Application of Intensified Heat Transfer for the Retrofit ......Ayub, Z. H., A new chart method for...

Application of Intensified Heat Transfer for

the Retrofit of Heat Exchanger Network

Centre for Process Integration © 2010

Yufei Wang, Ming Pan, Igor Bulatov, Robin Smith, Jin-Kuk Kim

Centre for Process Integration

School of Chemical Engineering and Analytical Science

The University of Manchester

Outline

1. Introduction

2.Modelling of shell-and-tube heat exchangers

3.Heuristic rules for HEN retrofit with HTE

4.Case study


4.Case study

5.Conclusion

1. Introduction


Heat exchanger network (HEN)

H1

H2

H3

C1

C2

C3


• Models used for units in heat- exchanger network (HEN) are very simple

• HEN design neglects the heat-exchanger details

• No account of pressure drops

LMT∆×A×U=Q

Specified overall U No details of geometry, just overall area

Not suitable for many retrofit applications

C4

HEN retrofit

H1

H2

H3

C1

C2

C3


• Account for detailed performance of heat exchangers

• Include pressure drop constraints

• Allow locations for appropriate use of heat transfer enhancement

Need an approach for retrofit

C4

Research objectives

� Develop a simple but accurate model for heat-exchanger details

� Propose appropriate heat transfer


� Propose appropriate heat transfer enhancement

� Develop a design method suitable for HEN retrofit with heat transfer enhancement

2. Modelling of shell-and-tube heat exchangers


Heat exchangers

� Double pipe (DPHEX)

two pairs of concentric pipes,

counter flow

- the simplest type

� Shell and tube (STHEX)

a bundle of tubes in a cylindrical shell,

combining parallel and counter flows


combining parallel and counter flows

- the most widely used type in the

chemical industries

� Plate and frame (PFHEX)

metal plates are used to separate and

transfer heat between two fluids

- the common typed in the food and

pharmaceutical industries

Limits of the existing STHEX models

� Lots of equations and empirical factors

unsuitable for HEN modelling, leading to large scale

problems

� Various assumptions

over or less estimate heat transfer coefficients and


over or less estimate heat transfer coefficients and

pressure drops

A simple but reliable model is required for estimating STHEX performances!

heating for PrRe024.0=Nu

4.0

i

8.0

i

New model of STHEX (tube-side)

Tube-side heat transfer coefficient (hi): (Based on Bhatti and Shah, 1987)

( )( )4/Dπρ

n/nm=v 2

ii

tpi

i iiiii µ/ρvD=Re iiPii k/µC=Pr

410Re ≥


cooling for PrRe023.0=Nu 4.0

i

8.0

i

i

( )iiii Nu×D/k=h

i 10Re ≥

4i 10<Re<2100

( )[ ] 31

iiii L/DPrRe86.1=Nu 2100Re i ≤

Bhatti, M. S., and R. K. Shah, Turbulent and transition convective heat transfer in ducts, in Handbook of Single-Phase

Convective Heat Transfer, S. Kakac¸ , R. K. Shah, and W. Aung, eds., Wiley, New York, Chap. 4, 1987.

Newadjusted value ( ) ]L/D+1[Pr)125(Re116.0=Nu

3/2

i

3/1

i

3/2

ii

New model of STHEX (tube-side)

Tube-side pressure drop (∆Pi): (Adopt existing method of Serth, 2007)

3000Re i ≥

ii Re/64=f 3000<Re i

2iiip vρLfn

=P∆

2585.0

ii Re4137.0=f


icfi Dg2

=P∆

c

2niiS

ni g

vρN75.0=P∆

nirfii P∆+P∆+P∆=P∆

Serth, R. W., Process heat transfer principles and applications, Elsevier Ltd, 2007.

c

2iip

r g

vρ)5.1n2(5.0

=P∆

New model of STHEX (shell-side)

Shell-side heat transfer coefficient (h0):

00h00z µvDρ=F

2F ≤

hm0

0

0h Sρ

m=v

For

Numerical correlations are proposed:


793.17+F78.76+F2223.9=F z2zs

2Fz ≤

5053.0c

6633.0zs BF4783.34=F

1000F<2 z ≤

( )0

3/1

00p3/2

0s

0 D

µCkF765.0=h

For

For

Graphical information is only available (Ayub, 2005)

Ayub, Z. H., A new chart method for evaluating single-phase shell side heat transfer coefficient in a single segmental shell

and tube heat exchanger. Applied Thermal Engineering, 25, 2412-2420, 2005.

New model of STHEX (shell-side)

Shell-side pressure drop (∆P0):

( ) 125.0

0s1 ReD00653543.0+0076.0=f

( ) 157.00s

32 ReD10×2835.2+0016.0=f

Baflle cut is specified

for 20% (Serth, 2007)])ff)(D/B1(25.1f[144=f 21s10

Centre for Process Integration © 2010L04 – 18 Modelling of Intensified Heat Transfer for the Retrofit of Heat Exchanger Networks

ec

20p0s0

Bc%20,fb Dg2

vρDf=P∆

1n

cmincBc%20,0f0f )B/B(P∆=P∆

0n0f0 P∆+P∆=P

c

20n0S

0n g

vρN75.0=P∆

Serth, R. W., Process heat transfer principles and applications, Elsevier Ltd, 2007.

New correlation for other baffle cuts are proposed:

%20=B cmin

New model of STHEX

U, LMTD, FT and A:

Energy balance:

( )]R+

D

DR+

h

1+

k2

D/DlnD+

Dh

D[=U

1

0Di

0Di

0tube

i00

ii

0

)TT(Cm=)TT(Cm inlet,ioutlet,ipiiinlet,0outlet,00p0


)TT(

)TT(

ln

)TT()TT(

=LMTD

inlet,ioutlet,0

outlet,iinlet,0

inlet,ioutlet,0outlet,iinlet,0

( )1+R+1+RS2

)1+R1+R(S2

ln)1R(

RS1

S1

ln1+R

=FT

2

2

2

eff0t LDπn=ALMTD×FT×U

)TT(Cm

=A�outlet,0inlet,00p0

Procedure of the new modelInput stream and geometry parameters of heat exchanger:

Thot, in, Tcold, in, Cphot, Cpcold,µhot,µcold, L, D0, ….

Calculate tube-side (∆Pi) Plain tube

correlations

Calculate tube-side (hi)

Dittus-Boelter correlation

Calculate shell-side (∆P0)

Simplified Delaware method

Calculate shell-side (h0)

Chart method

Calculate overall heat transfer coefficient


Assume hot stream outlet temperature (Thot, out)

Calculate LMTD, LMTD correction factor (F), and heat-transfer area based on tubes (A)

Calculate cold stream outlet temperature (Tcold, out)

Calculate overall heat transfer area with U

IA’ – A I ≤ ε Stop Yes No

Examples

Ten examples are considered for model validation:

Heat exchanger geometry:

Tube: 124 ~ 3983 Tube passes: 2 ~ 6 Tube length: 2.4 m ~ 9 mTube diameter: 15 mm ~ 25 mm Tube pattern: 30º, 45º, 60º, 90º Shell diameter: 0.489 m ~ 1.9 m Baffle spacing: 0.0978 m ~ 0.5 m


Shell diameter: 0.489 m ~ 1.9 m Baffle spacing: 0.0978 m ~ 0.5 mBaffle cut: 20% ~ 40% ……..

Stream Properties:

Specific heat (J/kg▪K): 642 ~ 4179 Thermal conductivity (W/m▪K): 0.08 ~ 0.137Viscosity (mPa▪s): 0.17 ~ 18.93Density (kg/m3): 635 ~ 1000

Example 1 Example 2 Example 3 Example 4 Example 5

Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side

Streams

Specific heat CP (J/kg·K) 2135 2428 4272 642 4179 4179 2470 2052 2273 2303

Thermal conductivity k (W/m·K) 0.123 0.106 0.685 0.085 0.633 0.623 0.137 0.133 0.08 0.0899

Viscosity µ (mPa·s) 2.89 1.2 0.17 0.20 0.62 0.71 0.40 3.60 18.93 0.935

Density ρ (kg/m3) 820 790 910 635 991 994 785 850 966 791

Flow rate mi (kg/s) 75.22 19.15 16.11 109.47 192.72 385.4 5.675 18.917 46.25 202.54

Inlet temperature Tin (°C) 51.7 210.0 150.0 207.0 48.0 33.0 200.0 38.0 227.0 131.0

Fouling resistance (m2·K/W) 0.00035 0.00035 0.0001 0.0005 0.0007 0.0004 0.00035 0.00053 0.00176 0.00053

Geometry of heat exchanger

Tube pitch PT (m) 0.0254 0.032 0.025 0.03175 0.03125

Number of tubes nt 528 296 3983 124 612

Details of examples



Number of tube passes np 6 2 2 4 2

Tube length L (m) 5.422 2.4 9 4.27 6

Tube effective length Leff (m) 5.219 2.24 8.821 4.17 5.903

Tube inner diameter Di (m) 0.0148 0.02 0.015 0.0212 0.02

Tube outer diameter D0 (m) 0.0191 0.025 0.019 0.0254 0.025

Shell inner diameter Ds (m) 0.771 0.7 1.9 0.489 0.965

Number of baffles nb 18 15 16 41 25

Baffle spacing B (m) 0.2584 0.14 0.5 0.0978 0.22

Inlet baffle spacing Bin (m) 0.4132 0.14 0.66 0.127 0.3117

Outlet baffle spacing Bout (m) 0.4132 0.14 0.66 0.127 0.3117

Baffle cut Bc 22% 20% 25% 20% 20%

Inner diameter of tube-side inlet nozzle Di,inlet (m) 0.128 0.3 0.438 0.1023 0.336

Inner diameter of tube-side outlet nozzle Di,outlet (m) 0.128 0.3 0.438 0.1023 0.336

Inner diameter of shell-side inlet nozzle D0,inlet (m) 0.259 0.15 0.337 0.0779 0.154

Inner diameter of shell-side outlet nozzle D0,outlet (m) 0.259 0.25 0.337 0.0779 0.154

Shell-bundle diametric clearance Lsb (m) 0.074 0.074 0.023 0.059 0.069

Details of examples (continued) Example 6 Example 7 Example 8 Example 9 Example 10

Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side

Streams

Specific heat CP (J/kg·K) 2477 2503 2505 1993 2512 2240 2555 2265 2430 4223

Thermal conductivity k (W/m·K) 0.076 0.08 0.093 0.103 0.089 0.091 0.083 0.091 0.0865 0.6749

Viscosity µ (mPa·s) 4.53 0.67 0.26 3.76 0.33 1.1 0.5 1.05 1.8 0.296

Density ρ (kg/m3) 937 748 662 846 702 801 743 798 786 957

Flow rate mi (kg/s) 32.24 130.288 71.3 202.54 76.92 405.1 17.657 202.542 60.23 23.9

Inlet temperature Tin (°C) 293.0 196.0 194.0 44.0 227.0 112.0 265.0 121.0 170.0 77.0

Fouling resistance (m2·K/W) 0.00176 0.00088 0.00053 0.00053 0.00053 0.00053 0.00053 0.00053 0.00088 0.00053


Tube pitch PT (m) 0.03125 0.03125 0.03125 0.03125 0.025

Number of tubes n 538 650 1532 407 582



Number of tube passes np 2 2 2 2 4

Tube length L (m) 6 5.7 9 5.5 7.1

Tube effective length Leff (m) 5.9 5.6 8.85 5.45 7.062

Tube inner diameter Di (m) 0.021 0.02 0.02 0.021 0.015

Tube outer diameter D0 (m) 0.025 0.025 0.025 0.025 0.019

Shell inner diameter Ds (m) 0.914 1.1 1.5 0.9 0.8

Number of baffles nb 24 14 17 29 20

Baffle spacing B (m) 0.232 0.35 0.489 0.18 0.33

Inlet baffle spacing Bin (m) 0.286 0.5227 0.539 0.205 0.4

Outlet baffle spacing Bout (m) 0.286 0.5227 0.539 0.205 0.4

Baffle cut Bc 20% 24.4% 38% 20% 40%

Inner diameter of tube-side inlet nozzle Di,inlet (m) 0.3048 0.3 0.337 0.337 0.154

Inner diameter of tube-side outlet nozzle Di,outlet (m) 0.3048 0.3 0.337 0.337 0.154

Inner diameter of shell-side inlet nozzle D0,inlet (m) 0.1541 0.3 0.255 0.102 0.203

Inner diameter of shell-side outlet nozzle D0,outlet (m) 0.1541 0.3 0.255 0.102 0.203

Shell-bundle diametric clearance Lsb (m) 0.068 0.082 0.071 0.067 0.066

Results (New model vs. HTRI/HEXTRAN)hi (W/m2.K)

0

1000

2000

3000

4000

5000

6000

7000

8000

0 1000 2000 3000 4000 5000 6000 7000 8000

HT

RI / H

EX

TR

AN

Pi (kPa)

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100

HT

RI / H

EX

TR

AN

HTRI HEXTRAN HTRI HEXTRAN Tube-side:Heat transfer

coefficient (hi)

Pressure drop (Pi)


0 1000 2000 3000 4000 5000 6000 7000 8000

New model

0 20 40 60 80 100

New model

h0 (W/m2.K)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

New model

HT

RI / H

EX

TR

AN

P0 (kPa)

0

10

20

30

40

50

60

70

80

90

100

0 20 40 60 80 100

New model

HT

RI / H

EX

TR

AN

HTRI HEXTRAN HTRI HEXTRAN Shell-side:Heat transfer

coefficient (h0)

Pressure drop (P0)

Modelling of heat exchanger

The new model:

� Fewer equations and empirical factors

(compared with the existing models)

� Reliable estimation for heat transfer coefficients and pressure

drops (compared with HTRI® and HEXTRAN®)


drops (compared with HTRI and HEXTRAN )

Limits:

� No phase change

� Phase change will be considered in future work

� Single segmental baffle

3. Heuristic rules for HEN retrofit with HTE

Centre for Process Integration © 2010L04 – 43 Modelling of Intensified Heat Transfer for the Retrofit of Heat Exchanger Networks

Existing design methods for HEN retrofit

Limits:

� Yee and Grossmann (1991), retrofit design

� Sorsak and Kravanjia (2004), different exchanger types

� Ponce-Ortega et al. (2008), phase changes


� Lots of topology modifications

� Too much repiping work

� No account of STHEX geometry modifications

Yee TF, Grossmann IE. A screening and optimization approach for the retrofit of heat exchanger networks. Industry

and Engineering Chemistry Research 1991; 30 (1): 146-162.

Sorsak A, Kravanja Z. MINLP retrofit of heat exchanger networks comprising different exchanger types. Computers

and Chemical Engineering 2004; 28: 235-251.

Ponce-Ortega JM, Jiménez-Gutiérrez A, Grossmann IE. Optimal synthesis of heat exchanger networks involving

isothermal process streams. Computers and Chemical Engineering 2008; 32: 1918-1942.

Existing design methods for HEN retrofit with HTE

Limits:

� Polley et al. (1992), potential analysis of heat recovery

� Zhu et al. (2000), network pinch approach

� Smith et al. (2009), structural modifications and cost- effective design

� Large scale problems


� Large scale problems

� No pressure drop restrictions

� Stream outlet temperatures change

Polley GT, Reyes Athie CM, Gough M. Use of heat transfer enhancement in process integration. Heat Recovery

Systems and CHP 1992; 12(3): 191-202.

Zhu X, Zanfir M, Klemes J. Heat transfer enhancement for heat exchanger network retrofit. Heat Transfer Engineering

2000; 21(2): 7-18.

Smith R, Jobson M, Chen L. Recent development in the retrofit of heat exchanger networks. Chemical Engineering

Transactions 2009; 18: 27-32.

Heat Exchanger Network Retrofit Through Heat Transfer Enhancement

P The methodology isHeuristic

P The objective of thismethodology is to findcandidates to be

Network structure analysis

Search exchangers in utility path(Heuristic rule 1)

Sensitivity analysis(Heuristic rule 2)

Check the pinching match (Heuristic rule 3)


candidates to beenhanced

P The methodology ismainly based onnetwork pinchapproach andsensitivity tables

Enhance the candidate exchanger

Any other good candidates? (Heuristic rule 4)

Yes

No

Still need improvement? Enhance pinching match (Heuristic rule 5)

Yes

Result

No

Heuristic methodology (Rule 1)

1N:1

2N:2

230

3N:3

200

4N:4

300

5N:5

100

6N:6

80

2

2

N :11

N:12

3

3

N:13

N:14

7N :19

1

1

N:9

N:10

8N :21

5

5

N:23

N:24

9N:25

4

4

N:15

N:16

10N :27

6N:18

H1

H2

H3

H4

C1

C2


7N:7

400

8N:8

25

7N :20

8N :22

9N:26

10N:28

6N :17

Steam

Cooling Water

Rule 1(Networkstructure analysis)

P Rule 1 is to find the potential candidates to be enhanced. Only thoseexchangers on a utility path and on a same stream with utilityexchanger will be selected.


1 N:1

2 N:2

2 3 0

3 N:3

2 0 0

4N:4

3 0 0

5

1 0 0

2 N:1 1 3

3

N:1 3 7 N:1 9

1 N:9 8 N:2 1

5 N:2 3 9 N:2 5

4N:1 5

10N:2 7

H1

H2

H3

H4

C1

Rule 2(Sensitivity graph)


Candidate

5N:5

6N:6

8 0

7N:7

4 0 0

8N:8

2 5

2N:1 2

3N:1 4

7N:2 0

1N:1 0

8N:2 2

5N:2 4

9N:2 6

4N:1 6

10N:2 8

6

6

N:1 7

N:1 8

C1

C2

Steam

Cooling Water

P Rule 2 is to analyze the energy saving potential of each candidateby using sensitivity tables.

Reasons for high sensitivity

� CP value of the hot stream (assuming the chosen utility exchanger is a

hot utility)

� The △Tmin between hot and cold stream

� The candidate position in network



1N:1

2N:2

230

3N:3

200

4N:4

300

5N :5

100

6N :6

80

400

2

2

N:11

N:12

3

3

N:13

N:14

7N:19

1

1

N:9

N:10

8N:21

5

5

N:23

N:24

9N:25

4

4

N:15

N:16

10N:27

6N:18

H1

H2

H3

H4

C1

C2

Candidate

Pinchingmatch

Rule 3(checknetwork pinch)


Candidate7N:7

8N :8

25

7N:20

8N :22

9N:26

10N :28

6N:17

Steam

Cooling Water

P Rule 3 is to check the network pinch which may influence the preformance ofcandidates.

P After checking the network pinch, the best candidate can be identified by theresults of sensitivity tables.


1N:1

2N:2

230

3N:3

200

4N:4

300

5N :5

100

6N :6

80

2

2

N:11

N:12

3

3

N :13

N :14

7N:19

1

1

N :9

N :10

8N :21

5

5

N:23

N:24

9N:25

4

4

N:15

N:16

10N :27

6N:18

H1

H2

H3

H4

C1

C2

Candidate Candidate


7N:7

400

8N :8

25

7N:20

8N :22

9N:26

10N :28

6N:17

Steam

Cooling Water

Rule 4(Enhance severalcandidates simultaneously)

P Rule 4 is to determine if there are some other exchangers can beenhanced.

P Sensitivity graphs will be applied again.


1N:1

2N:2

230

3N:3

200

4N:4

300

2N:11

3N:13

7N:19

1N:9

8N:21

5N:23

9N:25

4N:15

10N:27

H1

H2

H3

H4

Pinchingmatch

Rule 5(enhance both pinchingmatch and candidate


5N:5

100

6N:6

80

7N:7

400

8N:8

25

2N:12

3N:14

7N:20

1N:10

8N:22

5N:24

9N:26

4N:16

10N:28

6

6

N:17

N:18

C1

C2

Steam

Cooling Water

Candidate

P Rule 5 is to enhance pinching match to release the candidate torecover more heat

4. Case study


Case study


Case studyStream data and geometry of heat exchangers 20, 24, 26 and 28

Heat Exchanger 20 Heat Exchanger 24 Heat Exchanger 26 Heat Exchanger 28

Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side

Fluids H2 C2 H2 C3 H3 C3 H9 C3

Specific heat CP (J/kg·K) 2394 2310 2597 2444 2965 2526 2832 2609

Thermal conductivity k (W/m·K) 0.096 0.090 0.095 0.085 0.062 0.078 0.071 0.074

Viscosity µ (mPa·s) 0.67 0.90 0.44 0.80 0.10 0.69 0.30 0.57

Density ρ (kg/m3) 773 789 734 766 556 751 638 733

Flow rate mi (kg/s) 73.1 160.2 73.1 153.7 40.6 153.7 63.4 153.7

Inlet temperature Tin (°C) 200.0 128.4 253.2 166.0 293.7 192.9 290.4 207.2

Fouling resistance (m2·K/W) 0.00006 0.00036 0.00120 0.00072 0.00221 0.00080 0.00117 0.00088


Tube pitch PT (m) 0.03125 0.03125 0.03125 0.03125

Number of tubes nt 1532 1532 650 1532


Number of tubes nt 1532 1532 650 1532

Number of tube passes np 2 2 1 2

Tube length L (m) 11.3 8.5 5.5 8.5

Tube effective length Leff (m) 11.1 8.3 5.3 8.3

Tube conductivity ktube (W/m·K) 51.91 51.91 51.91 51.91

Tube pattern (tube layout angle) 90° 90° 90° 90°

Tube inner diameter Di (m) 0.02 0.02 0.02 0.02

Tube outer diameter D0 (m) 0.025 0.025 0.025 0.025

Shell inner diameter Ds (m) 1.5 1.5 1.1 1.5

Number of baffles nb 20 16 9 18

Baffle spacing B (m) 0.49 0.49 0.52 0.49

Inlet baffle spacing Bin (m) 0.95 0.57 0.71 0.57

Outlet baffle spacing Bout (m) 0.95 0.57 0.71 0.57

Baffle cut Bc 20% 20% 40% 20%

Inner diameter of tube-side inlet nozzle Di,inlet (m) 0.336 0.336 0.3 0.336

Inner diameter of tube-side outlet nozzle Di,outlet (m) 0.336 0.336 0.3 0.336

Inner diameter of shell-side inlet nozzle D0,inlet (m) 0.255 0.255 0.3 0.255

Inner diameter of shell-side outlet nozzle D0,outlet (m) 0.255 0.255 0.3 0.255

Shell-bundle diametric clearance Lsb (m) 0.074 0.074 0.082 0.074

Maximum pressure drops in shell and tube side (KPa) 100 100 100 100

Case study

Tube-side heat transfer enhancement for heat exchangers 20, 24, 26 and 28

Example 20 Example 24 Example 26 Example 28

Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side Shell-side Tube-side

H2 C2 H2 C3 H3 C3 H9 C3

New model

Pressure drop △P (KPa) 24.1 14.7 20.6 11.25 5.1 8.1 19.2 11.1

Film coefficient h (W/m2·K) 975 822 1117 824 753 961 979 894

Overall heat transfer coefficient U (W/m2·K) 321.4 219.1 169.8 211.1

HTRI


HTRI




Heat transfer enhancement of tube side




Case study

Optimization of HEN retrofit

For a given number of enhanced exchangers

� Increase energy saving

� Subject to maximum pressure drop constraints in


� Subject to maximum pressure drop constraints in

streams

Case study Initial situation Enhancement situation

Exchanger U

(kW/m2·K)

Area

(m2)

∆Tln

(°C)

Duty

(kW)

U

(kW/m2·K)

Area

(m2)

∆Tln

(°C)

Duty

(kW)

1 0.1400 167.6 48.2 1132 0.1400 167.6 48.2 1132

2 0.4690 90.4 143.4 6087 0.4690 90.4 140.3 5954

3 0.6270 89.9 73.0 4117 0.6270 89.9 73.0 4117

4 0.1850 153.0 75.2 2128 0.1850 153.0 75.1 2127

5 0.5720 97.4 100.9 5626 0.5720 97.4 100.9 5626

6 0.2040 653.1 45.7 6090 0.2040 653.1 45.6 6087

7 0.3540 13.3 43.3 204 0.3540 110.6 5.2 204

8 0.4130 23.4 56.6 548 0.4130 23.4 56.6 548

9 0.4130 47.3 35.4 693 0.4130 47.3 34.8 680

10 0.0990 282.8 90.4 2532 0.0990 282.8 90.4 2532

11 0.3730 55.5 65.7 1360 0.3730 55.5 65.7 1360

12 0.0842 225.4 46.8 889 0.0842 225.4 46.8 889


12 0.0842 225.4 46.8 889 0.0842 225.4 46.8 889

13 0.0628 380.8 89.6 2143 0.0628 380.8 91.3 2183

14 0.2720 81.2 86.9 1920 0.2720 81.2 87.7 1937

15 0.3520 31.3 90.2 993 0.3520 31.3 90.2 993

16 0.6730 113.1 110.5 8408 0.6730 113.1 109.0 8295

17 0.1280 191.1 122.2 2989 0.1280 191.1 122.2 2989

18 0.1880 188.9 40.0 1421 0.1880 188.9 40.2 1427

19 0.2000 97.9 84.5 1655 0.2000 97.9 84.3 1651

20 0.3210 1338.4 24.3 10450 0.4290 1338.4 18.2 10440

21 0.0527 220.2 20.1 233 0.0527 220.2 20.4 237

22 0.0752 768.5 23.1 1335 0.0752 768.5 23.1 1335

23 0.1430 390.9 35.6 1992 0.1430 390.9 35.6 1992

24 0.2190 1003.3 46.0 10100 0.2630 1003.3 41.8 11040

25 0.3520 63.1 210.3 4667 0.3520 63.1 195.2 4333

26 0.1700 1308.0 16.7 3718 0.1870 1308.0 16.3 3981

27 0.1950 223.5 42.1 1834 0.1950 223.5 42.2 1838

28 0.2110 1003.3 44.1 9333 0.2450 1003.3 39.4 9677

29 0.1260 227.1 88.1 2522 0.1260 227.1 85.6 2449

30 (hot utility) 0.5710 139.5 819.0 65240 0.5710 139.5 791.4 63040

31 0.5710 458.6 90.1 23600 0.5710 458.6 90.1 23600

32 0.8020 45.8 114.1 4190 0.8020 45.8 92.1 3384

Case study

Summary:

� Overall heat transfer coefficients of enhanced

exchangers increase

� Pressure drops restrictions are satisfied

� No topology modifications for HEN


� No topology modifications for HEN

� No many geometry modifications for exchangers,

just enhanced with tube-inserts

� Based on the new method, up to 3.4% reduction of

heat duty is achieved (65.24 MW to 63.04 MW)

5. Conclusion


Conclusion

• New model of heat exchanger

� Tube-side heat transfer coefficients and pressure drops

� Shell-side heat transfer coefficients and pressure drops

• Retrofit of HEN with heat transfer enhancement


� Increase overall heat transfer coefficients of enhanced exchangers

� Satisfy pressure drop constraints

� Increase energy saving

Acknowledgement

Financial support from Research Councils UK Energy Programme (EP/G060274/1; Intensified Heat Transfer for

Energy Saving in Process Industries) is gratefully


Energy Saving in Process Industries) is gratefully acknowledged.

Date post:	12-May-2020
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