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DESIGN OF DOUBLE PIPE HEAT EXCHANGER

Mrs. Kirti B.Zare1, Ms. Dipika Kanchan

2, Ms. Nupur Patel

3

1, 2, 3Chemical Engineering, D.Y. Patil Institute of Engineering, Management and Research,

Akurdi, Pune, (India)

ABSTRACT

Heat exchanger is one of the important devices in cooling and heating process in Factories, buildings,

transports and others. The heat exchanger is found in large Construction to support cooling process such as

fossil fuel power plant. In the present study, heat transfer from hot water to cold water by double pipe heat

exchanger consists concentric tube is experimentally investigated. The horizontal double pipe heat exchanger is

made from Galvanised iron tube with inner tube and outer tube. The inner tube is consists of 26mm internal &

34 mm outer diameter. The outer tube is consisting of 68 mm internal & 76 mm outer diameter.

A set of the experiments were carried out to investigate for counter flow & parallel flow to determine heat

transfer coefficient in a double pipe heat exchanger.

Keywords: Coefficient of heat transfer, counter flow, Double pipe, Heat Exchanger parallel flow.

I. INTRODUCTION

Horizontal double pipe heat exchanger uses various inserts inside tube so as to enhance heat transfer and hence

increase heat transfer coefficient [1, 2, 3]

.These types of heat exchangers found their applications in heat recovery

processes, air conditioning and refrigeration systems, chemical reactors, and food and dairy processes [2].

The

double pipe heat exchanger would normally be used for many continuous systems having small to medium

headuties. The heat exchanger is a device which transferred the heat from hot medium to cold medium without

mixed both of medium since both mediums are separated with a solid wall generally. There are many types of

heat exchanger that used based on the application. For example, double pipe heat exchanger is used in chemical

process like condensing the vapour to the liquid. When to construct this type of heat exchanger, the size of

material that want to uses must be considered since it affected the overall heat transfer coefficient. For this type

of heat exchanger, the outlet temperature for both hot and cold fluids that produced is estimated by using the

best design of this type of heat exchanger.

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Figure No: 1.1 Double pipe Heat Exchanger

The double pipe heat exchanger is used in industry such as condenser for chemical process and cooling fluid

process. This double pipe heat exchanger is designed in a large size for large application in industry. For this

research, the small heat exchanger of double pipe type is constructed which wants to make it practicality in daily

life such in cooling the hot air from engine bay into intake manifold of car[7].

To make this small double pipe

heat exchanger type become practicality, the best design for this small double pipe heat exchanger is choose.

The objectives of this research are as follows:

i. To study about heat transfer analysis in heat exchanger.

ii. To design the heat exchanger based on TEMA specification

The most popular are those of recuperative type. The fluids are physically separated by heat transfer surface and

the heat is transferred from hot to cold agent [4]

.

1.1 Classification According To Transfer Processes

Heat exchangers are classified according to transfer processes into indirect- and direct contact types.

1.1.1Indirect-Contact Heat Exchangers

In an indirect-contact heat exchanger, the fluid streams remain separate and the heat transfers continuously

through an impervious dividing wall or into and out of a wall in a transient manner. Thus, ideally, there is no

direct contact between thermally interacting fluids. This type of heat exchanger also referred to as a surface heat

exchanger, can be further classified into direct-transfer type, storage type, and fluidized-bed exchangers [12]

.

`fluids because each fluid flows in separate fluid passages. In general, there are no moving parts in most such

heat exchangers. This type of exchanger is designated as a recuperative heat exchanger or simply as a

recuperate. {Some examples of direct transfer type heat exchangers are tubular, plate-type, and extended surface

exchangers. Note that the term recuperate is not commonly used in the process industry for shell 4and-tube and

plate heat exchangers, although they are also considered as recuperates. Recuperates are further sub classified as

prime surface exchangers and extended-surface exchangers. Prime surface exchangers do not employ fins or

extended surfaces on any fluid side. Plain tubular exchangers, shell-and-tube exchangers with plain tubes, and

plate exchangers are good examples of prime surface exchangers. Recuperates constitute a vast majority of all

heat exchangers [13]

.

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1.1.1.2 Storage Type Exchangers

In a storage type exchanger, both fluids flow alternatively through the same flow passages, and hence heat

transfer is intermittent. The heat transfer surface (or flow passages) is generally cellular in structure and is

referred to as a matrix or it is a permeable (porous) solid material, referred to as a packed bed. When hot gas

flows over the heat transfer surface. The thermal energy from the hot gas is stored in the matrix wall, and thus

the hot gas is being cooled during the matrix heating period. As cold gas flows through the same passages later

(i.e., during the matrix cooling period), the matrix wall gives up thermal energy, which is absorbed by the cold

fluid. Thus, heat is not transferred continuously through the wall as in a direct-transfer type exchanger

(recuperate), but the corresponding thermal energy is alternately stored and released by the matrix wall [12]

. This

storage type heat exchanger is also referred to as a regenerative heat exchanger, or simply as a regenerator. The

actual time that hot gas takes to flow through a cold regenerator matrix is called the hot period or hot blow, and

the time that cold gas flows through the hot regenerator matrix is called the cold period or cold blow. For

successful operation, it is not necessary to have hot- and cold-gas flow periods of equal duration. There is some

unavoidable carryover of a small fraction of the fluid trapped in the passage to the other fluid stream just after

switching of the fluids; this is referred to as carryover leakage. In addition, if the hot and cold fluids are at

diff erent pressures, there will be leakage from the high-pressure fluid to the low-pressure fluid past the radial,

peripheral, and axial seals, or across the valves [13]

. This leakage is referred to as pressure leakage. Since these

leaks are unavoidable, regenerators are used exclusively in gas-to-gas heat (and mass) transfer applications with

sensible heat transfer; in some applications, regenerators may transfer moisture from humid air to dry air up to

about 5%. For heat transfer analysis of regenerators, the "-NTU method of recuperates needs to be modified to

take into account the thermal energy storage capacity of the matrix [12]

.

1.1.1.3 Fluidized-Bed Heat Exchangers

In a fluidized-bed heat exchanger, one side of a two-fluid exchanger is immersed in a bed of finely divided solid

material, such as a tube bundle immersed in a bed of sand or coal particles[11]

. If the upward fluid velocity on the

bed side is low, the solid particles will remain fixed in position in the bed and the fluid will flow through the

interstices of the bed. If the upward fluid velocity is high, the solid particles will be carried away with the fluid.

At a „„proper‟‟ value of the fluid velocity, the upward drag force is slightly higher than the weight of the bed

particles. As a result, the solid particles will float with an increase in bed volume, and the bed behaves as a

liquid. This characteristic of the bed is referred to as a fluidized condition. Under this condition, the fluid

pressure drop through the bed remains almost constant, independent of the flow rate, and a strong mixing of the

solid particles occurs [12]

. This results in a uniform temperature for the total bed (gas and particles) with an

apparent thermal conductivity of the solid particles as infinity. Very high heat transfer coefficients are achieved

on the fluidized side compared to particle-free or dilute-phase particle gas flows. Chemical reaction is common

on the fluidized side in many process applications, and combustion takes place in coal combustion fluidized

beds. The common applications of the fluidized-bed heat exchanger are drying, mixing, adsorption, reactor

engineering, coal combustion, and waste heat recovery [12]

.

1.2 Direct-Contact Heat Exchangers

In a direct-contact exchanger, two fluid streams come into direct contact, exchange heat, and are then separated.

Common applications of a direct-contact exchanger involve mass transfer in addition to heat transfer, such as in

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evaporative cooling and rectification; applications involving only sensible heat transfer are rare. The enthalpy of

phase change in such an exchanger generally represents a significant portion of the total energy transfer. The

phase change generally enhances the heat transfer rate. Compared to indirect contact recuperates and

regenerators, in direct-contact heat exchangers:

(1) Very high heat transfer rates are achievable

(2) The exchanger construction is relatively inexpensive

(3) The fouling problem is generally non-existent

The absence of a heat transfer surface (wall) between the two fluids. However, the applications are limited to

those cases where a direct contact of two fluid streams is permissible [10]

.

1.2.1 Immiscible Fluid Exchangers

In this type, two immiscible fluid streams are brought into direct contact. These fluids may be single-phase

fluids, or they may involve condensation or vaporization. Condensation of organic vapours and oil vapours with

water or air are typical examples [13]

.

1.2.2. Gas–Liquid Exchangers

In this type, one fluid is a gas (more commonly, air) and the other a low-pressure liquid (more commonly,

water) and are readily separable after the energy exchange. In either cooling of liquid (water) or humidification

of gas (air) applications, liquid partially evaporates and the vapour is carried away with the gas. In these

exchangers, more than 90% of the energy transfer is by virtue of mass transfer (due to the evaporation of the

liquid), and convective heat transfer is a minor mechanism [11]

. A „„wet‟‟ (water) cooling tower with forced- or

natural-draft airflow is the most common application. Other applications are the air-conditioning spray chamber,

spray drier, spray tower, and spray pond.

1.2.3 Liquid–Vapour Exchangers

In this type, typically steam is partially or fully condensed using cooling water, or water is heated with waste

steam through direct contact in the exchanger. Noncondensables and residual steam and hot water are the outlet

streams. Common examples are desuperheaters and open feed water heaters (also known as deaerators) in power

plants [10]

.

II.REALTED WORK

2.1 Scopes of Research

The scopes of this research are as follows:

i. Study on heat transfer for heat exchanger specific to double pipe heat Exchanger types.

ii. Design the double pipe heat exchanger by using Solid- Works

iii. Temperature distribution in parallel flow & counter flow heat exachger.

iv. Analysis the heat exchanger specific to flow rate of hot and cold fluid.

vi overall heat transfer coefficient in parallel & counter flow.

vii. To obtain effectiveness in parallel ae well as counter flow.

2.2 Significance of Research

The significances of this research are as follows:

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i. To determine the best design for double pipe heat exchanger type.

ii. To fabricate the double pipe heat exchanger.

Heat exchanger is a special equipment type because when heat exchanger indirectly fired by a combustion

process, it becomes furnace, boiler, heater, tube-still heater and engine. Vice versa, when heat exchanger make a

change in phase in one of flowing fluid such as condensation of steam to water, it becomes a chiller,

evaporator,sublimator, distillation-column reboiler, still, condenser or cooler-condenser. Heat exchanger may be

designed for chemical reactions or energy-generation processes which become an integral part of reaction

system such as a nuclear reactor, catalytic reactor or polymer [5]

. Normally, heat exchanger is used only for the

transfer and useful elimination or recovery of heat without changed in phase. The fluids on either side of the

barrier usually liquids but they can be gasses such as steam, air and hydrocarbon vapour or can be liquid metals

such as sodium or mercury. In some application, heat exchanger fluids may use fused salts [6]

.

III. EXPERIMENTAL SET UP

The important parts of experimental set-up are blower, the test section containing horizontal concentric copper

pipes, hot air tank and cold water tank, rotameter, monoblack pump, whose selection is already discussed in

previous section.

All these instruments are selected as per the requirements depending upon their measuring range, accuracy and

availability in the market. The test section is made up of copper tubes as it has higher thermal conductivity.

Specification:

1. Inner Tube Material: Galvanizing Iron

Internal diameter of inner tube (di) = 26mm

Outer diameter of inner tube (do) = 34 mm

Length of inner tube (Li) = 1.2 m

Thickness of inner Tube (ti) = 4 mm

2. Outer Tube Material: Galvanizing Iron

Internal diameter of inner tube (di) = 68mm

Outer diameter of inner tube (do) = 76 mm

Length of inner tube (Lo) = 1.2 m

Thickness of inner Tube (to) = 4 mm

3. Specific Heat of Water = 4.186 Kw/kg0K

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Figure No: 3.1 Inlet & Outlet flow of Double pipe Heat Exchanger

To achieve a particular engineering objective, it is very important to apply certain principles so that the

product development is done economically. This economic is important for the design and selection of good

heat transfer equipment. The heat exchangers are manufactured in different types, however the simplest

form of the heat exchanger consist of two concentric pipes of different diameters known as double pipe heat

exchanger. In this type of heat exchanger, one fluid flows through the small pipe and another fluid flows

through the space between both the pipes [7]

. The flows of these two different fluids, one is at higher

temperature called hot fluid and another is at lower temperature called cold fluid, can be in same or in

opposite directions. If the flows are in same direction then the heat exchanger is called as parallel flow heat

exchanger and if the flows are in opposite direction then the heat exchanger is called as counter flow heat

exchanger.

Figure No: 3.2 Double pipe heat exchangers with different flow and their respective temperature profile

for Parallel flow

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Figure No: 3.3 Figure No: 3.2 Double pipe heat exchangers with different flow and their respective

temperature profile for counter flow

Figure No: 3.4 Double pipe Heat Exchanger (Isometric view in solid works)

The further development is done in the heat exchangers to facilitate them in different applications as per

requirement. These heat exchangers are different from the conventional heat exchangers such that they have

large heat transfer surface area per unit volume and are known as compact heat exchanger [8]

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IV. RESULT

4.1 Parallel Flow:

Sr No.

Hot water

Flow rate Qh

(lpm)

cold water

Flow rate Qc

(lpm)

Hot water

Inlet temp.

Thi (T1)

Hot water

Outlet temp.

Thi (T2)

cold water

inlet Tci

(T3)

cold water

outlet Tco

(T4)

1. 1.1 4 51 49 29 30

2. 1.4 1 53 48 36 33

3. 1.5 0.9 55 47 38 31

Table No: 4.1 Parallel flow

Graph No: 4.1 Hot water profile for hot water flow rate vs. inlet temp. of hot water

Graph No: 4.2 Hot water profile for hot water flow rate vs. outlet temp. of hot water

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Graph No: 4.3 Cold water profile for cold water flow rate vs. inlet temp. of cold water

Graph No: 4.4 Cold water profile for cold water flow rate vs. outer temp. of cold water

4.2 counter flow:

Sr No.

Hot water

Flow rate Qh

(lpm)

cold water

Flow rate Qc

(lpm)

Hot water

Inlet temp.

Thi (T1)

Hot water

Outlet temp.

Thi (T2)

cold water

inlet Tci (T3)

cold water

outlet Tco

(T4)

1 1.1 4 51 48 29 30

2 1.4 1 53 49 36 33

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Graph No: 4. 5 Hot water profile for hot water flow rate vs. inlet temp. of hot water

Graph No: 4. 6 Hot water profile for hot water flow rate vs. outlet temp. of hot water

Graph No: 4. 7 Cold water profile for cold water flow rate vs. inlet temp. of cold water

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Graph No: 4. 8 Cold water profile for cold water flow rate vs. outlet temp. of cold water

V.CALCULATION

1. Heat Transfer from hot water (qn):

qn = mh. cph.(Thi- Tho)

2. Heat Transfer rate to cold water (qc):

qc = Mc Cpc (Tco-Tci)

3 . Average heat transfer rate (q) :

q = qn – qc / 2

4.L.M.T.D :

∆Tm = ∆Ti - ∆To / ln ( ∆Ti/ ∆To)

5.Oveall Heat transfer Based on Internal Area of Tube Ui =

q = Ui Ai (∆Tm)

Ai = π di L

6. Effectiveness :

n = Mh Cph ( Thi- Tho) / Mc Cpo ( Tco – Tci)

Sr

No.

qn ( Kwatt ) Qc (Kwatt) Average q ( K watt ) LMTD (0K) U ( Inner

Watt/m0K)

U ( Outer

Watt/m0K)

Effectiveness

(%)

Parallel Flow

1 0.2787 0.153 0.215 3 731.21 559.1 54.89

Counter Flow

2 0.229 0.278 0.2535 3.34 774.3 592.1 82.37

Table No: 5.1 Parallel & Counter flow effectiveness

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Graph No: 5.1Profile of Parallel flow

Graph No: 5.2Profile of counter flow

Graph No: 5.3 Effectiveness profile for parallel flow &counter flow

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V.CONCLUSION

Experimental investigations of heat transfer characteristics of double pipe heat exchanger fitted with inserted

concentric tubes for parallel & counter flow. The review indicates that Heat Exchangers are the heat transfer

devices which are used in different applications. The heat exchangers can be used to recover the resources like

water as it is converted into the steam which is condensed by using the condenser. Heat exchangers also useful

for the economical running of industries and to control the pollution as in case of economizer and air pre-heater.

A good agreement is obtained between the experimental results of counter & parallel flow in that counter flow is

more efficient for same flow rate.

REFERENCES

Journal Papers:

[1] Paisarn Naphon and Tanapon Suchana et al. “Heat transfer enhancement and pressure drop through the

horizontal concentric tube with twisted wire brush inserts”, International Communications in Heat and

Mass transfer, Volume 38, pp. 236-241, 2011.

[2] Sarma K. V., Sunder. L. S. and Sarma P. K., “Estimation of heat transfer coefficient and friction factor in

the transition flow with volume concentration of Al2O3 Nano fluid flowing in a circular tube and twisted

tape insert”, International Communications in Heat and Mass transfer 36, pp. 503-507, 2009.

[3] Sunder L. S. and Sarma K. V., “Turbulent heat transfer and friction factor of Al2O3 nanofluid in a circular

tube with twisted tape inserts”, International Communications in Heat and Mass transfer 53, pp.1409-

1416, and 2010.

[4] Nawras Shareef Sabeeh, Nawras Shareef Sabeeh,"Thermo-Hydraulic Performance of Horizontal

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[8] P. S. Amrutkar, S. R. Patil, “Automotive Radiator Performance-Review”, International Journal of

Engineering and Advanced Technology, Volume-2, Issue-3, Feb-2013.

[9] Bar-Cohen, A., M. Carvalho, and R. Berryman, eds., 1998, Heat exchangers for sustainable development,

Proc. Heat Exchangers for Sustainable Development, Lisbon, Portugal.

[10] Beck, D. S., and D. G. Wilson, 1996, Gas Turbine Regenerators, Chapman & Hall, New York. Bhatia, M.

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[11] Bliem, C., et al., 1985, Ceramic Heat Exchanger Concepts and Materials Technology, Noyes Publications,

Park Ridge, NJ.

[12] Shah, R. K., and A. C. Mueller, 1985, Heat exchangers, in Handbook of Heat Transfer Applications, W.

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Books:

[13] Ramesh K. Shah, Dusˇan P. Sekulic, Fundamentals Of Heat Exchanger Design, Rochester Institute of

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These:

[14] Mohamad Shafiq Bin Alias, “Design of Small Heat Exchanger (Double Pipe Type)”, University Malaysia

Pahang, December 2010.

Acknowledgments

This research was supported by Dr. D. Y. Patil Institute of Engineering, Management &Research, Akurdi, and

Pune.We are thankful to our Principal Dr. Mrs .A. V. Patil. for provided expertise that greatly assisted the

research.

We have to express our appreciation to the Mr.Bhushan Zare for sharing their pearls of wisdom with us during

the course of this research.