heating water

Figure 2-12
heat transfer
shell
tube
Figure 2-14
upper
manifold
shell
liquid
tube
liquid
shell
tubes
Figure 2-13
lower
manifold
Courtesy of Packless Industries
heat transfer area for many applications is excessive. In
some situations, this length issue is solved by coiling the
overall heat exchanger, as shown in Figure 2-13.
This component is called a coaxial tube-in-tube heat
exchanger. It is commonly used for water-to-refrigerant
heat transfer in heat pumps.
When coiling is not possible, multiple straight tubes are
used, as shown in Figure 2-14.
cross section
The tubes are welded or brazed to bulkhead plates near
each end of the heat exchanger. The two ends of the
exchanger serve as manifolds to distribute flow through the
multiple tubes. The second liquid passes through the shell
of the heat exchanger and around the outer surfaces of all
the tubes. These designs can be scaled up to products
capable of transferring several millions of Btu/hr.
Figure 2-15 shows an example of a large “tube bundle”
that would be inserted into an appropriately sized shell.
The baffle plates through which the tubes pass increase
turbulence within the shell, which increases the convective
heat transfer rate.
The tubes and shell are often made of different materials,
depending on the chemical nature of the fluids exchanging
heat, as well as the temperature and pressure at which the
heat exchanger is rated to operate.
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