Pipe sizing & Pressure drop

[MilosBog]

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

[aramis]

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.

[Peter_1]

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?

[Aik]

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 ;)

[MilosBog]

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/index.php/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.

[MilosBog]

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