Plate Fin Heat Ex Changers

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Looking Inside...Plate-Fin versusCoil-Wound Heat Exchangers



Contents.

3 Introduction

5 Overview

6 Plate-fn heat exchangers

Features

8 Coil-wound heat exchangers

10 Plate-fn versus coil-wound heat exchangers

Outlook

12 Attachments

Plate-fn heat exchanger structure (Attachment A)

Plate-fn heat exchanger abrication (Attachment B)

Brie comparison (Attachment C)

2



3

Introduction.

The abrication acility o The Linde Group is theEngineering Division, a competent and well-known

supplier o two special types o cryogenic heat ex-changers with an emphasis on LNG production andcryogenic gas processing.

Plate-in as well as coil-wound heat exchangers

are abricated at Linde´s acility in Schalchen. Here,in the south-east o Germany, some 700 highlyqualiied people are employed. Heat exchangers havebeen produced in various orms here or decades.

The speciic technical eatures are outlined anda technical comparison o coil-wound and plate-inheat exchanger is provided.



4

Plate-in heat exchanger

A brazed plate-in heat exchangeris a stack o alternating lat andcorrugated plates.



5

Coil-wound heat exchanger

Plate-in and coil-wound heat exchangers

are key components o cryogenic process

plants worldwide. With more than one cen-

tury o experience Linde is one o the majorplayers in this business. Linde is the only

company abricating both types o heat ex-

changers in its own acilities.

As o today, approx. 5000 plate-in heat ex-

changer blocks and some 1000 coil-wound

heat exchangers have been abricated by

Linde or a wide range o applications.

Due to a dearth o available inormation about

plate-in and coil-wound heat exchangers, these

items requently have the status o black boxes

in process plants. The objective o this paper is

to open these black boxes and to have a look

inside.

Furthermore this paper aims to provide a brie

comparison o the two types o heat exchang-

ers in order to amiliarize plant owners with the

typical eatures.

Overview.



Serrated ins

Perorated ins

6

General arrangement

A brazed plate-in heat exchanger is a stack

o alternating lat and corrugated plates. The

corrugations (ins) orm the low channels or

the diverse process luids. Each process stream

occupies a certain number o passages within

the stack. These are collected by hal-pipe

headers and nozzles to single point connections

on the inlet and the outlet o the respective proc-

ess stream. In this way, up to 10 process luids

can exchange heat in only one heat exchanger

block. Fig.1 is a sketch o the various types o

ins.

Materials and design temperature

Usually this type o heat exchanger is madeo aluminium alloys 3003 (blocks) and 5083

(all attachments). It is important to know that

with these standard materials the upper design

temperature is limited to +65°C due to code

requirements.

Fins

In order to meet the required perormance, Linde

can select the appropriate in out o about 50

dierent in types. In general a distinction is

made between perorated ins and serrated ins.

Serrated ins have higher heat transer coei-

cients than perormated ins. However, serrated

ins are more prone to ouling and result in high-

er pressure drop.

Fabrication

In order to bond the loose stack o plates and

ins to a rigid block, vacuum brazing is used. This

sophisticated process means spanning the loose

stack together and heating it in a vacuum ur-

nace up to a temperature o about 600°C. It

should be understood that this temperature is

very near the melting point o the aluminium

base materials. The iller material is clad by roll-

ing on both sides o each parting sheet. The ins

however are pure aluminium alloy without any

cladding. Ater the vacuum brazing the blocks

are completed by welding all the attachments

such as hal-pipe headers, nozzles, support

brackets and liting trunnions to the block.

Please reer to Attachment B on page 13).

Beneits

Vacuum brazed plate-in heat exchangers made

o aluminium oer a number o advantages:

They are extremely compact due to the use o

aluminium and highly eicient ins. The “heating

surace density“ can be greater than 1000 m²/m³.

Thus this type o heat exchanger is perectly

suitable or installations which require compact

design. The wide selection o heat transer ins

combines high heat transer rates with low pres-

sure drops (i.e. low energy consumption) intailor made heat exchangers. The ability to com-

bine up to 10 process streams in only one heat

exchanger system can eliminate the need or

multiple heat exchanger arrangements and the

interconnecting piping. The use o high strength

aluminium alloy results in light weight units thus

reducing drastically the oundation and support

requirements.

Knowing the limits

Knowing the technical advantages as well as the

corresponding limits o a plate-in heat exchanger

helps to make correct procurement decisions and

to avoid later disappointments and diiculties.

Due to their arrangement as a large and rigid

aluminium block, and considering the small gaps

inside, this type o heat exchanger cannot be

recommended or cases o operation such as :

– high temperature gradients(i.e. thermal shocks)

– high temperature dierences between

the cold and the warm process streams

– process streams containing particles or

suseptible to severe ouling

– cyclic loads (pressure and temperature)

– service which is known to be corrosive

to aluminium

Naturally Linde will advise a potential user

whether a plate-in heat exchanger is recom-

mendable or a speciied application or not.

Plate-in heat exchangers.

Fig.1



7

Plate-in and coil-wound heat exchangersare key components o cryogenic processplants worldwide.



History

Coil-wound heat exchangers have been manu-

actured by Linde since the early days, when Carl

von Linde liqueied air on an industrial scale or

the irst time in Munich, Germany in May 1885.

Improvements in aluminium welding technology

in the late 1950s made it possible to change

rom rather expensive and heavy copper to the

cheaper and lighter all-aluminium-designs.

More than one thousand coil-wound heat ex-

changers or various application and in diverse

materials such as stainless steel, special alloys,

copper and aluminium, with heating suraces

o up to 20,000 m² and unit weights o up to

170 metric tons have been abricated since.

General arrangement

A coil-wound heat exchanger is, in general, a

tubular heat exchanger; however, the bundle

does not consist o not using a straight tubes.

Tubes o relatively long length and small

diameter are wound in alternating directions

around a centre pipe (the so called mandrel).

In parallel a pressure vessel shell is prepared

and the complete tube bundle is inserted. All

single tubes start and terminate in tubesheets

which are integral parts o the pressure vessel

shell.

Features o Linde‘s coil-wound heat

exchangers in LNG baseload plants

Flexible tube bundle

Due to the lexible tube bundle arrangement

these heat exchangers can bear temperature

gradients and dierences clearly exceeding the

limits o other heat exchanger types (e.g. plate-

in heat exchangers).

No bundle sagging

Over the speciied design lie no considerable

bundle sagging is to be expected. This is due

to Linde´s sophisticated bundle support system.

Tube bundle beore insertion into thepressure vessel shell

8

Coil-wound heat exchangers.



Complete coil-wound heat exchangers during

installation on site

The tube bundles are designed and abricated to be

vibration-proo and sel-draining.

9

Best liquid distribution

Optimal liquid distribution o the shell side

2-phase stream over the whole cross section

o the bundle is achieved by internal phase sepa-

ration and special liquid distribution systems.

The latest liquid distributor design minimises the

liquid hold-up on top o the bundles, thus reduc-ing negative thermal eects during trip cases.

Tube arrangement

The tube bundles are designed and abricated

to be vibration-proo and sel-draining.

Tailor made materials

The pressure vessel shell is typically made o

aluminium alloy 5083. For the tubes, special

aluminium alloy and a non-standard (but ap-

proved) abrication procedure is used or tube

manuacturing.

Supporting the tube bundle

Each tube bundle is reely suspended rom a

special support system on top o each bundle.

Thus shrinkage and expansion o the tube bun-

dles due to rapid temperature changes during

start-up or shut-down occur with minimum

stresses between the tube bundle and the shell.The support system is designed to carry the

weight o the tube bundles, the luids and the

pressure drops.

Eliminating by-pass streams

Each tube bundle is wrapped into a “shroud“

which is seal welded on the upper side o the

shell to avoid any rerigerant passing between

the tube bundle and the shell.

In case o tube ailure the leaking tube can be

easily repaired by plugging the concerned tube.

In order to acilitate such repairs and to minimize

the shut-down time the installation o suitable

access holes is oreseen.



10

Attachment C (page 14) provides an overview

o the major dierences between plate-in and

coil-wound heat exchangers. The most impor-

tant eature o the plate-in heat exchanger is

the compact design. The coil-wound heat ex-

changer´s deining characteristic is its intrinsic

robustness.

The extreme compactness o the plate-in

heat exchangers becomes obvious when one

knows that both o the cold boxes1) shown

in this picture are designed or the same per-

ormance. These two cold boxes are installed in

an LNG peak shaving plant in South Arica.

The small coldbox on the let side contains a

plate-in heat exchanger. The much taller cold

box on the right side contains a coil-wound heat

exchanger.

Presently this peak shaving plant is operated

using the coil wound heat exchanger with

outstanding results regarding reliability and

turn-down behaviour.

For LNG baseload applications it is important

to know that typically the coil-wound heat ex-

changers are designed standing “cold side up -

warm side down“. This is another dierence

in comparison with plate-in heat exchangers.

This arrangement allows proper 2-phase distri-

bution o rerigerant vaporizing downwards on

the shell side o a coil-wound heat exchanger.

It is well suited or turndown operation.

A plate-in heat exchanger in similar service

usually vaporizes upwards. It requires a lot o

know-how and experience to design such a

plate-in heat exchanger or turn-down opera-

tion. I the design does not consider this prop-

erly, the vaporization in turn-down can create

luid luctuations causing cyclic thermal and

mechanical stresses.

1) A “cold box“ is understood to be a carbon steel

casing containing various process equipment

like heat exchangers, columns, instrumentation,

all interconnecting piping, etc. The thermal insu-

lation is typically expanded perlite.

Linde cold boxes in a LNG peak shaving plant

Plate-in versuscoil-wound heat exchangers.



11

Plate-in heat exchangers

Since Linde has entered into the business o

vacuum brazed plate-in heat exchangers in

1981, block sizes and design pressures have

increased step-wise. With a new vacuum ur-

nace recently commissioned Linde is now in

position to serve the market with single plate-in

heat exchanger blocks o about 1.5 x 3 x 8 m

in modular construction. Such extremely large

blocks drastically reduce the need or intercon-

necting piping and subsequently the danger o

maledistribution between parallel blocks.

At the same time the maximum design pres-

sures have reached a level o about 100 bar-g.

However it is important to know that the maxi-mum possible design pressure depends on the

respective block size. In order to urther increase

the eiciency and compactness o plate-in

heat exchangers new types o ins are being

developed applying e.g. smaller in pitches, etc.

Coil-wound heat exchangers

Linde‘s own test acilities and the R&D depart-

ment are the major sources o new ideas or

improvements. The development o new techni-

cal eatures is driven by the valuable eedback

rom plant operators and lessons learnt on cur-

rent jobs.

For Linde‘s coil-wound heat exchangers in LNG

baseload applications o the required perorm-

ance demands are continually increasing. Linde

has already brought the corresponding develop-

ments on the way in order to be able to oer the

most compact and highly eicient heat exchang-

ers.

The installation o coil-wound heat exchangers

on loating barges is another challenge. The

exposure o the tall heat exchanger structures

to the corresponding motions requires special

measures. Linde is thoroughly investigating

this issue, applying new ideas and experience

to inding the optimal solution.

The extremely compact design othe plate-in heat exchangers versusthe inherently robust design o thecoil-wound heat exchangers.

Outlook.



With a new vacuum urnace recently commissioned,Linde is now in position to serve the market withsingle plate-in heat exchanger blocks o about1.5 x 3 x 8 m in modular construction.

Plate-fn heat exchanger structure (Attachment A)

Block

Header

NozzleWidth

Stacking height

Length

Passage outlet

Cover sheet

Parting sheet

Heat transer fn

Distribution fn

Side bar

End bar

12

1

2

34

5

6

7

8

9

10

11

12

13



13

Parting sheets, cover sheets Fins

Header and nozzles

Side bars

Raw materials

Measuring, cutting

Washing

Raw materials

Stamping,

measuring, cutting

Washing

Stacking

Vaccumbrazing urnace

Raw materials

Measuring, cutting

Washing

Raw materials Raw materials Raw materials

Measuring, cutting Measuring, cutting

Assembly

Completion o heat exchanger

Testing

13



14

Brie comparison (Attachment C) Plate-in heat exchanger piped in cold box

Plate-fn heat exchanger Coil-wound heat exchanger

FeaturesExtremely compact

Up to ~10 streams

Extremely robust

Compact

Fluids Very cleanNon-corrosive

Heating surace 300 - 1000 m²/m³ 50 - 150 m²/m³

Materials Al Al, SS, CS etc.

Design temperatures -269°C to +65°C all

Applicationssmooth operation

limited installation space

temp. gradients

temp. dierences

Prices

~25 - 35 %

(without maniolds / steel casings) 100 %



15

With more than one century o experience,Linde is one o the major players in this businessand the only company abricating both types oheat exchangers in its own acilities.

Coil-wound heat exchanger



Engineering Division head oice:

Linde AG

Engineering Division

Pullach, Germany

Phone: +49.(0)89.7445-0

Fax: +49.(0)89.7445-4908

[email protected]

L N G / 3 . 2 . e

/ 0 9

Linde´s Engineering Division continuously develops extensive process engineering know-how in the planning,

project management and construction o turnkey industrial plants.

The range o products comprises:

− Petrochemical plants

− LNG and natural gas processing plants

− Synthesis gas plants

− Hydrogen plants

− Gas processing plants

− Adsorption plants

− Air separation plants

− Cryogenic plants

− Biotechnological plants

− Furnaces or petrochemical plants and refneries

Linde and its subsidiaries manuacture:

− Packaged units, cold boxes

− Coil-wound heat exchangers

− Plate-fn heat exchangers

− Cryogenic standard tanks

− Air heated vaporizers

− Spiral-welded aluminium pipes

Engineering Division headquarters:

Linde AG

E i i Di i i D C l Li d St 6 14 82049 P ll h G

More than 3,800 plants worldwide document the leading position of the Engineering Division in international plant construction.


Schalchen PlantTacherting, Germany

Phone +49.8621.85-0

Fax +49.8621.85-6620

[email protected]

Linde-KCA-Dresden GmbH

Dresden, Germany

Phone +49.351.250-30

Fax +49.351.250-4800

[email protected]

Selas-Linde GmbH

Pullach, Germany

Phone +49.89.7447-470

Fax +49.89.7447-4717

[email protected]

Cryostar SAS

Hésingue, France

Phone +33.389.70-2727

Fax +33.389.70-2777

[email protected]

Linde CryoPlants Ltd.

Aldershot, Great Britain

Phone +44.1.252.3313-51

Fax +44.1.252.3430-62

[email protected]

Linde Impianti Italia S.p.A.

Rome, ItalyPhone +39.066.5613-1

Fax +39.066.5613-200

[email protected]

Linde Kryotechnik AG

Pungen, Switzerland

Phone +41.52.3040-555

Fax +41.52.3040-550

[email protected]

Cryo AB

Göteborg, Sweden

Phone +46.3164-6800

Fax +46.3164-2220

[email protected]

Linde Process Plants, Inc.

Tulsa, OK, U.S.A.

Phone +1.918.4771-200

Fax +1.918.4771-100

[email protected]

Selas Fluid Processing Corp.

Blue Bell, PA, U.S.A.

Phone +1.610.834-0300

Fax +1.610.834-0473

[email protected]

Linde Engenharia do Brasil Ltda.

Rio de Janeiro, BrazilPhone +55.21.3545-2255

Fax +55.21.3545-2257

[email protected]

Linde Process Plants (Pty.) Ltd.

Johannesburg, South Arica

Phone +27.11.490-0513

Fax +27.11.490-0412

[email protected]

Linde-KCA Russia Branch

Moscow, Russia

Phone +7.495.646-5242

Fax +7.795.646-5243

[email protected]

Linde Arabian Contracting Co. Ltd.

Riyadh, Kingdom o Saudi Arabia

Phone +966.1.419-1193

Fax +966.1.419-1384

[email protected]

Linde Engineering Middle East LLC

Abu Dhabi, United Arab Emirates

Phone +971.2.4477-631

Fax +971.2.4475-953

[email protected]

Linde Engineering India Pvt. Ltd.

Vadodara, Gujarat, IndiaPhone +91.265.3056-789

Fax +91.265.2335-213

[email protected]

Linde Engineerig Far East, Ltd.

Seoul, South Korea

Phone +82.2789-6697

Fax +82.2789-6698

[email protected]

Linde Engineering Division

Bangkok, Thailand

Phone +66.2636-1998

Fax +66.2636-1999

[email protected]

Linde Engineering Co. Ltd.

Dalian, P.R. o China

Phone +86.411.39538-800

Fax +86.411.39538-855

[email protected]

Linde Engineering Co. Ltd.

Hangzhou, P.R. o China

Phone +86.571.87858-222

Fax +86.571.87858-200

[email protected]

Linde Engineering Division

Beijing Representative OiceBeijing, P.R. o China

Phone +86.10.6437-7014

Fax +86.10.6437-6718

[email protected]

Linde AG Taiwan Branch


Taipei, Taiwan

Phone +886.2.2786-3131

Fax +886.2.2652-5871

[email protected]

Linde Australia Pty. Ltd.

Chatswood N.S.W., Australia

Phone +61.29411-4111

Fax +61.29411-1470

[email protected]

Designing Processes- Constructing Plants.

Plate Fin Heat Ex Changers

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