Types of Heat Exchangers

In the industrial world, many processes need to run at a specific temperature. Effective thermal management is necessary to maintain an accurate temperature of the application. Heat exchangers are used for thermal management. The heat transfer takes place between liquid to liquid or gas to gas or liquid to gas. The heat transfer takes place between hot medium and cold medium that are separated by a solid wall to eliminate any chances of mixing.

Heat exchangers can be classified into different categories depending upon their design, construction material, heat transfer mechanism, and fluid flow directions. Heat exchangers are designed in different shapes and sizes according to the requirements of the application and are used for both the purposes, of heating and cooling.

Classification based on design

Heat exchangers are available in different designs that include shell and tube type, double pipe, plate, finned pipe, finned plate, condensers, boilers, and evaporators.

Shell and tube type

This is one of the most efficient types of heat exchangers. In this type of device, there are small tubes placed parallel to each other inside this big shell tube. One liquid passes through the small tubes and the other medium passes through the main shell tube. If hot liquid passes through the small tube then in the outer shell cold liquid passes. If cold liquid passes through the small tubes then hot liquid passes through the outer shell tube. Heat exchange occurs between cold and hot liquid using the surface of the small tubes. If one small pipe is passing inside the big shell pipe, then it is called a Double pipe heat exchanger.

Finned Tube Type

In this type of heat exchanger, one liquid passes through the tube, and the tube is attached with the fins on its outer surface. The idea behind attaching fins to the tube is to increase the heat transfer area. If hot liquid passes through the tube then as a result tube and fins get hot and they release heat into the surrounding atmosphere. The overall effect is the hot liquid passing through the tube gets cool. If the cold liquid is passed through the tube then the tube and the fins get cold and they extract heat from the surrounding weather and get hot and as a result, the liquid passing through the tube gets hot.

Plate heat exchangers

In this type of device, thin plates are attached in parallel, and series so that the pair of plates form a channel in which one liquid flows. After one pair of the plates, a passage is created and in the passage, another liquid flows. If the first liquid flowing in the pair of the plate is hot then the other liquid flowing in the passage is cold. The surface of the plate between hot and cold liquid is transferring heat between the two mediums. Fins can be attached to the plates to increase the heat transfer rate and these types of devices are called plate fin heat exchangers.

Boilers, condensers, and evaporators are also considered heat exchangers. In these devices, the medium is changing its phase. In condensers, heated gas is condensed and changes its phase from gas to liquid. In boilers and evaporators, the liquid is changing its phase to gas as a result of the heat transfer process.