A Double pipe heat exchanger is one of the simplest form of Shell and Tubular Heat Exchanger. Here, just one pipe inside another larger pipe. To make an Unit very Compact, The Arrangement is made Multiple Times and Continues Serial and Parallel flow. One fluid flows through the inside pipe and the other flows through the annulus between the two pipes.Double pipe heat exchanger design is rather straightforward. It uses one heat exchanger pipe inside another. After determining the required heat exchanger surface area, for either counter flow or parallel flow, the pipe sizes and number of bends for the double pipe heat exchanger can be selected.

In double pipe heat exchanger design, an important factor is the type of flow pattern in the heat exchanger. A double pipe heat exchanger will typically be either counterflow or parallel flow. Crossflow just doesn’t work for a double pipe heat exchanger. The flow pattern and the required heat exchange duty allows calculation of the log mean temperature difference. That together with an estimated overall heat transfer coefficient allows calculation of the required heat transfer surface area. Then pipe sizes, pipe lengths and number of bends can be determined.

The wall of the inner pipe is the heat transfer surface.This is also called as a hairpin Heat Exchanger. These are may have only one inside pipe, or it may have multiple inside tubes, but it will always have the doubling back feature shown. In some of the Special Cases the Fins also Used in Tube side.