The shell and tube heat exchanger is composed of a shell, a heat transfer tube bundle, a tube sheet, a baffle plate (baffle plate) and a tube box. The shell is mostly cylindrical, and a tube bundle is installed inside, and the two ends of the tube bundle are fixed on the tube plate. There are two kinds of hot and cold fluids for heat exchange, one is flowing inside the tube, called the tube-side fluid; the other is flowing outside the tube, called the shell-side fluid. In order to improve the heat transfer coefficient of the fluid outside the tube, several baffles are usually installed in the shell. The baffle can increase the velocity of the shell-side fluid, forcing the fluid to pass through the tube bundle multiple times in a specified distance, and enhancing the degree of fluid turbulence. The heat exchange tubes can be arranged in equilateral triangles or squares on the tube sheet. The equilateral triangle arrangement is relatively compact, the fluid outside the tube is highly turbulent, and the heat transfer coefficient is large; the square arrangement is convenient for cleaning outside the tube, and is suitable for fluids that are prone to scaling.
Each time the fluid passes through the tube bundle is called a tube pass; each time the fluid passes through the shell is called a shell pass. The picture shows the simplest single-shell single-pipe heat exchanger, referred to as 1-1 type heat exchanger for short. In order to increase the fluid velocity in the tube, partitions can be set in the tube boxes at both ends to divide all the tubes into several groups. In this way, the fluid passes through only a part of the tube at a time, and thus returns to and from the tube bundle multiple times. This is called a multi-tube pass. Similarly, in order to increase the flow velocity outside the tube, a longitudinal baffle can also be installed in the shell to force the fluid to pass through the shell space multiple times, which is called multiple shell pass. Multi-tube and multi-shell processes can be used together.