If the temperature of the cold and hot fluid in the heat exchanger is regulated by the process conditions, there is no problem of determining the temperature of both ends of the fluid. If one of the fluids is known only of the inlet temperature, the outlet temperature shall be determined by the designer. For example, cooling a hot fluid with cold water, the inlet temperature of cold water can be estimated according to the local temperature conditions, and the cold water temperature at the outlet of the heat exchanger needs to be determined according to economic balance. In order to save water, the outlet temperature of water can be increased, but the heat transfer area needs to be increased; In order to reduce the heat transfer area, the water quantity should be increased. The two are contradictory. The operating conditions of the design task book of chemical principles course give the temperature of the cold and hot fluid in the heat exchanger, so there is no problem of determining the temperature of both ends of the fluid. 2.4 specification and arrangement method of pipes (1) when selecting the diameter of seal gasket of Shandong heat exchanger, the flow rate shall be higher as far as possible, but generally it shall not exceed the flow rate range described above. The liquid with easy scaling and high viscosity should adopt larger pipe diameter. There are only a few standards of the series of tube heat exchanger in China ф twenty-five × 2mm and ф nineteen × 2mm two sizes of pipe. The selection of pipes can be referred to GB151-1999. Because the design requires soybean oil as the medium of heat transfer, the viscosity is large, 19 is selected × 2mm two sizes of pipe. The selection of pipes can refer to GB151-1999 for sealing gasket of Shandong heat exchanger. Because soybean oil is required to be the heat transfer medium with high viscosity, the selection is required ф twenty-five × 2mm。 ( 2) The choice of pipe length is based on the principle of convenient cleaning and reasonable use of pipe. Long pipes are not easy to clean and easy to bend. If the normal steel pipe is 6m long, the reasonable length of the heat exchanger shall be 1.5, 2, 2.5, 3, 4.5 or 6m. The four pipe lengths are also used in the series of standards. In addition, the pipe length and shell diameter should be suitable, generally l/d is 4-10 (for small diameter heat exchanger, it can be larger). 3M is selected in this design to meet the heat exchange requirements in accordance with the arrangement of pipes and the number of pipes（ 3) As mentioned above, the arrangement method of pipes on the tube plate includes equilateral triangle, square straight line and square staggered column, etc. The advantages of the equilateral triangle arrangement are: the strength of the tube plate is high; The fluid short circuit is less and the fluid outside the pipe is disturbed greatly, so the convection heat transfer coefficient is higher; More tubes can be arranged in the same shell diameter. The advantages of square in-line arrangement are that it is easy to clean the outer wall of the column pipe, and is suitable for the case where the fluid in the shell is easy to produce dirt; But the convective heat transfer coefficient is more positive than that of the sealing gasket angle row 25 of Shandong heat exchanger × 2mm。 ( 2) The choice of pipe length is based on the principle of convenient cleaning and reasonable use of pipe. Long pipes are not easy to clean and easy to bend. If the normal steel pipe is 6m long, the reasonable length of the heat exchanger shall be 1.5, 2, 2.5, 3, 4.5 or 6m. The four pipe lengths are also used in the series of standards. In addition, the pipe length and shell diameter should be suitable, generally l/d is 4-10 (for small diameter heat exchanger, it can be larger). 3M is selected in this design to meet the heat exchange requirements in accordance with the arrangement of pipes and the number of pipes（ 3) As mentioned above, the arrangement method of pipes on the tube plate includes equilateral triangle, square straight line and square staggered column, etc. The advantages of the equilateral triangle arrangement are: the strength of the tube plate is high; The chance of short circuit is less and the fluid outside the tube is disturbed greatly, so the heat coefficient of the gasket of the convection heat exchanger is higher; More tubes can be arranged in the same shell diameter. The advantages of square in-line arrangement are that it is easy to clean the outer wall of the column pipe, and is suitable for the case where the fluid in the shell is easy to produce dirt; But the convective heat transfer coefficient is lower than that of the 8 columns in the positive triangle row. The square staggered arrangement is between the two above, that is, the convective heat transfer coefficient (which is more than that in-line arrangement) can be improved appropriately. The design adopts the equal edge triangle row arrangement, the water corrosion degree to the pipe is not high, the heat transfer coefficient is higher than the gas, the liquid as the medium heat exchanger（ 4) The spacing of pipes arranged on the tube plate (refers to the center distance between two adjacent pipes) varies with the connection method between the pipe and the tube plate. Generally, the expansion method takes t= (1.3-1.5) d column as low. The square staggered arrangement is between the two above, that is, the convective heat transfer coefficient (which is more than that in-line arrangement) can be improved appropriately. The design adopts the equal edge triangle row arrangement, the water corrosion degree to the pipe is not high, compared with the gas Shandong heat exchanger gasket, the liquid as the medium heat exchanger is more important is the high heat transfer coefficient.