Shell and tube heat exchangers are a type of heat exchanger design. It is the most common type of heat exchanger in refineries and other large chemical processes and is suitable for high pressure applications. As the name suggests, this type of heat exchanger consists of a housing (a large pressure vessel) and a bundle of tubes. One fluid flows through the tube and the other flows through the tube (through the shell) to transfer heat between the two fluids. This group of tubes is called a tube bundle and can be composed of several types of tubes: flat, longitudinal fins, etc.
Two different initial temperature fluids flow through the heat exchanger. One flows through the tube (tube side) and the other flows out of the tube but inside the shell (shell side). Heat is transferred from one fluid to the other through the tube wall, from the tube side to the shell side, or vice versa. On the side of the casing or tube, the fluid can be a liquid or a gas. In order to effectively transfer heat, a large heat transfer area should be used, resulting in the use of many tubes. In this way, waste heat can be used. This is an effective way to save energy.
A heat exchanger having only one phase (liquid or gas) on each side may be referred to as a single phase or single phase heat exchanger. A two-phase heat exchanger can be used to heat a liquid into a gas (steam), sometimes referred to as a boiler, or to cool the steam to condense it into a liquid (referred to as a condenser) side. Boilers in steam locomotives are usually large, usually cylindrical, shell-and-tube heat exchangers. In large power plants with steam driven turbines, a shell tube surface condenser is used to condense the vented steam into the turbine to form condensed water that is recycled to the steam in the steam generator.