Fw: LMNO Engineering Newsletter

> LMNO Engineering, Research, and Software, Ltd.
> The fluid mechanics calculations website: <a href="http://www.LMNOeng.com">http://www.LMNOeng.com</a>
> 7860 Angel Ridge Rd. Athens, OH 45701 USA (740) 592-1890
> <a href="/group/PipingDesign/post?postID=PTLRjNEQYfqQALJW7pkTg4A5Xwc5XfuYGjiJp0PR7AppVPxK1WJGjV6KRO2jLmkIxGheOShs2Z1Q">LMNO@LMNOeng.com</a>
>
> Newsletter. Vol. 4, No. 11. September 21, 2002
>
> Pressurized Non-Circular Ducts/Conduits
>
> Recently, we have been receiving a lot of inquiries asking how to model
non-circular pressurized conduits. Our free calculation titled "Non-Circular to Circular Pipe Conversions" at http://www.LMNOeng.com/PipeDuct.htm will help. The calculation allows one to use the circular pipe design calculations ("Design of Circular Water Pipes" and "Design of Circular Liquid and Gas Pipes") for non-circular cross-sections.
>
> If you have a rectangular or annular cross-section, the non-circular
calculation will convert your geometry to an equivalent diameter (called hydraulic diameter) which can then be used in the circular design calculations to predict velocity. However, to calculate the flowrate, take the velocity from the design calculation page and copy it to the non-circular calculation page so that the velocity is multiplied by the actual duct area. This will give the correct flowrate. The flowrate output in the circular design calculation is computed as VA where A=(pi/4)D^2, which is incorrect for a non-circular cross-section. Even though the D is the hydraulic diameter, (pi/4)D^2 is not equal to the area computed from the actual duct geometry. Type some sample numbers in the non-circular calculation to prove it to yourself, then compare the calculation's area to (pi/4)D^2 using your calculator.
>
> Conversely, if you use "Design of Circular Water Pipes" to determine a
pipe diameter based on a required velocity, the non-circular calculation can be used to convert the diameter to a height and width of a rectangular duct or an inner and outer diameter for an annular cross-section. For the same reasons as in the previous paragraph, the circular pipe design calculations cannot be used to compute hydraulic diameter based on flowrate, since A=(pi/4)D^2 is used.
>
> Thank you for your interest in the LMNO Engineering newsletter,
> Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)
> LMNO Engineering, Research, and Software, Ltd.
> http://www.LMNOeng.com <a href="/group/PipingDesign/post?postID=PTLRjNEQYfqQALJW7pkTg4A5Xwc5XfuYGjiJp0PR7AppVPxK1WJGjV6KRO2jLmkIxGheOShs2Z1Q">LMNO@LMNOeng.com</a>
>
> LMNO Engineering's previous newsletters can be viewed at
<a href="http://www.LMNOeng.com/Newsletters/newsletter4.htm">http://www.LMNOeng.com/Newsletters/newsletter4.htm</a>
>
>
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> (c) 2002 LMNO Engineering, Research, and Software, Ltd.
Received on Sun Sep 22 01:19:00 2002