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Loss coefficient K in a pipe?

  1. Jun 16, 2016 #1
    1. The problem statement, all variables and given/known data

    Screen_Shot_2016_06_16_at_8_30_06_pm.png
    2. Relevant equations
    N/A

    3. The attempt at a solution
    Usually we are given a table, but how do we calculate the loss coefficient between 2 different pipes with different diameters? In this case, between the 5 and the 3 cm^2 pipes?
     
  2. jcsd
  3. Jun 16, 2016 #2

    SteamKing

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    The K-factors for a given diameter of pipe are proportional to the fourth power of that diameter, as described in this article:

    http://www.pipeflowcalculations.com/pipe-valve-fitting-flow/flow-in-valves-fittings.php

    The usual method is to express the K-factors or equivalents for the system in terms of one common pipe size.
     
  4. Jun 16, 2016 #3
    You should be able to look up the equation for the loss coefficient for the transition between two pipes of different diameter. Do you not have a text book?
     
  5. Jun 16, 2016 #4
  6. Jun 16, 2016 #5
    My textbook just says to refer to appendix for K values. It doesn't say anything between the transition of 2 different pipes with different diameters.
     
  7. Jun 16, 2016 #6

    SteamKing

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    The K-factor for each length of straight pipe is f (L/D). Call one K-factor K-3 for the 3-cm. pipe and the other K5 for the 5-cm. pipe.

    Now, according to the relation

    ##\frac{K_a}{K_b}=(\frac{d_a}{d_b})^4##

    If you make Ka = K3, then Kb becomes K5. Putting the value of the K-factor for the 5-cm. straight pipe into the relation will give you the equivalent K-factor as if the 5-cm. pipe was actually 3-cm. pipe.
     
  8. Jun 17, 2016 #7
    What geometries does it give K values for?
     
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