Shell-and-tube condensers, also known as tube-and-shell or bundle-type condensers, are a typical type of heat exchanger with a long history of industrial application and continue to hold a leading position among all heat exchangers. The main components of a shell-and-tube condenser include the shell, tube bundle, tube plate, and end caps. The shell is typically circular, containing parallel tube bundles that are fixed at both ends to the tube plate.

Two fluids are used for heat exchange inside a shell and tube heat exchanger: one flows inside the tubes, known as the tube side; the other flows outside the tubes, referred to as the shell side. The wall of the tube bundle serves as the heat transfer surface. To enhance the heat transfer coefficient of the fluid outside the tubes, a certain number of transverse baffle plates are typically installed inside the shell. These baffles not only prevent short-circuiting of the fluid, increase fluid velocity, but also force the fluid to cross the tube bundle multiple times along specified paths, significantly increasing turbulence. The commonly used baffles are crescent-shaped and disc-shaped, with the former being more widely applied. Each time the fluid passes through the tube bundle is called a tube pass, and each time it passes through the shell is called a shell pass. To increase the fluid velocity inside the tubes, appropriate baffles can be set in the end caps, dividing all the tubes evenly into several groups. This allows the fluid to pass through only a portion of the tubes each time, traveling back and forth through the bundle multiple times, known as multi-pass. Similarly, to increase the fluid velocity outside the shell, longitudinal baffles can be installed within the shell to make the fluid pass through the shell space multiple times, referred to as multi-shell passes. Inside a tube heat exchanger, due to the different temperatures of the fluids inside and outside the tubes, the temperatures of the shell and the tube bundle are also different.