Tubular (also known as shell-and-tube type) heat exchangers are the most typical type of wall-mounted heat exchangers. They have a long history in industrial applications and still occupies the leading position in all heat exchangers.The tubular heat exchanger is mainly composed of shell, tube bundle, tube plate and a head. The shell is mostly circular, and a parallel tube bundle is arranged inside and fixed on the tube sheet.
Two fluids that exchange in a tubular heat exchanger, one flowing in the tube called the tube path; and the other is flowing outside the tube called the shell side. The wall surface of the tube bundle is the heat transfer surface. In order to increase the heat transfer coefficient of the fluid outside the pipe, a certain number of transverse baffles are installed in the shell. The baffle plate not only prevents fluid short circuit, increases fluid velocity, but also forces the fluid to flow through the tube bundle multiple times in a prescribed path, so that the degree of turbulence is increased. Commonly used baffles are rounded and disc shaped, the former is more widely used. In order to increase the speed of the fluid in the tube, an appropriate partition can be placed in the ends of the two ends to divide the entire tube into several groups on average. In this way, the fluid can pass through the tube bundle multiple times only through a part of the tube at a time, which is called multi-tube. Similarly, in order to increase the flow rate outside the pipe, a longitudinal baffle can be installed in the shell to allow the fluid to pass through the shell space multiple times, which is called a multi-shell process. In a tubular heat exchanger, the temperature of the shell and the bundle are different due to the different fluid temperatures inside and outside the tube.