Double Pipe Heat Exchanger
A double pipe heat exchanger, in its simplest form is just one pipe inside another larger pipe. One fluid flows through the inside pipe and the other flows through the annulus between the two pipes. The wall of the inner pipe is the heat transfer surface. The pipes are usually doubled back multiple times as shown in the diagram at the left, in order to make the overall unit more compact.
The term ‘hairpin heat exchanger’ is also used for a heat exchanger of the configuration in the diagram. A hairpin heat exchanger may have only one inside pipe, or it may have multiple inside tubes, but it will always have the doubling back feature shown.
Advantages :
Double pipe heat exchangers can handle high pressures and temperatures well.
When they are operating in true counterflow, they can operate with a temperature cross.
The cold side outlet temperature is higher than the hot side outlet temperature.
