The Combined Effects of Angle of Attack and Louver Angle of a Winglet Pair on Heat Transfer Enhancement

Heat transfer is a naturally occurring phenomenon which can be greatly enhanced by introducing longitudinal vortex generators (VGs). As the longitudinal vortices can potentially enhance heat transfer with small pressure loss penalty, VGs are widely used to enhance the heat transfer of flat-plate type heat exchangers. However, there are few researches which deal with its thermal optimization. Three dimensional numerical simulations are performed to study the effect of angle of attack and attach angle (angle between VG and wall) of vortex generator on the fluid flow and heat transfer characteristics of a flat-plate channel. The flow is assumed as steady state, incompressible and laminar within the range of studied Reynolds numbers (Re = 380, 760, 1140). In the present work, the average and local Nusselt number and pressure drop are investigated for Rectangular vortex generator (RVG) with varying angle of attack and attach angle. The numerical results indicate that the heat transfer and pressure drop increases with increasing the angle of attack to a certain range and then decreases with increasing angle of attack. Moreover, the attach angle also plays an importance role; a 90° attach angle is not necessary for enhancing the heat transfer. Usually, heat transfer enhancement is achieved at the expense of pressure drop penalty. To find the optimal position of vortex generator to obtain maximum heat transfer and minimum pressure drop, the data obtained from numerical simulations are used to train a BRANN (Bayesian-regularized artificial neural network). This in turn is used to drive multi-objective genetic algorithm (MOGA) to find the optimal parameters of VGs in the form of Pareto front. The optimal values of these parameters are finally presented.

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Optimization of shape and angle of attack of winglet vortex generator in a rectangular channel for heat transfer enhancement

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2015.01.044 ◽

2015 ◽

Vol 81 ◽

pp. 376-387 ◽

Cited By ~ 49

Author(s):

Azita Abdollahi ◽

Mehrzad Shams

Keyword(s):

Heat Transfer ◽

Heat Transfer Enhancement ◽

Rectangular Channel ◽

Angle Of Attack ◽

Vortex Generator ◽

Transfer Enhancement

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The Effect of the Corrugation Rib Angle of Attack on the Fluid Flow and Heat Transfer Characteristics Inside Corrugated Ribbed Passage

Journal of Heat Transfer ◽

10.1115/1.4003668 ◽

2011 ◽

Vol 133 (8) ◽

Cited By ~ 4

Author(s):

A. M. I. Mohamed ◽

R. Hoettiba ◽

A. M. Saif

Keyword(s):

Heat Transfer ◽

Fluid Flow ◽

Heat Transfer Enhancement ◽

Angle Of Attack ◽

Navier Stokes ◽

Transfer Enhancement ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Flow And Heat Transfer ◽

Flow Field Characteristics

Heat transfer enhancement using corrugated ribbed passages is one of the common enhancement techniques inside heat exchangers. The present study investigated numerically the effect of the corrugation rib angle of attack on the fluid flow and heat transfer characteristics inside the corrugated ribbed passage. The commercial computational fluid dynamics code PHOENICS 2006 was used to perform the numerical analysis by solving the Navier–Stokes and energy equations. The experimental part of this study was used only to validate the numerical model, and a good agreement between the experimental results and the model was obtained. The flow field characteristics and heat transfer enhancement were numerically investigated for different corrugated rib angles of attack as follows: 90 deg, 105 deg, 120 deg, 135 deg, and 150 deg. The corrugation rib angle of attack has a great effect on the reversed flow zone, the flow reattachments, and the enhancement of the heat transfer coefficient through the duct. The recommended rib angle of attack, which gives the optimum thermohydraulic performance, is found to be between 135 deg and 150 deg. The value of the maximum thermohydraulic performance is about 3.6 for the 150 deg rib angle of attack at a Reynolds number equal to 10,000.

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Effect of the angle of attack of a rectangular wing on the heat transfer enhancement in channel flow at low Reynolds number

Heat and Mass Transfer ◽

10.1007/s00231-017-2244-8 ◽

2017 ◽

Vol 54 (5) ◽

pp. 1441-1452 ◽

Cited By ~ 4

Author(s):

Assadour Khanjian ◽

Charbel Habchi ◽

Serge Russeil ◽

Daniel Bougeard ◽

Thierry Lemenand

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Heat Transfer Enhancement ◽

Channel Flow ◽

Low Reynolds Number ◽

Angle Of Attack ◽

Transfer Enhancement ◽

Low Reynolds

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Optimization of the Angle of Attack of Delta-Winglet Vortex Generators Over a Bank of Elliptical-Tubes Heat Exchanger

Volume 8A: Heat Transfer and Thermal Engineering ◽

10.1115/imece2013-64179 ◽

2013 ◽

Author(s):

K. Godazandeh ◽

M. H. Ansari ◽

B. Godazandeh ◽

M. Ashjaee

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Heat Transfer Enhancement ◽

Cfd Simulation ◽

Angle Of Attack ◽

Vortex Generators ◽

Design Parameters ◽

Geometrical Parameters ◽

Transfer Enhancement ◽

The Impact

In order to reach a more efficient and compact heat exchanger, it is essential to optimize the design, having in mind the impact of different geometrical parameters. Many of the previously cited studies in the area of heat transfer enhancement using vortex generators were confined only to defined points in the possible design space. Thus, a multi-objective optimization study is particularly suitable in order to cover this space entirely. A CFD simulation along with Pareto method were used to simulate the air flow and heat transfer and optimize the design parameters. The angle of attack of a pair of delta-winglets mounted behind each tube is varied between β = −90° and β = +90°. Three elliptical tube rows with inline arrangements are investigated for Reynolds numbers from 500 to 1500 (based on the inlet properties). Use of delta-winglets as heat transfer enhancement elements increases the performance of elliptical-tubes heat exchanger. This enhancement is mainly due to the fact that delta-winglets increase the level of vorticity inside these devices and thus the mixing of the fluid is enhanced.

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Experimental study of heat transfer enhancement in solar air heater with different angle of attack of V-down continuous ribs

10.1063/1.4949309 ◽

2016 ◽

Cited By ~ 5

Author(s):

Tri Istanto ◽

Dominicus Danardono ◽

Indri Yaningsih ◽

Agung Tri Wijayanta

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Heat Transfer Enhancement ◽

Angle Of Attack ◽

Solar Air Heater ◽

Transfer Enhancement ◽

Air Heater

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Be´nard Instability of Nanofluids

ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference, Volume 2 ◽

10.1115/ht2007-32068 ◽

2007 ◽

Author(s):

D. Y. Tzou ◽

Emily J. Pfautsch

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Brownian Motion ◽

Heat Transfer Enhancement ◽

Critical Rayleigh Number ◽

Critical Value ◽

Characteristic Dimension ◽

Turbulent Regime ◽

Combined Effects ◽

Transfer Enhancement

Be`nard instability in nanofluids is investigated in this work. With the combined effects of Brownian motion and thermophoresis of nanoparticles incorporated in natural convection, the critical Rayleigh number governing the transition from laminar to turbulent regime is shown to be 18.11, as compared to 1715.14 in regular fluids. The lower critical value, by as much as two orders of magnitude, reveals that there is heat transfer enhancement by turbulence. This effect is much more significant than the heat transfer enhancement by increased thermal conductivity alone. A nondimensional analysis is performed to extract the dominating parameters governing the turbulence enhancement. Their effects are illustrated along with the characteristic dimension of the Be`nard cells.

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