Classification of heat exchangers

Transfer of heat from one fluid to another is an important operation for most of the chemical industries. The most common application of heat transfer is in designing of heat transfer equipment for exchanging heat from one fluid to another fluid. Such devices for efficient transfer of heat are generally called Heat Exchanger. Heat exchangers are normally classified depending on the transfer process occurring in them. General classification of heat exchangers is shown in the Figure 1.1.

 Amongst of all type of exchangers, shell and tube exchangers are most commonly used heat exchange equipment. The common types of shell and tube exchangers are:

Fixed tube-sheet exchanger (non-removable tube bundle): 

The simplest and cheapest type of shell and tube exchanger is with fixed tube sheet design. In this type of exchangers the tube sheet is welded to the shell and no relative movement between the shell and tube bundle is possible (Figure 1.2).

 Removable tube bundle: 

Tube bundle may be removed for ease of cleaning and replacement. Removable tube bundle exchangers further can be categorized in floatinghead and U-tube exchanger.

 Floating-head exchanger:

 It consists of a stationery tube sheet which is clamped with the shell flange. At the opposite end of the bundle, the tubes may expand into a freely riding floating-head or floating tube sheet. A floating head cover is bolted to the tube sheet and the entire bundle can be removed for cleaning and inspection of the interior. This type of exchanger is shown in Figure 1.3.

 U-tube exchanger:

This type of exchangers consists of tubes which are bent in the form of a „U‟ and rolled back into the tube sheet shown in the Figure 1.4.

This means that it will omit some tubes at the centre of the tube bundle depending on the tube arrangement. The tubes can expand freely towards the „U‟ bend end. The different operational and constructional advantages and limitations depending on applications of shell and tube exchangers are summarized in Table 1.1. TEMA (USA) and IS: 4503-1967 (India) standards provide the guidelines for the mechanical design of unfired shell and tube heat exchangers. As shown in the Table 1.1, TEMA 3-digit codes specify the types of front-end, shell, and rear-end of shell and tube exchangers.

NPTEL – Chemical Engineering – Chemical Engineering Design - II

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