shell adn tube he design

8/7/2019 Shell Adn Tube HE Design

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CONDENSERCONDENSER

Gulfam Shahzad

2007-chem-77


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CondenserCondenserThe process of converting the vapour phase into the

liquid phase by removing the heat.

Types of condensers

Contact condensers

Surface condensers


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Surface condenser

Total condenser Partial condensers

Vertical Horizontal

In TubecondenserIn Shellcondensers In ShellcondensersIn TubeCondenser


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HHEATEAT EEXCHANGERSXCHANGERS

DEFINITION

Heat exchanger is the equipment used to exchangeheat between two fluids with different temperaturethrough a fixed wall without mixing the two.

USE

They are widely used in refineries and chemicalplants

To cool or heat a fluid (gas or liquid)

To condense vaporized material To evaporate a liquid To recover waste heat boiler


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KKEYEY CCHARACTERISTICSHARACTERISTICS TTOO

DDESIGNESIGN HHEATEAT EEXCHANGERXCHANGER

The material wall between the fluid must have a

higher thermal conductivity and corrosion

resistance. The heat transfer area to fluid volume ratio must

be as large as possible. The flow rate of fluid must be as fast as possible.

The turbulence rate of fluid must be as high aspossible.


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CCLASSIFICATIONLASSIFICATION OOFF HHEATEAT

EEXCHANGERXCHANGERHeat exchangers are classified on the following bases

Contacting techniques Construction

Flow arrangement Surface compactness


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PPRELIMINARYRELIMINARY

SSELECTIONELECTION

Scraped wall heat exchanger is not desired

Gasketed & Welded plate heat exchanger is not

desired Spiral plate & tube heat exchanger is not desired

Double pipe heat exchanger is not desired Shell & tube heat exchanger is desired


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SSELECTIONELECTION CRITERIACRITERIA Cost

Efficiency

Space Materials

Maintenance


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TTYPESYPES OOFF SSHELLHELL & T& TUBEUBE

HHEATEAT EEXCHANGERXCHANGER

This classification is based on the type of tube

bundle fitting in the shell Fixed tube type

U-Tube type

Floating head type


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AAPPLICATIONPPLICATION OFOF HEATHEAT

EXCHANGERSEXCHANGERS Heaters And Coolers

Vaporizer

Reboiler Evaporator

Fired exchanger

Chiller


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TTUBESIDEUBESIDE ANDAND SHELLSIDESHELLSIDE

FLUIDFLUID ALLOCATIONALLOCATIONThe criteria for fluid allocation

The most corrosive to be tubeside

The higher pressure fluid to be tubeside

Severe fouling fluids shall be allocated the side which

is accessible

Shellside boiling or condensation is usually preferred


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MAIN PARTS OF SHELL ANDMAIN PARTS OF SHELL AND

TUBE HEAT EXCHANGERTUBE HEAT EXCHANGER


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DDESIGNESIGN STEPSSTEPS

Define the duty: heat-transfer rate, fluid flow rates, andtemperatures.

Collect together the fluid physical properties required:density, viscosity and thermal conductivity.

Calculate the weighted temperature difference LMTD Select the trail value for heat transfer coefficient Ud

Calculate the area required A. Decide the exchanger layout.

Calculate the individual coefficients during condunsationand desuper heating.

Calculate the overall coefficient and compare with thetrial value.

Calculate the pressure drop on shell and tube side


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Water (coldfluid)

T = 25 oC

P = 101.3 KPa

Benzene Water mix (hot Fluid)m = 53668 Kg/ hrT = 126 oC

P = 101.3 KPa

Benzene Water mix

(hot Fluid)

T = 80o

C

Water (Cold Fluid)T = 35 oC

11--2PASS SHELL2PASS SHELL SHELLSHELL ANDAND

TUBE HEAT EXCHANGERTUBE HEAT EXCHANGER


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HHEATEAT LOADLOADHEAT LOAD

Q = Qdes + Qcond = mCp(T2 T1) + m

=14.65x1.37x(126-82) + 14.65x430

=7311 KJ/s

Mwater = Q/ Cpx(t2-t1)

= 7311/4.18x10

= 174.9 Kg/STwater due to condensation

Twater= Qcond / MwaterCpwater= 8.76 oC


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LMTDLMTD

Desuperheat (T)d

(T)des = LMTD = 67.37oC

Qd/ (T)des = 901.26/67.37

= 13.37

Weighted tw =

= 53.36o

C

tq (7 /

Q

Condensation (T)cond

(T)cond = LMTD = 52oC

Qd/ (T)cond

= 6410.3/52

= 123.3

Hot FluidoC

Cold

Fluid oC

Diff

126 High Temp 35 91

82 Low Temp 33.76 48.24

Hot

Fluid oC

Cold

Fluid oC

Diff

82 High Temp 33.76 48.24

80 Low Temp 25 56

Desuperheat Condensation


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HHEATEAT TTRANSFERRANSFERAAREAREAAssume Overall Heat Transfer coeffecient

Ud = 700 W/m

2 o

CA =Q/Ud t

= 195 m2


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TTUBEUBE DDIMENSIONSIMENSIONS

(C(COLDOLD FLUIDFLUID)) 16 BWG O D = D0 = 19mm ID = Di = 0.620in, 15.75mm

Pitch = 1.25Do = 23.75 mm

Length of tube Lt = 6.1 m

Area of one tube at = X D0 X L

= 0.364 mNo. of tubes Nt = A/ at

=534Tube side passes n = 2


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CCALCULATIONALCULATION FFOROR FFILMILM

CCOEFFICIENTSOEFFICIENTSTube side (cold fluid)

= 0.18m

= 970Kg/m s

= 0.97 m/s

= 17563

D = ID = 15.75 mm

= 8.75 * 10-4 Kg/ms (Process Heat transfer by kern Fig: 14)

= 995 Kg/m3

t

tt

awG !

Q

tDG!Re

V

tV !

n

aNa

ttt

v!d


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TTUBEUBE SSIDEIDE HTHT

CCOEFFECIENTOEFFECIENThi = 800 Btu/hr ft

2 oF

= 4542 W/m2 oC (Process Heat transfer by kern Fig: 14)

hio = 3572 W/m2 oC

ODIDh io /4542 v!

19/77.154542 v!hio


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SSHELLHELL DDIMENSIONSIMENSIONS (H(HOTOT

FFLUIDLUID))Shell ID = 27 in = 0.6858 mBaffle spacing = 0.3048 m

Shell passes = 1

Tube pitch = 1.25Do

= 23.75 mm

Equivalent dia De =

=

= 0.0135 m

Clerarance C = Pt Do

= 23.75 19

= 4.75 mm

22 19917.075.2319

10.1v

22 917.010.1 ot DPDo


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CCONTONTDD

Shell side crossflow area

= 0.0418 m2

Mass Velocity

= 356.6 Kg/m2 s

Reynold no.

= 4.8 x 105

ts PBCIDa /vv!

s

ss

a!

Q

seD v!eR


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JJhh & P& Prr

Jh = 410 (Process Heat transfer by kern Fig: 14)

= 1.128

Cp = 0.48 Btu/lb oF = 4.17 Kj/kg oC ( kern Fig 3 )

= 0.01cP = 0.01x10-3 Kg/ms ( kern Fig 15) = 0.0103 Btu/hrft

2oC = 0.058 J/s m2 oC (kern Table 5)

O

Qv!

pCrP


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UU FORFOR DDESUPERHEATESUPERHEAT

= 567 W/m2 oC

Clean Overall coeffecient Udes, Desuperheat

= 490 W/m2 oC

3/1re

Ho

Djh

Ov!

3/1128.144.0

0103.0410 v!

oio

oiodes

hh

hhU

v!

3572567

3572567

v!


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CCONDENSATIONONDENSATION

Assume condensation occurs over 80% of the tube length

L = 6.1x0.8 = 4.88 m

= 162 Kg/(hr) (lin m)

Assume

hcond = 210 Btu/hr ft2 oC = 1192 W/m2 oC

3/2t

scond

Lv! 3/255988.4

53668

v!


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CCONTONTDD

Assume

hcond = 210 Btu/hrft2oC = 1192 W/m2 oC

hio = 661.333 Btu/hrft2 oC = 3572 W/m2 oC

Avg shell side temp during condensation Ta=81 oC

Avg Tube side temp ta = 30oC

tw = 42.3oC

taTahh

htt

condio

conda

!


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UU FORFOR CCONDENSATIONONDENSATION

tf = 61.6oC

At tf 61.6oC

sf = 0.88 ( kern Fig 6 )

f = 0.41cP = 0.41x10-3Kg/m s ( kern Fig 14)

f = 0.092 Btu/hrft2oC = 0.52 J/s m2 oC (kern Table 5)

hcond = 210 Btu/hrft2oC (So assumed value is correct)

Clean Over all coeffecient Ucond, condensation:

Ucond = 905 W/m2 oC

2

waf

tTt

!

condio

condiocond

hh

hh

v!


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CCLEANLEAN SSURFACEURFACEAAREAREAClean surface area required

= 27.2 m2

= 136.5 m2

Checking assumed condensing lenhth L

(So assumed value is correct)

desdes

desdes

TU

QA

)((v!

condcond

condcond

TU

QA

)((v!

%82100 !v descond

cond

AA

A


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WWEIGHTEDEIGHTED OVERALLOVERALL

COFFECIENTCOFFECIENTWeighted clean overall coffecient

= 835.5 W/m2 oC

Dirt Factor Rd

= 2.3x10-4

Ud = 699.97 W/m2 oC (So assumed value is correct)

A

AUUc

v!

5.1362.272.274

905.

136

905

vv!

UdUc

UdUcRd

v

!

7008357005.835

v!


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TTUBEUBE SSIDEIDE PPRESSURERESSURE

DDROPROP Return loss

N= 2V = 3.2 ft/s

Pr = 0.56 psi

PT

= Pt + Pr

= 1.74 + 0.56

= 2.3 psi

g

V

s

n

d!(

2

4Pr

2


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SSHELLHELL SSIDEIDE PPRESSURERESSURE

DDROPROP Desuper heatRe = 481410 = 0.001 ft2/in2 ( kern Fig 14)

Ldes = 6.1 x 0.2 = 1.22 m = 4 ft

No fo crosses (N+1) = 12Ldes/B = 4Specific Gravity s = 0.0141

Pdes = 1.3 psi

Jvvvv

vvv!(

SD

DfPdes

e

s

2

sG10

1022.5

)1(


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SSHELLHELL SSIDEIDE PPRESSURERESSURE

DDROPROP CondensationLcond = 6.1 x 0.8 = 4.88 m = 16 ftNo fo crosses (N+1) = 12Lcon/B = 16

Specific Gravity s = 0.0149

(Kern Eqn 12.47)

Pcond = 0.98 psi

Ps = Pdes + Pcond = 2.28 psi

Jvvvv

vvv!(

SD

NDfPcon

e

s

2

s

101022.5

)1(

2

1


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SSPECIFICATIONPECIFICATION SHEETSHEETSPECIFICATION SHEET FOR 1-2 PASS SHELL SHELL AND TUBE

HEAT EXCHANGER

Unit Heat Exchanger

Item No. E-201

Type Fixed Head. No. of Item 1

Function To condense stream from sulphonator

Operation Continuous

Heat duty 7311 KJ/s Heat transfer area 195 m2

Overall HT coefficient 700 W/m2

Dirt factor 0.000232


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SSPECIFICATIONPECIFICATION SHEETSHEETShell side Tube side

Fluid circulated Hot Fluid Cold Fluid

Flow rates 53668 Kg/hr 629640Kg/hr

TemperatureInlet = 1260C

Outlet = 800C

Inlet=25 0C

Outlet=35 0C

Pressure 101.3 KPa 101.3 KPa

Pressure drop 15.7 KPa 15.85 KPa

Material of

constructionStainless Steel Stainless steel

Specifications I.D = 0.6858 m

Clearance = 4.75 mm

No. of baffles =18

Baffle spacing

=0.3048

m

OD = 19 mm 16 BWG

Pitch = 23.75 mmTriangulararrangement,

Length = 6.1 m

Nt = 534

No. ofPasses = 2

shell adn tube he design

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