Tubular exchanger is the most widely used heat exchanger on chemical and alcohol production. It is mainly composed of shell, tube plate, heat exchange tube, head, baffle and so on. Required material, can be made of ordinary carbon steel, copper, or stainless steel. During heat exchange, a fluid enters through the connecting pipe of the head, flows in the pipe, and flows out through the outlet pipe at the other end of the head. Another fluid enters by the nozzle of the shell and flows out from another nozzle on the shell. This is called the shell process. The structure of the tube heat exchanger is simple, compact and cheap, but the outside of the tube can not be cleaned mechanically. The heat exchanger tube bundle is connected to the tube plate, which is welded to both ends of the shell respectively, and is connected to the top cover. The top cover and the shell are provided with a fluid inlet and outlet pipe. A series of baffles perpendicular to the tube bundle are usually arranged outside the tube. At the same time, the connection between tube and tubesheet and shell is rigid, while outside the tube are two kinds of fluid with different temperature. Therefore, when the temperature difference between the tube wall and the shell wall is large, due to the thermal expansion of the two are different, a large thermal stress is generated, so that the tube twists or loosens the tube from the tube plate, or even destroys the heat exchanger.