Let’s test everyone: Does the heat exchange area of a U-tube include the bent section?
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This post was last edited by kareale88 on 2019-7-2 at 19:01. Let’s test everyone: Does the heat exchange area of a U-tube include the curved part as well?
GB151 stipulates that \"the heat exchange area generally does not include the area of the U-shaped bend sections.\" This means that in most U-tube heat exchangers (especially those that are horizontal), the bend sections represent \"dead zones\" for heat exchange in the shell side; the heat exchange efficiency in these areas is significantly lower than that in the straight tube sections, which is why they are generally not included in the total heat exchange area. However, as long as the inlet and outlet positions in the shell side are designed properly and all elbow sections are included, the heat exchange area of the elbow sections should be taken into account. In such cases, the U-shaped elbow section should be included in the heat exchange area; especially for large heat exchangers, whether this part of the heat exchange area is taken into account has a significant impact. For example, when the shell side is used for phase-change heat transfer, such as in condensers or kettle evaporators, the U-shaped bend section will undoubtedly play a role in heat transfer. Therefore, whether to take into account the area of the U-shaped elbow section needs to be analyzed on a case-by-case basis; there is no universal rule.
According to current standards, it is generally not included, but as I know, the high and low pressure feedwater heaters in power plants are included (following the practice of imported units)
As analyzed above, if the bent pipe section cannot effectively participate in heat exchange, it is not taken into consideration; whereas in a kettle-type evaporator structure, the bent pipe section should be included in the heat exchange area. However, in the devices I have developed before, the heat exchange area of the elbow sections in the kettle-type evaporators was not taken into account; looking back, it seems that this was an oversight. Thank you for the detailed analysis from above.
Does a structure in which the bottom of the U-tube is flat, with small radii at both ends of the U-shape connecting to the straight tube sections, count as part of the area?
According to GB151, it is generally not included