# Equivalent length of helical coil

 Register Blogs Members List Search Today's Posts Mark Forums Read August 18, 2017, 22:26 Equivalent length of helical coil #1 New Member   Jeffrey Join Date: Sep 2016 Posts: 6 Rep Power: 8 Hello, I am trying to calculate the equivalent length of a copper winding with several mitered joint extensions on both ends in order to divide it into equally flowing sections. Through some searching online I found a site that lists Appendix A-29 from the Crane Flow of Fluids paper. I've seen some other calculations online that use just the number in the K coefficient to calculate the equivalent length of fittings and bends. So my question is should I use the formula KB = (n - 1)(0.25pi fT r/d + .5K) + K to calculate the equivalent length of the coil section since it is a series of 90 degree bends? My thought is, if you just use the number in the K coefficient, then giving that a value of x in the above formula you can factor out the fT and get: (L/D)eq = (n - 1) (.25pi r/d + .5x) + x My math so far for this is as follows, any help on everything I am wrong on would be appreciated: Copper size = .5" X .75" X .100" wall tube = .3 X .55 inside dimensions Equivalent Diameter = 4A / P = 4*.3*.55/(.3+.3+.55+.55) = .3882 (L/D)eq for mitered 90 = 60 Leq = 60 * .3882 = 23.2941 winding r/d = 3.625/.3882 = 9.337 (L/D)eq for 10 = 30 (L/D)eq = (60 - 1) (.25pi * 3.625/.3882 + .5 * 30) + 30 (L/D)eq = 1347.6681 Leq = 1347.6681 * .3882 = 523.2123 Segments: 2", mitered 90, 4", mitered 90, 2", mitered 90, 3", mitered 90, 26", mitered 90, 2", mitered 90, 2", 60 turn coil, 2", mitered 90, 2", mitered 90, 26", mitered 90, 3", mitered 90, 2" mitered 90, 4" mitered 90, 2" 12 mitered Joints = 23.292 * 12 = 279.5294 82" of straight length 523.2123 Winding Equivalent Length Total Equivalent Length = 885" Edit: OK, so after more research, I now know that K = fT(L/D)eq so that made everything click better. So, I quess the equation would be (L/D)eq = (n - 1) (.25pi r/D + .5(L/D)eq) + (L/D)eq and I believe this is what I should be using for my application. I also think I'm supposed to be using the equation 1.30(a * b)^.625 / (a + b)^.25 for my equivalent pipe diameter (D) instead of the 4A / P equation; is that correct? I also realized that I was using the number of turns in my coil instead of the number of 90 degree turns in the coil, so it should be (240 - 1) instead of (60 - 1). Last edited by Jeffreyb723; August 19, 2017 at 01:20. Reason: Found mistakes and learned more  Thread Tools Search this Thread Show Printable Version Email this Page Search this Thread: Advanced Search Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are Off Pingbacks are On Refbacks are On Forum Rules Similar Threads Thread Thread Starter Forum Replies Last Post [DesignModeler] Orifice baffles in helical coil phreddy ANSYS Meshing & Geometry 0 April 12, 2017 11:17 sarsam.9296 FLUENT 3 January 14, 2016 03:02 [DesignModeler] Splitting the helical coil into 2 volumes for meshing tshv247 ANSYS Meshing & Geometry 11 November 20, 2015 02:06 tshv247 Visualization & Post-Processing 0 July 10, 2014 09:16 [DesignModeler] Best way to model helical coil ritodip ANSYS Meshing & Geometry 0 March 27, 2014 00:34