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KOLEJ UNIVERSITI TEKNOLOGI TUN HUSSEIN ONN

BORANG PENGESAHAN STATUS TESIS0

JUDUL: DESIGN OF HEAT EXCHANGER NETWORK USING PINCH METHOD

SESI PENGAJIAN: 2006/2007

Saya WAN NURD IY AN A BINTI WAN MANSOR

mengaku membenarkan tesis ( syarat-syarat kegunaan seperti berikut:

: ini disimpan di Perpustakaan dengan

1. Tesis adalah hakmilik Kolej Universiti Teknologi Tun Hussein Onn. 2. Perpustakaan dibenarkan membuat salinan untuk tujuan pengajian sahaja. 3. Perpustakaan dibenarkan membuat salinan tesis ini sebagai bahan pertukaran antara institusi

pengajian tinggi. 4. **Sila tandakan (J):

SULIT

T E R H A D

(Mengandungi maklumat yang berdai jah keselamatan atau kepentingan Malaysia yang termaktub di dalam A K T A R A H S I A R A S M I 1972)

(Mengandungi maklumat T E R H A D yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)

TIDAK T E R H A D

(TAND A T ^ N G A N PENULIS) ( T A N D A T A N G A N J E N Y E L I A )

Alamat Tetap: 27, Jalan Taman Gombak 3, Taman Gombak, 68100, Gombak. Selanpor.

Tarikh: November 2006

PROF. DR. V D A Y R. R A G H A V A N Nama Penyelia

Tarikh: 2 . I f t k November 2006

Potong yang tidak berkenaan. Jika tesis ini SULIT atau TERHAD, sila lampirkan surat dari pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh tesis ini perlu dikelaskan sebagai SULIT atau TERHAD. Tesis dimaksudkan sebagai tesis bagi Ijazah Doktor Falsafah dan Saijana secara penyelidikan, atau disertasi bagi pengajian secara kei ja kursus dan penyelidikan, atau Laporan Projek Saijana Muda (PSM).

"I hereby declare that I have read this report and in my opinion this report in terms of

content and quality requirement fulfills the purpose for the conferring of the Master 's

Degree in Mechanical Engineering".

Signature : ' l i ® ^

Name of Supervisor : PROF. DR. VIJAY R. RAGHAVAN

Date NOVEMBER 2006

•\jiiWt

PKOF. DR. VIJAY R. RAGHAVAN Department vt l:! i-h & Automotive Engineering Faculty of Mechanical & Manufacturing Engineering Kolej Universiti Teknologi Tun Hussein Onn

DESIGN OF HEAT EXCHANGER NETWORK

USING PINCH METHOD

WAN NURDIYANA BINTI WAN MANSOR

A dissertation submitted as partial fulfillment of the requirement for the award of

the Master's Degree in Mechanical Engineering

Department of Mechanical Engineering

Faculty of Mechanical and Manufacturing Engineering

Kolej Universiti Teknologi Tun Hussein Onn

NOVEMBER 2006

ii

"I declare that this thesis entitled 'Design of Heat Exchanger Network Using Pinch

Method' is the result of my own work except as cited in references".

Signature

Name of Author

Date

Y s t f p S .

WATsLNURDIYANA BINTI WAN MANSOR

NOVEMBER 2006

I l l

S'OA, rivy, jxurui/ij,,

^VQ. C^HAJQA tt\& lUlXXMl2ti£LQ4lCl£ f

xiv

ACKNOWLEDGEMENT

W i t h a deep sense o f gratitude, I wish to express m y sincere thanks to m y

supervisor, Professor Dr . V i j a y R. Raghavan for his immense help in p lanning and

executing the works in t ime. H e is not only a great professor w i th deep vision but

also and most importantly a k ind person. H i s trust and determination inspired me in

the most important moments o f m a k i n g right decisions and I am glad to work w i th

him. T h e confidence and dynamism with which P r o f V i j a y guided the work requires

no elaboration.

I also want to thank m y parents, who taught m e the value o f hard work by

their o w n example. I wou ld l ike to share this moment o f happiness wi th m y parents,

brothers and sisters. T h e y rendered me enormous support during the whole tenure o f

my studies.

F ina l ly , I w o u l d l ike to thank all whose direct and indirect helped me

complet ing m y thesis in t ime.

xiv

ABSTRACT

Chemica l or o i l ref ineiy processes ut i l ize huge amounts o f energy in their routine

operations. There fore , it is v i ta l for such industries to find ways o f m a x i m i z i n g the use

o f energy and make the system more eff ic ient through reduction in energy, water and

raw mater ial consumption. W a s t e energy can be transferred to another process and that

w i l l increase the prof i tabi l i ty o f the industries. W h e n the use o f a heat exchanger

network (HEN) is considered for these tasks, the f r a m e w o r k developed in this study can

be implemented to m a k e a cost-benefit analysis.

Th is thesis represents a f r a m e w o r k for generat ing the H E N over a specif ied range

o f variat ions in the f l o w rates and temperature o f the streams. So that the heat exchanger

area, n u m b e r o f heat exchange units and load on the heat exchangers can be estimated.

T h e proposed method to analyze and design the H E N is cal led pinch method, wh ich is

one o f the most practical tools and used to improve the ef f ic iency o f energy usage, fuel

and water consumption in industrial processes. Th is method investigates the energy

f lows wi th in a process and identif ies the most economical ways o f m a x i m i z i n g heat

recovery. Th is method consists o f five major steps to f o l l o w , w h i c h w i l l finally lead to

H E N design. T h e steps are: ( 1 ) choose a m i n i m u m temperature approach temperature

( D T m i n ) , ( 2 ) construct a temperature interval d iagram, ( 3 ) construct a cascade d iagram

and determine the m i n i m u m ut i l i ty requirements and the p inch temperature, ( 4 ) calculate

the m i n i m u m number o f heat exchangers above and b e l o w the pinch and (5 ) construct

the heat exchanger network .

T h e emphasis o f this work has been on the designing o f the H E N . H o w e v e r , to

demonstrate the practical impl icat ions o f p inch analysis, D T m i n and the heat exchanger

costs, it is necessary to estimate the heat transfer area o f the H E N , wh ich w i l l help in

arr iv ing at the total cost inc luding capital and running costs o f the designed H E N . T h e

effect o f changing the D T m i n gave a good indicat ion on the overal l costs.

xiv

ABSTRAK

Industri pemprosesan k i m i a atau penapisan minyak banyak menggunakan tenaga

dalam rutin harian mereka. M a k a industri-industri sebegini perlu mencari a l temat i f

untuk memaks imumkan penggunaan tenaga dan memast ikan sistem yang digunakan

adalah efisyen melalui pengurangan da lam penggunaan tenaga, air dan juga bahan

mentah. H a b a buangan daripada proses yang di jalankan boleh dikitar dan diguna semula

untuk digunakan di da lam proses yang lain. Jadi, b i ia alat penukar haba digunakan di

dalam proses yang disebutkan di atas, m a k a ke i ja di da lam tesis ini boleh digunakan

untuk mengurangkan penggunaan kos untuk industri tersebut.

Tesis ini mempersembahkan ja lan ke i j a untuk merekabentuk 'Rangkaian

Penukar Haba ' . Hasi lnya , kawasan yang diperlukan untuk membina alat-alat penukar

haba ini boleh dikira, begitu j u g a bi langan unit yang diperlukan dan bebanan yang

dikenakan kepada alat penukar haba boleh dianggarkan. Rangkaian yang diusulkan ini

menggunakan kaedah yang dikenal i sebagai Kaedah Pinch. ICaedah ini merupakan

kaedah yang pa l ing praktikal dan digunakan untuk meningkatkan penggunaan tenaga, air

dan bahan mentah secara efisyen. Kaedah ini mengenalpasti tenaga yang boleh dial irkan

dari buangan kepada proses yang berguna dan seterusnya dapat memaks imumkan

penggunaan tenaga. Kaedah ini mengandungi l i m a langkah yang per lu di ikuti: (1 ) p i l ih

suhu rendah yang dibenarkan, ( 2 ) b ina diagram jarak-suhu, ( 3 ) b ina diagram Cascade

dan tentukan keperluan tenaga m i n i m u m , (4 ) k ira bi langan alat penukar haba yang

diperlukan dan (5 ) b ina rangkaian alat penukar haba.

O b j e k t i f u tama tesis ini adalah merekabentuk rangkaian alat penukar haba,

namun sebagai pelengkap kepada keperluan ekonomi , tesis ini turut mendemonstrasi

kesan daripada penggunaan kaedah pinch ini dengan suhu m i n i m u m yang dipi l ih dan

j u g a kos untuk membina rangkaian alat penukar haba. Kos-kos ini termasuk kos untuk

m e m b i n a kawasan, kos pembuatan alat penukar haba dan lain-lain. Kos ini disebut

Vlll

sebagai kos u t a m a y a n g mei ibatkan kos permulaan untuk memulakan operasi. M a n a k a l a

kos tahunan atau kos yang perlu ditanggung sepanjang industri ini menjalankan operasi

mereka termasuk kos untuk membel i tenaga, minyak , air dan lain-lain. Dengan menukar

ni la i suhu m i n i m u m yang dipi l ih di da lam langkah (1), kos-kos yang disebutkan akan

berubah dan di sini akan w u j u d t i t ik op t imum yang boleh diaplikasi oleh pihak industri.

V l l l

T A B L E O F C O N T E N T S

C H A P T E R C O N T E N T S P A G E

D E C L A R A T I O N i i

D E D I C A T I O N in

A C K N O W L E D G E M E N T iv

A B S T R A C T v

A B S T R A K vi

T A B L E O F C O N T E N T S v i i i

L I S T O F T A B L E S xi

L I S T O F F I G U R E S x i i

N O M E N C L A T U R E x i v

L I S T O F A P P E N D I X E S xv i i

1 I N T R O D U C T I O N

1.1 Background o f the Prob lem 3

1.2 Object ives 4

1.3 Scope o f W o r k 5

1.4 T h e Importance o f the Research 5

I I L I T E R A T U R E R E V I E W

2.1 Introduction to Hea t Exchanger N e t w o r k Analysis 8

2.2 Pinch Design M e t h o d 9

2 .21 Pinch Appl icat ion 15

2.3 Mathemat ica l Programming Approach 17

2 .3 .1 Sequential Approach 17

2 .3 .2 Simultaneous Approach 18

RESEARCH METHODLOGY

3.1 Introduction 22

3.1.1 O v e r v i e w o f Pinch Design M e t h o d 22

3 .1 .2 W h a t is Pinch Technology? 23

3.1.3 Object ives o f P inch Analysis 24

3 .2 Steps in Pinch Analysis 26

3 .2 .1 Thermal Da ta for Process and U t i l i t y Streams 26

3 .2 .2 Step 1: Choose a M i n i m u m Approach Temperature

( D T m i n ) 2 7

3.2.3 Step 2: Construct a Temperature Interval D i a g r a m 28

3.2.4. Step 3: Construct a Cascade D i a g r a m 29

3.2.5 Step 4: Calculate the M i n i m u m N u m b e r o f H e a t

Exchanger 30

3 .2 .6 Step 5: Design the Heat Exchanger N e t w o r k 30

3.2.6.1 Design above the Pinch 31

3 .2 .6 .2 Des ign b e l o w the Pinch 32

3.3 Composi te Temperature Enthalpy D i a g r a m 32

3.4 H e a t Transfer Area Calculat ion 33

3.5 Basic Design Procedure o f a H e a t Exchanger 34

3.6 T h e Design o f Shel l -and-Tube H e a t Exchangers 35

3.6.1 Hea t Transfer and Pressure Drop Calculations 36

3 .6 .1 .1 Shel l -Side H e a t Transfer Coef f ic ient 3 7

3 .6 .1 .2 Shel l -Side Pressure Drop 39

3.6 .2 Rat ing Procedure 41

3.6.3 Approx imate Design M e t h o d 43

3.6.3.1 Exchanger D imens ion 44

I V A N A L Y S I S A N D D I S C U S S I O N

4.1 Introduction and the D a t a Prob lem 46

4.2 M i n i m u m temperature approach o f 10°C 4 7

4.3 Des ign A b o v e the Pinch 50

4.4 Des ign B e l o w the Pinch 52

4.5 Analysis for the M i n i m u m Temperature

Approach o f 15°C 56

4.6 Analysis for the M i n i m u m Temperature

Approach o f 20 °C 60

4 .7 Shel l -and-Tube H e a t Exchanger 65

4.8 H e a t Exchanger Specif ication 68

4.9 Discussion 69

V C O N C L U S I O N A N D R E C O M M E N D A T I O N

5.1 Conclusion 71

5.2 Recommendat ion 72

R E F E R E N C E S 73

A P P E N D I X E S 79

xiv

LIST OF TABLES

TABLE NO. TITLE PAGE

1.1 PS Gantt Chart 6

3.1 Typica l Va lues o f D T m i n in Industrial Processes 28

4.1 Stream and T h e r m a l D a t a for Pinch Analysis 4 7

4 .2 Processes-to-Process Exchanger A r e a 55

4.3 H o t U t i l i t y Exchanger Area 55

4.4 C o l d Ut i l i t y Exchanger Area 55

4.5 Processes-to-Process Exchanger A r e a 58

4.6 H o t Ut i l i ty Exchanger A r e a 59

4 .7 Cold Ut i l i ty Exchanger A r e a 59

4.8 Processes-to-Process Exchanger A r e a 62

4 .9 H o t Ut i l i ty Exchanger Area 63

4 .10 Co ld Ut i l i ty Exchanger Area 63

4.11 S u m m a i y o f the Calculated Stream D a t a 63

4 .12 Hea t Exchanger Specif ication Used in the Design 69

xn

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 On ion D i a g r a m o f H ierarchy in Process Design 2

2.1 Shel ls-and-Tube Hea t Exchanger 8

3.1 Strategy for the H E N synthesis using pinch approach 25

3.2 Basic Log ic Structure for Process Hea t Exchanger Des ign 34

4.1 Temperature Intervals D iagram wi th D T m i n 10°C 64

4.2 Cascade D i a g r a m w i t h D T m i n 10°C 49

4.3 H e a t L o a d A b o v e the Pinch Point 50

4.4 Hea t L o a d B e l o w the Pinch 51

4.5 Des ign o f H E N A b o v e the Pinch Point 52

4.6 Des ign o f H E N B e l o w the Pinch 53

4 .7 Temperature Enthalpy D i a g r a m

for the Case o f D T m i n is 10°C 54

4.8 Temperature Interval D i a g r a m

for the Case o f D T m i n = l 5°C 56

4.9 Cascade D i a g r a m for the Case o f D T m i n = 1 5 ° C 57

4 .10 Designs A b o v e the Pinch 5 7

4 .11 Designs B e l o w the Pinch 58

4 .12 Temperature Interval D i a g r a m

for the Case o f D T m i n = 2 0 ° C 60

4.13 Cascade D i a g r a m 61

4 .14 Designs A b o v e the Pinch 61

4.15 Designs B e l o w the Pinch 62

4 .16 T h e Ef fect o f U s i n g D i f fe rent D T m i n 64

4.17 Shel l -and-Tube Hea t Exchanger w i th

one-shell and two-passes 65

4 .18 T h e Types o f Front E n d Used in the Design 66

4 .19 T h e Types o f Shells Used in the Des ign 67

4 .20 T h e Types o f Rear E n d Used in the Design 68

xiv

NOMENCLATURE

A H e a t Exchangers A r e a

As Shel l -Side or T u b e Outside Surface A r e a

Cp Specific H e a t Capacity

d0 T u b e D iamete r

DP s-actual Actual Pressure D r o p in the Shel l -Side

DPs-id Ideal Pressure D r o p in the Shel l -Side

A Shell D i a m e t e r

DTin, Temperature D i f fe rence at Each Interval

D T m i n M i n i m u m A l l o w a b l e Temperature D i f fe rence

F L M T D Correct ion Factor

F, Correction Factor for the T u b e Outside D iamete r and T u b e L a y o u t

F2 Correct ion Factor for the N u m b e r o f T u b e Passes

F3 Correct ion Factor Var ious R e a r - E n d H e a d Designs

h Heat Transfer Coef f ic ient

H D D H u m i d i f i c a t i o n - D e h u m i d i f i c a t i o n Desal inat ion

H E N Hea t Exchanger N e t w o r k

Ihd Ideal H e a t Transfer Coef f ic ient

hs Shel l -Side H e a t Transfer Coef f ic ient

Jb Correct ion Factor for B u n d l e

Jo Correct ion Factor for B a f f l e Conf igurat ion

Ji Correct ion Factor for B a f f l e Leakage Effects

Jr Correct ion Factor for A n y Adverse Temperature Gradient

Js Correction Factor for L a r g e r B a f f l e Spacing

k Therma l Conduct iv i ty

L T u b e Length

Leff Effect ive T u b e Length

xiv

L M T D Logar i thmic M e a n Temperature Di f ference

L P L inear Programming

m F l o w Rate

m C p Hea t Capacity F l o w Rate

MTT.P M i x e d Integer L inear Programming

M 3 N L P M i x e d Integer Nonl inear Programming

M O - M I L P M u l t i - O b j e c t i v e M i x e d - I n t e g e r L inear Programming

NH N u m b e r o f Baf f les

N L P Nonl inear Programming

NK CC N u m b e r o f T u b e R o w s Crossed D u r i n g F l o w Through One Crossf low in

the Exchanger

TV,. CTl. N u m b e r o f T u b e R o w s Crossed in Each Baf f le W i n d o w

N , N u m b e r O f Tubes

N u Nusselts N o .

P D M Pinch Design M e t h o d

Ps Temperature Effectiveness

O Hea t Supp ly /Demand

Qmailable Heat Ava i lab le

Q C Co ld Enthalpy

Q H H o t Enthalpy

O m t Hea t for Each Interval

RS Heat Capacity Rat io

S T H X Shel l -and-Tube Hea t Exchanger

T E M A Tubular Exchanger Manufacturers ' Association

T - H Temperature-Enthalpy

T - I Temperature Interval

T i n Supply Temperature

Tout Target Temperature

U Overal l Hea t Transfer Coef f ic ient

US Overal l Shel l -Side Heat Transfer Coeff ic ient

W W o r k D o n e

x v i

AH Enthalpy Change

AP Pressure Drop

APb,id Ideal Pressure Drop in the Central Section

APcr Pressure D r o p in the Central (Crossf low) Section

AP,-0 Pressure Drop in the Shel l -Side Inlet A n d Outlet Sections

APW Pressure D r o p in the W i n d o w Area

Q) Correction Factor for Bypass F l o w

Q Correct ion Factor for Tube - to -Ba f f l e and Baf f le - to-Shel l Leakage

Streams

6 ' Correction Factor for In le t and Outlet Sections

t| Viscosi ty

p Densi ty

xvii

LIST OF APPENDIXES

APPENDIX TITLE PAGE

A Tube outside (shell side) surface area A s as a function o f

shell inside diameter and effect ive tube length 80

B Va lues o f F i for Var ious T u b e Diameters and Layouts 81

C Va lues o f F2 for Var ious N u m b e r s o f Tube-Passes 82

D Va lues o f F 3 for Var ious T u b e Bundle Constructions 83

E Typ ica l Ref inery Process 84

F Or ig ina l Paper o f Barbara et al. ( 2 0 0 4 ) 85

1

C H A P T E R I

I N T R O D U C T I O N

T h e transfer o f thermal energy is one o f the most important and frequently

used processes in engineer ing. T h e transfer o f heat is usual ly accompl ished b y a heat

exchanger. A s a heat transfer device, it is the funct ion o f a heat exchanger to transfer

heat as e f f ic ient ly as possible. T h i s makes it the u l t imate device o f choice, for

instance, w h e n it comes to saving energy b y recover ing wasted heat and m a k i n g it

useful again. W h e n there is a waste o f energy or a hot stream that is not recovered, a

pre-heater or recuperator can convert that hot stream into a useful source o f heat i n

other applications.

W h e n designing heat exchangers and other unit operations, l imits exist that

constrain the design. These l imi tat ions are imposed by the first and second laws o f

thermodynamics . I n heat exchangers, a close approach b e t w e e n hot and cold streams

requires a large heat transfer area. W h e n e v e r the dr iv ing force for heat exchange is

smal l , the equipment needed for transfer becomes large and it is said that the design

has a "p inch" . W h e n considering systems o f m a n y heat exchangers, it is ca l led a heat

exchanger n e t w o r k ( H E N ) . T h e r e w i l l exist somewhere in the system a po int where

the dr iv ing force for energy exchange is m i n i m u m . Th is represents a p inch o r p inch

point . T h e successful design o f these ne tworks involves discover ing w h e r e the p i n c h

exists and using this in fo rmat ion at the p inch point to design the w h o l e ne twork . Th is

design process is cal led p i n c h technology.

2

T h e H E N synthesis has been one o f the most w e l l studied in process synthesis

dur ing the last three decades and has been w i d e l y appl ied, especial ly in the

pet ro leum re f in ing and petrochemical industry. T o i l lustrate the role o f H E N in the

overal l process design, consider the "on ion d iagram" ( L i n h o f f et. al., 1982 ) as s h o w n

be low. T h e design o f a process starts w i t h the reactors in the "core" o f the onion.

O n c e feeds, products, recycle concentrations and f lowrates are k n o w n , the separators

( the second layer o f the onion) can be designed. T h e basic process heat and mater ia l

balance is n o w in place, and the H E N (the third layer) can be designed. T h e

remain ing heat ing and cool ing duties are handled by the ut i l i ty system ( the four th

layer) . T h e process ut i l i ty system m a y be a part o f a centralised si tewide u t i l i ty

system.

R < i r i t : l a 6 9 r i p

o 2 (5 Cl

3

be set prior to the design of the heat exchanger network. The pinch design method

ensures that these targets are achieved during the network design.

Process integration using pinch technology offers a chronicle approach to

generate targets for minimum energy consumption before heat recovery network

design. Heat recovery and utility system constraints are then considered in the design

of the core process. Interactions between the heat recovery and utility system are also

considered. The pinch design can reveal opportunities to modify the core process to

improve heat integration. The pinch approach is unique because it treats all processes

with multiple streams as a single, integrated system. This method helps to optimize

the heat transfer equipment during the design of the equipment.

1.1 Background of the Problem

As the heat exchanger consumes energy vastly, it is vital to find a method to

improve the use of energy and reduce capital and utilities cost. Finding ways to

reduce and conserving energy are always a smart way to cut cost. Reduced energy

usage is a big selling point for end users. If the functionality of a product is similar to

the competition, benefits like energy usage win customers. The benefit of reduced

usage cost over time allows manufacturers to charge a higher premium while saving

the customer money in the long run.

Excessive energy consumption by using hot and cold utilities influences the

global cost of industrial processes. The supply and removal of heat in a modern oil

refinery process plant represents an important problem in the process design of the

plant. The cost of facilities to accomplish the desired heat exchange between the hot

and cold media may cost up to one third of the total cost of the plant. To meet the

goal of maximum energy recovery or minimum energy requirement (MER) an

appropriate HEN is required. The design of such a network is not an easy task