Enhancing heat transfer in a plate-fin heat sink using delta winglet vortex generators

2013 ◽  
Vol 67 ◽  
pp. 666-677 ◽  
Author(s):  
Hung-Yi Li ◽  
Ci-Lei Chen ◽  
Shung-Ming Chao ◽  
Gu-Fan Liang
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Vortex Generators ◽  
Enhancing Heat Transfer ◽  
Delta Winglet

scholarly journals Heat Transfer Enhancement of Plate-Fin Heat Sinks with Different Types of Winglet Vortex Generators

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5219
Author(s):  
Jin-Cherng Shyu ◽  
Jhao-Siang Jheng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Sink ◽  
Heat Sinks ◽  
Vortex Generators ◽  
Airflow Velocity ◽  
Delta Winglet ◽  
The Heat Transfer Coefficient

Because the delta winglet in common-flow-down configuration has been recognized as an excellent type of vortex generators (VGs), this study aims to experimentally and numerically investigate the thermo-hydraulic performance of four different forms of winglet VGs featuring sweptback delta winglets in the channel flow in the range 200 < Re < 1000. Both Nusselt number and friction factor of plate-fin heat sinks having different forms of winglets, including delta winglet pair (DWP), rectangular winglet pair (RWP), swept delta winglet pair (SDWP), and swept trapezoid winglet pair (STWP), were measured in a standard wind tunnel without bypass in this study. Four rows of winglets with in-line arrangement were punched on each 10-mm-long, 0.2-mm-thick copper plate, and a total of 16 pieces of copper plates with spacing of 2 mm were fastened together to achieve the heat sink. The projected area, longitudinal and winglet tip spacing, height and angle of attack of those winglets were fixed. Besides that, three-dimensional numerical simulation was also performed in order to investigate the temperature and fluid flow over the plate-fin. The results showed that the longitudinal, common-flow-down vortices generated by the VGs augmented the heat transfer and pressure drop of the heat sink. At airflow velocity of 5 m/s, the heat transfer coefficient and pressure drop of plain plate-fin heat sink were 50.8 W/m2·K and 18 Pa, respectively, while the heat transfer coefficient and the pressure drop of heat sink having SDWP were 70.4 W/m2·K and 36 Pa, respectively. It was found that SDWP produced the highest thermal enhancement factor (TEF) of 1.28 at Re = 1000, followed by both RWP and STWP of similar TEF in the range 200 < Re < 1000. The TEF of DWP was the lowest and it was rapidly increased with the increase of airflow velocity.

Improving Flow Circulation in Heat Sinks Using Quadrupole Vortices

2009 ◽  
Author(s):  
Timothy J. Dake ◽  
Joseph Majdalani
Keyword(s):  
Heat Transfer ◽  
Heat Sink ◽  
Leading Edge ◽  
Vortex Generators ◽  
Experimental Simulation ◽  
Second Phase ◽  
Performance Study ◽  
Planar Laser ◽  
Flow Circulation ◽  
Two Phases

In this paper, we show that improved air circulation above a heat sink is possible using thin winglet-type vortex generators that can be passively retrofitted to an existing unit. By mounting these vortex generators on the leading edge of heat sink fins, pairs of counter-rotating vortices are induced within the interfin spacing. The vortices disturb the boundary layers and serve to mix the air in the interfin channel. The devices we have designed are passive and can be added to existing systems using a simple clip-on mechanism. In this study, several designs are experimentally investigated for the purpose of identifying the optimal configuration that will be most conducive to flow enhancement and, therefore, heat transfer augmentation. Using the typical operational range of air velocities for PCs, routers and servers, an experimental simulation of the interfin channel reveals that certain vortex generators, when placed upstream, can outperform others in their ability to fill the channel with pairs of strong vortices. Multiple pairs can also be generated to further accentuate the heat transfer using dual vortex generators. A description of the specific shapes is furnished here along with particulars of the performance study. By control and manipulation of the vortices, our results suggest the possibility of optimizing the generator design. Experimentation was conducted in two phases. The first phase is a study of the ability to generate and control vortices within the fin channel. This aspect was simulated using a Lexan mock-up of the fin channel that permits introduction of glycerin smoke to visualize the shape, size, strength and structure of the vortices. The clear Lexan permitted viewing of the vortices by passing a red planar laser through the apparatus. The second phase involved using the optimization data gained in the first phase to generate vortices in an actual heat sink fitted with thermocouples to measure the temperatures at various points during heating.

Fluid Flow and Heat Transfer Behavior for Turbulent Flows in a Tube With Vortex Generator Pairs for an Efficient Heat Exchanger

2018 ◽  
Author(s):  
Md. Islam ◽  
Z. Chong ◽  
S. Bojanampati
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Flow Behavior ◽  
Vortex Generator ◽  
Tube Diameter ◽  
Vortex Generators ◽  
Blockage Ratio ◽  
Delta Winglet

Various technologies have been developed to enhance flow mixing and heat transfer in order to develop an efficient compact heat exchanging devices. Vortex generators/turbulent promoters generate the vortices which reduce the boundary layer thickness and introduce the better mixing of the fluid to enhance the heat transfer. In this research experimental investigations have been carried out to study the effect of delta winglet vortex generator pairs on heat transfer and flow behavior. To generate longitudinal vortex flow, two pairs of the delta winglet vortex generators (DWVG) with the length of 10mm and winglet-pitch to tube-diameter ratio (PR = 4.8) are mounted on the inner wall of a circular tube. The DWVG pairs with two different winglet-height to tube-diameter ratios (Blockage ratio, BR = 0.1 and 0.2), three attack angles (α = 10°, 20°, 30°) and three spacings between leading edges (S = 10, 15 and 20mm) are studied. The experiments were conducted with DWVGs pairs for the air flow range of Reynolds numbers 5000–25000. The influence of the DWVGs on heat transfer and pressure drop was investigated in terms of the Nusselt number and friction factor. The experimental results indicate that DWVG pair in a tube results in a considerable enhancement in Nusselt number (Nu) with some pressure penalty. It is found that DWVG increases Nu up to 85% over the smooth tube. It is also observed that Nusselt number increases with Re, blockage ratio and attack angle. Friction factor decreases with Re but increases with blockage ratio, spacing and attack angle. And 30° DWVG pair with S = 20mm, BR = 0.2 gets the highest friction factor. The Highest thermal performance enhancement (TPE) was noticed for α = 10°, S = 20mm, BR = 0.2 for turbulent flows. To obtain qualitative information on the flow behavior and vortex structures, flow was visualized by laser sheet using smoke as a tracer supplied at the entrance of the test section. The generation and development of longitudinal vortices influenced by DWVG pairs were clearly observed.

scholarly journals Recent Advances in Heat Transfer Enhancements: A Review Report

2010 ◽  
Vol 2010 ◽  
pp. 1-28 ◽  
Author(s):  
M. Siddique ◽  
A.-R. A. Khaled ◽  
N. I. Abdulhafiz ◽  
A. Y. Boukhary
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Porous Media ◽  
High Thermal Conductivity ◽  
Vortex Generators ◽  
Two Phase ◽  
Enhancement Method ◽  
Enhancing Heat Transfer ◽  
Porous Fins ◽  
Two Phase Heat Transfer

Different heat transfer enhancers are reviewed. They are (a) fins and microfins, (b) porous media, (c) large particles suspensions, (d) nanofluids, (e) phase-change devices, (f) flexible seals, (g) flexible complex seals, (h) vortex generators, (i) protrusions, and (j) ultra high thermal conductivity composite materials. Most of heat transfer augmentation methods presented in the literature that assists fins and microfins in enhancing heat transfer are reviewed. Among these are using joint-fins, fin roots, fin networks, biconvections, permeable fins, porous fins, capsulated liquid metal fins, and helical microfins. It is found that not much agreement exists between works of the different authors regarding single phase heat transfer augmented with microfins. However, too many works having sufficient agreements have been done in the case of two phase heat transfer augmented with microfins. With respect to nanofluids, there are still many conflicts among the published works about both heat transfer enhancement levels and the corresponding mechanisms of augmentations. The reasons beyond these conflicts are reviewed. In addition, this paper describes flow and heat transfer in porous media as a well-modeled passive enhancement method. It is found that there are very few works which dealt with heat transfer enhancements using systems supported with flexible/flexible-complex seals. Eventually, many recent works related to passive augmentations of heat transfer using vortex generators, protrusions, and ultra high thermal conductivity composite material are reviewed. Finally, theoretical enhancement factors along with many heat transfer correlations are presented in this paper for each enhancer.

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