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.

scholarly journals Characteristics of Flow Symmetry and Heat Transfer of Winglet Pair in Common Flow Down Configuration

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 209 ◽  
Author(s):  
KeWei Song ◽  
WeiNa Shi ◽  
Xiang Wu ◽  
LiangBi Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Flow Region ◽  
Vortex Generators ◽  
Transfer Performance ◽  
Vortex Interaction ◽  
Longitudinal Vortices ◽  
Delta Winglet ◽  
The Common ◽  
Flow Symmetry

The effect of transverse pitch between a pair of delta-winglet vortex generators arranged in a common flow down configuration on the symmetrical flow structure and heat-transfer performance was numerically investigated. The results showed that symmetrical longitudinal vortices form a common flow down region between the vortices. The fluid is induced to flow from the top towards the bottom of the channel in the common flow region, which is advantageous to the heat transfer of the bottom fin. The vortex interaction increases and the vortex intensity decreases along with the decrease in transverse pitch of vortex generators. Vortex interaction has a slight influence on pressure penalty. The Nusselt number decreases with increasing vortex interaction. The vortices gradually attenuate and depart from each other during the process of flowing downward. A reasonable transverse pitch of delta-winglet vortex generators in a common-flow-down configuration is recommended for high thermal performance.

THERMAL PERFORMANCE OF SINE WAVE FIN-AND-OVAL TUBE HEAT EXCHANGERS

2013 ◽  
Vol 21 (01) ◽  
pp. 1350008 ◽  
Author(s):  
NAE-HYUN KIM ◽  
KANG-JONG LEE ◽  
JI-CHAO HAN ◽  
BYUNG-NAM CHOI
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Sine Wave ◽  
Heat Transfer Characteristics ◽  
Round Tube ◽  
Flow And Heat Transfer ◽  
Wave Channel ◽  
Oval Tube

Experiments were conducted on sine wave fin-and-tube heat exchangers having oval tubes of 0.6 aspect ratio. Twelve samples having different fin pitches and tube rows were tested. Eight herringbone wave fin-and-tube heat exchangers having round tubes were also tested. For round tube samples, the effect of tube row on j factor is not prominent. For oval tube samples, however, the highest j factor is observed for two row configuration, whereas the lowest one is observed for one row configuration. Possible reasoning is provided considering the flow and heat transfer characteristics of sine wave channel combined with connecting oval tubes. The friction factor decreases as number of tube row increases. Comparison with round tube samples reveals that airside performance of oval fin-and-tube heat exchangers is generally superior except for one-row configuration.

A REVIEW ON THE HEAT-TRANSFER PERFORMANCE AND PRESSURE-DROP CHARACTERISTICS OF VARIOUS ENHANCED TUBES

2012 ◽  
Vol 20 (04) ◽  
pp. 1230003 ◽  
Author(s):  
S. LAOHALERTDECHA ◽  
A. S. DALKILIC ◽  
S. WONGWISES
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Enhanced Tubes ◽  
Smooth Tubes ◽  
Enhanced Tube ◽  
The Common ◽  
Passive Technique

The enhanced tube is a kind of the passive technique for improving the thermal performance of the heat exchangers with a little increase of the friction penalty. They have stated to use instead of the common smooth tubes for designing of the heat exchangers. The size of these heat exchangers can be reduced considerably by using the enhanced tubes instead of smooth tubes. Normally, they are divided into four groups: the corrugated tube, ribbed tube, grooved tube, and fluted tube. Compared with the common smooth tube, many researchers reported that use of the enhanced tubes dramatically increases the heat-transfer performance, both theoretically and experimentally. Focusing on the advantages of the enhanced tubes, this article summarizes the published studies on the heat-transfer and pressure-drop characteristics of the enhanced tubes, both experimental and quantitative investigations.

Investigation on Heat Transfer Performance and Flow Resistance Characteristics in Finned-Tube Heat Exchangers With Different Vortex Generator Positions

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Wang Qiang ◽  
Qian Zuoqin ◽  
Cheng Junlin ◽  
Ren Jie ◽  
Huang Weilong
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Flow Resistance ◽  
Heat Transfer Performance ◽  
Finned Tube ◽  
Transfer Performance ◽  
Wake Region ◽  
Local Pressure ◽  
Comprehensive Performance

The numerical simulation was carried out to investigate mechanism of the heat transfer enhancement in the fin-and-tube heat exchangers. As known, the vortex generators (VGs) were widely used to improve the thermal performance with bad flow resistance characteristics and led to bad comprehensive performance. This paper aims to expound the mechanism of thermal hydraulic characteristics and explore the effect of VGs position on the comprehensive performance. Three types of fins (type 1, type 2, and type 3) were discussed in this paper. The j factor, f factor, and performance evaluation (PEC) of three types of VGs in different positions were discussed and compared. Based on the numerical results, a detailed description of the effect of three types of VGs on the heat transfer performance and flow resistance characteristics was presented at different Reynolds number in the range between 1300 and 2000. In addition, local velocity distribution, local temperature distribution, and local pressure drop distribution were analyzed and discussed. And the effect of VG angle on the thermal performance and flow resistance was presented. It can be concluded that the main heat transfer occurred in the region before the tube, and the wake region behind the tube was harmful to improve the thermal performance and reduce the flow resistance. Besides, VG in the wake region was obviously beneficial to the enhancement of the thermal performance with less energy loss.

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 Numerical Analysis on Thermohydraulic Performance of the Tube Inserted with Rectangular Winglet Vortex Generators

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 179
Author(s):  
Yicong Li ◽  
Zuoqin Qian ◽  
Qiang Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Circular Tube ◽  
Vortex Generators ◽  
Transfer Performance ◽  
Empirical Formulas ◽  
Influence Mechanism ◽  
Simulation Results ◽  
The Impact

The aim of this design was to improve the heat transfer performance significantly due to larger turbulent region and much vortices formed by tube inserted. In this article, the BSL k-ω model was chosen as turbulence model to simulate the thermohydraulic performance of the proposed tubes inserted with rectangular winglet vortex generators (RWVGs) when the Re was set as 5000 to 15,000. The reliability of the simulation results was obtained by comparing with the empirical formulas and experimental results. By means of numerical simulation, the influence mechanism of geometric parameters of RWVGs on thermal-hydraulic performance in tubes was analyzed. And the impact of three configurational parameters on the thermal performance was studied, namely the angle α, the height H and the number N of the RWVGs, respectively. The results revealed that the capacity of heat transfer in tubes with RWVG inserts was obviously larger than that in ordinary circular tube. In addition, it could be seen from the results that both Nu and f increased with the increase of H and N. At the same time, the case of α = 135° showed the greatest enhancement of thermal performance than the case of α = 45° and α = 90°.The PEC achieved the highest value of 1.23 when the height H of RWVG was 0.7 mm, the number N was 20, and angle α was 135°.

Ultra-Compact Micro-Scale Heat Exchanger for Advanced Thermal Management in Data Centers

2021 ◽  
Author(s):  
Raffaele L. Amalfi ◽  
Todd Salamon ◽  
Filippo Cataldo ◽  
Jackson B. Marcinichen ◽  
John R. Thome
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Operating Conditions ◽  
Transfer Performance ◽  
Two Phase ◽  
Maximum Heat ◽  
Pressure Drops

Abstract The present study is focused on the experimental characterization of two-phase heat transfer performance and pressure drops within an ultra-compact heat exchanger (UCHE) suitable for electronics cooling applications. The UCHE is composed of a double-side-copper finned plate with an optimized geometry that enhances the heat transfer performance and flow stability, while minimizing the pressure drops. These features make the UCHE the ideal component for thermosyphon cooling systems, where low pressure drops are required to achieve high passive flow circulation rates and thus achieve high critical heat flux values. The UCHE's thermal-hydraulic performance is first evaluated in a pump-driven system at the Laboratory of Heat and Mass Transfer (LTCM-EPFL), where experiments include many configurations and operating conditions. Then, the UCHE is installed and tested as the condenser of a thermosyphon loop that rejects heat to a pumped refrigerant system at Nokia Bell Labs, in which both sides operate with refrigerants in phase change (condensation-to-boiling). Experimental results demonstrate high thermal performance with a maximum heat dissipation density of 5455 (kW/m3/K), which is significantly larger than conventional air-cooled heat exchangers and liquid-cooled small pressing depth brazed plate heat exchangers. Finally, a thermal performance analysis is presented that provides guidelines in terms of heat density dissipations at the server- and rack-level when using passive two-phase cooling.

Heat Transfer Enhancement and Pressure Drop Performance for Fin and Tube Compact Heat Exchangers with Radiantly Arranged Rectangular Winglet-Type Vortex Generators

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Rimjhim Raj Singh ◽  
H.C. Thakur
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Exchangers ◽  
Main Flow ◽  
Vortex Generators ◽  
Flow Structures ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Compact Heat Exchangers ◽  
Existing Structures

In this paper, heat transfer enhancement has been numerically investigated for fin and tube compact heat exchangers with radiantly arranged rectangular winglets and has been compared with the existing structures. In the proposed structure, there are total 12 winglets, 3 on each tube arranged radiantly with an attack angle of 60 each. Investigation has been carried out on low Reynolds number from 400-800 heat transfer is compared with other structures without winglet as baseline arrangement, prevailing rectangular winglet arrangement and wavy down rectangular winglet arrangement. The simulation results show that the radiantly arranged winglet that guides the fluid from main flow to the wall creates collision and leads to turbulence behind the tube. It is found that newly proposed structure with radiantly arranged winglets has the highest heat transfer rate, as compared to the existing structures and this can replace the previous structures. The heat transfer characteristics and flow structures are numerically investigated in ANSYS.

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