Calculating Head Loss in a Mitre Bend Air Passage for Beginners

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Discussion Overview

The discussion revolves around calculating the total head loss in an air passageway system featuring a mitre bend. Participants explore the principles of fluid mechanics, specifically focusing on the challenges of determining k-values for bends and friction factors in a context where the passage is not a traditional pipe but a cut into ductile iron material.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant expresses confusion about calculating head loss due to sharp bends in an air passageway and seeks guidance on specific k-values and turbulent friction factors.
  • The participant provides details about the geometry and material of the passage, including diameters before and after the bend, the degree of the bend, and the initial air flow rate.
  • Another participant suggests self-learning through external resources but does not address the specific technical questions raised.
  • The original poster clarifies that existing resources do not provide the necessary information for their specific material and geometry, emphasizing the need for precise values to minimize assumptions.
  • A request for a drawing is made to aid in understanding the problem better.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the best approach to calculate head loss, and multiple competing views on how to obtain necessary data remain unresolved.

Contextual Notes

The discussion highlights limitations in available resources for specific materials and geometries, as well as the challenge of applying general fluid mechanics principles to a unique application.

Trigger32
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I am trying to find the total head loss of an air passageway system but I have not taken a fluids class. I have been trying to teach myself the equations and principles but it tends to be very confusing without guidance. So here is my question:

I have a wheel-end knuckle with an air passage put through it. The passage is not a pipe but a diameter cut into the actual material (ductile iron). The passage takes two 90 degree sharp bends and then exits the knuckle. Now i am fairly certain that I understand how to calculate a straight line head drop with no bends. My confusion is coming from finding specific k-values for these pipe bends and also completely turbulent friction factors.

If someone could show me a calculation and also explain what they are doing for one bend, I think that I could solve the rest of the problem.

Here are some details of my passage:
Diameter before bend - 10 mm
Diameter after bend - 9.5 mm
Degree of bend - 90
Material Type - Ductile Iron
Initial air flow rate- 0.3 cfs

P.S. I believe this would be considered a Mitre Bend because it as a sharp angle (not sure though)
 
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Dear Trigger32 the best way to learn is to teach yourself through Easy-learning documents and it is for your best if you print the documents and not read them online, I will give you this link that will help you in fluid mechanics and solving your problem.
http://www.firavia.com/mecheng.html
 
Last edited by a moderator:
I appreciate your sharing this knowledge site with me, but I do not think this is helping me. I've already read through many of these short guides and for some reason I can't find what I am looking for. My problem stems from the fact that none of the charts that I can find have the specific materials and geometries of my passageways. I would like to make as little assumption as possible because this is for a real application.

My specific problem I think (unless I'm going about this the wrong way) is I can not find values for my mitered bend size. Here are the dimensions again and some added data, if anyone can just walk me through an example or post a chart, I would really appreciate it.

Dia. before bend = 10 mm
Dia. after bend = 9.5 mm
Geometry - Circular cross section
Matl. = Ductile Iron
Initial air velocity entering bend = 361.63 ft/s

Head loss per this fitting = ?
 
can you please give a drawing?
 

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