For shell-and-tube heat exchangers, should tubes with a diameter of 19 or 25 be used?
Thread Content
When choosing tubes with a diameter of 19 or 25 for shell-and-tube heat exchangers, is there any basis for making such a choice? I seek advice from those who are more knowledgeable
The smaller the tube, the larger the heat transfer area per unit volume of the heat exchanger. For clean fluids, the pipe diameter can be smaller; otherwise, it can be larger
Choose a tube with a smaller diameter: as the Reynolds number increases, the heat transfer coefficient on the tube side increases, the overall heat transfer coefficient rises, and the heat exchange area decreases relatively. However, it is a bit more troublesome to manufacture: the number of tube holes increases.
Both types of tubes can be used. The finer the tube, the higher the flow velocity and the convective heat transfer coefficient, but the resistance also increases.
In general, it is better to choose 25, as it has a low fouling thermal resistance and allows the heat transfer coefficient to remain stable over time.
Selection criteria: 1. Flow velocity restriction within the pipe, that is, the matching of the flow area, flow rate, and number of pipes inside the pipe； 2. Heat transfer load limitation: smaller pipe diameters result in a larger heat transfer area per unit volume ； 3. Limitations due to medium scaling, in accordance with the requirements for tube cleaning operations ； 4. Resistance drop limitation requirements ； 5. Requirements for welding processes, etc