process presentation shell and tube heat exchanger galfar

7/22/2019 Process Presentation Shell and Tube Heat Exchanger Galfar

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Qayyum KhanGalfar Engineering & Contracting SAOG, Lead Process Engineer

Email: [email protected] Tel.: +968 24525424 GSM-95942025

Fax: +968 24525385 Always remember: "Do not draw conclusions until you know all the facts''



Hot In Hot Out

Cold Out Cold In



.



Pr.60 bar Temp

201°CPr.1 bar

Temp 15°C Pr.60 bar Temp

50°C

Pr.1 bar

Temp 15°C



TheThe two fluids flow right angle to each other .two fluids flow right angle to each other .



Parameters Hot fluid Cold fluid SI units

Mass flow rate M m Kg/s

Inlet temperature T1 t1 C or K

Outlet temperature T2 t2 C or K

Inlet enthalpy H1 h1 J/Kg

Average specific heat C c J/Kg K

Heat flow rate Q Q W



.t2 Cold.t2 Cold OutOut



T

H



Streams Locations Typical values Comments

A Tube –to- baffle <20%

B Main (cross flow) Min. 60% for turbulentflow & 40% for laminar

flow

Should bemaximum

C Bundle –to –shell <10% Add sealing strips

a e-to- e < se ou esegmental baffles



= tube itch,

d 0 = tube outside diameter,

Ds = shell inside diameter, m,

I B = baffle spacing, m.

Gs= Ws/As

Us= Gs/

,

Ws = fluid flow on the shell side Kg/s

As=cross flow area m 2



= 2‐

Re= Usde / μUs= Gs/

L= Tube length

Jf= friction factor



Advantage Advantage-- True countercurrent flow,True countercurrent flow, CanCan handle large Temperaturehandle large Temperaturecrosscross DisadvantageDisadvantage-- Required large plot area.Required large plot area.



Types of shellTypes of shell-- andand-- tube Heat Exchangerstube Heat Exchangers-- – –

22--UU--TubeTube33--FloatingFloating --headhead

Advantage Advantage-- Can handle high Temp, pressure and flow ratesCan handle high Temp, pressure and flow rates DisadvantageDisadvantage-- vibrationsvibrations



Advantage- less operating cost, CW saving Disadvantage- High capital cost, more hot fluid outlet T, more plot area



Advantage- less plot area, T cross, close temp approach m tat on - an e up to ar, , ew ven or



Advantage- very less fouling, good flow

distribution, true countercurrent Limitation- can handle up to 25 bar, 400 °C,

few vendor



1.1. Stat ionary HeadStationary Head -- ChannelChannel 14.14. Float ing Head Cover Floating Head Cover

2.2. Stationary Head FlangeStationary Head Flange -- Channel or BonnetChannel or Bonnet 15.15. Floating Head Cover FlangeFloating Head Cover Flange

.. ..

4.4. Stationary Head NozzleStationary Head Nozzle 17.17. Tie Rods & SpacersTie Rods & Spacers

5.5. Stat ionary Tube SheetStationary Tube Sheet 18.18. BafflesBaffles

.. ..

7.7. ShellShell 20.20. Pass Part it ionPass Partition

8.8. Shell Cover Shell Cover 21.21. Vent ConnectionVent Connection

.. e angee ange -- a onary ea na onary ea n .. ra n onnec onra n onnec on

10.10. Shel l FlangeShell Flange -- Rear Head EndRear Head End 23.23. Instrument ConnectionInstrument Connection

11.11. Shel l NozzleShell Nozzle 24.24. Suppor ting SaddleSupporting Saddle

12.12. Shel l Cover FlangeShell Cover Flange 25.25. Lifting LugLifting Lug

13.13. Float ing Tube SheetFloating Tube Sheet



Δ P D E C

E A S E

F R O M E T

X



SINGLE &DOUBLE SEGMENTAL BEFFLESSINGLE &DOUBLE SEGMENTAL BEFFLES

PRESSURE DROP IS LESSER FOR DSB THAN THE SSBPRESSURE DROP IS LESSER FOR DSB THAN THE SSB



Window

Window

PRESSURE DROP FOR NTIW IS LOWER THAN DSB AND SSBPRESSURE DROP FOR NTIW IS LOWER THAN DSB AND SSB



Preferred for single-phase applications Preferred for condensers and vaporisers

Horizontal Vertical

Baffle cut is the height of the segment removed form the baffle.

Baffle cuts from 15 to 45% are used but 20 to 25 % is optimum generally.



1 2 BGM



1:2 BGM



.t2 Cold.t2 Cold OutOut .t1 Cold.t1 Cold InIn



-- HTRIHTRI (Heat Transfer Research Inst itute operated by United State)(Heat Transfer Research Inst itute operated by United State)

--



DESIGN

RATING SIMULATION

CALCULATION

MODE

Heat Trans er Research Institute HTRI Xist software



FLUID VELOCITY IN BOTH TUBE AND SHELL SIDE

TUBE SIDE HEAT TRANFER COEFFICIENT

SHELL SIDE HEAT TRANSFER COEFFICIENT

SHELL SIDE PRESSURE DROPFLOW-INDUCED VIBRATION

STREAM ANALYSIS

OVER DESIGN

.



. .

1 Heat exchanger selection guide line EP-2005-5186

2 Fouling resistance to heat transfer equipments DEP-20.21.00.31

3 Shell and tube heat exchangers DEP-31.21.01.30

4- HTRI Manual

5 American Tubular Heat Exchanger Manufactures Association Team standard

6 British standard BS 3274

7 Coulsion and Richardson Volume -1 and 6

8 Shell and Tube Heat Exchanger for General Refinery Services API-660

9 Air-cooled Heat Exchangers for General Refinery services API-661

10 Plate Heat Exchangers for General Refinery services - Part -1Plate and Frame Heat Exchan er

API-662



60



To Improve Tube side Heat TransferCoefficient:Decrease number of tubesDecrease number of tubes

Change to larger diameter tubes for laminar flowChange to larger diameter tubes for laminar flow

Decrease tube length for laminar flowDecrease tube length for laminar flow

ange u a oca onange u a oca on



To ReduceTo Reduce Shell sideShell side Pressure Drop:Pressure Drop:

Increase Baffle Spacing within limitsIncrease Baffle Spacing within limits

Increase baffle cut percentageIncrease baffle cut percentageChange baffle type to double segmental or NTIWChange baffle type to double segmental or NTIWChange shell type from E to J or X Change shell type from E to J or X Increase no. of shellsIncrease no. of shells--inin--parallelparallelDecrease no. of shellsDecrease no. of shells--inin--seriesseriesncrease s e ame erncrease s e ame er

Increase shell nozzle sizeIncrease shell nozzle sizeProvide annular distributorsProvide annular distributors

Change tube layout to square from triangularChange tube layout to square from triangularIncrease tube pitchIncrease tube pitch



Decrease Baffle Spacing within limitsDecrease Baffle Spacing within limitsProvide sealin stri s or dumm rodsProvide sealin stri s or dumm rodsDecrease baffle cut percentageDecrease baffle cut percentageChange baffle type to single segmental, if otherwiseChange baffle type to single segmental, if otherwise Apply tight clearances Apply tight clearances

ange s e ypeange s e ypeIncrease no. of shellsIncrease no. of shells--inin--seriesseriesDecrease shell diameterDecrease shell diameterChan e fluid allocationChan e fluid allocation

Change tube layout to triangular from squareChange tube layout to triangular from squareDecrease tube pitchDecrease tube pitchIf shellIf shell--side fluid is clean gas, use fin tubesside fluid is clean gas, use fin tubes

ecrease num er o tu esecrease num er o tu esIncrease number of tube passesIncrease number of tube passes

Change fluid allocationChange fluid allocation



--Draft : Forced vs. InducedDraft : Forced vs. Induced

Advantages of forced draft

Easier accessibility for maint.

Lower power consumption

Advantages of induced draft

Better air distributionReduced hot air recirculation

Better stack effect

Better protection from the elements



Process Requirements:-

Exchanger should give satisfactory thermal & hydraulic performance from thestart of operation to shut-down.

-

Exchanger should withstand mechanical stresses during installation, start-up,

- , ,Exchanger also should withstand thermal stresses induced by temperaturedifferences

Maintenance Re uirements:-

Exchanger configuration should be such that it permits

vulnerable to corrosion, erosion or vibration damage.

temperature differences.



Cost Requirements:-

Exchanger should be most economically designed utilizing the allowablepressure drop as much as possible

Other Requirements:-

m a ons on exc anger ame er, eng , we g , u e spec ca ons ueto client requirements, site requirements, lifting & servicing capabilities orinventory considerations require thorough evaluation.



a. Overdesign

b. Shell side and tube side

velocity, heat transfer

100o

112,000 kg/h

.

c. Stream analysis40o 70o

75o



Performing the design for a specified dutyPerforming the design for a specified duty

Hot stream:Hot stream:Flow rate = 112 000Flow rate = 112 000

kg/h = 31.11 kg/seckg/h = 31.11 kg/secTin = 100Tin = 100 °°C, Tout =C, Tout =

°°

100o

112,000 kg/h

Physical propertiesPhysical properties

Cold stream:Cold stream:40o 70o

, ,

= 28.39 kg/sec= 28.39 kg/secTin = 40Tin = 40 °°C, Tout = 70C, Tout = 70

°°

75o

Physical propertiesPhysical properties



Predicting the performance of a specified heat

exc anger or a g ven se o n e or ou e con ons

Nil overdesignb. Shell side and tube side velocit

heat transfer coefficient and pr.

drop

100o

112,000 kg/h

.

40o ?

?



Questions: Why are gas htc’sQuestions: Why are gas htc’slow?low?

Are gas htc’s always low? Are gas htc’s always low?

low thermal conductivity, h α k low thermal conductivity, h α k 0.670.67

low densitylow densityPressure drop α GPressure drop α G22/ρ/ρ

Therefore, if ρ is low, G (ρ V) is required to be low.Therefore, if ρ is low, G (ρ V) is required to be low.

Since h α GSince h α G0.80.8 , a low G means a low HTC. , a low G means a low HTC.

I gas pressure s g , ts HTC w e muc g er.I gas pressure s g , ts HTC w e muc g er.



1.1. SimpleSimple construction, lowconstruction, low

2. Differential expansion not2. Differential expansion notpossiblepossible

. uts e o tu es cannot. uts e o tu es cannotbebe mechanically cleanedmechanically cleanedbut inside tube cleaning isbut inside tube cleaning is

ossible.ossible.1.



◦◦ Cleaning insideCleaning insidetu estu es s cu ts cu t

◦◦ Low costLow cost

◦◦ bundlebundle

◦◦ Permits thermalPermits thermalexpansionexpansion



Removable tubeRemovable tubebundlebundle

Permits thermalPermits thermalexpansionexpansion

Tube cleaningTube cleaningpossible inside andpossible inside andoutsideoutside

High costHigh cost



UU – – Overall Heat Transfer CoefficientOverall Heat Transfer Coefficient

Depends onDepends on

Exchanger configurationExchanger configuration

Operating ParametersOperating Parameters

ou ng ac orou ng ac or



AIR AIR--COOLED HEAT EXCHANGER COOLED HEAT EXCHANGER

Induced draftInduced draft

OPTIMISE AIR AND WATER COOLINGOPTIMISE AIR AND WATER COOLINGOnly water cooling: both in/out temps low, e.g., 50 C/45 COnly water cooling: both in/out temps low, e.g., 50 C/45 C(Air + water) cooling: inlet temp high, outlet temp. low, e.g., 100 C/40 C(Air + water) cooling: inlet temp high, outlet temp. low, e.g., 100 C/40 C

n y a r coo ng: ot n et an out et temp s g , e.g.,n y a r coo ng: ot n et an out et temp s g , e.g.,



Multiple shells in seriesMultiple shells in series

-- Handle temperature crossHandle temperature cross--

-- Reduce penalty due to temp.Reduce penalty due to temp.

profile distortionprofile distortion

-- en s e s are requ re anyway,en s e s are requ re anyway,examine putting them in series.examine putting them in series.

-- Advantageous when MOC Advantageous when MOC

varies with temperaturevaries with temperature



Determine operating envelope

Eliminate types that can not meet envelope

ze ea exc anger an anc ary equ pmen ers)

Eliminate types that don't fit any shape and weight restrictions

Estimate Capex, Opex and potential deferments for each remaining type

Select type with the required availability and lowest life cost cycle cost



ssume

Calculate MTD

Find A from Q = U.A.MTD

From tube OD and length, determine no. of tubes, tube pitchand no. of tube passes.

Size nozzles

Determine shell ID and assume baffle type/spacing/cut

Run rating program and see results for velocities, streamanalysis, pressure drop, overdesign and vibration

Re-run until design is optimum



Process Requirements(Thermal and Hydraulic)

Mechanical Requirements(Mechanical &Thermal stress)

Cost Requirements (Capex+Opex)

Other Requirements

I. L/D Ratio

II. Weight

I. Lifting and servicing capabilities



Q‐In which service impingement plates shall be used?

‐ u u v y u

abrasive particles .

Q‐why we are using log mean temperature difference instead of normal difference?Ans – As the temperature of fluids changes along the length of the heat exchanger

so the properties of the fluids also changes with the length .LMTD gives the most

accurate result in compression of ∆T.

Qayyum KhanGalfar Engineering & Contracting SAOG, Lead Process Engineer

Email: [email protected] Tel.: +968 24525424 GSM-95942025

Fax: +968 24525385 Always remember: "Do not draw conclusions until you know al l the facts''

process presentation shell and tube heat exchanger galfar

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