International Journal of Mechanical, Civil, Automobile and Structural Engineering (IJMCAS)

Vol. 1, Issue. 1, April 2015 ISSN (Online): 2395-6755

1

Abstract:- The computational fluid dynamics (CFD)

is the science of predicting fluid flow, heat transfer, mass transfer, chemical reactions, and related

phenomena by solving the mathematical equations

which govern these processes using a numerical

process. Various researches are going on to avoid

scaling (or) fouling formation in shell and tube heat

exchanger and increase the rate of heat transfer. Here

we are introduce our concept to avoid scaling by

wounding the copper coil on the shell and tube in the

heat exchanger. Different case of heat exchangers are

analyzing by CFD simulation software and

comparing the result of rate of heat transfer.The copper coil made with sharp edges wound on the

tube. So, it reduce the fouling formation 85-90% and

enhance the rate of heat transfer when compare to

other type of heat exchanger.

Keywords: CFD simulation software, copper coil

(plain and sharp), Shell and Tube type Heat

exchanger.

I. INTRODUCTION

Computational Fluid Dynamics (CFD) as it is

popularly known is used to generate flow simulations

with the help of computer. CFD involves the solution

of the governing loss of fluid dynamics numerically. The complex sets of partial differential equation of

solved on the geometrical domain divided into small

volumes, commonly known as a mesh or grid.

Different diameters of tube and different mass flow

rates are considered to examine the optimal flow

distribution and this problem has been subjected to

effect of materials (Aluminum, copper and alloys)

used for tube manufacturing on heat transfer

rate[1].To verify the shell and tube heat exchanger

designed with the use of the Kerns method by the use of CFD. It is used to study the

Temperature and velocity profiles through the tubes

and the shell [2]. Using the ANSYS software, the

thermal analysis of shell and tube heat exchanger is

carried out by varying the tube materials. The Tubular heat exchanger can be designed for high

pressures relative to environment and high pressure

differences between the fluids. It is used primarily for

liquid to liquid [3].The heat transfer enhancement in

a heat exchanger tube by installing seven different

baffle arrangements. The rate of heat transfer is

maximum for rectangular and triangular baffle

because behind maximum heat transfer rate was that

due to use of baffles, turbulence was increased as

they allow more mixing of fluid layers and resulted in

increase of heat transfer through the heat exchanger tube [4]. The steady of increase in computing power

has enable model to react for multiphase flows in

realistic geometry with good resolution in [5]. This

system is used to study a fin-and-tube heat

exchanger. The purpose of the work was investigate

the possibilities of eventually using CFD calculations

for design of heat exchangers instead of expensive

experimental testing and prototype production. Here

created a model of a two-row fin and tube heat

exchanger by using open source Salome software in

[6]. Introducing continuous helical baffles in the shell

side of the heat exchanger and small corners at variable angles of the liquid flow are the result of

introduction of segmental baffles which improves

heat transfer and huge decline in pressure thus

increasing the fouling resistance in [7].The optimum

pin shape based on minimum pressure drop and

maximizing the heat transfer across the automobile

engine body. The results indicate that the drop shaped

pin fins show improved results on the basis of heat

transfer and pressure drop by comparing other fins.

The reason behind the improvement in heat transfer

by drop shape pin fin was increased wetted surface area and delay in thermal flow separation from drop

shape pin fin in [8].The phenomenon of forced

convection with turbulent flow of industrial processes

is complicated to develop analytically. The only key

to the problem is empirical models and numerical

solutions. The heat transfer coefficient (h) and

friction factor are very important parameters for fluid

flow systems due to their use in determining the heat

transfer rate and the pressure drop of the system

Comparison of Epoxy Composites using E-Glass/Carbon

Reinforcements 1M.Arun Kumar,

2K.Dinesh Kumar,

3S.Karthick

1Assistant Professor, Department of Mechanical Engineering, JIT Thopur, India 2,3

UG Students, Department of Mechanical Engineering, JIT Thopur, India

International Journal of Mechanical, Civil, Automobile and Structural Engineering (IJMCAS)

Vol. 1, Issue. 1, April 2015 ISSN (Online): 2395-6755

2

respectively. Then CFD simulation compared with

experimental data for air flow [9]. Heat transfer

enhancement by Plain and curved winglet type vertex

generators with punched holes, the flow resistance is

also lower in case of curved winglet type than

corresponding plain winglet vertex generators (VGs).

The best results for heat transfer enhancement is

obtained at high Reynolds number values (Re

>10000) by using VGs. This work presents a

numerically study on the mean nusselt number,

friction factor and heat enhancement characteristics

in a rectangular channel having a pair of winglet type VGs under uniform heat flux of 416.67 w/m2. The

result indicate the advantages of using curved winglet

VGs with punched holes for heat transfer

enhancement [10].Comparative study between

Helical coil and Straight tube heat exchanger, here

present two conditions are, In the first condition-

When cold water mass flow rate is constant and hot

water mass flow rate increased the effectiveness

decreases. Second condition-Increase in cold water

mass flow rate for constant hot water mass flow rate

in increase in effectiveness.Helical coil counter flow is most effective in all these conditions and straight

tube parallel flow heat exchanger is least effective.

Because the helical coil tube heat exchanger, the

increased heat transfer coefficients are a consequence

of the curvature of the coil, which induces centrifugal

force to act on moving fluid, resulting in the

development of secondary flow. Due to the curvature

effect, the fluid streams in the outer side of the pipe

moves faster than the fluid streams in the inner side

of pipe in [11].

II. GEOMETRICAL MODELING AND MESH GENERATION

A. Methodology:

For CFD simulation, first of all, the geometry of the

shell and tube heat exchanger was created by using

SOLIDWORKS. The geometry of the heat exchanger tube is in 3D view. After the geometry

creation, Extracting the fluid region is the next step in

which all the surfaces, which are in the contact of

fluid are taken alone and all other surfaces are

removed completely. To keep the domain air /water tight some extra surfaces are created. This clean up is

done in ANSA meshing tool which is very robust

clean up tool.After cleaning up the geometry surface

mesh is generated in ANSA tool itself. All the

surfaces are discredited using tri surface element .As

the geometry has some complicated and skewed

surfaces tri surface elements are used to capture

the geometry. Volume mesh is generated in T-

Grid which is a robust volume mesh generator.

Volume is dicretized using tetrahedron .Each and

every cell centroid is the co-ordinate at which the

navier-stokes system of equations are solved.

ANSYS-FLUENT was used as the solver. Here the

fluid flow is assumed to be three dimensional and

turbulent.Afterselection of turbulence model

boundary conditions are specified. Fluent has

capability to store value of physical parameters for

any point in the domain for analysis. Seven points

were created to store the value of physical parameters such as temperature, velocity, and pressure. FLUENT

is now ready to simulate flow problem. Finally, post

processing was done for result analysis.

B. Geometric Modeling: Geometric model is generated in SOLIDWORKS which

is very popular modeling software. The generated model

is exported to the further process in the form of .IGES as

it is a third party format which can be taken into any other

tools. Here, Two type of copper coil is used (sharp and

flat edge) to create some kind of localized suction in

between the copper coils due to the condensation process.

So, it avoids the scale or fouling formation. The Sharp

edge copper coil is more efficient when compared with

the Flat edge copper coil.

C .Meshing Of CFD Domain:

After making the geometry of the domain, next step is to

mesh the domain. The CFD tool was used to create the

fine mesh quality. In considering case-1, case-2 (sharp

grooves) and case-3 (plain grooves), the surface and

volume mesh is generated with 5.25 and 18.89 lakhs, 5.09

and 18.96 lakhs,4.27 and 17.24 lakhs respectively. This

mesh contains tetrahedral cells having triangular faces at

the boundaries are shown in fig-1,2,3.The mesh details

are given below

International Journal of Mechanical, Civil, Automobile and Structural Engineering (IJMCAS)

Vol. 1, Issue. 1, April 2015 ISSN (Online): 2395-6755

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MESH DETAILS:

BASE CASE

Figure-1Base case of shell and tube heat exchanger

This structure shows the general layout of shell and

tube heat exchanger in meshed condition by using

ANSA tool.

MODIFICATION-1

Figure-2 Shell and tube heat exchanger with sharp

edged grooves in meshed condition

This structure shows the layout of shell and tube heat

exchanger with wounding of sharp edged grooves in

meshed condition.

MODIFICATION-2

Figure-3 shell and tube heat exchanger with plain

edged grooves in meshed condition

This structure shows the layout of shell and tube heat

exchanger with wounding of plain edged grooves in

meshed condition.

III. Boundary Conditions: After mesh generation, boundary condition are

defined for CFD domain as shown in table 1. Specify

boundary condition icon is used to create boundaries. In FLUENT launcher, both fluid and

solid can be defined.Generally, the copper materials

used in this analysis. The fluid used in this analysis is

water vapour. The material and fluid properties are

mentioned in table 2.

Table 1: Fluid and Wall boundary conditions

Steam and coolant water Fluid zone

Tube thickness and copper

wire

Solid zone

Coolant inlet Velocity inlet with varying

velocity Coolant outlet Pressure outlet

Steam inlet Mass flow inlet with mass flow

rate 0.5of 0.5 kg/s Steam outlet Pressure outlet

Coolant tube wall No slip and conduction heat

transfer

Shell wall No slip and adiabatic wall

MODEL

SURFACE

MESH Quality

Volume

MESH Quality

BASE CASE 525670 0.6

1889715 0.8499

MODIFICA

TION 1

(SHARP

GROOVES)

509450 0.6

1896024 0.8599

MODIFICA

TION2 (

PLAIN

GROOVES)

427000 0.6

1724411 0.9324

International Journal of Mechanical, Civil, Automobile and Structural Engineering (IJMCAS)

Vol. 1, Issue. 1, April 2015 ISSN (Online): 2395-6755

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Table 2: Fluid and Solid properties considered for

analysis

IV. GOVERNING EQUATIONS OF FLUID DYNAMICS

The basic governing equations 7.1 7.4, which describe the fluid dynamics, are used to solve the steam and water

flow. The energy equation 7.5 was used to define the

conductive heat transfer across the fluid through the solid

region.

Conservation of Mass

+ div( (7.1)

Conservation of X Momentum

+ div (

+ div( SMx(7.2)

Conservation of Y Momentum

+ div (

+ div ( SMy(7.3)

Conservation of Z Momentum

+div (

+div ( SMz(7.4)

Conservation of Energy

Internalenergy:

+div( ( )+

(7.5)

A. EVAPORATION-CONDENSATION MODEL

The evaporation-condensation model is a mechanistic

model with a physical basis. It is available with the

mixture and Eulerian multiphase models. The liquid-

vapour mass transfer (evaporation and condensation) is

governed by the vapour transport equation

v)+ v v)=mlv mvlWhere,

v Vapour phase, - vapour volume fraction, v vapour

density, v -vapourphasevelocity.mlvandmvl are the

rates of mass transfer due to evaporation and

condensation, respectively.These rates use units of

kg/s/m3.

As shown in the right side of Equation 5.6, ANSYS

FLUENT defines positive mass transfer as being from the

liquid to the vapour for evaporation-condensation

problems. Based on the following temperature regimes,

the mass transfer can be described as follows,

If T>Tsat Evaporation =mlvcoeff*ll (T-Tsat) / Tsat

If T

International Journal of Mechanical, Civil, Automobile and Structural Engineering (IJMCAS)

Vol. 1, Issue. 1, April 2015 ISSN (Online): 2395-6755

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The rate of heat transfer depends upon the turbulence

intensity, different cases [Base, Modification 1(sharp

groove), Modification 2(plain edge)] of rate of heat

transfer was analyzed in CFD simulation software.

Thedetails are mentioned in table 3.

RESULT OF MODIFICATION-1

STATIC PRESSURE

Figure-4 Static pressure for modification-1in Fluent

analysis

It is the flow of static pressure Fluent layout of shell

and tube heat exchanger with wounding of sharp edged

grooves.

STATIC TEMPERATURE

Figure-5 Static temperature for modification-1 in fluent

layout

It represent the flow of static temperature range in the

Fluent of shell and tube heat exchanger for

modification-1.

TURBULENT INTENSITY

Figure-6 Turbulent intensity for modification-1 in

fluent layout.

It shows the maximum turbulentintensity in fluent

layout.

VELOCITY CONTOURS

Figure-7 Velocity contours for modification-1 in

fluent layout

The velocity flow diagram is represented in ANSYS

Fluent. In this case represent the maximum velocity

contours.

TABLE-3 TEMPERATURE(K)

MODEL

STEAM-

INLET

TEMPERAT

URE (K)

STEAM-

OUTLET

TEMPERA

TURE (K)

BASE

MODEL

373

321.09

MODIFICAT

ION 1

(SHARP

GROOVES)

373

317.67

MODIFICAT

ION2 (

PLAIN

GROOVES)

373

319.41

International Journal of Mechanical, Civil, Automobile and Structural Engineering (IJMCAS)

Vol. 1, Issue. 1, April 2015 ISSN (Online): 2395-6755

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