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  1. #1
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    Pipe sizing & Pressure drop



    Hi All,
    i have strange question for which only the real experst can help:
    Liquid lines are not sized properly and pressure drop is arround 7K (3bar). There is a liquid line reciever so no subcooling is available. What should be done in this case? Except replacing the lines of course (completly not an option)?
    Any answer could help!
    Thanks


    Be careful about reading health books. You may die of a misprint.

  2. #2
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    Re: Pipe sizing & Pressure drop

    Quote Originally Posted by MilosBog View Post
    Hi All,
    ... What should be done in this case? Except replacing the lines of course (completly not an option)?
    Any answer could help!
    Thanks
    You discarded your best option!

    Second option:

    Install a subcooler after the liquid receiver with a capacity of mass flow x average Cp at the temperatures of the refrigerant x (7k + safety factor). Or mass flow x enthalpy difference between conditions at expansion device – enthalpy at receiver (+ safety factor).

    Safety factor depends if you expect more than 7k in any situation yearly or it is a reliable value but I would add at least 2k, just in case.

    If you cannot get the 7k because the liquid temperature is closer than that from ambient, then use a HE if you have this extra capacity in your system. Otherwise you will have to use another media like water.

  3. #3
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    Re: Pipe sizing & Pressure drop

    The solution Aramis gave has become a standard solution in supermarkets where they use Danfoss AKV's. But are you able MilosBlog to calculate that HE?
    Anyhow, if you don't change your lines, your system will consume too much energy due to this dp. Solve the cause, don't try to find a solution for a problem of others.
    You said also "There is a liquid line reciever so no subcooling is available" Why do you conclude this?
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  4. #4
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    Re: Pipe sizing & Pressure drop

    Quote Originally Posted by Peter_1 View Post
    Anyhow, if you don't change your lines, your system will consume too much energy due to this dp.
    If you don't change your lines and haven't enough subcooling you will have a big problem with "flashing gas". Anyway, if you have enough subcooling, liquid velocity would be to high and can damage solenoids or AKV.
    If you want to get right solution - you have learn and understand physical processes in refrigeration systems
    In some places will have to think ...

  5. #5
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    Re: Pipe sizing & Pressure drop

    Gents,
    pipe lines dont depend on me, i am searching only for an alternative solution for a short period. Later who messed up he needs to change(wasnt me )

    Liquid line reciever
    http://hvac-talk.com/vbb/archive/ind.../t-140113.html


    In Germany each figure is checked (mostly) and without calculation i dont do anything. When i gather facts and figures, correct calculation, than i can advice investor and technical control.
    With regards to calculating HE - i havent done it in practise but on faculty we done calculation of single stage cycle with internal heat exchanger.
    Be careful about reading health books. You may die of a misprint.

  6. #6
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    Re: Pipe sizing & Pressure drop

    But advice for HE is for sure apritiated i can calculate how much KW is needed and also pressure drops but if there is something else required for sizing - advice

    Thank you all for replys
    BR
    Be careful about reading health books. You may die of a misprint.

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