scholarly journals NUMERICAL INVESTIGATIONS ON HEAT TRANSFER AND FLOW STRUCTURE IN A CIRCULAR TUBE WITH VARIOUS SHAPES OF WINGLET VORTEX GENERATORS

2016 ◽  
Vol 7 ◽  
Author(s):  
Withada Jedsadaratanachai ◽  
Amnart Boonloi
Keyword(s):  
Heat Transfer ◽  
Flow Structure ◽  
Circular Tube ◽  
Vortex Generators ◽  
Numerical Investigations

3D numerical study on flow structure and heat transfer in a circular tube with V-baffles

2015 ◽  
Vol 23 (2) ◽  
pp. 342-349 ◽  
Author(s):  
Withada Jedsadaratanachai ◽  
Nuthvipa Jayranaiwachira ◽  
Pongjet Promvonge
Keyword(s):  
Heat Transfer ◽  
Flow Structure ◽  
Circular Tube ◽  
Numerical Study

Numerical Investigation of Heat Transfer Enhancement on a Small Scale Vortex Generator

2009 ◽  
Author(s):  
Jiansheng Wang ◽  
Zhiqin Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Rectangular Channel ◽  
Vortex Generator ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Small Scale ◽  
Transfer Enhancement

The heat transfer characteristic and flow structure of fluid in the rectangular channel with different height vortex generators in small scale are investigated with numerical simulation. Meantime, the properties of heat transfer and flow of fluid in the rectangular channel are compared with the channel which located small scale vortex generator. The variation law of local heat transfer and flow structure in channel is obtained. The mechanism of heat transfer enhancement of small scale vortex generators is discussed in detail. It is found that the influence of vortex generator on heat transfer is not in proportion to the size of vortex generator. What is more, turbulent flow structure near the wall, which influences the temperature distribution near the wall, induces the variety of local heat transfer. The fluid movement towards to the wall causes the heat transfer enhanced. On the contrary, the fluid movement away from the wall decreases the local heat transfer.

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.

Experimental and Numerical Visualization of Counter Rotating Vortices

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Jeongmoon Park ◽  
Axy Pagan-Vazquez ◽  
Jorge L. Alvarado ◽  
Leonardo P. Chamorro ◽  
Scott Lux ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Structure ◽  
Stability Region ◽  
Vortex Generator ◽  
Vortex Generators ◽  
Vortical Flow ◽  
Taper Angle ◽  
Numerical Visualization ◽  
The Stability ◽  
Upstream Flow

Visualization of the flow structure generated by passive vortex generators continues to be a matter of research in the fluid mechanics and heat transfer communities. In this study, self-sustaining counter-rotating vortex pairs (CVP) generated from a series of vortex generators (VG) have been characterized numerically and experimentally to understand the effects of the VG parameters on vortical flow structure formation. Four different types of VGs were considered by varying the taper angle from 0° to 19.3° at a fixed inclination angle of 24.5° and a Reynolds number of 1965. Flow fields were experimentally visualized using a smoke technique. Each VG induced a coherent CVP flow structure in the wake region despite the fact that the upstream flow was laminar. CVPs initially dominate flow dynamics over a certain streamwise length; however, Kelvin-Helmholtz (KH) instability appears to affect the spatial evolution of CVP longitudinally. The CVP within the stability region were reconstructed digitally in 3D by interpolating several 2D smoke images taken at various spanwise planes. The smoke results indicate that as taper angle decreases, the onset location of KH instability decreases. Furthermore, the CVP trajectory within the stability region was observed to be predominantly controlled by a two-dimensional inviscid process, while the effects by the free stream were not significant. Based on the experimental observations and the numerically reconstructed 3D CVP flow structures, VG with smaller taper angle results in CVPs with higher circulation, which is a positive aspect for mass and heat transfer applications. Preliminary numerical simulations based on RANS have shown that heat transfer enhancement is about 50% in the region near the rectangular vortex generator.

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