journal of xi'an university of architecture & technology

A STUDY ON ANALYSIS OF CFD ANALYSIS OF HEAT TRANSFER ENHANCEMENT IN

SHELL BY USING PASSIVE TECHNIQUE

D.Ravi1, P.Radha Krishna Prasad

2

Assistant Professor, Department of Mechanical Engineering, Chaitanya Bharathi Institute of Technology,

Gandipet, Hyderabad, Telangana, India.500075..

Assistant Professor, Department of Mechanical Engineering, Chaitanya Bharathi Institute of Technology,

Gandipet, Hyderabad, Telangana, India.500075..

ABSTRACT:

The heat transfer enhancement is very important many engineering applications to increase the

performance of heat exchangers. The active techniques required external power like surface vibrations,

electrical fields etc and the passive techniques are those which does not required any external power but

the inserts are required to disturb the flow like tape inserts etc moreover literature survey says passive

techniques gives more heat transfer rate without external power requirement by keeping different tape

inserts. However CFD tool is very important and effective tool to understanding heat transfer

applications. Computational heat transfer flow modeling is one of the great challenges in the classical

sciences. By incorporating the inserts the heat transfer enhancement is increased due to its importance in

different applications. By CFD modeling by taking concentric tube by considering with and without

inserts we conclude that heat transfer enhancement by using ANSYS Fluent version 14.5.

The Heat exchanger is a device which used to transfer heat from one fluid to another through a

solid medium or interface. There is various type of heat exchanger available. In this paper shell and tube

type heat exchanger is selected. Our objective was to change the cross section of tube to improve the

efficiency of the heat exchanger. Square, Square with fillet and a hexagonal cross section of tubes is

selected for the study. Design of new shell and tube heat exchanger is done using standard designing

procedure and 3D modeling is done in Solid works 2018. Finite Element Analysis software ANSYS

Workbench 18.0 is used to perform CFD analysis under a standard working condition to find performance

parameter. We found that the hexagonal cross-section provides more effective heat exchange due to

increase in the convective surface.

KEYWORDS: Heat Exchanger, Shell and Tube Type, CFD, Tube cross-section, Design, and Analysis

• INTRODUCTION

The heat transfer enhancement technology (HTET) has been developed and widely

applied to heat exchanger applications over last decade, such as refrigeration, automotives,

process industry, nuclear reactors, and solar water heaters. Till date, there have been many

attempts to reduce the sizes and the costs of the heat exchangers and their energy consumption

with the most influential factors being heat transfer coefficients and pressure drops, which

generally lead to the incurring of less capital costs.

Journal of Xi'an University of Architecture & Technology

Volume XIII, Issue 5, 2021

ISSN No : 1006-7930

Page No: 404

HTET can offer significant economic benefits in various industrial processes. By

“augmentation” we mean an enhancement in heat transfer, over that which is existent on the

reference surface for similar operating conditions.

Bergles and Webb [1, 2] have reported comprehensive reviews on techniques for heat

transfer enhancement. For a single-phase heat transfer, the enhancement has been brought using

roughened surfaces and other augmentation techniques, such as swirl/vortex flow devices and

modifications to duct cross sections and surfaces. These are the passive augmentation techniques,

which can increase the convective heat transfer coefficient on the tube side. Many techniques for

the enhancement of heat transfer in tubes have been proposed over the years.

Siddique et al. [3] reported the following heat transfer enhancers in his review paper: (a)

extended surfaces including fins and microfins, (b) porous media, (c) large particles suspensions,

(d) nanofluids, (e) phase-change devices, (f) flexible seals, (g) flexible complex seals, (h) vortex

generators, (i) protrusions, and (j) ultrahigh thermal conductivity composite materials. Many

methods that assist in heat transfer enhancement effects have been extracted from the literature.

Among of these methods discussed in the literature are using joint fins, fin roots, fin

networks, biconvections, permeable fins, porous fins, and helical microfins and using

complicated designs of twisted-tapes. The authors concluded that more attention should be made

towards single phase heat transfer augmented with microfins in order to alleviate the

disagreements between the works of the different authors.

Due to the high consumption and the reducing availability of fossil fuel resource, high thermal

performance heat exchanger is subject to great interest over decades. Typically, two fluids with different

temperature circulate through the heat exchanger in natural or forced convection manners and the thermal

energy is exchanged via surfaces during the process. The performance of heat exchanger is dependent on

various factors such as mass flow rate of the fluids, length of fluid travel, number and arrangement of

baffle plates etc.

To improve the efficiency of the heat exchanger, maximizing the surface area of the wall between

two fluids and minimizing resistance flow passing across the exchanger are two most concerned focuses.

The increase of area is the most direct way to exchange more thermal energy. Performance enhancement

of heat exchangers has been a hot topic for researchers all around to obtain the optimal output from a heat

exchanger for the same amount of work done on it in order to conserve energy and money. Heat exchanger

is a piece of equipment built for efficient heat transfer from one medium to another.

They facilitate the exchange of heat between two fluids that are at different temperatures while keeping

them from mixing with each other. Different applications of heat exchanger are condensers, evaporators,

boilers conditionation and refrigeration etc. Heat exchanger is used in automobile radiators and coolers. Heat

exchangers are also abundant in chemical and process industries. We will consider only the more common

types here for discussing some analysis and design methodologies. Heat exchangers are p o pul ar used in



ISSN No : 1006-7930

Page No: 405

industrial and engineering applications. The design procedure of heat exchangers is quite complicated, as it

needs exact analysis of heat transfer rate, efficiency and pressure drop apart from issues such as long- term

performance and the economic aspect of the equipment. By incorporating different techniques we conclude

that heat transfer coefficient increases with the cost of pressure drop. Heat transfer enhancement techniques are

classified as follows.

1.1 Passive Techniques:

• Passive techniques are geometrical change or with disturbing the fluid by keeping inserts.

They promote higher heat transfer coefficients by disturbing or altering the existing flow

behaviour (except for extended surfaces) which also leads to increase in the pressure drop.

Heat transfer augmentation achieved by following

• Treated Surfaces: Treated surfaces are applicable primarily in two-phase heat transfer, and

they consist of a variety of structured surfaces (continuous or discontinuous integral surface

roughness or alterations) and coatings. In the event that this treatment provides a “roughness”

to the surface, its size (normal protrusion to the surface) is not large enough to influence

single-phase forced convection

• Rough surfaces: Structured roughness can be integral to the surface, or the protuberances can

be introduced in the form of wire-coil-type inserts. The former can be produced by machining

(e.g., knurling, threading, grooving), forming, casting, or welding, and the resulting surface

proturberances or grooves can be two dimensional or discrete three-dimensional in their

geometrical arrangement

• Extended surfaces: Extended or finned surfaces are perhaps the most widely used and

researched of all enhancement techniques. Enhanced heat transfer from finned surfaces by

buoyancy-driven natural or free convection has been considered primarily for cooling of

electrical and electronic devices and for hot-water baseboard room heaters. building/room

heating equipment, the use of baseboard heaters has declined considerably; in fact, this

practice is close to being discontinued.

• Swirl flow devices: Swirl flow devices generally consist of a variety of tube inserts,

geometrically varied flow arrangements, and duct geometry modifications that produce

secondary flows. Typical examples of each of these techniques include twisted-tape inserts,

periodic tangential fluid injection, and helically twisted tubes.

• Coiled tubes: A coiled or curved tube has long been recognized as a swirl-producing flow

geometryThe secondary fluid motion is generated essentially by the continuous change in

direction of the tangential vector to the bounding curved surface of the duct, which results in

the local deflection of the bulk flow velocity vector.

• LITERATURE REVIEW

In this paper, Study is conducted on CFD analysis of heat exchanger with helically coiled tube.

Due to comparatively more surface area than standard heat exchanger, it is proved to be more effective

and efficient. [1]



ISSN No : 1006-7930

Page No: 406

In this paper, a heat transfer characteristic of different cross section has been conducted. They

have also incorporated waviness on channel by varying the Reynolds number and the amplitude of

waviness. It was found that this different cross section with wavy channel provide high heat transfer

coefficient (HTC) and would be effective in thermal applications. .[2]

In this paper, an attempt has been made to investigate the complex flow and temperature pattern

in such a short shell and tube type heat exchanger, with and without baffles in the shell side Heat

exchangers are analysed using CFD code OpenFOAM-2.2.0 for different mass flow rates. The effect of

flow field on shell side heat transfer coefficient and a comparison with analytical methods are

presented.[3]

This literature review focuses on the applications of Computational Fluid Dynamics (CFD) in the

field of heat exchangers. It has been found that CFD has been employed for the following areas of study

in various types of heat exchangers: fluid flow misdistribution, fouling, pressure drop and thermal

analysis in the design and optimization phase.[4]

The article presents passive heat transfer enhancement method in the form of baffles to increase

the energy efficiency of the heat exchanger. Most of the work focuses on the impact of geometrical

parameters of the coil itself. This article successfully proves that it is possible to increase the efficiency of

heat exchange in the heat exchanger shell type coil with baffle inserts. [6]

In this paper Finite Volume Method is used for numerical analysis of an internally finned axi-

symmetric tube heat exchanger. In this paper the computational fluid dynamics is used for parametric

study. The results obtained from the study for a steady and laminar flow of fluid under mixed flow

convection heat transfer condition shows that there exists an optimum number for fins to keep the pipe

wall temperature at a minimum. [7]

The paper represents that the heat transfer enhancement in a heat exchanger tube by installing fins

on the outer surface of hot water tube. Design process for heat exchanger is carried out in AUTODESK

INVENTOR and fluid domain is formed in ANSYS workbench. After finding the solution the results are

compared between the two designs for counterblow. According to results, it concluded that in case of fin

is used; effectiveness also increases due to use of fins.

[8]In this study the analytical design of the heat exchanger has been validated based on the results

obtained from the Computational fluid dynamics analysis. In this paper the standard k-ε modeling is used

in CFD analysis. In this paper the theoretically and analytically heat transfer rate of double pipe heat

exchanger is calculated. By comparing these results, the results show that the design and analysis of the

double pipe heat exchanger has been a great success. [9]The paper represents that Experimental Study on

Heat Transfer and Friction Factor in Laminar Forced Convection overflag Tube in Channel Flow.

The experiments were conducted at a flat tube in the flow direction, the five air velocity between

0.2 and1.0 m/s, and Reynolds number based on the hydraulic diameter (Re Dh) was considered from

124.5 to622.5. The uniform heat fluxes supplies are at the surface of the tube are 354.9, 1016.3 and

1935.8 W/m2 respectively. The results shows that the average Nusselt number increase with increase

Reynolds number with any heat flux supply tested and also the pressure drop increased and friction factor

decrease with increasing of free stream velocity. [10]



ISSN No : 1006-7930

Page No: 407

III.OBJECTIVE

• To improve the performance of heat exchanger by changing tube geometry.

• To test the performance using Computational Fluid Dynamics (CFD) using appropriate simulation

tools.

IV.PROBLEM DEFINITION

Heat exchangers are devices which do not require power to operate themselves, but they need

power in order to pump the working fluid in and out of the device’s system. The Performance will be

enhanced if the power required to pump the fluids is within acceptable limits according to the heat

transfer occurring between the fluids, i.e. the effectiveness and efficiency of the heat exchanger. There are

three goals that are normally considered in the optimal design of heat exchangers: (1) Minimizing the

pressure drop (pumping power), (2) Maximizing the thermal performance and (3) Minimizing the entropy

generation (thermodynamic), which are to be achieved in any possible way known or not known. Thus, an

optimum method is to be evaluated, for which the performance of heat exchanger is boosted for same

pumping power and ideally without any pressure drops.

• METHODOLOGY

• Studying the existing heat exchanger working characteristics, effectiveness, effectiveness,

efficiency, losses etc.

• Generating 3D model of existing heat exchanger using Solidworks software.

• Theoretical calculations for new models.

• Selecting of parameters for CFD analysis.

• Obtaining its CFD model and simulating its working condition.

• Implementing methods that are ought to improve the performance of heat exchanger.

• Performing CFD analysis in ANSYS Fluent on new models

• Comparing the results with the original model.

VI.THEORETICAL CALCULATION

Th1 – Inlet temperature of the hot fluid

Th2 – Outlet temperature of the hot fluid

Tc1 – Inlet temperature of the Cold fluid

Tc2 (CFD) – Simulation value of Inlet cold fluid

Tc2 – Outlet temperature of the cold fluid

Qh –heat loss by hot fluid

Qc – heat gain by cold fluid

Mc–mass flow rate of the cold fluid (kg/s)



ISSN No : 1006-7930

Page No: 408

Cpc– Specific heat capacity of cold fluid (kJ/kg-k)

Mh– mass flow rate of the hot fluid (kg/s)

Mch– Specific heat capacity of hot fluid (kJ/kg-k)

Case1: Circular tube (original) model [12]

Th1 = 353.15 Th2 = 345.035

Tc1 = 293.15 Tc2=?

Qh = Qc

Mh * Cph * (Th1-Th2) = Mc * Cpc * (Tc2 -Tc1)

0.694*40182 (353.15-345.035) = 1.7767*4.182 (Tc2 -293.15)

Tc2 = 296.3198148 K

Case2: Square tube model

Th1 = 353.15 Th2 = 345.508

Tc1 = 293.15 Tc2=?

Qh = Qc


0.694*40182 (353.15-345.508) = 1.7767*4.182 (Tc2 -293.15)

Tc2 = 296.1350554 K

Case3: Square tube model

Th1 = 353.15 Th2 = 345.062

Tc1 = 293.15 Tc2=?

Qh = Qc


0.694*40182 (353.15-345.062) = 1.7767*4.182 (Tc2 -293.15)



ISSN No : 1006-7930

Page No: 409

Tc2 = 296.3092683 k

Case4: Square with fillet tube model

Th1 = 353.15 Th2 = 302.784

Tc1 = 293.15 Tc2=?

Qh = Qc


0.694*40182 (353.15-302.784) = 1.7767*4.182 (Tc2 -293.15)

Tc2 = 312.8235543 K

VII. 3D MODELING

Fig 1: heat exchanger tube cross sections

Above fig shows different cross sections (circular, hexagonal, square, and square with fillet) of tube selected for study.



ISSN No : 1006-7930

Page No: 410

Fig 2: Circular c/s tube Heat Exchanger model

Above fig shows Heat Exchanger 3D model having circular cross section of tube.

Fig 3: Square c/s tube Heat Exchanger model

Above fig shows Heat Exchanger 3D model having square cross section of tube.

Above fig shows Heat Exchanger 3D model having square with fillet cross section of tube.



ISSN No : 1006-7930

Page No: 411

Fig 4: Hexagonal c/s tube Heat Exchanger model

Above fig shows Heat Exchanger 3D model having hexagonal cross section of tube.

VIII. CFD SIMULATION

Fig 5: Temperature plot of all domains of circular c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of all domains of circular cross section tube Heat Exchanger.

Fig 6: Temperature plot of Temperature plot of Cold fluid of circular c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of Cold fluid of circular cross section tube Heat Exchanger.



ISSN No : 1006-7930

Page No: 412

Fig 7: Temperature plot of Temperature plot of hot fluid of circular c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of hot fluid of circular cross section tube Heat Exchanger.

Fig 8: Temperature plot of all domains of Square c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of all domains of Square cross section tube Heat Exchanger.



ISSN No : 1006-7930

Page No: 413

Fig 9: Temperature plot of Cold fluid of Square c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of Cold fluid of Square cross section tube Heat Exchanger.

Above fig shows CFD analysis and result of Temperature plot of hot fluid of Square cross section tube Heat Exchanger.

Fig 10: Temperature plot of all domains of Square with Fillet c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of all domains of Square with Fillet cross section tube H. E.

Fig 13: Temperature plot of Cold fluid of Square with Fillet c/s tube H.E

Fig 11: Temperature plot of hot fluid of Square with Fillet c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of Cold fluid of Square with Fillet cross section tube Heat

Exchanger.



ISSN No : 1006-7930

Page No: 414

Fig 12: Temperature plot of hot fluid of Square with Fillet c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of hot fluid of Square with Fillet cross section tube Heat

Exchanger.

Fig 13: Temperature plot of all domains of Hexagonal c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of all domains of Hexagonal cross section tube Heat Exchanger.



ISSN No : 1006-7930

Page No: 415

Fig 14: Temperature plot of Cold fluid of Hexagonal c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of Cold fluid of Hexagonal cross section tube Heat Exchanger.

Fig 15: Temperature plot of hot fluid of Hexagonal c/s tube H.E

Above fig shows CFD analysis and result of Temperature plot of hot fluid of Hexagonal cross section tube Heat Exchanger.

IX.RESULT

Formulae

• Percentage of difference between T-cfd

and T-c2 [(Tc2 - Tc2-CFD)/Tc2]*100

• Heat transfer

Mh * Cph * (Th1-Th2)

• Effectiveness

[Mh * Cph * (Th1-Th2)] / [Mh * Cph * (Th1-Tc1)]

X. CONCLUSION

From the results and data obtained from CFD we have concluded that K-w turbulence model

provide better suitability to our simulation. Model with hexagonal tube provides better effectiveness than

other models. Heat transfer rate in the heat exchanger with hexagonal tube also provides good heat

transfer rate. Increasing effectiveness of heat exchanger increases its performance in its respective



ISSN No : 1006-7930

Page No: 416

application.CFD analysis is carried out by taking double pipe heat exchanger with cold and hot fluids

with different boundary conditions by incorporating helical tape inserts .

It can be concluded as follows: By using passive techniques that is by inserting helical tape

inserts the heat transfer enhancement increased by 10-15% with the cost of reasonable allowable pressure

drop .In this report we achieved enhancement of heat transfer effectively. Future work may be extended

to:

� Material should be changed to Aluminum to copper or which is having high

thermal conductivity materials

� Combination of techniques may be used to enhancement of heat transfer coefficient

by compound techniques.

� Reduce the width of helical tape inserts with low Reynolds number.

� By varying low Reynolds numbers check the Heat transfer enhancement coefficient

REFERENCES

• Vijaya Kumar Reddy, Sudheer Prem Kumar, Ravi Gugulothu, Kakaraparthi Anuja and Viajaya Rao, “CFD Analysis of a Helically Coiled Tube in

Tube Heat Exchanger”, Materials Today: Proceedings 4, 2341–2349, 2017.

• Karan Ghule, M.S. Soni, “Numerical Heat Transfer Analysis of Wavy Micro Channels with Different Cross Sections”, Energy Procedia, vol. 109,

pp. 471 – 478, (2017),.

• Eshita Pal, Inder Kumar, Jyeshtharaj B. Joshi, N.K. Maheshwari, “CFD simulations of shell-side flow in a shell-and-tube type heat exchanger with

and without baffles”, Chemical Engineering Science, vol. 143, pp. 314–340, 2016.

• M. M. Bhutt, Nasir H., M. Bashir, Kanwar N. Ahmad, Sarfaraz Khan, “ Review on CFD use in the various design of heat exchangers ”, Applied

Thermal Engineering, 32, pp.1-12, 2012.

• Lu Ma, Ke Wang, Minshan Liu, Dan Wang, Tong Liu, Yongqing Wang, Zunchao Liu, “Numerical study on performances of shell-side in trefoil-

hole and quatrefoil-hole baffle heat exchangers”, Applied Thermal Engineering, vol. 123, pp. 1444-1455, 2017.

• R Andrzejczyk, T Muszynski, “Geometrical and Thermodynamic characteristics of mixed convection heat transfer in the shell and coil tube heat

exchanger with a number of baffles”, Applied Thermal Engineering, volume 121, pp115-125, 2017.

• S.K.Routa, D. N. Thatoia, A.K. Acharya, D. P. Mishra, “CFD supported performance estimation of an internally finned tube heat exchanger under

mixed convection flow”, Procedia Engineering 38, pp. 585-597, 2012.

• N T Anoop.K.S, Deepak.C.S, E..P.Kuriakose, Habeeb Rahman.K.K, Karthik.K.V, “Computational fluid dynamics of the tube in tube heat

exchanger with fins”, International Research Journal of Engineering and Technology, volume 3, issue 4, 2016

• J Johnson, Abdul, A Shani, Harif, H Hameed, Nithin, “Computational fluid dynamics of double pipe heat exchanger”, International Journal of

Science, Engineering and technology research, volume 4, issue 5, 2015

• Tahseen Ahmad Tahseena, M.M. Rahman and M. Ishaka, “Experimental study on Heat transfer and friction factor in laminar forced convection

over flat tube over channel flow”, International conference on thermal engineering, volume 105, pp. 46-55, 2015

• Shrikant, R. Sivakumar, N. Anantharaman, M. Vivekenandan, “CFD simulation study of shell and tube heat exchangers with different baffle

segment configurations”, Applied Thermal Engineering, Volume 108, Pages 999-1007, 2016.

• Mustapha Mellal, Redouane Benzeguir, Djamel Sahel, Houari Ameur, “Hydro-thermal shell-side performance evaluation of a shell and tube

exchanger under different baffle arrangement and orientation”, International Journal of Thermal Sciences, volume 121, page no 138-149, 2017.

• Al-Fahed S, and Chakroun W, 1996. Effect of tube -tape clearance on heat transfer for fully developed turbulent

flow in a horizontal isothermal tube, Int. J. Heat Fluid Flow, Vol. 17, No. 2, pp. 173-178.

• Al-Fahed S, Chamra L.M, and Chakroun W, 1998. Pressure drop and heat transfer comparison for both microfin

tube and twistedtape inserts in laminar flow, Experimental Thermal Fluid Science, Vol. 18, No. 4, pp. 323–333.

• Akhavan-Behabadi M.A, Ravi Kumar, Mohammadpour .A and Jamali-Asthiani .M, 2009. Effect of twisted tape

insert on heat transfer and pressure drop in horizontal evaporators for the flow of R-134a, International Journal of

Refrigeration, Vol. 32, No. 5, pp. 922-930.

• Akhavan-Behabadi M. A., Ravi Kumar and A. Rajabi-Najar, 2007. Augmentation of heat transfer by twisted tape

inserts during condensation of R-134a inside a horizontal tube, Heat and Mass Transfer, Vol. 44, No. 6, pp. 651-657

• S.K.Saha A.Dutta “ Thermo hydraulic study of laminar swirl flow through a circular tube fitted with twisted tapes”

Trans. ASME Journal of heat transfer June 2001, Vol-123/ pages 417-427.



ISSN No : 1006-7930

Page No: 417

• Watcharin Noothong, Smith Eiamsa-ard and Pongjet Promvonge” Effect of twisted tape inserts on heat transfer in

tube” 2nd joint international conference on “sustainable Energy and Environment 2006” Bangkok, Thiland.

• Paisarn Naphon “Heat transfer and pressure drop in the horizontal double pipes with and without twisted tape insert”

2005 Elsevier Ltd.

• Smith Eiamsa-ard , Chinaruk Thianpong, Pongjet Promvonge “ Experimental investigation of heat transfer and flow

friction in a Circular tube fitted with regularly spaced twisted tape elements” International Communications in Heat

and Mass Transfer Vol. 33, Dec 2006.

• Ashis K. Mazumder, Sujoy K. Saha “Enhancement of Thermo hydraulic Performance of Turbulent Flow in

Rectangular and Square Ribbed Ducts With Twisted-Tape Inserts” Journal of Heat Transfer AUGUST 2008, Vol.

130.

• M. Siddique, A.-R. A. Khaled, N. I. Abdulhafiz, and A. Y. Boukhary” Review Article Recent Advances in Heat

Transfer Enhancements: A Review Report” International Journal of Chemical Engineering Volume 2010 (2010),

Article ID 106461, 28 pages



ISSN No : 1006-7930

Page No: 418

journal of xi'an university of architecture & technology

Documents