Shandong heat exchanger gasket 2. According to material classification: it is divided into metal material and non-metal material heat exchanger. 3. According to the structure classification: divided into shell and tube heat exchanger and plate heat exchanger. Medium 1) shell and tube heat exchanger: it is characterized by round shell with tube bundle. A kind of medium flows through the channel in the heat exchange tube and its through part (called Shell Side). It can be divided into: floating head heat exchanger, U-tube heat exchanger, casing heat exchanger, fixed tubesheet heat exchanger, etc. 2) Plate heat exchanger: it is made up of thin plates pressed into various shapes to form heat transfer surface. Cold and hot media flow between two adjacent plates respectively. Common plate heat exchangers are plate heat exchanger, umbrella plate heat exchanger, spiral plate heat exchanger and plate shell heat exchanger. Although the heat transfer efficiency of plate heat exchanger is high, its application is limited due to its low strength and poor sealing performance. Therefore, shell and tube heat exchanger is widely used in petroleum and chemical industry, which has been used as traditional heat exchange equipment. 1. Overall structure and characteristics of shell and tube heat exchanger 1) floating head heat exchanger the tube sheet at one end of floating head heat exchanger is fixed. It is rigidly connected with the shell, and the tube sheet at the other end is movable and not connected with the shell. One side of the movable tubesheet is called floating head. The tube bundle of floating head heat exchanger can be drawn out from the shell of the heat exchanger, so the outer wall of the tube is easy to clean, and the tube bundle can expand and contract freely in the shell, so there is no temperature difference stress; But the structure is complex, the cost is high, and if the floating head is not tightly sealed, the two kinds of fluid will be mixed. Floating head heat exchanger is suitable for the occasions where the temperature difference between cold and hot fluid is large (generally, the temperature difference between cold flow inlet and hot flow inlet can reach 110 ℃), and the medium is easy to scale and needs cleaning. Most of the shell and tube heat exchangers used in refineries are floating head type The overall structure diagram is shown in FIG. 12) fixed tubesheet heat exchanger this kind of heat exchanger has the advantages of simple structure, light weight and low cost. In the case of the same shell, it can arrange more heat transfer tubes than other types of tubular heat exchanger. However, the temperature difference between the shell and the tube layer should not be too large. When the temperature difference is too large, a large thermal stress will be generated, which will cause the joint between the tube and the tube sheet to loosen and cause leakage. In addition, the tubesheet of this kind of heat exchanger is fixed, so it is difficult to repair, replace the tube or clean the shell with gasket. The heat exchanger is suitable for the case that the medium on the shell side is not easy to scale or has scale but can be cleaned chemically; The difference of expansion between shell wall and tube wall caused by temperature difference is not big, or the pressure of shell side is not high though the expansion difference is big The overall structure is shown in Figure 2; 2-tubesheet; 3-tube; 4-shell; 5-flange; 6,7-connecting pipe; 8-support; 9-baffle plate 3) U-tube heat exchanger this kind of heat exchanger is different from fixed tube sheet and floating head type, only one tube sheet is used as sealing gasket of heat exchanger, the heat exchange tube is U-shaped, both ends are fixed on the same tube sheet; The tube plate and the shell are fixed together by bolts. The structure of the heat exchanger is simple and the cost is low. The tube bundle can expand freely in the shell without temperature difference stress. The tube bundle can also be pulled out for cleaning and a tube sheet is saved; However, it is difficult to clean the inside of the U-shaped tube and it is not convenient to replace the tube. Because the radius of the U-shaped elbow cannot be too small, compared with other shell and tube heat exchangers, the U-shaped elbow has less pipe layout and less compact structure. It is suitable for high temperature, high pressure and corrosive fluid with large temperature difference between cold and hot fluid and clean pipe The overall structure is shown in Fig. 34) kettle type heat exchanger. The shell diameter of this kind of heat exchanger is generally 1.5 ~ 2.0 times of the tube bundle diameter. The tube bundle is biased below the shell, which submerges the tube bundle and forms a certain vapor-liquid separation space at the upper part of the tube bundle. This heat exchanger is mostly used as evaporator, reboiler of distillation column or waste heat boiler with single gasket. The tube bundle can be fixed tubesheet type, floating head type or U-type as required.