Heat Transfer and Fluid Flow in a Square Duct With 12 Different Shaped Vortex Generators

1999 ◽  
Vol 122 (2) ◽  
pp. 327-335 ◽  
Author(s):  
T.-M. Liou ◽  
C.-C. Chen ◽  
T.-W. Tsai
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Delta Wing ◽  
Fluid Dynamic ◽  
Vortex Generator ◽  
Hydraulic Diameter ◽  
Longitudinal Vortex ◽  
Laser Doppler Velocimeter ◽  
Mean Velocity ◽  
Single Vortex

Detailed local Nusselt number distributions in the first pass of a sharp turning two-pass square channel with various configurations of longitudinal vortex generator arranged on one wall were measured using transient liquid crystal thermography. Flow patterns and friction factors were measured by the use of laser-Doppler velocimeter and pressure transducer, respectively. The Reynolds number, based on channel hydraulic diameter and bulk mean velocity, was fixed at 1.2×104. The vortex generator height-to-hydraulic diameter ratio and pitch-to-height ratio were 0.12 and 10, respectively. Comparisons in terms of heat transfer augmentation and uniformity and friction loss are first performed on 12 configurations of single longitudinal vortex generator. The fluid dynamic mechanisms and wall confinement relevant to heat transfer enhancement are then documented for three-selected vortex generator models. In addition, the differences in fluid flow and heat transfer characteristics between a single vortex generator and a vortex generator array are addressed for the delta wing I and 45 deg V (with tips facing upstream) models which provide better thermal performance among the 12 configurations examined. The direction and strength of the secondary flow with respect to the heat transfer wall are found to be the most important fluid dynamic factors affecting the heat transfer promotion through the channel wall, followed by the convective mean velocity, and then the turbulent kinetic energy. [S0022-1481(00)01202-0]

scholarly journals Heat Transfer and Fluid Flow in a Square Duct With 12 Different Shaped Vortex Generators

1999 ◽  
Author(s):  
Tong-Miin Liou ◽  
Chung-Chu Chen ◽  
Tzi-Wei Tsai
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Secondary Flow ◽  
Fluid Dynamic ◽  
Vortex Generator ◽  
Flow Patterns ◽  
Hydraulic Diameter ◽  
Longitudinal Vortex ◽  
Mean Velocity

Detailed local Nusselt number distributions, streamwise mean flow patterns and cross-sectional secondary flow patterns, and friction factors in the first pass of a sharp turn two-pass square channel with various configurations of longitudinal vortex generator arranged on one wall were measured using transient liquid crystal thermography, laser-Doppler velocimetry, and pressure transducer probing, respectively. The Reynolds number, based on channel hydraulic diameter and bulk mean velocity, was fixed at 1.2 × 104. The vortex generator height-to-hydraulic diameter ratio and pitch-to-height ratio were 0.12 and 10, respectively. Comparisons in terms of heat transfer augmentation and uniformity and friction loss are first performed on 12 configurations of longitudinal vortex generator. The fluid dynamic mechanisms and wall confinement relevant to heat transfer enhancement are then documented for three-selected vortex generator models. In addition, the differences in fluid flow and heat transfer characteristics between a single vortex generator and a vortex generator array are addressed for the delta wing 1 U and 45° V U models which provide better thermal performance. The direction and strength of the secondary flow with respect to the heat transfer wall are found to be the most important fluid dynamic factors affecting the heat transfer promotion through the channel wall, followed by the convective mean velocity, and then the turbulent kinetic energy. Furthermore, the effects of the two-dimensional heat conduction near the vortex generator edge and unseen heat transfer areas on the Nusselt number estimation are documented in detail.

Fluid Flow and Heat Transfer in a Rotating Two-Pass Square Duct With In-Line 90-deg Ribs

2002 ◽  
Vol 124 (2) ◽  
pp. 260-268 ◽  
Author(s):  
Tong-Miin Liou ◽  
Meng-Yu Chen ◽  
Meng-Hsiun Tsai
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Secondary Flow ◽  
Separation Bubble ◽  
Hydraulic Diameter ◽  
Duct Flow ◽  
Mean Velocity ◽  
Number Ratio ◽  
Sharp Turn

Laser-doppler velocimetry and transient thermochromic liquid crystal measurements are presented to understand local fluid flow and surface heat transfer distributions in a rotating ribbed duct with a 180 deg sharp turn. The in-line 90-deg ribs were arranged on the leading and trailing walls with rib height-to-hydraulic diameter ratio and pitch-to-height ratio of 0.136 and 10, respectively. The Reynolds number, based on duct hydraulic diameter and bulk mean velocity, was fixed at 1.0×104 whereas the rotational number varied from 0 to 0.2. Results are compared with those of the rotating smooth duct flow in terms of maximum streamwise mean velocities Umax/Ub and turbulence intensities u′max/Ub, skewness of mean velocity profiles, secondary flow pattern, turn-induced separation bubble, and turbulence anisotropy. Nusselt number ratio mappings are also provided on the leading and trailing walls. The relationships between the fluid flow and local heat transfer enhancement are also documented. It is found that the rotating ribbed duct flow provides higher Umax/Ub,u′max/Ub, and stronger total averaged secondary flow and, hence heat transfer is enhanced. Comparisons with heat transfer data published by other research groups are also made. Furthermore, simple linear correlations between regional averaged Nusselt number ratio and rotation number are developed.

Fluid Flow and Heat Transfer in a Rotating Two-Pass Square Duct With In-Line 90° Ribs

2001 ◽  
Author(s):  
Tong-Miin Liou ◽  
Meng-Yu Chen ◽  
Meng-Hsiun Tsai
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Secondary Flow ◽  
Separation Bubble ◽  
Hydraulic Diameter ◽  
Duct Flow ◽  
Mean Velocity ◽  
Number Ratio ◽  
Sharp Turn

Laser-Doppler velocimetry and transient thermochromic liquid crystal measurements are presented to understand local fluid flow and surface heat transfer distributions in a rotating ribbed duct with a 180° sharp turn. The in-line 90° ribs were arranged on the leading and trailing walls with rib height-to-hydraulic diameter ratio and pitch-to-height ratio of 0.136 and 10, respectively. The Reynolds number, based on duct hydraulic diameter and bulk mean velocity, was fixed at 1.0×104 whereas the rotational number varied from 0 to 0.2. Results are compared with those of the rotating smooth duct flow in terms of maximum streamwise mean velocities (Umax/Ub) and turbulence intensities (u′max/Ub), skewness of mean velocity profiles, secondary flow pattern, turn-induced separation bubble, and turbulence anisotropy. Nusselt number ratio mappings are also provided on the leading and trailing walls. The relationships between the fluid flow and local heat transfer enhancement are also documented. It is found that the rotating ribbed duct flow provides higher Umax/Ub, u′max/Ub, and stronger total averaged secondary flow and, hence heat transfer is enhanced. Comparisons with heat transfer data published by other research groups are also made. Furthermore, simple linear correlations between regional averaged Nusselt number ratio and rotation number are developed.

Computation of Spatially Periodic Turbulent Fluid Flow and Heat Transfer in a Channel With Various Rib Shapes

1995 ◽  
Author(s):  
Tong-Miin Liou ◽  
Shih-Hui Chen
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Cross Sections ◽  
Hydraulic Diameter ◽  
Wall Region ◽  
Mean Velocity ◽  
Turbulent Fluid Flow ◽  
Turbulent Fluid ◽  
Flow And Heat Transfer ◽  
Spatially Periodic

Periodic fully developed turbulent fluid flow and heat transfer in a channel with four shapes, namely, triangular, semicircular, semielliptic, and square cross sections, of rib pairs periodically mounted on two opposite walls has been investigated computationally with a curvilinear nonorthogonal body-fitted coordinate system. The Reynolds number based on the channel hydraulic diameter and bulk mean velocity, the rib pitch-to-height ratio, and the rib height-to-channel hydraulic diameter ratio are 1.3×104, 10, and 0.08, respectively. The standard k-ε turbulence model together with the two-layer wall region treatment was applied to solve the accelerating, decelerating, separating, recirculating, reattaching and redeveloping flows. The predicted fluid flow and heat transfer results were tested by previous laser-Doppler and holographic interferometry data, and reasonable agreement was achieved. The two layer treatment shows a superiority to the conventional wall function in predicting near wall mean velocity and peak turbulent kinetic energy. Triangular-shaped rib is favorable for a compromise between the thermal performance and possible presence of hot spots.

A Comparative Study of Fin-and-Tube Heat Exchangers With Various Fin Patterns

2008 ◽  
Author(s):  
L. H. Tang ◽  
G. N. Xie ◽  
M. Zeng ◽  
M. Lin ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Delta Wing ◽  
Vortex Generator ◽  
Reynolds Numbers ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
Algorithm Optimization ◽  
Different Types ◽  
High Reynolds

Air-side heat transfer and friction characteristics of five kinds of fin-and-tube heat exchangers, with the number of tube rows (N = 12) and the diameter of tubes (Do = 18 mm), have been experimentally investigated. The test samples consist of five types of fin configurations: Crimped spiral fin, plain fin, slit fin, fin with delta-wing longitudinal vortex generators and mixed fin with front 6-row vortex-generator fin and rear 6-row slit fin. The heat transfer and friction factor correlations for different types of heat exchangers are obtained with the Reynolds numbers ranging from 4000 to 10000. It is found that crimped spiral fin provides higher heat transfer and pressure drop than the other four fins. The air-side performance of heat exchangers with crimped spiral fin, plain fin, slit fin, fin with delta-wing longitudinal vortex generators and mixed fin with front 6-row vortex-generator fin / rear 6-row slit fin has been evaluated under four sets of criteria and it is shown that the heat exchanger with mixed fin (front vortex-generator fin and rear slit fin) has better performance than that with fin with delta-wing vortex generators, and the slit fin offers best heat transfer performance at high Reynolds numbers. Based on Genetic Algorithm optimization results it is indicated that the increase of length and decrease of height may enhance the performance of vortex generator fin.

scholarly journals Numerical Simulation of Turbulent Fluid Flow and Heat Transfer in a Ribbed Rotating Two-Pass Square Duct

2005 ◽  
Vol 2005 (2) ◽  
pp. 152-160 ◽  
Author(s):  
Tong-Miin Liou ◽  
Shih-Hui Chen ◽  
Yi-Chen Li
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Hydraulic Diameter ◽  
Mean Velocity ◽  
Square Duct ◽  
Turbulent Fluid Flow ◽  
Turbulent Fluid ◽  
Flow And Heat Transfer ◽  
Number Ratio

The local turbulent fluid flow and heat transfer in a rotating two-pass square duct with 19 pairs of in-line90∘ribs have been investigated computationally. A Reynolds-averaged Navier-Stokes equation (RANS) with a two-layerk−εturbulence model was solved. The in-line90∘ribs were arranged on the leading and trailing walls with rib height-to-hydraulic diameter ratio and pitch-to-height ratio of0.136and 10, respectively. The Reynolds number, based on duct hydraulic diameter and bulk mean velocity, was fixed at1.0×104whereas the rotational number varied from 0 to0.2. Results are validated with previous measured velocity field and heat transfer coefficient distributions. The validation shows that the effect of rotation on the passage-averaged Nusselt number ratio can be predicted reasonably well; nevertheless, the transverse mean velocity and, in turn, the distribution of regional-averaged Nusselt number ratio are markedly underpredicted in the regions toward which the Coriolis force is directed. Further CFD studies are needed.

Heat Transfer Effects of a Longitudinal Vortex Embedded in a Turbulent Boundary Layer

1987 ◽  
Vol 109 (1) ◽  
pp. 16-24 ◽  
Author(s):  
P. A. Eibeck ◽  
J. K. Eaton
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Delta Wing ◽  
Stanton Number ◽  
Longitudinal Vortex ◽  
Test Facility ◽  
Pressure Probe ◽  
Transfer Effects ◽  
Heat Transfer Effects

The heat transfer effects of an isolated longitudinal vortex embedded in a turbulent boundary layer were examined experimentally for vortex circulations ranging from Γ/U∞δ99 = 0.12 to 0.86. The test facility consisted of a two-dimensional boundary-layer wind tunnel, with a vortex introduced into the flow by a half-delta wing protruding from the surface. In all cases, the vortex size was of the same order as the boundary-layer thickness. Heat transfer measurements were made using a constant-heat-flux surface with 160 embedded thermocouples to provide high resolution of the surface-temperature distribution. Three-component mean-velocity measurements were made using a four-hole pressure probe. Spanwise profiles of the Stanton number showed local increases as large as 24 percent and decreases of approximately 14 percent. The perturbation to the Stanton number was persistent to the end of the test section, a length of over 100 initial boundary-layer thicknesses. The weakest vortices examined showed smaller heat transfer effects, but the Stanton number profiles were nearly identical for the three cases with circulation greater than Γ/U∞δ99 = 0.53 cm. The local increase in the Stanton number is attributed to a thinning of the boundary layer on the downwash side of the vortex.

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