A Shell and Tube Exchanger consists of a number of tubes mounted inside a
cylindrical shell. typical unit that may be found in a petrochemical
plant. Two fluids can exchange heat, one fluid flows over the outside of the
tubes while the second fluid flows through the tubes. The fluids can be single
or two phase and can flow in a parallel or a cross/counter flow arrangement.
The shell and tube exchanger consists of four major parts:
·
Front end–this is where the
fluid enters the tube side of the exchanger.
·
Rear end–this is where the
tube side fluid leaves the exchanger or where it is returned to the front
header in exchangers with multiple tube side passes.
·
Tube bundle–this comprises of
the tubes, tube sheets, baffles and tie rods etc. to hold the bundle together.
·
Shell—this contains the tube
bundle.
The popularity of shell and tube exchangers has resulted in a standard being developed for their designation and use. This is the Tubular Exchanger Manufactures Association (TEMA) Standard. In general shell and tube exchangers are made of metal but for specialist applications (e.g., involving strong acids of pharmaceuticals) other materials such as graphite, plastic and glass may be used. It is also normal for the tubes to be straight but in some cryogenic applications helical or Hampson coils are used. A simple form of the shell and tube exchanger is the Double Pipe Exchanger. This exchanger consists of a one or more tubes contained within a larger pipe. In its most complex form, there is little difference between a multi tube double pipe and a shell and tube exchanger. However, double pipe exchangers tend to be modular in construction and so several units can be bolted together to achieve the required duty. The book by E.A.D. Saunders [Saunders (1988)] provides a good overview of tubular exchangers