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isharma1-Visitor
1-Visitor
February 21, 2016
Solved

Mathcad confused when solving equations with units in them.

Dear All,

I was trying to solve the variable d, diameter of the pipe.

I could not get the solution. Can any one help me to solve in mathcad.

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Fred_KohlheppAnswer
23-Emerald I
February 22, 2016

Sorry, I don't like your equations.  Try this:

Note:  LAMINAR FLOW ONLY!!

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12 replies

LucMeekes23-Emerald V
23-Emerald V
February 22, 2016

If you want to solve symbolically, it's better to keep the symbols (by having them undefined), rather than their values.

Besides, the symbolic solver does not work with units, it treats them as (undefined) variables.

Normally assignments (Like V:=Q/A) are not allowed inside a solve block. Only equations (with the bold equals-sign) are.

Success!
Luc

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Fred_Kohlhepp23-Emerald IAnswer
23-Emerald I
February 22, 2016

Sorry, I don't like your equations.  Try this:

Note:  LAMINAR FLOW ONLY!!

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    isharma1-VisitorAuthor
    1-Visitor
    February 22, 2016

    Thank you for your kind response.

    I worked as per your suggestion, I simplified the equation and I got the answer as below.

    However, as the Re value I found above 2300 , its turbulent flow. I tried to solve these equations to find ID.

    I can not simplify here the equations. There fore, I need to go by Solve or Find function. It will be helpful if you can guide here.

    234.jpg

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    Fred_Kohlhepp23-Emerald I
    23-Emerald I
    February 22, 2016

    Your units don't balance:

    (Reynold's Number does:

    So you still have something fundamentally wrong.  If you get Reynold's Number you can approximate the Friction factor.  See Attached

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    Fred_Kohlhepp23-Emerald I
    23-Emerald I
    February 23, 2016

    Best I can do; given pipe length and pressure drop, find diameter and velocity.  Not thrilled about the accuracy.

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