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Homework Help: Question on combining 2 streams of different pressure

  1. Jun 19, 2010 #1
    1. The problem statement, all variables and given/known data

    Well I was given an assignment to find ways to solve the the problem of how to mix the 2 streams in the digram together at the lowest cost possible.

    The pressures of the 2 streams that are being mixed together are 10 bar and 30 bar

    The fear is that instead of combining into 1 stream, the flow from the 30 bar will flow into the 10bar stream and damage the pump

    [PLAIN]http://img94.imageshack.us/img94/1051/drawing1x.jpg [Broken]

    2. Relevant equations

    3. The attempt at a solution

    The only way i can think of so far is to just add in a tank at the intersection where the 2 streams meet to store both streams before i pump them out as 1 combined stream. But however i don't think it is very cost effective. So i stuck to as how i can continue.
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jun 20, 2010 #2


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    Staff Emeritus
    Science Advisor

    What about using a throttling process on the high pressure line.

    Also, think about relationship between pressure (and pressure drop) and fluid velocity, e.g., Bernoulli's equation.

    Certainly the two streams would have to enter a chamber with a pressure less than 10 bar.
  4. Jun 20, 2010 #3
    Hey thanks for the reply :D

    Hmmm... By throttling process do u mean adding in a throttling valve? Im not sure if i gt it right but a throttling valve will change the velocity of the fluid and so based Bernoulli's equation the pressure would also change???.

    Also while searching i also came across Pressure Reducing Valves PRV.

    Is there a difference between the the throttling valves and the PRV???
  5. Feb 24, 2011 #4
    If you are worried about the low pressure pump, just protect it with a check valve. As long as the pressure at the mixing point is less than 10 bar, you won't have a problem.
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