Effects of winglets to augment tube wall heat transfer in louvered fin heat exchangers

Louvered fins are used in compact heat exchangers to increase heat transfer by interrupting thermal boundary layer growth thereby increasing the convective heat transfer coefficients and reducing the air side resistance. Recently, it has been experimentally shown that heat transfer along the tube wall can be augmented by the placement of delta winglets on the louvers at an angle to the flow. The focus of this combined experimental and computational study is to determine the effect of realistic winglets on tube wall heat transfer. Comparisons of the computational simulations were made to the experimental results, which were obtained using a twenty times scaled model. Winglet performance characteristics were studied on solid louvers and pierced louvers whereby the latter simulates what would occur for a manufactured louver having a winglet. For a solid louver having a winglet, the tube wall heat transfer augmentation was found to be as high as 5.4%. Pierced louver cases were observed to produce slightly higher heat transfer augmentations than solid louver cases. Computational results suggest that the mechanism behind tube wall heat transfer augmentation is flow redirection and not winglet induced vortices.

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Pressure Drop and Heat Transfer Characteristics of Louvered Fin Heat Exchangers

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.465-466.500 ◽

2013 ◽

Vol 465-466 ◽

pp. 500-504 ◽

Cited By ~ 1

Author(s):

Shahrin Hisham Amirnordin ◽

Hissein Didane Djamal ◽

Mohd Norani Mansor ◽

Amir Khalid ◽

Md Seri Suzairin ◽

...

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Heat Transfer Rate ◽

Heat Exchangers ◽

Transfer Rate ◽

Three Dimensional ◽

Considerable Effect ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Louvered Fin

This paper presents the effect of the changes in fin geometry on pressure drop and heat transfer characteristics of louvered fin heat exchanger numerically. Three dimensional simulation using ANSYS Fluent have been conducted for six different configurations at Reynolds number ranging from 200 to 1000 based on louver pitch. The performance of this system has been evaluated by calculating pressure drop and heat transfer coefficient. The result shows that, the fin pitch and the louver pitch have a very considerable effect on pressure drop as well as heat transfer rate. It is observed that increasing the fin pitch will relatively result in an increase in heat transfer rate but at the same time, the pressure drop will decrease. On the other hand, low pressure drop and low heat transfer rate will be obtained when the louver pitch is increased. Final result shows a good agreement between experimental and numerical results of the louvered fin which is about 12%. This indicates the capability of louvered fin in enhancing the performance of heat exchangers.

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Parametrical Study of the Flat-Tube and Pin Fin Heat Exchangers

Volume 8: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A and B ◽

10.1115/imece2007-42894 ◽

2007 ◽

Author(s):

Maria Pascu ◽

Naser Sahiti ◽

Franz Durst

Keyword(s):

Heat Transfer ◽

Heat Exchanger ◽

Automobile Industry ◽

Heat Exchangers ◽

Unit Area ◽

Pin Fin ◽

Flow Length ◽

Louvered Fin ◽

Pin Fins ◽

Constant Versus

The main objective of the present work was the derivation of heat transfer and pressure drop characteristics for pin fins which could be applied in heat exchangers used in the automobile industry. For this, 34 models of pin fin heat exchangers, characterized by a pin diameter of 0.35 mm, with both inline and staggered arrangements, were numerically investigated. The numerical results were validated through various comparison and validation procedures. The best performing pin fin configuration was determined by employing the performance plot: heat transfer per unit volume (or per unit area, if the pin height is constant) versus the energy input reduced to the same parameter as the heat transfer (volume or area). The heat exchanger performance plot showed that, for the investigated flow length, the staggered pin fin configuration performs better when compared to the inline arrangement. In order to prove the industrial applicability of these results, a louvered fin heat exchanger, commonly used as a car radiator, was experimentally investigated. A comparison of the best performing pin fin heat exchanger with the louvered fin model revealed an enhancement in the heat transfer of the pin fin model of 35%.

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Experimental Study on Heat Transfer Performances of Flat Tube Bank Fin Heat Exchanger Using Four Different Fin Patterns

Journal of Heat Transfer ◽

10.1115/1.4038419 ◽

2018 ◽

Vol 140 (4) ◽

Author(s):

Feng-Cai Zheng ◽

Song Liu ◽

Zhi-Min Lin ◽

Jaafar Nugud ◽

Liang-Chen Wang ◽

...

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Heat Exchangers ◽

Transfer Enhancement ◽

Tube Bank ◽

Number Range ◽

Flat Tube ◽

Louvered Fin ◽

Delta Winglet ◽

Better Than

Air-side heat transfer and flow friction characteristics of four different fin patterns suitable for flat tube bank fin heat exchangers are investigated experimentally. The fin patterns are the fin with six dimples, the fin with nine dimples, the double louvered fin, and the fin with delta-winglet vortex generators (VGs). The corresponding plain fins (plain fin I and plain fin II) are used as the references for evaluating the thermal performances of these fin patterns under identical pump power constraint. The performance of the fin with the six dimples is better than that with nine dimples. The performance of the fin with delta-winglet VGs is better than that of the double louvered fin, and the performance of the latter is better than that of the fins with six or nine dimples. In the tested Reynolds number range, the heat transfer enhancement performance factor of the fin with six dimples, the fin with nine dimples, the double louvered fin, and the fin with delta-winglet VGs is 1.2–1.3, 1.1–1.2, 1.3–1.6, and 1.4–1.6, respectively. The correlations of Nusselt number and friction factor with Reynolds number for the fins with six/nine dimples and the double louvered fin are obtained. These correlations are useful to design flat tube bank fin heat exchangers.

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The Experimental Investigation of Fouling Phenomenon in Tubular Heat Exchangers by Heat Transfer Resistance Monitoring (HTRM) Method

Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C ◽

10.1115/imece2008-68366 ◽

2008 ◽

Cited By ~ 1

Author(s):

M. Izadi ◽

D. K. Aidun ◽

P. Marzocca ◽

H. Lee

Keyword(s):

Heat Transfer ◽

Heat Exchangers ◽

Evaluation System ◽

Tube Wall ◽

Quantitative Information ◽

Fouling Resistance ◽

Output Data ◽

Transfer Resistance ◽

Geometrical Characteristics ◽

On Line

The aim of this paper is to describe a monitoring system for fouling phenomenon in tubular heat exchangers. This system is based on a physical model of the fouling resistance. A mathematical model of the fouling resistance is also developed based on applied thermal heat, the inside heat transfer coefficient and geometrical characteristics of the heat exchanger. The resulting model is a function of measured quantities such as water and tube wall temperatures, fluid flow velocities, and some physical properties of the fluid flowing inside the tubes such as viscosity, conductivity, and density. An on-line fouling evaluation system has been prepared and heat transfer resistance for selected solutions has been measured in real time by this system. Experimental results provide quantitative information of liquid-side fouling on heat transfer surfaces, and its effects on the thermal efficiency. Output data is significantly important for the design, and for formulating operating and cleaning schedules of the equipment.

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Experimental Investigation and Comparison on Fin Surfaces Performance of Flat Tube Heat Exchangers

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.354-355.389 ◽

2011 ◽

Vol 354-355 ◽

pp. 389-393 ◽

Cited By ~ 4

Author(s):

Jun Qi Dong ◽

Qian Chen ◽

Wu Jie Wei

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Pressure Drop ◽

Heat Exchangers ◽

Transfer Enhancement ◽

Air Velocity ◽

Flat Tube ◽

Louvered Fin ◽

Performance Of Heat Transfer ◽

Offset Strip Fin

An experimental study has been carried out to investigate the heat transfer and pressure drop characteristics of flat tube heat exchangers with plain, wavy, louvered and offset strip fin surfaces. Results are presented as plots of Colburn j factor and friction factor f against Reynolds in the range of 600-6500. Additionally, the dimensional heat transfer coefficient and pressure drop are presented as a function of frontal air velocity. Finally, two comparison methods are adopted to evaluate the air side performance of the plain fin, wavy fin, louvered fin and offset strip fin surface. The results show that the offset strip fin has the best performance of heat transfer enhancement.

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Air-Side Heat Transfer and Pressure Drop Characteristics of Multi-Louver Fin and Flat Tube Heat Exchangers

10.1115/imece2000-1312 ◽

2000 ◽

Author(s):

Man-Hoe Kim ◽

Clark W. Bullard

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Heat Exchangers ◽

Water Flow Rate ◽

Cross Flow ◽

Reynolds Numbers ◽

Flat Tube ◽

Louvered Fin ◽

Flow Heat ◽

Fanning Friction Factor

Abstract An experimental study on the air-side heat transfer and pressure drop characteristics for multi-louvered fin and flat tube heat exchangers has been performed. For 45 heat exchangers with different louver angles (15–29°), fin pitches (1.0, 1.2, 1.4 mm) and flow depths (16, 20, 24 mm), a series of tests were conducted for the air-side Reynolds numbers of 100–600, at a constant tube-side water flow rate of 0.32 m3/h. The inlet temperatures of the air and water for heat exchangers were 21°C and 45°C, respectively. The air-side thermal performance data were analyzed using effectiveness-NTU method for cross-flow heat exchanger with both fluids unmixed. The heat transfer coefficient and pressure drop data for heat exchangers with different geometrical configurations were reported in terms of Colburn j-factor and Fanning friction factor f, as functions of Reynolds number based on louver pitch. Correlations for j and f factors are developed and compared to other correlations.

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Louver Finned Heat Exchangers for Automotive Sector: Numerical Simulations of Heat Transfer and Flow Resistance Coping With Industrial Constraints

Journal of Heat Transfer ◽

10.1115/1.4024758 ◽

2013 ◽

Vol 135 (12) ◽

Cited By ~ 8

Author(s):

M. Ferrero ◽

A. Scattina ◽

E. Chiavazzo ◽

F. Carena ◽

D. Perocchio ◽

...

Keyword(s):

Heat Transfer ◽

Numerical Simulations ◽

Heat Exchangers ◽

Geometrical Parameters ◽

Pressure Drops ◽

Compact Heat Exchangers ◽

Optimum Configuration ◽

Louvered Fin ◽

Multiple Regression Technique ◽

Louvered Fins

Louvered fins perform better than any other geometry in accomplishing the task of enhancing heat transfer of compact heat exchangers without prohibitive costs and pressure drops. For this reason, they are widely adopted for automotive applications. However, in order to improve louvered-fin compact heat exchangers, it is strongly required to understand how louvered fins behave regarding both heat transfer and pressure drop taking into account industrial constraints. For this purpose, numerical simulations based on the equations of thermofluid dynamics have been developed for this study. In particular, boundary heat flux and pressure distributions have been analyzed along the louvered-fin assembly and around the louvers, and even the effects of the flat portions (central and lateral louvers) have been investigated. In particular, the effects of the main geometrical parameters, such as fin pitch, louver pitch, and louver angle, have been evaluated by performing simulations on 40 different configurations. The results show that there is not one optimum configuration for the heat exchangers. Finally, a detailed procedure for the optimization of louvered-fin compact heat exchangers, considering industrial constraints is suggested according to multiple regression technique of the numerical results.

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