The influence of shell-side temperature difference of fixed tube sheet heat exchanger on heat exchanger selection

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This post was last posted by dpp0512 on 2023-3-2 11:37 Editor: In the design and calculation of fixed tube sheet heat exchangers, we often encounter situations where the temperature difference between the tube and shell side is large. For example, if the shell side is steam, the temperature is above 150 degrees, and if the tube side is hot water, it may be 70-75 degrees. In this way, the operating temperature difference on the tube and shell side can reach a maximum of 80 degrees. However, the difference in metal wall temperature is not particularly large. Generally, heat exchanger design materials say that if the temperature difference is less than 50 degrees, you can choose a fixed tube plate heat exchanger. If the temperature difference is 50-120 degrees, you need to add an expansion joint. For higher temperatures, you need to consider other types, such as U-shaped or floating head.； Here, I would like to ask him whether he refers to the working temperature temperature difference or the average metal wall temperature difference, because when the equipment professional considers thermal compensation, it calculates the thermal expansion based on the average metal wall temperature on the tube shell side, and then determines whether the fixed tube sheet heat exchanger needs to add expansion joints, etc. ； In addition, there is another situation where the operating temperature difference is relatively small under normal working conditions, but the temperature difference may be relatively large during start-up conditions. This start-up condition may last from a few hours to more than ten hours. Whether the start-up conditions should be considered when considering thermal expansion issues is also a special case. The temperature of the inlet steam may be significantly higher than the temperature during normal operation when the tower top condenser is started. I hope you can get your answers, thank you!