Rectangular-Plate Turbulator Effects on Heat Transfer and Near-Wall Flow Characteristics in Fan Flows

2004 ◽  
Vol 20 (1) ◽  
pp. 33-41 ◽  
Author(s):  
T.Y. Chen ◽  
Y.H. Chen
Keyword(s):  
Heat Transfer ◽  
Rectangular Plate ◽  
Flow Characteristics ◽  
Fluid Flows ◽  
Mean Velocity ◽  
Heat Transfer Augmentation ◽  
Flow Parameters ◽  
Wall Flow ◽  
Aluminum Plates ◽  
Near Wall

ABSTRACTHeat transfer and near-wall flow characteristics in an inherently swirling fan flow, containing rectangular-plate turbulators with 45° and 90° angles of attack, were experimentally investigated. The heat transfer characteristics for uniform flows with the turbulators were also investigated for comparison. Eight heated aluminum plates, installed along a bottom duct-wall, were used as the heat transfer surfaces, which allows the studies of heat transfer variations along the duct and the studies of the relations between the local fluid flows and heat transfer variations. Three-component mean and fluctuating velocities were measured using a laser Doppler velocimetry to obtain the near-wall flow parameters, including the axial mean velocity, axial vorticity and turbulent kinetic energy. The temperatures on the eight heat transfer surfaces were measured using thermocouples to obtain the Stanton number distributions. Results suggest that the rectangular-plate turbulators in fan flows may cause the increases in the near-wall flow parameters and, consequently, augment the heat transfer, especially around the flow reattachment regions. Also, the rectangular-plate turbulator effect on heat transfer augmentation in fan flows may be as attractive as that in uniform flows at the investigated X/H ranges.

Fluid Flow and Heat Transfer in Duct Fan Flows with Top-Wall Rectangular-Wing Turbulators

2008 ◽  
Vol 24 (2) ◽  
pp. N15-N19
Author(s):  
T. Y. Chen ◽  
Y. H. Chen
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Bottom Wall ◽  
Flow Structures ◽  
Mean Velocity ◽  
Flow Parameters ◽  
Flow And Heat Transfer ◽  
Wall Flow ◽  
Near Wall

ABSTRACTFluid flow and heat transfer in duct fan flows with a 90° rectangular-wing turbulator, mounted on the top duct wall, were experimentally studied and compared with the bottom-wall turbulator results. Threecomponent velocities were measured to characterize the flow structures and to obtain near-wall flow parameters. Temperatures on heat transfer surfaces were measured to obtain Nusselt number distributions. Results show that the turbulator has the effect to increase the near-wall axial mean velocity, axial vorticity and turbulent kinetic energy, and, consequently, augment the heat transfer. The axial mean velocity and axial vorticity play an influential role on the heat transfer distributions for the flows across the top-wall and bottom-wall turbulators, respectively.

scholarly journals Heat Transfer Augmentation

2020 ◽  
Vol 5 (4) ◽  
pp. 475-478
Author(s):  
Ifeoma B. Asianuaba
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Heat Transfer Enhancement ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Transfer Enhancement ◽  
Related Field ◽  
Heat Transfer Augmentation ◽  
Flow Parameters ◽  
The Heat Transfer Coefficient

This article presents a brief review of various methodologies applied for heat transfer enhancement in laminar flow convection regime. Experimental setup for laminar flow convection heat transfer enhancement using insertions has been explained along with the associated results. Nusselt’s number is found to be a key parameter for investigatigation in order to perceive the enhancement in heat transfer. Similarly, the magnetohydrodynamic mixed convection heat transfer enhancement technique has also been explored. The results of isotherms and fluid flow parameters are discussed which directly affect the heat transfer coefficient. This review article complements the literature in related field and thus will be helpful in order to carry out further experiments in heat transfer enhancement in future.

Heat Transfer in a Radially Rotating Four-Pass Serpentine Channel With Staggered Half-V Rib Turbulators

2000 ◽  
Vol 123 (1) ◽  
pp. 39-50 ◽  
Author(s):  
G. J. Hwang ◽  
S. C. Tzeng ◽  
C. P. Mao ◽  
C. Y. Soong
Keyword(s):  
Heat Transfer ◽  
Flow Characteristics ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Enhancement ◽  
Serpentine Channel ◽  
Ribbed Channel ◽  
Flow Parameters ◽  
Rib Turbulators ◽  
Rib Arrangement

The present work is concerned with experimental investigation of the convective heat transfer in a radially rotating four-pass serpentine channel. Two types of staggered half-V rib turbulators are considered to examine their effects on heat transfer enhancement. The coolant air is pressurized and pre-cooled to compensate for the low rotating rate and low temperature or density difference in key parameters of thermal and flow characteristics. The geometric dimensions are fixed, whereas the ranges of the thermal and flow parameters in the present measurements are 20,000⩽Re⩽40,000,0⩽Ro⩽0.21, and Gr/Re2∼O10−2. The present results disclose the effects of the pressurized flow, rib arrangement, channel rotation, and centrifugal buoyancy on the local heat transfer in each passage of the channel. Finally, the present data are fitted on correlation equations for evaluation of local heat transfer in the rotating four-pass ribbed channel configurations considered.

Numerical Analysis of Plume Structures of Fluids on a Horizontal Heated Plate

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
T. Praphul ◽  
P. J. Joshy ◽  
P. S. Tide
Keyword(s):  
Heat Transfer ◽  
Rayleigh Number ◽  
Three Dimensional ◽  
Boussinesq Approximation ◽  
Cube Root ◽  
Heated Plate ◽  
Steady State Model ◽  
Increasing Trend ◽  
Wall Flow ◽  
Near Wall

Numerical investigations have been carried out to predict the near-wall dynamics in indirect natural convection for air (Pr = 0.7) and water (Pr = 5.2). Near-wall flow structures appear to be line plumes. Three-dimensional laminar, steady-state model was used to model the problem. Density was formulated using the Boussinesq approximation. Flux scaling, plume spacing and plume lengths obtained numerically are found to have the same trend with the results available in the literature. Plume length and Nusselt number, Nu exhibits an increasing trend with an increase in Rayleigh number, RaH for both Pr fluids. The plume spacing is found to have an inverse relationship with RaH. The cube root of Rayleigh number based on plume spacing, Raλ1/3 is found to have a slight dependence on the dimensionless plume spacing, λ/H. Nu scales as Nu∼CRaHn, n = 0.26 for air and n = 0.3 for water. Heat transfer is thus found to be dominated by near-wall phenomenon. Nu shows a nonlinear relationship with LpH/A and is found to be an accurate representation of heat transfer.

Fluid Flow in a 180 deg Sharp Turning Duct With Different Divider Thicknesses

1999 ◽  
Vol 121 (3) ◽  
pp. 569-576 ◽  
Author(s):  
Tong-Miin Liou ◽  
Yaw-Yng Tzeng ◽  
Chung-Chu Chen
Keyword(s):  
Heat Transfer ◽  
Laser Doppler Velocimetry ◽  
Fluid Flows ◽  
Internal Cooling ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Square Duct ◽  
Measured Velocity ◽  
The Past ◽  
Flow Features

The effect of divider thickness on fluid flows in a two-pass smooth square duct with a 180 deg straight-corner turn is an important issue to the turbine blade internal cooling but has not been explored in the past. Laser-Doppler velocimetry measurements are thus presented for such a study at a Reynolds number of 1.2 × 104 and dimensionless divider thicknesses (Wd*) of 0.10, 0.25, 0.50. Results are presented in terms of various mean velocity components in two orthogonal streamwise planes and three cross-sectional planes, the local and regional averaged turbulent kinetic energy and resultant mean velocity distributions, and complemented by the liquid crystal measured heat transfer coefficient contours. The measured velocity data are able reasonably to explain published and present measured heat transfer results. Wd* is found to have profound effects on the flow features inside and immediately after the turn. The turbulence level and uniformity in the region immediately after the turn respectively decrease and increase with increasing Wd*.

Heat Transfer Augmentation for Air Jet Impinged on Rough Surface

1997 ◽  
Author(s):  
W. M. Chakroun ◽  
S. F. Al-Fahed ◽  
A. A. Abdel-Rehman
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Flow Characteristics ◽  
Mean Velocity ◽  
Potential Core ◽  
Transfer Data ◽  
Nusselt Numbers ◽  
Air Jet ◽  
Rough Plate ◽  
The Mean

An experimental investigation of heat transfer from round air jet impinging normally from below on flat square plates was performed. Smooth and rough plates were used to collect heat transfer data as well as velocity and turbulence intensity profiles. The heat transfer data have been collected for Reynolds numbers ranging from 6500 to 19000. The nozzle-to-plate distances ranged from 0.05 to 15 to cover both the potential core of the jet and the far region. The study was made to investigate the effect of roughness on the local and average heat transfer values and on the fluid characteristics. The roughness was composed of cubes of 1mm dimension distributed uniformly along the plate. The local and average Nusselt numbers for the rough plate showed an increase ranging from 8.9% to 28 % over those obtained for the smooth plate. Roughness was seen to have a strong effect on the flow characteristics, it affected the mean velocity as well as the turbulence intensity of the flow. The mean velocity profiles for the smooth case at r/D = 1 and r/D = 2.5 had steeper near-wall velocity gradient compared with the rough case. Roughness caused an increase in the turbulence intensity of the flow.

scholarly journals Enhanced heat transfer in H2O inspired by Al2O3 and γAl2O3 nanomaterials and effective nanofluid models

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110236
Author(s):  
Adnan ◽  
Umar Khan ◽  
Naveed Ahmed ◽  
Syed Tauseef Mohyud-Din
Keyword(s):  
Heat Transfer ◽  
Colloidal Suspension ◽  
Fluid Motion ◽  
Flow Characteristics ◽  
Heat Transfer Analysis ◽  
Flow Parameters ◽  
Thermal Improvement ◽  
Infinite Region ◽  
Layer Region ◽  
Performance Rate

Currently, thermal improvement in the nanofluids over a curved Riga sheet is a topic of interest and attained popularity among the researchers. Therefore, the colloidal suspension of water suspended by [Formula: see text] and [Formula: see text] over a curved Riga surface is modeled for the heat transfer analysis. The nondimensionalization of the model is accomplished via invertible variables. On the basis of dynamic viscosities and thermal conductivities of [Formula: see text] and [Formula: see text] nanoparticles, two nanofluid models developed over a semi-infinite region. Then, the models solved numerically and found graphical results for the flow characteristics, thermophysical properties and local thermal performance rate by altering the pertinent flow parameters. It is examined that the fluid motion rapidly decreases for [Formula: see text] and momentum boundary layer region decreases. The squeezed and curvature parameters lead to reduce in the nanofluid velocity. The temperature of more magnetized enhances significantly. Thermophysical characteristics of the nanofluids enhance for higher volumetric fraction factor. More heat transfer at the Riga surface for higher M and R.

scholarly journals Fluid Flow in a 180 Deg Sharp Turning Duct With Different Divider Thicknesses

1998 ◽  
Author(s):  
Tong-Miin Liou ◽  
Yaw-Yng Tzeng ◽  
Chung-Chu Chen
Keyword(s):  
Heat Transfer ◽  
Laser Doppler Velocimetry ◽  
Fluid Flows ◽  
Internal Cooling ◽  
Mean Velocity ◽  
Cross Sectional ◽  
Square Duct ◽  
Measured Velocity ◽  
The Past ◽  
Flow Features

The effect of divider thickness on fluid flows in a two-pass smooth square duct with a 180 deg straight-corner turn is an important issue to the turbine blade internal cooling but has not been explored in the past. Laser-Doppler velocimetry measurements are thus presented for such a study at a Reynolds number of 1.2 × 104 and dimensionless divider thicknesses (Wd*) of 0.10, 0.25, 0.50. Results are presented in terms of various mean velocity components in two orthogonal streamwise planes and three cross-sectional planes, the local and regional averaged turbulent kinetic energy and resultant mean velocity distributions, and complemented by the liquid crystal measured heat transfer coefficient contours. The measured velocity data are able to reasonably explain published and present measured heat transfer results. Wd* is found to have profound effects on the flow features inside and immediately after the turn. The turbulence level and uniformity in the region immediately after the turn respectively decrease and increase with increasing Wd*.

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