Selection of shell-and-tube heat exchangers

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The selection of shell and tube heat exchangers involves three steps: 1. Process calculation for selecting shell and tube heat exchangers: (1) Calculate the amount of heat that needs to be transferred based on the type of fluid, the flow rate of the cooling fluid, the inlet and outlet temperatures, and the operating pressure. (2) Select the materials for pipes and shells based on the corrosivity of the fluid and its other properties. Based on the processing characteristics of the materials, factors such as the flow rate and pressure of the fluid, its temperature, the temperatures of the heat exchange tubes and the shell, the amount of heat that needs to be transferred, the cost involved, and the ease of maintenance and cleaning, it is determined which type of shell-and-tube heat exchanger to use. (3) Determine the flow space of the fluid, that is, identify what fluids are present in the tube side and the shell side respectively. (4) Determine the flow direction of the two fluids involved in the heat exchanger, to decide whether it will be co-current, counter-current, or cross-flow. And calculate the effective average temperature difference of the fluid. (5) Initially select the heat transfer coefficient K based on experience, and estimate the required heat transfer area A. (6) Based on the calculated heat transfer area A, and referring to China’s standard series for shell-and-tube heat exchangers, the basic parameters of the heat exchanger are initially determined (such as tube diameter, number of tube passes, number of tubes, tube length, tube arrangement pattern, type and layout of baffles, and structural parameters like shell diameter). (7) Perform verification of the heat transfer coefficient and calculation of the pressure drop based on the established standard series dimensions. Finally, select a heat exchanger according to standards or carry out mechanical design. 2. Selection, design, and calculation for shell-and-tube heat exchangers: The mechanical design calculations include: (1) Calculation of the wall thicknesses of the shell and the tube sheet; (2) Design of the connection structure between the tubes and the tube sheet; (3) Design of the connection structure between the shell and the tube sheet; (4) Calculation of the thickness of the tube sheet; (5) Structural design of components such as baffle plates and support plates; (6) Calculation of the stresses on the heat exchange tubes and the shell due to combined effects of temperature differences and fluid pressure; (7) Verification of the pulling force on the tubes and their stability; (8) Determination of whether expansion joints are necessary, and if so, selection of the appropriate type of expansion joint along with related calculations. (9) Selection of takeovers, takeover flanges, vessel flanges, supports, etc., and design for hole reinforcement. 3. Method of indicating the model of shell-and-tube heat exchangers: 1.1〉The first letter indicates the type of the front tube box; 2〉The second letter indicates the type of the shell; 3〉The third letter indicates the type of the rear structure. 2. Nominal diameter (mm): For kettle-type reboilers, it is expressed as a fraction, with the numerator representing the inner diameter of the tube box and the denominator representing the inner diameter of the cylinder. 3. Design pressure for the tube/shell side, in MPa. When the pressures are equal, only Pt should be indicated. 4. Nominal heat exchange area, in ㎡. 5. When Al, Cu, Ti heat exchange tubes are used, an equal sign followed by the material name should be added after LN/d; for example, LN/D Cu. LN – – – Nominal length, in m. d – – – Outer diameter of the heat exchange tube, in mm