A shell and tube heat exchanger is a cylindrical vessel
housing a set of tubes (called the tube bundle) containing
a fluid at some temperature and immersed in another
fluid at a different temperature. The transfer of heat
occurs between the fluid flowing over the tubes and the
fluid flowing inside the tubes. The fluid flow inside the
tubes is said to be “tube side” and the fluid flow external
to the tube bundle is said to be “shell side”.
While there is an enormous variety of specific design
features that can be used in shell and tube exchangers,
the number of basic components is relatively small.

Drajad Agus Widodo

Fundamentals of Shell and Tube Heat
Exchangers

A shell and tube heat exchanger is a cylindrical vessel
housing a set of tubes (called the tube bundle) containing
a fluid at some temperature and immersed in another
fluid at a different temperature. The transfer of heat
occurs between the fluid flowing over the tubes and the
fluid flowing inside the tubes. The fluid flow inside the
tubes is said to be “tube side” and the fluid flow external
to the tube bundle is said to be “shell side”.
While there is an enormous variety of specific design
features that can be used in shell and tube exchangers,
the number of basic components is relatively small.

Tubes

The tubes are the basic component of the shell and tube
exchanger, providing the heat transfer surface between
one fluid flowing inside the tube and the other fluid
flowing across the outside of the tubes. The tubes may be
seamless or welded and most commonly made of copper
or steel alloys. Other alloys of nickel, titanium, or
aluminum may also be required for specific applications.
The tubes may be either bare or with extended or
enhanced surfaces on the outside. Extended or enhanced
surface tubes are used when one fluid has a substantially
lower heat transfer coefficient than the other fluid.
Extended surfaces, (finned tubes) provide two or four
times as much heat transfer area on the outside as the
corresponding bare tube, and this area ratio helps to
outside heat transfer coefficient.
More recent developments are: a corrugated tube which
has both inside and outside heat transfer enhancement, a
finned tube which integral inside turbulators as well as
extended outside surface, and tubing which has outside
surfaces designed to promote nucleate boiling.

Tube Sheets

The tubes are held in place by being inserted into holes in
the tube sheet and there either expanded into grooves cut
into the holes or welded to be tube sheet where the tube
protrudes from the surface. The tube sheet is usually a
single round plate of metal that has been suitably drilled
and grooved to take the tubes (in the desired pattern), the
gaskets, the spacer rods, and the bolt circle where it is
fastened to the shell. However, where mixing between the two fluids (in the event of leaks where the tube is
sealed into the tube sheet) must be avoided, a double tube
sheet may be provided.

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