How to determine the dimensions of a non-circular cross-section given the equivalent diameter
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As the title suggests, given the equivalent diameter, how can the specific dimensions of a rectangular cross-section be determined? There are two statements: (1) Equivalent diameter = perimeter of the cross-section/π, and (2) Equivalent diameter = 2ab/(a+b). Which of these two statements is correct? Or what occasions are each suitable for? Regarding rectangular cross-sections, how is the length-to-width ratio determined?
This post was last edited by hgjoys on 2009-9-25 at 14:49. The equivalent diameter of a rectangular cross-section is equal to 2ab/(a+b); knowing only the equivalent diameter of a rectangular cross-section does not allow one to determine the two unknown values a and b.
In calculations in some chemical engineering fields, many formulas require the diameter to be substituted. Both formulas are correct; the first one is used for irregular cross-sections – the wetted perimeter divided by the cross-sectional area ； The latter is used for the regular (square) cross-section. The aspect ratio for rectangles is listed in many design manuals; just look it up and you’ll be fine.
3# 000009005CE51E: The book states that the equivalent diameter = 4 × pipe cross-sectional area / wetted perimeter. You mentioned another calculation method: “for irregular cross-sections – wetted perimeter divided by cross-sectional area.” I’ve never seen such a rule; where can this calculation method be found? I’d like to hear more in detail; I want to learn *it*.
It cannot be calculated; there are many solutions, and it is necessary to consider the specific circumstances.
The equivalent area cannot be calculated using the equivalent diameter