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Water pipe flow

  1. May 1, 2014 #1
    Hey Guys!

    This is my first post so I apologize beforehand if there are any mistakes with my post :D

    But my question is...

    I have 2 water pipes that are connected to one pipe in the middle, but the distance from the 2 water pipes to the connection point are not necessarily the same. The distance from water pipe with 80 celsius hot water to connection point is 1 m, and the distance from the water pipe with 20 celsius cold water is 1,5 m(Like you can read I like to use SI-units). The water flows from to tanks placed above so the gravity force affect the water to flow through the pipes(A little sketch should be attached).

    I know the value of all most everything in this systems except the pressure, so feel free to ask.

    But How do I find the flow rate of the water from both the cold and warm water pipes when I want the output temperature to be 60 celsius?

    I found this calculator online:


    but I don't understand where this equation is from? I mean why do you need to use the specific water gravity?

    If there are anyone who can explain this equation or know how to solve this problem, I would be very grateful.

    Attached Files:

  2. jcsd
  3. May 1, 2014 #2
    Assuming perfect mixing they will sum linearly so you want a 2:1 mixing ratio of hot to cold. Lengths will not matter in this approximation
  4. May 1, 2014 #3
    Try looking into the mixing perfect gas laws, PV=mRT may help with this
  5. May 1, 2014 #4


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    Staff Emeritus
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    Homework Helper

    It's not clear how this helps the OP. AFAIK, he is dealing only with mixing liquids at different temperatures.
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