The shell and tube heat exchanger is composed of a shell, a heat transfer tube bundle, a tube sheet, a baffle (baffle) and a tube box. The shell is mostly cylindrical and has a tube bundle inside, and both ends of the tube bundle are fixed on the tube plate.The two fluids that exchange heat flow inside and outside the tube. 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 fluid velocity on the shell side and force the fluid to pass through the tube bundle multiple times in a prescribed way to enhance the degree of fluid turbulence.The heat exchange tubes can be arranged in an equilateral triangle or square on the tube plate.In the shell-and-tube heat exchanger, the inner tube and the tube sheet are welded with end face welding and inner hole welding.The welding and fixing of heat exchange tubes and tube sheets mainly include:
(1) When the distance between the heat exchange tubes in the shell and tube heat exchanger is very short and the tube sheet is relatively thin, it is impossible to use expansion joints to fix it
(2) When the thermal cycle intensity is relatively large or the temperature difference is high
(3) When the pressure of the medium is high and there are particularly strict standards for the fixed seal of the equipment
(4) The inconvenient maintenance of the shell and tube heat exchanger. For example, it is used in the heat exchanger of atomic energy production of some chemical production
End welding is logically not within the scope of fusion welding. According to its application standards, it can be divided into:
(1) Strength welding (to ensure the fixed strength between the two parts of the tube and the heat exchange tube sheet);
(2) Seal welding (only for the purpose of sealing).
The shell-and-tube heat exchanger end welding joint has the characteristics of simple welding, appearance inspection and maintenance, so there are many people who use this method. If there is a weld between the heat exchange tube and the tube sheet, it can not be used under the condition of severe vibration and gap corrosion.