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DESIGN AND FABRICATION OF

CROSS FLOW HEAT EXCHANGER

A PROJECT REPORT

Submitted by

JESU JAFFRIN.T.X. 312212114047

K.CHANDRA SHEKHAR 312212114027

ANIRUDDAN.M 312212114010

ASHWIN.S 312212114703

in partial fulfillment for the award of degree

of

BACHELOR OF ENGINEERING

In

MECHANICAL ENGINEERING

SSN COLLEGE OF ENGINEERING, CHENNAI – 603 110

ANNA UNIVERSITY: CHENNAI – 600 025

APRIL 2015

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ANNA UNIVERSITY: CHENNAI – 600 025

BONAFIDE CERTIFICATE

Certified that this project report “DESIGN AND FABRICATION OF CROSS

FLOW HEAT EXCHANGER“ is the bonafide work of “JESU JAFFRIN.T.X.,

K.CHANDRA SHEKHAR, M.ANIRUDDAN, ASHWIN.S” who carried out the

project work under my supervision.

SIGNATURE SIGNATURE

Dr. V. E. ANNAMALAI Dr. R.PRAKASH

HEAD OF THE DEPARMENT ASSOCIATE PROFESSOR

Mechanical Engineering, Mechanical Engineering

SSN College of Engineering, SSN College of Engineering

OMR, Kalavakkam – 603 110 OMR, Kalavakkam – 603 110

SUBMITTED FOR THE VIVA VOCE EXAM HELD ON: _______________

INTERNAL EXAMINER EXTERNAL EXAMINER

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ACKNOWLEDGEMENT

We are grateful to our Principal, Dr. S. Salivahanan for

providing us an opportunity to for carrying out on our project.

We sincerely thank our Head of the Department, Dr. V. E.

Annamalai for granting us permission to carry out our Design

and Fabrication Project.

We would like to express our gratitude to our guide

Dr.R.Prakash, for his valuable guidance and support

throughout the period of this project work.

We also like to thank Mr.J.R.Thomas Xavier,Annai Theres &

Co,Nagercoil for providing us the workspace and helping us

fabricate this project.

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TABLE OF CONTENTS

TITLE PAGE

ABSTRACT (v)

LIST OF SYMBOLS (vi)

1.INTRODUCTION

1.1.Exhaust Gas 1

1.1.1.Composition of Exhaust Gas

1.2.Heat Exchanger 2

` 1.2.1.Types of Heat Exchanger

1.2.2.Cross Flow Heat Exchanger

1.3.Objective 4

2.DESIGN MODEL CALCULATIONS 5

3.CAD MODELLING 9

4.FABRICATION OF HEAT EXCHANGER 11

5.EXPERIMENTAL SETUP 16

6.REFERENCES 21

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ABSTRACT

A heat exchanger is a device built for effective heat transfer

from one medium to another. The media may be separated

by a solid wall to prevent direct contact or they may be in

contact with one another. They are widely used in space

heating, refrigeration, air conditioning power plants,

chemical plants, petrochemical plants, petroleum refineries

etc. A heat exchanger is an important component of internal

combustion engines.

The objective of the present work is to design and fabricate

a multi-pass cross flow heat exchanger. Multi pass heat

exchangers provide better cooling effect when compared to

single pass heat exchangers. Instead of using fluid coolant,

air from a forced draft fan is used as the cooling medium.

The secondary objective of this project is to study the

feasibility of this heat exchanger to cool exhaust gases for

the purpose of Exhaust Gas Recirculation.

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LIST OF SYMBOLS:-

Re - Reynold’s number No unit

Nu – Nusselt’s number No unit

ρ – Density of fluid m³/kg

V’ – Volume flow rate m³/s

M’ – Mass flow rate kg/s

V – velocity of fluid m/s

Pr – Prandtl number No unit

h – Heat transfer coefficient W/m²-K

k – Thermal conductivity W/m-K

γ – Kinematic viscosity m²/s

ϵ - Effectiveness No unit

cp – Specific heat J/kg-K

N – No of Thermal units No unit

1

UNIT – I

INTRODUCTION

1.1.Exhaust Gas

Exhaust gas or flue gas is emitted as a result of the combustion

of fuels such as natural gas, gasoline/petrol, diesel fuel, fuel oil

or coal. According to the type of engine, it is discharged into the

atmosphere through an exhaust pipe, flue gas stack or propelling

nozzle. It often disperses downwind in a pattern called an

exhaust plume.

1.1.1 Compsition of Exhasut gas

The largest part of most combustion gas is nitrogen (N2), water

vapor (H2O) (except with pure-carbon fuels), and carbon

dioxide (CO2) (except for fuels without carbon); these are not

toxic or noxious (although carbon dioxide is a greenhouse gas

that contributes to global warming). A relatively small part of

combustion gas is undesirable noxious or toxic substances, such

as carbon monoxide (CO) from incomplete combustion,

hydrocarbons (properly indicated as CxHy, but typically shown

simply as "HC" on emissions-test slips) from unburnt fuel,

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nitrogen oxides (NOx) from excessive combustion temperatures,

ozone (O3), and particulate matter (mostly soot).

1.2. Heat Exchanger

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. They are widely used in space heating,

refrigeration, air conditioning, power plants, chemical plants,

petrochemical plants, petroleum refineries, natural gas

processing, and sewage treatment. 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.

1.2.1.Types of Heat Exchanger

Shell and tube heat exchanger

Plate heat exchanger

Plate and shell heat exchanger

Adiabatic wheel heat exchanger

Plate fin heat exchanger

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Pillow plate heat exchanger

Fluid heat exchangers

Waste Heat Recovery Units

Dynamic scraped surface heat exchanger

Phase-change heat exchangers

Direct contact heat exchangers

1.2.2. Cross Flow Heat Exchanger

Cross flow heat exchangers are commonly used in gas heating or

cooling. A tube bundle carries a heating or cooling fluid (either

gas or liquid), normally perpendicular to a gas flow which

passes over the tubes and allows heat to be transferred between

the fluids. Cross flow heat exchangers can be of the mixed or

unmixed type. The mixed type is the simpler of these designs in

which the gas is mixed and not separated into channels.

A car radiator and an air conditioner evaporator coil are

examples of cross flow heat exchangers. In both cases

evaporator coil heat transfer is taking place between a liquid

flowing inside a tube or tubes and air flowing past the tubes.

With a car radiator, the hot water in the tubes is being cooled by

air flowing through the radiator between the tubes. With an air

conditioner evaporator coil, air flowing past the evaporator coils

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is cooled by the cold refrigerant flowing inside the tube(s) of the

coil. Cross flow heat exchangers are typically used for heat

transfer between a gas and a liquid as in these two examples.

1.3.Objective

The objective of the present work is to design and fabricate a

multi pass cross flow heat exchanger for the purpose of cooling

exhaust gases from internal combustion engines. This setup

makes use of air from a forced draft fan flowing perpendicular

to the exhaust gases to cool the exhaust gases. The secondary

objective of this project is to study the feasibility of this heat

exchanger for the purpose of Exhaust gas Recirculation.

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UNIT – II

DESIGN MODEL CALCULATIONS

For Exhaust gas [CO – Carbon monoxide]

Inlet Temperature, T hi = 100°C

Total inlet area across the bank of tubes, A e = 29 × 4 (.012 ×

.002) m²

Density, ρ e = 0.916 kg/m³

Volume Flow Rate, V’ e = 0.038976 m³/s

Mass Flow Rate, M’ e = V’ e × ρ e = 0.038976 × 0.916 = 0.0357

kg/s

Velocity of Exhaust Gas, v e = V’ e / A e = 0.038976

2.784 ×10³ = 14 m/s

Where, A e = 29 × 4 × 0.012 × 0.002 = 2.784 × 10³ m²

Reynold’s No, Re = 𝑣 𝑒 ×𝑑

𝛾, (d = 4A/P =

4∗29∗4∗.012∗.002

2∗(.012 + 0.002) = 3.43 ×

10³ m)

Prandtl No, Pr = 0.718

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Specific heat, C p = 1043 J/kg-K

Thermal conductivity, k = 0.03012 W/m-K

Nusselt’s no, Nu = 3.66+5.597

2 = 4.6285 (pg 128) [2b/2a = 1/6]

Nu = hL/k

h , heat transfer coefficient = 𝑁𝑢 × 𝑘𝐿⁄ =

4.6285 ×0.03012

.45 × 2 =

0.1549 W/m²-K

For Coolant gas (Dry air)

Circular cross-section with diameter, d c = 0.1 m

Area of cross-section, 𝐴 𝑐 = 𝜋𝑟2 = 7.85 × 10⁻³ m²

Inlet temperature, T ci = 30°C

Density of dry air, ρ c =1.165 kg/m³

Kinematic viscosity, γ c = 16 × 10⁻⁶ m²/s

Prandtl no, Pr = 0.701

Specific heat, c pc = 1005 J/kg-K

Thermal conductivity, k c = 0.02675 W/m-K

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Volume flow rate, V’ c = 20000 lph = 20000

3600 ×10³ = 5.554 × 10⁻³

m³/s

Mass flow rate, m’ c = V’ c × ρ c = 5.554 × 10⁻³ × 1.165 = 6.472

× 10⁻³ kg/s

Velocity of coolant gas, v c = 𝑉′𝑐

𝐴 𝑐 =

5.554 × 10⁻³

7.85 ×10⁻³ = 0.708 m/s

Reynold’s no, Re c = 𝑣𝑑

𝛾 =

0.708 ×0.1

16 ×10⁻⁶ = 4425 (Turbulent)

Nusselt’s no, Nu = 0.023 × 𝑅𝑒0˙8 × 𝑝𝑟⁰˙⁴ = 0.023 × (4425)⁰˙⁸

× (0.701)⁰˙⁴

= 16.47

Average Nusselt’s no, Nu’ = Nu[1 + 1.4

𝑥

𝑑

] = 247.05

(Fully developed x/d=.01/.1=.1)

Nu’ = ℎ𝑑

𝑘

h = 𝑁𝑢′𝑘

𝑑 =

247.05 ×0.02675

0.1 = 66.1 W/m²-K

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Cross flow (both fluids unmixed)

Effectiveness, ε = 1 − 𝑒(𝑒(−𝑁𝐶𝑛)−1)×𝐶

𝑛

Overall heat transfer coefficient, U = 20 W/m²-K

Area, A = (29 × 4) × 2 × h (l + b) = 29 × 8 × 0.9 [0.012 + 0.002]

= 2.9232 m²

C min = (m c × c c) = 6.50436 W/K

C max = (m e × c e) = 37.2351 W/K

C= 𝐶 𝑚𝑎𝑥

𝐶 𝑚𝑖𝑛 = 5.725

N = 𝑈𝐴

𝐶 𝑚𝑖𝑛 =

20 ×2.9232

6.50436 = 8.988

n = N⁻⁰˙²² = 0.617

ε = 1 − 𝑒(𝑒(−8.988 ×5.725 ×0.617)−1)×5.725

0.617 =0.9

9

UNIT - III

CAD MODELLING

ISOMETRIC VIEW

10

TOP VIEW

11

UNIT - IV

FABRICATION OF HEAT EXCHANGER

The various processes involved in the fabrication of heat

exchanger are discussed briefly in this unit. The machining

processes are as follows:

SHIELDED METAL ARC WELDING:-

Shielded metal arc welding (SMAW), also known as manual

metal arc welding (MMA or MMAW), flux shielded arc welding

or informally as stick welding, is a manual arc welding process

that uses a consumable electrode coated in flux to lay the weld.

An electric current, in the form of either alternating current or

direct current from a welding power supply, is used to form an

electric arc between the electrode and the metals to be joined.

The workpiece and the electrode melts forming the weld pool

that cools to form a strong joint. As the weld is laid, the flux

coating of the electrode disintegrates, giving off vapors that

serve as a shielding gas and providing a layer of slag, both of

which protect the weld area from atmospheric contamination.

This process is used to weld the elements forming the base

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GAS WELDING

Oxy-fuel welding (commonly called oxyacetylene

welding, oxy welding, or gas welding in the U.S.) and oxy-fuel

cutting are processes that use fuel gases and oxygen to weld and

cut metals, respectively. French engineers Edmond Fouché and

Charles Picard became the first to develop oxygen-

acetylene welding in 1903.Pure oxygen, instead of air, is used to

increase the flame temperature to allow localized melting of the

workpiece material (e.g. steel) in a room environment. A

common propane/air flame burns at about 2,000 °C (3,630 °F), a

propane/oxygen flame burns at about 2,500 °C (4,530 °F), and

an acetylene/oxygen flame burns at about 3,500 °C (6,330 °F).

Oxy-fuel is one of the oldest welding processes, besides forge

welding. Still used in industry, in recent decades it has been less

widely utilized in industrial applications as other specifically

devised technologies have been adopted. It is still widely used

for welding pipes and tubes, as well as repair work. It is also

frequently well-suited, and favored, for fabricating some types

of metal-based artwork. As well, oxy-fuel has an advantage over

electric welding and cutting processes in situations where

accessing electricity (e.g., via an extension cord or portable

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generator) would present difficulties; it is more self-contained,

and, hence, often more portable.

SOLDERING

Soldering is a process in which two or more metal items are

joined together by melting and flowing a filler metal (solder)

into the joint, the filler metal having a lower melting point than

the adjoining metal. Soldering differs from welding in that

soldering does not involve melting the work pieces. In brazing,

the filler metal melts at a higher temperature, but the work piece

metal does not melt. In the past, nearly all solders

contained lead, but environmental concerns have increasingly

dictated use of lead-free alloys for electronics and plumbing

purposes.This process is used for joining the various electrical

connections

TURNING

Turning is a engineering machining process in which a cutting

tool, typically a non-rotary tool bit, describes a helical toolpath

by moving more or less linearly while the workpiece rotates.

The tool's axes of movement may be literally a straight line, or

they may be along some set of curves or angles, but they are

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essentially linear (in the nonmathematical sense). Usually the

term "turning" is reserved for the generation of external surfaces

by this cutting action, whereas this same essential cutting action

when applied to internal surfaces (that is, holes, of one kind or

another) is called "boring". Thus the phrase "turning and boring"

categorizes the larger family of (essentially similar) processes.

The cutting of faces on the workpiece (that is, surfaces

perpendicular to its rotating axis), whether with a turning or

boring tool, is called "facing", and may be lumped into either

category as a subset. This process is used in the fabrication of

the forced draft fan.

BORING

In machining, boring is the process of enlarging a hole that has

already been drilled (or cast), by means of a single-point cutting

tool (or of a boring head containing several such tools), for

example as in boring a gun barrel or an engine cylinder. Boring

is used to achieve greater accuracy of the diameter of a hole, and

can be used to cut a tapered hole. Boring can be viewed as the

internal-diameter counterpart to turning, which cuts external

diameters.

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There are various types of boring. The boring bar may be

supported on both ends (which only works if the existing hole is

a through hole), or it may be supported at one end(which works

both as through holes and blind holes). Lineboring (line boring,

line-boring) implies the former. Backboring (back boring, back-

boring) is the process of reaching through an existing hole and

then boring on the "back" side of the workpiece (relative to the

machine headstock).

Boring is used to machine the motor shaft to connect the motor

to the fan.

16

UNIT - V

EXPERIMENTAL SETUP

HEAT EXCHANGER:-

Cross flow heat exchangers are commonly used in gas heating or

cooling. A tube bundle carries a heating or cooling fluid (either

gas or liquid), normally perpendicular to a gas flow which

passes over the tubes and allows heat to be transferred between

the fluids. Cross flow heat exchangers can be of the mixed or

unmixed type. The mixed type is the simpler of these designs in

which the gas is mixed and not separated into channels.

The heat exchanger used is a cross flow, multi pass heat

exchanger with air cooling.

17

MOTOR AND FAN:-

The motor used is a 0.25hp,2880 rpm.

The fan is a 6 leaf, 25cfm

ENGINE:-

The engine used was a single cylinder , 4 stroke, 1500 rpm,

dieseil engine with a hydraulic dynamometer loading

arrangement.

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PROCEDURE:-

1. Calculate the maximum load that can be applied to

dynamometer using the engine details.

2. Check the following before starting the engine as precautions,

(a) Lubricating oil level.

(b) Fuel level in the tank.

(c) Ensure that there is no load in the engine.

(d) Whether all the fuel values in the line to the engine is open

condition.

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3. The engine is started rotating the crank by means of hand

crank lever.

4. Decompression lever is pressed for easy cranking.

5. Adjust the cooling water to the required level.

6.Switch on the forced draft fan and connect the exhaust gas the

heat exchanger by means of a connecting pipe.

7. Note the exhaust gas temperature at the inlet of the haet

exchanger and at the outlet of the heat exchanger.

8. The experiment is repeated for different values of load

applied to the engine and the readings are tabulated.

9. Note the following

Manometer reading

Time duration for 10 cc of fuel consumption in the burette.

Time duration for 3 rev. of energy meter Disc.

Load applied.

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TABULATION:-

S.No Load

applied to

the

engine(kg)

Time taken for

10 cc fuel

consumption(s)

Exhaust

gas

temperature

at inlet

Exhaust

gas

temperature

at outlet

1. 0 99.6 89 35

2. 0.5 81.22 109 36

3. 1 73.22 122 38

4. 1.5 65.93 146 41

5. 2 59.56 164 44

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UNIT - VI

REFERENCES

1. “Automobile Engineering” vol.2 by Dr.Kirpalsingh,11th

edition pgs.335-351.

2. Heat and Mass transfer by Dr.Yahya

3. Method of operating heat exchangers by Hoechst Ceramtec

Aktiengesellschaft patent US5531265 dated.November 1, 1994

4. International Journal of Heat and Mass Transfer, Volume 81,

February 2015, Pages 542-553

5. Applied Thermal Engineering, Volume 30, Issue 10, July

2010, Pages 1170-1178