TYPES OF HEAT EXCHANGERS
In a heat exchanger there is no direct contact between the two fluids. The heat is transferred
from the hot fluid to the metal isolating the two fluids and then to the cooler fluid.
Types of Heat Exchanger Construction
Although heat exchangers come in every shape and size imaginable, the construction of most heat
exchangers fall into one of two categories: tube and shell, or plate. As in all mechanical devices,
each type has its advantages and disadvantages.
Tube and Shell
The most basic and the most common type of heat exchanger construction is the tube and
shell, as shown in Figure 1. This type of heat exchanger consists of a set of tubes in a
container called a shell. The fluid flowing inside the tubes is called the tube side fluid
and the fluid flowing on the outside of the tubes is the shell side fluid. At the ends of
the tubes, the tube side fluid is separated from the shell side fluid by the tube sheet(s).
The tubes are rolled and press-fitted or welded into the tube sheet to provide a leak tight
seal. In systems where the two fluids are at vastly different pressures, the higher pressure
fluid is typically directed through the tubes and the lower pressure fluid is circulated on
the shell side. This is due to economy, because the heat exchanger tubes can be made
to withstand higher pressures than the shell of the heat exchanger for a much lower cost.
The support plates shown on Figure 1 also act as baffles to direct the flow of fluid within
the shell back and forth across the tubes.