Standards

TEMA stands for Tubular Exchanger Manufacturers Association Specifying that workhorse of the process industries , the shell and tube heat exchanger , is usually a straightforward exercise in these days of computer-aided design packages , but you do need to ask the right questions . David Knightbridge offers a brief guide to that common query : ‘ which type of TEMA exchanger ?’

By David Knightbridge , IEng - UK Sales Manager , Funke

The advent of modern computer programmes has enabled many of us to thermally rate heat exchangers quickly and accurately . But how do we decide which design of heat exchanger for a given application will satisfy the operating conditions , all the mechanical / thermal criteria , and give a cost-effective solution ? Many customers have asked what forms the basis of a heat exchanger design for their particular enquiry . I well recall in my earlier years as a junior applications engineer , my mentor of the time showing me how to make a selection , saying that the enquiry we were looking at ‘ was leading him by the nose ’ to a certain type of heat exchanger design . His experience gained over the years enabled him to do this , but what was the thought process that went into selecting the right type of heat exchanger ? In some cases there can be more than one solution .

Obviously it is not possible to cover all aspects of design or all available TEMA types of heat exchanger in just a few short lines , but the table and diagrams overleaf show some of the more commonly used types of TEMA heat exchangers . All the types shown in the table can be designed in accordance with TEMA B , C and R codes . The table is intended as a general guide only and does not purport to cover all aspects of design . Full technical advice can be given by a heat exchanger applications engineer . Another question that is often asked is ‘ what is the difference between the three types of TEMA B , C and R codes ?’ To answer that in detail would require a full

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Which type of TEMA Heat Exchanger ?

Below 190 ° C

Above 190 ° C

AEW BEW

Externally sealed Floating tube sheet

Yes Yes Yes No No No No No

AEP BEP

Outside packed floating head

Yes Yes Yes Yes Yes ² No No No

AEL BEM Fixed tube sheet No Yes Yes ¹ Yes ¹ Yes Yes Yes ³ No

NEN

Fixed tubesheet , channel integral with tubesheet

No Yes Yes ¹ Yes ¹ Yes Yes Yes ³ No

AEU BEU U tube Yes No Yes Yes Yes Yes Yes ⁴ Yes

AET BET

Pull-through floating head

Yes Yes Yes Yes Yes Yes No Yes

AES BET

Floating head with backing device

Yes Yes Yes Yes Yes Yes No Yes

Notes : 1 . Expansion bellows may be required . 2 . Tube side only . 3 . Shell side only . 4 . Shell side only if tube bundle welded into shell and therefore not removable .

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