The main form of wall type heat exchanger between shell and tube heat exchanger is also called tube and shell heat exchanger. The heat transfer surface is composed of tube bundles, two ends of the pipe are fixed on the tube plate, and the tube bundle and tube plate are then sealed in the shell. Two kinds of fluid branch and shell side. The advantages of tube side (shell, inbboutbb, tside) (tube, inatoutat, 2-4 heat exchanger) are further increased for 1-2 heat exchanger, which further increases the advantages of tube side and shell shell heat exchanger with strong structure and wide range of application for pressure and temperature. The cleaning in the pipe is convenient, and the cleaning fluid should be carried out on the shell side. The treatment capacity is large. The disadvantages of heat transfer efficiency, compact structure, metal consumption per unit heat exchange area are not as good as those of new heat exchanger. Another main type of wall heat exchanger. The main feature of the cold and hot fluid is cross flow. According to the different surface structure of heat exchange, it can be divided into tube bundle type, tube fin type, tube belt type, plate fin type, etc. 3. Cross flow heat exchanger tube bundle tube fin plate fin 4 plate heat exchanger: composed of cold and hot fluid flowing in each channel interval, which is characterized by convenient removal and cleaning by a group of parallel thin plates with the same geometric structure, so it is suitable for the fluid containing easily scaling. The plate heat exchanger has the advantages of compact structure, small volume and light weight. The turbulence degree of the fluid is large, and the heat transfer effect is better. Plate heat exchanger is easy to clean and maintain. The defect is long around the sealing, easy to leak. The pressure bearing capacity was low (P < 2MPa). The flow resistance is large and the treatment capacity is small. 5. Spiral plate heat exchanger: the heat exchange surface is made of two metal plates. It has the advantages of compact structure and large heat transfer area per unit volume. Both fluids can flow at high speed