scholarly journals Heat transfer augmentation characteristics of a fin punched with curve trapezoidal vortex generators at the rear of tubes

2021 ◽  
pp. 352-352
Author(s):  
Zhimin Lin ◽  
Zhaocheng Wang ◽  
Sha Li ◽  
Liangbi Wang ◽  
Yongheng Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Secondary Flow ◽  
Thermal Performance ◽  
Mechanical Energy ◽  
Vortex Generators ◽  
Flow Strength ◽  
Longitudinal Vortices ◽  
Close Relationship ◽  
Wake Zone ◽  
Outside Diameter

The thermal-hydraulic characteristics of a novel fin punched with curve trapezoidal vortex generators (CTVGs) are investigated numerically. The effects of multi-parameters including the geometry of CTVG, the location of CTVGs, and working condition on thermal performance are considered. On one hand, CTVGs can availably lessen the size of tube wake zone, decrease the mechanical energy consumption and heighten the fin heat transfer ability in this area. On the other hand, the secondary flow strength is strengthened because the longitudinal vortices generated by CTVGs, which efficiently enhances the heat transfer on the fin downstream CTVGs. Close relationship exists between the volume-averaged secondary flow strength and the mean Nusselt number. For studied cases, the optimal circumferential location angle of ? = 90? is found, while the optimal radial location Dg is about 1.8 times the tube outside diameter. The smaller is the height or base length of CTVGs, the better the thermal performance of the enhanced fin punched with CTVGs. Better thermal performance is achieved as the fin spacing is about 0.24 times the tube outside diameter.

scholarly journals Flow Symmetry and Heat Transfer Characteristics of Winglet Vortex Generators Arranged in Common Flow up Configuration

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 247 ◽  
Author(s):  
Kewei Song ◽  
Lu Wang ◽  
Yajun Hu ◽  
Qi Liu
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Flow Region ◽  
Vortex Generators ◽  
Heat Transfer Characteristics ◽  
Longitudinal Vortices ◽  
The Common ◽  
Flow Symmetry

The generation of longitudinal vortices is an effective method for promoting thermal performance with a relative low-pressure penalty in heat exchangers. The winglet pair can generate symmetrical longitudinal vortices on the cross-section of the channel. The heat transfer and pressure-loss characteristics of a pair of winglet vortex generators with different transverse pitches are numerically studied in this paper. The winglet pair arranged in a common flow up configuration generates a pair of symmetrical longitudinal main vortices with counter-rotating directions. The symmetrical flow structure induces fluid to flow from the bottom towards the top of the channel in the common flow region between the longitudinal vortices. The flow symmetry of the longitudinal vortices and the heat transfer performance are strongly affected by the transverse pitch of the winglet pair owing to the interaction between the longitudinal vortices. The optimal transverse pitch of the studied winglet pair with the best thermal performance is reported. The increments in the vortex intensity and the Nusselt number for the optimal pitch are increased by up to 21.4% and 29.2%, respectively.

Thermal performance enhancement in a wedge duct with in-line pin fins combined with vortex generators

2019 ◽  
Vol 29 (8) ◽  
pp. 2545-2565
Author(s):  
Safeer Hussain ◽  
Jian Liu ◽  
Lei Wang ◽  
Bengt Ake Sunden
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Thermal Performance ◽  
Performance Enhancement ◽  
Numerical Study ◽  
Vortex Generators ◽  
Content Type ◽  
Pin Fin ◽  
Pin Fins ◽  
Cooling Enhancement

Purpose The purpose of this paper is to enhance the heat transfer and thermal performance in the trailing edge region of the vane with vortex generators (VGs). Design/methodology/approach This numerical study presents the enhancement of thermal performance in the trailing part of a gas turbine blade. In the trailing part, generally, pin fins are used either in staggered or in-line arrangements to enhance the heat transfer. In this study, based on the idea from heat exchangers, pin fins are combined with VGs. A pair of VGs is embedded in the boundary layer upstream of each pin fin in the first row of the pin fin array having an in-line configuration. The effects of the VG angle relative to the streamwise direction and streamwise distance between the pin fin and VGs are investigated at various Reynolds numbers. Findings The results indicated that the endwall heat transfer is enhanced with the addition of VGs and the heat transfer from the surfaces of the pin fins. The level of heat transfer enhancement compared to the case without VGs is more significant at high Reynolds number. The surfaces of the VGs also show a significant amount of heat transfer. Study of the angle of the attack suggested that a high angle of attack is more appropriate for pin fin cooling enhancement whereas an intermediate gap between the VGs and pin fins shows considerable improvement of thermal performance compared to the small and large gaps. The phenomenon of heat transfer augmentation with the VGs is demonstrated by the flow field. It shows that the enhancement of heat transfer is governed by the mixing of the flow as a result of the interaction of vortices generated by the VGs and pin fins. Originality/value VGs are used to disturb the thermal boundary layer. It shows that heat transfer is augmented as a result of the interaction of vortices associated with VGs and pin fins.

Generation of Longitudinal Streamwise Vortices—A Device for Improving Heat Exchanger Design

1994 ◽  
Vol 116 (3) ◽  
pp. 588-597 ◽  
Author(s):  
G. Biswas ◽  
P. Deb ◽  
S. Biswas
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Delta Wing ◽  
Rectangular Channel ◽  
Point Of View ◽  
Vortex Generators ◽  
Pair Type ◽  
Longitudinal Vortices ◽  
Flat Surfaces ◽  
Heat Exchanger Design

Laminar flow and heat transfer characteristics in a rectangular channel, containing built-in vortex generators of both the slender delta-wing and winglet-pair type, have been analyzed by means of solution of the full Navier–Stokes and energy equations. Each wing or winglet pair induces the creation of streamwise longitudinal vortices behind it. The spiraling flow of these vortices serves to entrain fluid from their outside into their core. These vortices also disrupt the growth of the thermal boundary layer and serve ultimately to bring about the enhancement of heat transfer between the fluid and the channel walls. The geometric configurations considered in the study are representative of single elements of either a compact gas-liquid fin-tube crossflow heat exchanger or a plate-fin crossflow heat exchanger. Physically, these vortex generators can be mounted on the flat surfaces of the above-mentioned heat exchangers by punching or embossing the flat surfaces. They can also act as spacers for the plate fins. Because of the favorable pressure gradient in the channel, the longitudinal vortices are stable and their influence persists over an area many times the area of the slender vortex generators. From a heat transfer point of view, the delta-wing generator is found to be more effective than the winglet-pair. However, most convective heat transfer processes encounter two types of loss, namely, losses due to fluid friction and those due to heat transfer across finite temperature gradient. Because these two phenomena are manifestations of irreversibility, an evaluation of the augmentation techniques is also made from a thermodynamic viewpoint. Conclusions that are drawn thus include discussion about the influence of vortex generators (wings/winglets) on irreversibility.

Heat Transfer Augmentation and Flow Visualization With Delta Winglets in a Tube: A Numerical Approach

2020 ◽  
Author(s):  
Md. Islam ◽  
Liang Guangda ◽  
Md. Mahbub Alam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Thermal Performance ◽  
Performance Enhancement ◽  
Swirling Flow ◽  
Circular Tube ◽  
Vortex Generator ◽  
Attack Angle ◽  
Maximum Enhancement ◽  
Longitudinal Vortices

Abstract In this research, heat transfer and pressure penalty from a circular tube with delta winglets insert are numerically investigated through Computational Fluid Dynamics (CFD) methodology. Numerical analysis with and without vortex generators (VGs) insert in a tube are done for a turbulent air flow, Reynolds number ranging from 6000 to 33000, under constant heat flux condition on the circular tube model surface. In our current research, we employed the shear stress transport (SST) k-omega model. The Nusselt number and friction factor results show the influence of the VGs insert on thermal performance. Effects of different winglet attack angles and blockage ratios on thermal performance enhancement were examined. Thermal performance is enhanced 5.1–30.7% using winglets in a tube. It is observed that small blockage ratio, B = 0.1 performed better than its counterpart of 0.2 and 0.3 for all the Reynolds number and for the same attack angle. The attack angle β = 15° and 30° showed better thermal performance enhancement at lower Re while at higher Re, β = 15° showed better performance. The maximum enhancement obtained for β = 30° and B = 0.1. Winglet vortex generator could create swirling flow when attack angle is 0 or 15°. When attack angle is increased, both swirling flow and longitudinal vortices appeared. At attack angle of 45°, large longitudinal vortices was found.

Heat Transfer in Round Tube with Rectangular-Winglet Vortex Generators

2014 ◽  
Vol 931-932 ◽  
pp. 1173-1177
Author(s):  
Sompol Skullong ◽  
Pongjet Promvonge
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Thermal Performance ◽  
Circular Tube ◽  
Convection Heat Transfer ◽  
Test Tube ◽  
Tube Diameter ◽  
Vortex Generators ◽  
Longitudinal Vortex ◽  
The One

Effect of 30° rectangular-winglet vortex generators (WVGs) mounted in the central core of a circular tube on convection heat transfer and friction loss is experimentally investigated in the present work. The rectangular-WVGs with two different winglet-height to tube-diameter ratios (called blockage ratio, BR = b/D = 0.1 and 0.2) and three winglet-pitch to tube-diameter ratios (PR=P/D=0.5, 1.0, and 1.5) are introduced. In the experiment, air at ambient condition is passed through the uniform heat-fluxed circular tube for Reynolds numbers (Re) in a range of 500024,000. The use of WVGs is to generate longitudinal vortex flows in the tube. The experimental results of heat transfer and pressure loss presented in terms of Nusselt number and friction factor are compared between the inserted and the smooth tubes. It is found that the BR and PR provide a significant effect on the thermal performance of the test tube. The results reveal that at smaller PR, the WVG with BR=0.2 provides the highest heat transfer and friction factor but the one with BR=0.2, PR=1.5 yields the best thermal performance.

Augmentation of Heat Transfer by Creation of Streamwise Longitudinal Vortices Using Vortex Generators

2012 ◽  
Vol 33 (4-5) ◽  
pp. 406-424 ◽  
Author(s):  
Gautam Biswas ◽  
Himadri Chattopadhyay ◽  
Anupam Sinha
Keyword(s):  
Heat Transfer ◽  
Vortex Generators ◽  
Longitudinal Vortices

Comparison of Wing-Type Vortex Generators for Heat Transfer Enhancement in Channel Flows

1994 ◽  
Vol 116 (4) ◽  
pp. 880-885 ◽  
Author(s):  
St. Tiggelbeck ◽  
N. K. Mitra ◽  
M. Fiebig
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Delta Wing ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Number Range ◽  
Longitudinal Vortices

Longitudinal vortices can be generated in a channel flow by punching or mounting small triangular or rectangular pieces on the channel wall. Depending on their forms, these vortex generators (VG) are called delta wing, rectangular wing, pair of delta winglets, and pair of rectangular winglets. The heat transfer enhancement and the flow losses incurred by these four basic forms of VGs have been measured and compared in the Reynolds number range of 2000 to 9000 and for angles of attack between 30 and 90 deg. Local heat transfer coefficients on the wall have been measured by liquid crystal thermography. Results show that winglets perform better than wings and a pair of delta winglets can enhance heat transfer by 46 percent at Re=2000 to 120 percent at Re=8000 over the heat transfer on a plate.

scholarly journals Heat Transfer Characteristic on Wing Pairs Vortex Generator using 3D Simulation of Computational Fluid Dynamic

2021 ◽  
Vol 3 (2) ◽  
pp. 215-224
Author(s):  
Petrus Setyo Prabowo ◽  
◽  
Stefan Mardikus ◽  
Ewaldus Credo Eukharisto ◽  
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamic ◽  
Flow Characteristics ◽  
Vortex Generator ◽  
Transfer Characteristic ◽  
Vortex Generators ◽  
Working Fluid ◽  
Longitudinal Vortices ◽  
Delta Winglet ◽  
Fluid Flow Characteristics

Vortex generators are addition surface that can increase heat transfer area and change the fluid flow characteristics of the working fluid to increase heat transfer coefficient. The use of vortex generators produces longitudinal vortices that can increase the heat transfer performance because of the low pressure behind vortex generators. This investigation used delta winglet vortex generator that was combined with rectangular vortex generator to Reynold numbers ranging 6,000 to 10,000. The parameters of Nusselt number, friction factor, velocity vector and temperature distribution will be evaluated.

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