U-tube design

It is determined based on the required heat exchange area and the length of the straight section of the U-tube. When calculating the heat exchange area of a U-tube heat exchanger, it is generally not necessary to take into account the area of the curved section of the U-tube

Thank you for your answer. I already know that, but I would like to ask: since there are groups of tubes of different lengths, how do we determine how many tubes are needed for each group?

It’s quite troublesome to calculate this by hand; mainly, one has to do the calculations in groups of two rows at a time. Pay attention to the minimum bending radius for the middle two rows; the values for the rest can be calculated accordingly. I created an Excel sheet for calculating the number of U-tubes – by entering a few parameters, the results are generated automatically, and it is also possible to determine the heat exchange area and the weight of the U-tubes. The link to the post is as follows: http://bbs.hcbbs.com/thread-407046-1-1.html

In a standard U-tube design, each bent section is concentric; therefore, although the unfolded lengths of the various U-tubes differ, the length of the straight sections is the same. Once the length of the straight sections is known, and the heat exchange area is also known, it becomes possible to determine the number of tubes required.

Although GB151 standard states that the arc-shaped sections are not included in the heat exchange area, I believe that the heat release due to condensation outside the tubes should still be taken into account, especially in cases where there are many tubes and the total length of the tubes is not very large.

Trying to take a shortcut again; it’s not easy! Method of determination: 1. First, draw a diagram of the tube sheet holes to facilitate determining the number of U-tubes in each group. 2. Determine the center distance between the U-tubes in each group; based on this, calculate the bending radius of the U-tubes in that group, and determine the length of tube required for the bent section. 3. Determine the length of the straight section of the heat exchange tube. I just drew a few schematic diagrams to take a look; the distance between the straight sections of the heat exchanger isn’t necessarily a fixed value (it could be, in theory, but considering the bending process, each section needs to be appropriately lengthened). 4. 3*2+2 represents the length of a single heat exchange tube in this set. This post was last edited by cuiwei4260 on 2009-4-22 07:51.]

I also think that the length of the straight sections of the U-tube is the same; it’s just the radius of curvature that varies. The total length of the heat exchange tubes should be determinable based on the spacing between them. The total length needs to be calculated manually, by first determining the length of the outermost sections and then those of the inner sections. Last edited in this post by wode*aohei on 2009-4-20 08:28

The moderator on the 4th floor explained it in the most detail; I have also learned from that. Additionally, according to standard GB151, the bent parts of the U-shaped tubes do not need to be taken into account – the poster only needs to calculate the straight sections!