“CFD ANALYSIS HELICAL COIL HEAT EXCHANGER”ijariie.com/AdminUploadPdf/CFD_ANALYSIS_HELICAL_COIL_HEAT_E… · Shinde Digvijay D. et al. [3] studied the experimental investigation

Vol-3 Issue-2 2017 IJARIIE-ISSN(O)-2395-4396

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“CFD ANALYSIS HELICAL COIL HEAT

EXCHANGER” Umang K Patel

1, Prof. Krunal Patel

2

1ME scholar, Mechanical Department, LDRP-ITR, Gandhinagar, India

2Professor, Mechanical Department, LDRP-ITR, Gandhinagar, India

ABSTRCT

Heat exchanger are important engineering system with wide variety of application including power plants,

refrigeration and air conditioning system, heat recovery system, nuclear reactors, chemical processing and food

industries. Working towards the goal of saving energies and to make concise design for mechanical and chemical

devices and plants, heat transfer play major role in design of heat exchangers. We are not use application of

external power, but we can improve the heat transfer rate by modifying the design by providing the helical tubes,

extended surface or swirl flow devices. We improve the heat transfer rate from helical coil tube-in-tube heat

exchangers to use Computational Fluid Dynamics (CFD). My project aims to perform a numerical study of helical

coil tube-in-tube heat exchanger with water as both hot and cold fluid.To improve the effectiveness, D/d geometrical

parameter will be varied for different boundary conditions. The impact of this modification on Cold water

temperature, Hot water temperature, Cold water velocity, Hot water velocity, Reynolds number, with respect to D/d

will also be studied.

Keywords: Helical coil heat exchanger, Heat transfer, Nusselt number, LMTD, Reynolds number

1 INTRODUCTION

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

media may be separated by a solid wall to prevent mixing or they may be in direct contact. The classic example of a

heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows

through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Heat exchange

between flowing fluids is one of the most important physical process of concern, and a variety of heat exchangers

are used in different type of installations, as in process industries, compact heat exchangers nuclear power plant,

food processing, refrigeration, etc. The purpose of constructing a heat exchanger is to get an efficient method of heat

transfer from one fluid to another, by direct contact or by indirect contact.

1.1 CHARACTERSTIC OF HELICAL COIL

Fig. 1 gives the schematic of a helical coil. The pipe has an inner diameter 2r. The coil has a diameter of

2Rc (measured between the centers of the pipes), while the distance between two adjacent turns, called pitch is H.

The coil diameter is also called pitch circle diameter (PCD). The ratio of pipe diameter to coil diameter (r/Rc ) is

called curvature ratio, The ratio of pitch to developed length of one turn (H/2rRc ) is termed non-dimensional pitch,

A. Consider the projection of the coil on a plane passing through the axis of the coil. The angle, which projection of

one turn of the coil makes with a plane perpendicular to the axis, is called the helix angle, Similar to Reynolds

number for flow in pipes, Dean Number is used to characterize the flow in a helical pipe.



Fig 1Basic geometry of a helical pipe

1.2 Heat Transfer Coefficient:

Convective heat transfer is the transfer of heat from one place to another by the movement of fluids due to

the difference in density across a film of the surrounding fluid over the hot surface. Through this film heat transfer

takes place by thermal conduction and as thermal conductivity of most fluids is low, the main resistance lies there.

Heat transfer through the film can be enhanced by increasing the velocity of the fluid flowing over the surface which

results in reduction in thickness of film.

The equation for rate of heat transfer by convection under steady state is given by

( ) Where, h is the film coefficient or surface coefficient

A is the area of the wall,

TW is the wall temperature,

Tatm is surrounding temperature.

The value of „h‟ depends upon the properties of fluid within the film region; hence it is called „Heat

Transfer Coefficient‟. It depends on the different properties of fluid, dimensions of the surface and velocity of the

fluid flow (i.e. nature of flow).

The overall heat transfer coefficient is the overall transfer rate of a series or parallel combination of

convective and conductive walls. The „overall Heat Transfer Coefficient‟ is expressed in terms of thermal

resistances of each fluid stream. The summation of individual resistances is the total thermal resistance and its

inverse is the overall heat transfer coefficient, U.

1.3 Applications

Use of helical coils for heat transfer applications:

1) Helical coils are used for transferring heat in chemical reactors and agitated vessels because heat transfer

coefficients are higher in helical coils. This is especially important when chemical reactions have high

heats of reaction are carried out and the heat generated (or consumed) has to be transferred rapidly to

maintain the temperature of the reaction. Also, because helical coils have a compact configuration, more

heat transfer surface can be provided per unit of space than by the use of straight tubes.

2) Because of the compact configuration of helical coils, they can be readily used in heat transfer application

with space limitations, for example, in steam generations in marine and industrial applications.

3) The helically coiled tube is eminently suited for studying the characteristics of a plug flow reactor in

reaction kinetic studies because the secondary motion present in the helical coil destroys the radial

concentration gradient.



4) The existence of self induce radial acceleration field in helical coils makes helical coils most desirable for

heat transfer and fluid flow applications in the absence of gravity field, such as for space ships in outer

space. Helical coiled tubes have been and are used extensively in cryogenic industry for the liquefaction of

gases.

2 LITERATURE REVIEW Primoz Poredos et al. [2] have studied the thermal characteristics of a concentric-tube helical coil heat

exchanger which is a key element in local ventilation device. Central element of local ventilation device is

concentric tube heat exchanger which is made of a corrugated tube surface. The heat transfer rate can be increased

by increasing the convective heat transfer coefficient or by increasing the heat transfer surface area. So they have

formed corrugated tube concentric counter flow heat exchanger which have sinusoidal, wavy surface in longitudinal

direction of inner tube, which enables heat transfer enhancement. Wilson plot method is used to determine

convective heat transfer coefficient on inside and outside of inner tube of concentric tube heat exchanger with

different corrugation ratios. It is found that highest heat transfer rate was obtained for maximum stretched tube with

corrugation ratio of 1.401, which enables greater effectiveness or a more compact design of concentric tube counter

flow heat exchanger. In comparison with smooth tube, the corrugated tube had a 1.104-3.955 times higher value of

heat transfer surface area and also pressure drop is 3-3.5 times higher than in smooth tube.

Shinde Digvijay D. et al. [3] studied the experimental investigation on heat transfer in cone shaped helical

coil heat exchanger. They also compared heat transfer in cone shaped helical coil heat exchanger with simple helical

coil heat exchanger. For comparative analysis they used both coils with (9.53mm outer dia.),(8.41mm inner dia.) &

axial length of 6096mm. for simple helical coil 7 turns & for conical coil 10 turns with cone angle 65. The

experiment is conducted for different flow rates and calculations are carried out. It was found that the effectiveness

of cone shaped helical coil heat exchanger is more as compared to simple helical coil. In case of cone shaped helical

coil heat exchanger Nusselt no. is higher than simple helical coil. They were found that the heat transfer rate for

cone shaped helical coil is more as compared to simple helical coil. The heat transfer rate for cone shaped helical

coil is 1.18 to 1.38 times more as compared to simple helical coil.

Seyed Faramarz Ranjbar et al. [4] discussed the various parameters affecting on heat transfer characteristics

of helical double tube heat exchanger by using well known Fluent Computational Fluid Dynamics (CFD) software.

They considered the different parameters which affect on heat transfer rate of helical double tube heat exchanger are

coil radius, coil pitch and diameter of tube. For this purpose they used pipes made up of copper with hot water in

inner tube at 60 degree & cold water in annulus tube at 22.1 degree. It was found that the increase of curvature ratio

increases the heat transfer coefficient. By increasing the number of coils there is decrease in heat transfer coefficient

.As inner tube & inner dean number increases, the Nusselt no. also increases resulting in increase in heat transfer

rate. Increasing the pitch of heat exchanger, there decrease in overall heat transfer coefficient which is negligible.

Sagar Suryakant Pol [5] carried out the designing of helical tube in tube coil heat exchanger by taking

reference of designing of helical coil in shell heat exchanger. He developed an experimental setup and carried out

tests for both parallel and counter flow configuration. From observations he calculated capacity ratio, heat transfer

coefficient, effectiveness, Log Mean Temperature Difference (LMTD) for both parallel and counter flow

configuration and compare both the configurations. For this he considered two fluids like one is vegetable oil (SAE

20W40) oil in inner tube & cold water in outer tube. The results showed that for a heat exchanger with counter flow

configuration the capacity ratio increases with increase in mass flow rate and maximum capacity ratio is 0.215. For a

heat exchanger with parallel flow configuration the capacity ratio increases with increase in mass flow rate and

maximum capacity ratio is 0.2. Helical coil in coil heat exchanger with counter flow configuration is 1.27 times

effective than helical coil in coil heat exchanger with parallel flow configuration.

3 EXPERIMENTAL SETUP

Experimental-Setup consists of following parts:-

1. Tube-In-Tube Helical Coil Heat Exchanger

2. Tank with thermostatic heater

3. Water Reservoir

4. Flow Control valve

5. Pressure Indicator

6. J-Type thermocouples



Fig 2 Experimental-Setup Tube-in-Tube Helical Coil Heat Exchanger

Cold tap water will be used for the fluid flowing in the outer tube. The water in the outer tube will be

circulated. The flow will control by a valve, allowing flows to be control and measure between 200 and 500 LPH.

Hot water for the inner tube was heated in a tank with the thermostatic heater set at 600C. This water will be

circulated via pump. The flow rate for the inner tube will control by flow metering valve as described for the outer

tube flow. Flexible PVC tubing will use for all the connections. J-Type thermocouples will insert into the flexible

PVC tubing to measure the inlet and outlet temperatures for both fluids. Temperature data will be recorded using a

creative temperature indicator.

Actual dimensions of tube-in-tube helical coil heat exchanger

Table 1 Dimensional Parameters of Heat Exchanger

Dimensional parameters Heat Exchanger

di, mm 10

do, mm 12

Di, mm 23

Do, mm 25

Curvature Radius, mm 125

Stretch Length, mm 3992

Wire diameter, mm 1.5

Curvature ratio 0.1

No. of Turns 4

4 SIMULATION OF TUBE IN TUBE HELICAL COIL HEAT EXCHANGER

4.1 CFD METHODOLOGY

For simulation of tube in tube Helical coil heat exchanger, First we have to creat a heat exchanger model

using creo software. After creating the geometry and doing the meshing in ANSYS 14.5 the problem is analysed in

ANSYS 14.5 .As this is counter flow of inner hot fluid flow and outer cold fluid flow so there is two inlet and outlet



respectively. There is a pipe which separate the two flow which is made by copper. Inner fluid is take as hot water

and outer fluid is take cold water.

Import CAD geometry to ANSYS environment

Extract fluid domain

Apply boundary conditions (Pressure, Velocity, Mass flow rate, Temperature)

Selecting CFD model (energy, turbulence)

Processing simulation

Monitoring residuals

Plotting results

Creo model of tube in tube helical coil heat exchanger are

Fig 3 Creo model of tube in tube helical coil heat exchanger

Boundary condition for CFD Analysis

Table 2 Boundary condition for CFD Analysis

Sr.No. Parameters Range

1. Inner tube flow rate 120-480 LPH

2. Outer tube flow rate 480 LPH

3. Inner tube inlet temperature ( ) 60

4. Inner tube outlet temperature ( ) 40-52

5. Outer tube inlet temperature ( ) 30

6. Outer tube outlet temperature ( ) 30-42

5 RESULT & DISCUSSION

5.1 CFD RESULT

For CFD analysis, we were taken constant cold water flow rate =480 LPH and different hot water flow rate i.e.

120LPH,240LPH,360LPH,480LPH for validation of above experimental results.



Fig 4 Meshing applied on helical coil heat exchanger fluid domain

Fig 5 Pressure drop in inner tube at mass flow rate of 480 LPH (hot fluid)



Fig 6 Temperature distribution in inner tube at mass flow rate of 480 LPH (hot fluid)

Fig7 Velocity distribution in inner tube at mass flow rate of 480 LPH (hot fluid)

5.2 Effect of D/d Ratio on Design Parameters

We can take hot fluid flow rate 120 LPH & cold fluid flow rate 480 LPH was constant and changes D/d

Ratio 12.5,17.5, 22.5 & 32.5. CFD simmultion was carried out by



Fig 8 Velocity contour for hot fluid (D/d = 32.5)

Fig 9 Pressure contour for hot fluid (D/d = 32.5)



Fig 10 Temperature contour for hot fluid (D/d = 32.5)

5.3 COMPARE EXPERIMENTAL AND CFD RESULT OF TUBE IN TUBE HELICAL COIL HEAT

EXCHANGER

Table 3 COMPARE EXPERIMENTAL AND CFD RESULT OF TUBE IN TUBE HELICAL COIL HEAT

EXCHANGER

Sr.no. Hot water

flow

rate(LPH)

Effectiveness Reynold number Hot fluid Velocity Nussult number

Exp CFD Exp CFD Exp CFD Exp CFD

1 120 0.8138 0.6782 5230.34 5424.65 0.4246 0.4332 32.13 30.09

2 240 0.5416 0.6772 10461.39 10884.37 0.8492 0.8692 41.60 30.29

3 360 0.4515 0.4966 15692.09 16320.30 1.2738 1.3033 38.48 36.17

4 480 0.4062 0.4401 20922.79 22060.52 1.6985 1.7617 36.96 36.80

From above Experimental and CFD result, We obtained graph for Effectiveness, hot fluid reynold number,hot fluid

velocity & Nussult number



Chart 1 Experimental Vs CFD result of Effectiveness

Chart 2 Experimental Vs CFD result of Hot fluid reynold number

120 240 360 480

CFD 0.6782 0.6772 0.4966 0.4401

Exp 0.8138 0.5416 0.4515 0.4062

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

CFD

Exp

Effectiveness

Eff

ecti

ven

ess

120 240 360 480

cfd 5424.65 10884.37 16320.3 22060.52

Exp 5230.34 10461.39 15692.09 20922.79

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

cfd

Exp

Hot Fluid Reynold number

Rey

nold

num

ber



Chart 3 Experimental Vs CFD result of Hot fluid velocity

Chart 4 Experimental Vs CFD result of Nusselt number

120 240 360 480

CFD 0.4332 0.8692 1.3033 1.7617

Exp 0.4246 0.8492 1.2738 1.6985

0

0.5

1

1.5

2

2.5

3

3.5

4

CFD

Exp

Hot fluid Velocity

Vel

oci

ty

120 240 360 480

CFD 31.09 30.29 36.17 36.8

Exp 32.13 41.6 38.48 36.96

0

10

20

30

40

50

60

70

80

CFD

Exp

Nuss

elt

num

ber

Nusselt number



5.4 Effect of D/d Ratio

CFD simulation was carried out considering different D/d ratios. The table below highlights the boundary

conditions used.

Table 4 Effect of D/d ratio on Design Parameters

Outer

Dia.

(mm)

Inside

Pipe Dia.

(mm)

D/d

Cold Fluid Hot Fluid

Flow

(LPH)

Pressure

(Pa)

Temp.

(0K)

Flow

(LPH)

Pressure

(Pa)

Temp.

(0K)

125 10 12.5 480

1.01E+05 303 120

1.01E+05 313

175 10 17.5 480 1.01E+05 303 120

1.01E+05 313

225 10 22.5 480 1.01E+05 303 120

1.01E+05 313

325 10 32.5 480

1.01E+05 303 120

1.01E+05 313

Chart 5 Effect of D/d Ratio on Cold Fluid Temperature

1 2 3 4

Temp.range 3.9982 4.4972 4.735 5.2111

D/d Ratio 12.5 17.5 22.5 32.5

0

5

10

15

20

25

30

35

0

1

2

3

4

5

6

Temp.range

D/d Ratio

Tem

per

ature

k

D/d

Rat

io

Effect of D/d on Cold fluid Temperature



Chart 6 Effect of D/d Ratio on Hot Fluid Temperature

Chart 7 Effect of D/d Ratio on Cold Fluid Velocity

1 2 3 4

Temp.range 13.852 13.648 13.802 13.596

D/d Ratio 12.5 17.5 22.5 32.5

0

5

10

15

20

25

30

35

13.45

13.5

13.55

13.6

13.65

13.7

13.75

13.8

13.85

13.9

Temp.range

D/d Ratio

D/d

Rat

io

Tem

per

ature

k

Effect of D/d on Hot fluid Temperature

1 2 3 4

Velocity 0.4317 0.4338 0.4352 0.4354

D/d Ratio 12.5 17.5 22.5 32.5

0

5

10

15

20

25

30

35

0.429

0.43

0.431

0.432

0.433

0.434

0.435

0.436

Velocity

D/d Ratio

D/d

Rat

io

Cold

Flu

id V

eloci

ty (

m/s

)

Effect of D/d on Cold fluid Velocity



Chart 8 Effect of D/d Ratio on Hot Fluid Velocity

Chart 9 Effect of D/d Ratio on Cold Fluid Reynold Number

1 2 3 4

Velocity 0.4398 0.4226 0.437 0.4263

D/d Ratio 12.5 17.5 22.5 32.5

0

5

10

15

20

25

30

35

0.41

0.415

0.42

0.425

0.43

0.435

0.44

0.445

Velocity

D/d Ratio

D/d

Rat

io

Ho

t f

luid

Vel

oci

ty (m

/s)

Effect of D/d on Hot Fluid Velocity

1 2 3 4

Reynold num. (Re) 35598 40178 44398 50380

D/d Ratio 12.5 17.5 22.5 32.5

0

5

10

15

20

25

30

35

0

10000

20000

30000

40000

50000

60000

Reynold num. (Re)

D/d Ratio

Effect of D/d on Cold fluid Reynold

D/d

Rat

io

Rey

nold

num

. (R

e)



Chart 10 Effect of D/d Ratio on Hot Fluid Reynold Number

6 CONCLUSION

1. Heat transfer analysis of a helically coil heat exchanger using CFD code ANSYS 14.5 has been present in

this paper.

2. As per the results obtained through simulation, it is observed that the data is in good agreement with

experimental results.

3. By comparing these Experimental and CFD results of wire wounded Tube in Tube Helical Coil Heat

Exchanger, we observed that as the inner tube flow rate (LPH) increases Temperature difference also

increases, So Log mean temperature difference (LMTD) is increases with increasing inner tube flow rate,

for constant Cold Water Flow Rate.

4. We know that Nusselt Number is directly proportional to inner heat transfer coefficient (hi), So that

Nusselt Number is increases with increasing inner tube flow rate, for constant Cold Water Flow Rate.

5. With increase in the Reynolds number, the Nusselt number for the inner tube increase. However, with

increases in flow rate turbulence between the fluid element increases which will enhance the mixing of the

fluid and ultimately the Nusselt number or the heat transfer rate increases.

REFERENCES

1) Umang k Patel, Prof Krunal Patel, “A review on investigation of helical coil heat exchanger”, International

Journal of Advance Research and Innovative Ideas in Education, ISSN(O) : 2395-4396, Volume-3 Issue-1

2017

2) Primo Poredos, Tomaz Suklje, Saso Medved, Ciril Arkar,An experimental heat-transfer study for a heat-

recovery unit made of corrugated tubes, Applied Thermal Engineering 53 (2013) 49-56.

3) Shinde Digvijay D, Dange H. M., Heat Transfer Analysis of a Cone Shaped Helical Coil Heat Exchanger,

International Journal of Innovations in Engineering and Technology, Vol. 3 Issue 1. ISSN: 2319 – 1058.

4) Seyed Faramarz Ranjbar, Mir Hatef Seyyedvalilu, The effect of geometrical parameters on heat transfer

coefficient in helical double tube, exchangers, Journal of Heat and Mass Transfer Research 1 (2014) 75-82.

5) Sagar Suryakant Pol, Design, Fabrication and Testing Of Helical Tube in Tube Coil Heat Exchanger,

International Journal of Engineering and Technical Research, ISSN: 2321-0869, Volume-2, Issue-12,

December 2014.

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Reynold num. (Re) 22665 24931 28364 31678

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0

5

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0

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25000

30000

35000

Reynold num.(Re)

Rey

nold

num

. (R

e)

Effect of D/d on Hot fluid Reynold num

D/d

Rat

io



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“CFD ANALYSIS HELICAL COIL HEAT EXCHANGER”ijariie.com/AdminUploadPdf/CFD_ANALYSIS_HELICAL_COIL_HEAT_E… · Shinde Digvijay D. et al. [3] studied the experimental investigation