1, Selection of heat exchange tube specifications and arrangement
The smaller the diameter of the heat exchange tubes of the tube heat exchanger, the larger the heat transfer area per unit volume of the heat exchanger. Therefore, the pipe diameter for clean fluids can be smaller. However, for fluids that are unclean or prone to scaling, the pipe diameter should be larger to avoid blockage. Considering the convenience of manufacturing and maintenance, the specifications of the heating pipe should not be excessive.
Determine the number of tubes based on the selected tube diameter and flow rate, and then determine the tube length based on the required heat transfer area. The actual pipe length should be reasonably cut based on the factory steel pipe length. The length of steel pipes produced in my country is mostly6m,9m, so the pipe length in the series of standards is1.5m,2m,3m,4.5m,6mand9msix kinds,Among them3mand6mrelatively common.at the same time,The length of the pipe should be adapted to the pipe diameter,The ratio of general pipe length to pipe diameter,Right nowL/Dapprox.4~6. 
The tubes are arranged in two ways: equilateral triangle and square. Compared with squares, the arrangement of equilateral triangles is relatively compact, the fluid turbulence outside the tube is high, and the surface heat transfer coefficient is large. Although the square arrangement is relatively loose and has poor heat transfer effect, it is easy to clean outside the tube and is more suitable for fluids that are prone to scaling. For example, if the square-arranged tube bundle is rotated obliquely,45°Installation can increase the surface heat transfer coefficient.
2, tube sheet 
fixedTube and tube heat exchangerThe tube plates at both ends are connected and fixed with the shell by welding.  The function of the tube sheet is to connect the heated tube bundles together and separate the fluids on the tube side and shell side. 
3, head and pipe box 
There are two types of heads: square and round. Square is used for shells with small diameters.(Generally less than400mm), round shape for large diameter housings.
The tube box of the tube heat exchanger is the end cover of the heat exchanger, also called the distribution room. Used to distribute liquid and function as a seal. When the pressure is low, a flat cover can be used; when the pressure is high, a convex cover can be used, and the flange is connected to the tube sheet. During maintenance, the pipe box can be removed to clean or replace the pipes.