Heat exchangers (HEX) are one of the most important parts of industries like chemical, medical, or many other industries. These systems are used to transfer or “exchange” thermal energy (heat) between two fluids which can be gas or liquid. Heat exchangers can be found in different types such as double pipe, shell & tube, spiral tube, plate, etc. but the two first types are and specially shell & tube exchangers are more common in industries.
There are two main flows in each exchanger named cold and hot flows. The cold flow is the one that its temperature increases in the exchanger and hot flow is the one that its temperature decreases. Depending on the arrangement of these two flows, heat exchangers can be classified in two main groups: cocurrent and Countercurrent flow. In cocurrent flow arrangement, both cold and hot flows enter the exchanger in the same head, but in countercurrent arrangement, cold flow enters in one head and the hot flow enters in the other head. Besides this classification, there are other classifications depending on compactness, usage, number of fluids, etc.
Heat exchangers work based on convective heat transfer. In this heat transfer mechanism, the transfer rate depends on many factors such as flow velocity, pipe or tube surface, flow arrangement, etc. Therefore it’s not easy to design an effective exchanger for certain conditions.