayer through appropriate wall and near-wall streamwise-periodic disturbances. Experiments are performed in a low-turbulence wind-tunnel with a high-aspect-ratio rectangular channel having either (a) two-dimensional periodic microgrooves on the wall, or (b) two-dimensional microcylinders placed in the immediate vicinity of the wall. It is found that micro-disturbances placed inside the sublayer induce favorable heat-transport augmentation with respect to the smooth-wall case, in that near-analogous momentum and heat transfer behavior are preserved; a roughly commensurate increase in heat and momentum transport is termed favorable in that it leads to a reduction in the pumping power penalty at fixed heat removal rate. The study shows that this favorable performance of microcylinder-equipped channel flows is achieved for microcylinders placed inside y+ ≃20, implying a dependence of the optimal position and size on Reynolds number. For microgrooved channel flows, favorable augmentation is obtained for a wider range of Reynolds numbers; however, optimal enhancement still requires a matching of geometric perturbation with the sublayer scale.

Simulation of Turbulent Heat Transfer in a Tube Fitted with Twisted Tape Placed Separately from the Tube Walls

2015 ◽  
Vol 751 ◽  
pp. 245-250 ◽  
Author(s):  
Niwat Piriyarungroj ◽  
Smith Eiamsa-ard ◽  
Pongjet Promvonge ◽  
Petpices Eiamsa-Ard ◽  
Chinaruk Thianpong
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Transfer Rate ◽  
Reynolds Numbers ◽  
Turbulent Heat Transfer ◽  
Twisted Tape ◽  
Turbulent Heat ◽  
Clearance Ratio ◽  
Constant Wall Temperature

The effects of loose-fit twisted tape (LFT) on the heat transfer rate, friction factor, fluid phenomena and thermal performance of a tube under constant wall temperature are examined. It is observed that apart from the rise of Reynolds number, the reduction of the clearance ratio (c/D) leads to an increase in the heat transfer and pressure loss. According to the numerical results, the heat transfer and friction factor in the tubes with loose-fit twisted tape (LFT) for the smallest clearance ratio of c/D = 0.05 are higher those other clearance ratios. In addition, the thermal performances of clearance ratio c/D = 0.05 are found to be higher than those other clearance ratios (c/D) for all Reynolds numbers examined.

scholarly journals Simulation of Turbulent Heat Transfer Augmentation with Hybrid Nanofluid

2018 ◽  
Vol 11 (4) ◽  
pp. 28-34
Author(s):  
Adnan Mohammed Hussein
Keyword(s):  
Heat Transfer ◽  
Volume Fraction ◽  
Simple Algorithm ◽  
Turbulent Heat Transfer ◽  
Hybrid Nanofluid ◽  
Turbulent Heat ◽  
Straight Tube ◽  
Al2o3 Nanoparticles ◽  
New Class ◽  
Heat Transfer Augmentation

Study of heat transfer augmentation with hybrid nanofluid represents a new class of heat transfer augmentation. The CFD model by using commercial software depending on finite volume technique and adopting SIMPLE  algorithm is performed. Mixture of Aluminum Nitride (AlN) and alumina (Al2O3)  nanoparticles into water as a basefluid is  classified as a new class of hybrid nanofluids  that can augment heat transfer. The nanofluid  volume fraction and Reynolds number are in  the range of (1% to 4%) and (5000 to 17000) respectively. The size diameter of  nanoparticles and heat flux around a horizontal straight tube are fixed at 30 nm and 5000 w/m2 respectively. The numerical solution has been  successfully validated by using an  experimental data available in the literature. Results show that combination of AlN - Al2O3 nanoparticles into water basefluid tends to  augment significant heat transfer performance.

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