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Heat Exchangers

November 15, 2005

S.S. Thambad

CES- Inspection


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Outline

Heat Exchanger:

Heat exchanger is an equipment, whicheffects the transfer of heat from one fluid

to another through metal walls.

Types of heat exchanger:

Based on service

Based on construction


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Types of Exchangers Based on ServiceExchanger:

It is a unit that exchanges heat between two process streams without phasechange; i.e. liquids are not evaporated nor condensed.

Examples: LAB - EA213, EA161

Cooler:

Cools the process fluids without phase change.

Examples: All cooling water exchangers in plants LAB - EA305- Reactioncooler, PX -E1009, E8073 .

Condenser: Condenses process vapor stream.

Examples: Some of the Fin fan Cooler LAB - EC401, PX-E1033

Re-boiler:

Provides latent heat of vaporization to bottom of distillation / fractionation

column. Examples:

LAB - EA405 Rerun column reboiler & PX E1035 Stripper column reboiler

Pre-heater: Uses steam or hot process stream to heat & or vaporize the feed to

processing unit. Air Pre-heater of fired heaters. APH of PX-D5001, LAB-BA801,


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Types of Exchangers Based on Construction:

Tubular heat exchanger:

U tube type heat exchanger Fixed tubesheet heat exchanger

Floating head type heat exchanger

Hair pin type Pipe in pipe heat exchanger

Fin fan type exchanger

Plate type heat exchanger

Spiral plate type heat exchanger


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Major Parts of shell & tube heat exchanger:

TubesideFlow In

Shellside

Flow In

Shellside

Flow Out

TubesideFlow Out

Shell

Tube Bundle

Tube Sheet

Channel

Baffles

Nozzle


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Exch. Major Parts & Generally used MOC Shell:

Carbon steel (CS), Stainless steel (SS), Titanium, Carbon steel claddedwith SS, Titanium or Monel

Channel:

Generally similar to tube MOC.

Carbon steel (CS) , Stainless steel (SS), Titanium, Carbon steelcladded with SS, Titanium or Monel

Tube sheet: Carbon steel (CS), Stainless steel (SS), Titanium , Carbon steel cladded

with SS, Titanium or Monel

Tubes:

Carbon steel (CS), Stainless steel (SS), Admiralty Brass, Titanium (Ti) ,Monel

Tubes are available in different diameters. Commonly used OD:

3/8" - 9.5 mm 5/8 16 mm, - 19.05 mm, 1 25.4 mm, 2 50.8 mm


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Exch. Major Parts & Generally used MOC

Gasket:

CAF (Asbestos), Iron jacketed gasket with Asbestos

Spiral wound gasket ( SS, Monel, Titanium filled with PTFE, Grafoil,

Asbestos) Solid flat metal : Soft Iron, Aluminum, Copper, Brass, Monel, SS

O rings,

Baffles: Types of baffles:

Segmental baffle , Strip baffle, Disc and doughnut baffle, Orifice baffle, Longitudinal baffle

Tie Rods & Spacer Tubes:

MOC of baffles, tie rods, spacer tubes are similar to tube MOC or shell

MOC.

Tube Pattern, Pitch: Triangular, Square

Tube to tubesheet Joints: Welded with light expansion, Expanded,expanded with seal welded.


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Selection Of Heat Exchanger:

It must meet the process requirements

It must withstand the service condition

It must be maintainable.

Exchanger Cost

Capital cost of installation

Area occupied by the equipment

Availability and cost of water

Pressure drop


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Significance of Different Types of Heat Exch.

U Tube:

Only one tube sheet required, tube bends in U shape,Bundle is removable

Application Best Suited:

High temperature difference on shell & tube side

Clean service on tube side

Limitations:

Higher tube side velocities can cause erosion on tubeends

Fouling / subsequent cleaning problem


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Floating Head Type:

One tubesheet floats in shell and bundle may be

removable from shell, back cover can be removed to

expose tube ends.


High temperature difference on shell & tube side

Cleaning possible with floating end cover

Limitations:

Internal gasket offer danger of leakage

Only horizontal units


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Fixed Tube sheet Exchanger:

Both tubesheet fixed to shell.


For cleaner fluid on shell side

Low cost

Limitations:

Temp. difference on shell side & tube side should be less

than 93 deg c.


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Hair Pin Type Exchanger:

Extended surface due to longitudinal finning. Tubebundle can be removed from shell for cleaning.


Smaller transfer area required

Suitable for higher pressure requirement

Low space

Limitations:

Smaller capacity


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Significance of Different Types of Heat Exch.Plate Type Heat Exchanger

Composed of metal formed thin plates separated bygasket.


1/3 to 1/2 area required compared to shell & tube type -

Compact design Higher efficiency - Higher surface area

Limitations:

Temperature / pressure limitation due to gasket

(Temp limitation max 300 deg C). Cleaner fluid requirement


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Spiral Plate Type Heat Exchanger

Concentric plates, no bypassing , higher turbulence.


Improved overall heat transfer coeff. - curved flow

Scrubbing effect due to spiral passage - fouling factor1/3 of shell & tube

Thermal insulation is not required.

Limitations:

Process corrosion

Suspended materials

Low capacity

Difficulty in fabrication


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Applicable Codes & Standards:

ASME SEC VIII Rules for Construction of

D1/D2 Pressure Vessels

TEMA Standards of the Tubular

Exchanger Manufacturer's

Association API 660 Shell and Tube Heat

Exchangers for General

Refinery Services

API 661 Air-Cooled Heat Exchangers

for General Refinery Service


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TEMA Classifications

TEMA Class Application Example

________________________________________________________________________________________________________________________________

R Severe environments Refineries

C Moderate service Building

services,commercial,and generalprocess

industries

B Chemical process Chemicalmanufacturing


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TEMA Types


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Significance of Different Types of Heat Exch.Fin Fan Cooler

No shell required, Header ends similar shell & tube type.


High level of heat removal is required

Where cooling water not available.

Where ambient temp is low

Limitations:

Problem of frequent fouling and corrosion.

Higher investment 4 to 10 times more ground space in shell & tube type


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Air-Cooled Heat Exchangers

Forced-draft

Air forced across tube bundle by fan located in airplenum below bundle. (Fin fan coolers)

Induced-Draft

Fan located above hood covering tube bundle. Air pulled across tube bundle and exhausted

through hood. (PTA Air fin coolers)

Humidified Forced-Draft Air humidified before forced across tubes.

Evaporation draws heat from air and cools airbelow temperature of process fluid.


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Horizontal Tube, Induced-Draft Air-Cooled Heat Exchanger

InletNozzles

ReturnHeaders

Fan Ring

Supports

Drive Assembly

Tube Bundle

OutletNozzles

OutletHeaders

InletHeaders

Hood or Plenum

Fan



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Typical Air-Cooled Heat Exchanger

Header

Nozzle

Header

Tube spacer Side Frame

Fins

Tube Support(bottom)

Tube

Air SealLifting LugTube Keeper

(top)Air Seal

Air Seal


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Typical Forced-Draft Air-Cooled Heat Exchanger

SupportsPlenum

Fan Ring

Fan

OutletNozzles

InletHeaders

DriveAssembly

Outlet

Headers

Inlet Nozzles Tube Bundle

ReturnHeader(s)


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Humidified Forced-Draft Heat Exchanger

TubeBundle

Fine Water Mist

Hot Air

Header

Plenum

Chamber

ForcedDraft Fan

Water HeaderNozzles (above

fan Typical)

Header

Partition Plate

Process Nozzle

Process Nozzle

Water HeaderNozzles (belowfan Sometimes)

U T b t H t E h


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U Tube type Heat Exchanger

U T b t p H t E h n r


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U Tube type Heat Exchanger

Front End

Stationary Head TypeShell Type

Rear End

Head Type

C E U

Channel Integral

with Tube sheet and

Removable Cover

One Pass Shell U-Tube Bundle

Fi ed T besheet t pe He t E ch n er


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Fixed Tubesheet type Heat Exchanger

Front EndStationary Head

Type Shell TypeRear End

Head TypeA E M

Channel andRemovable Cover

One Pass ShellFixed TubesheetStationary Head

TEMA Designation System Example


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TEMA Designation System Example

Type S Split-RingFloating Head

Type E ShellSingle-Pass

Type A Channel

23ShellI.D.

Straight Tube

Length 192(16 0)

TEMA Size and Type Normally Written: 23192 AES


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Hair Pin type Heat Exchanger

Return Bend(welded)

Shell Cover Gasket

ShellExternal Fin Pipe

Shell End PieceTwin Flange

ShellCover

Vent

DrainSliding

Support

Fixed

Support


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Plate-and-Frame Heat Exchanger

Cin

SeparatingSheet

BinAout Nozzle

Header

CorrugatedSheet

Side Bar

Distributor

EffectiveLength

EffectiveWidth

Heat TransferSection

DistributionSection

Cout

Ain Bout

B

A

A Two-Pass Plate and Frame Flow Arrangement


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Plate-and-Frame Heat Exchanger

Spiral Flow-Spiral Flow Heat Exchanger


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Thank

you

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