W A T E R - C O O L E D C O N D E N S E R S .
Condensing water must be noncorrosive, clean,
inexpensive, below a certain maximum temperature,
and available in sufficient quantity. The use of
corrosive or dirty water results in high maintenance
costs for condensers and piping. Dirty water, as from a
river, can generally be economically filtered if it is
noncorrosive; corrosive water can sometimes be
economically treated to neutralize its corrosive
properties if it is clean. An inexpensive source of water
that must be filtered and chemically treated will
probably not be economical to use without some means
of conservation, such as an evaporative condenser or a
Water circulated in evaporative condensers and
cooling towers must always be treated to reduce the
formation of scale, algae, and chalky deposits.
Overtreatment of water, however, can waste costly
chemicals and result in just as much maintenance as
shell-and-coil water-cooled condenser (fig. 7-15) is
simply a continuous copper coil mounted inside a steel
shell. Water flows through the coil, and the refrigerant
vapor from the compressor is discharged inside the
shell to condense on the outside of the cold tubes. In
many designs, the shell also serves as a liquid receiver.
The shell-and-coil condenser has a low
manufacturing cost, but this advantage is offset by the
disadvantage that this type of condenser is difficult to
service in the field. If a leak develops in the coil, the
head from the shell must be removed and the entire coil
pulled from the shell to find and repair the leak. A
continuous coil is a nuisance to clean, whereas straight
tubes are easy to clean with mechanical tube cleaners.
In summary, with some types of cooling water, it may
be difficult to maintain a high rate of heat transfer with
a shell-and-coil condenser.
shell-and-tube water-cooled condenser shown in
figure 7-16 permits a large amount of condensing
surface to be installed in a comparatively small space.
The condenser consists of a large number of 3/4- or
5/8-inch tubes installed inside a steel shell. The water
flows inside the tubes while the vapor flows outside
around the nest of tubes. The vapor condenses on the
outside surface of the tubes and drips to the bottom of
the condenser, which may be used as a receiver for the
storage of liquid refrigerant. Shell-and-tube
condensers are used for practically all water-cooled
To obtain a high rate of heat transfer through the
surface of a condenser, it is necessary for the water to
pass through the tubes at a fairly high velocity. For this
reason, the tubes in shell-and-tube condensers are
separated into several groups with the same water
traveling in series through each of these various
groups. A condenser having four groups of tubes is
known as a four-pass condenser because the water
flows back and forth along its length four times.
Four-pass condensers are common although any
reasonable number of passes may be used. The fewer
the number of water passes in a condenser, the greater
the number of tubes in each pass.
The friction of water flowing through a condenser
with a few passes is lower than in one having a large
number of passes. This means a lower power cost in
pumping the water through a condenser with a smaller
number of passes.
The use of tube-within-a-tube for condensing purposes
is popular because it is easy to make. Water passing
Figure 7-15.A typical shell-and-coil water-cooled condenser.