A heat exchanger is a device built to transfer heat from one medium to another. The medium may be separated by a solid wall or streams they may be in direct contact with each other. Heat exchangers are widely used in industrial plants.

Heat exchangers are available in a wide variety of configurations.

Shell and tube heat exchangers consist of a series of tubes terminated on a tubesheet and inserted in to a shell. One stream will flow inside the tubes while the second fluid will flow outside of the tubes and inside of the shell. This allows for heat to be transferred from one stream to the other.

Plate and frame heat exchangers are composed of multiple thin plates that are gasketted and bolted together on a frame. The gasketing is such that each of the two fluid streams flow in between every other plate. The design and configuration of these exchangers generates very large surface areas for heat transfer.

Regenerative heat exchangers use the heat medium from a process to warm the fluids. These exchangers are used only for gases.

Plate fin heat exchangers use "sandwiched" passages containing fins to increase the effectiveness of the unit. The process streams can be either crossflow or counterflow. They are usually made of aluminium alloys. Plate and fin heat exchangers are mostly used for low temperature services.

Scraped surface heat exchangers are mainly used for heating or cooling high-viscosity products, crystallization processes, evaporation and high-fouling applications. The fluid is comes in contact with a heated or cooled surface and the surface is continuously scraped.