View Full Version : Prssure drop in discharge line.

24-09-2002, 05:12 PM
Measure in a carrier 30hk chiller, 2 circuits, each with a 40HP 06E compressor, R22, water cooled condenser.
The high pressure gauge is connected to compresssor head, and it is 1 bar( about 15PSI) higher than measuring from condensor(16bar vs. 15 bar) .
I remember design book said that pressure drop in discharge line is expected not excess 2 F saturated temp lost. but 1 bar drop is about 5F lost

Is it a design bug?

24-09-2002, 05:52 PM
Hi, Lin:)
if your conenser pressure is at condenser outlet it is about right, but if the second higher pressure is being measured at the condenser inlet the pressure drop is too high.
A high pressure drop in the discharge line may be a design error, or more likly your are now evaporating higher causing an increased mass and volume flow around the refrigeration system. Is the plant being used for the purpose it was designed for?
Regards Andy.

Prof Sporlan
24-09-2002, 10:06 PM
Lin, pls provide the discharge line OD and equivalent length. This information will help determine if the discharge line is undersized.

25-09-2002, 01:23 AM
The pressure is measured on the top of condenser vessel. the evaporating pressure is 4.5Bar.
there are a shutoff valve(Open completely of course), muffle, and about 1.5 meter pipe, i will get the OD later.

28-09-2002, 07:15 PM
I've come across discharge mufflers on chillers and also drilled plates fitted between service valve and compresssor (standard fitting) on Carrier compressor/ receiver sets.
i would try these for P.D. before ripping out your condensor pipes
hope this is helpfull!

29-09-2002, 10:23 AM
Hi, Lin:)
the muffler would cause a pressure drop due to the nature of it's design, along with the service valve this could be the region of what you are seeing.
This unit is a package unit? Sometimes when the pipe runs are short a designer would cut corners, remember these units are made in mulitiples, if you use a smaller line size you are saving not just on pipe but on the line components, when taking this over a number of units built per year the savings can be considerable.
If the pressure drop is not causing any problems in the system and your are happy to live with the slight ineffeciency I would leave it. On the other hand if a change of pipe is envisaged you will have to up the size of the muffler also (check sizing from a manufacturers chart), the pressure drop is a product of all the discharge line components not just the pipe size.
Another possibility is that the muffler has be added and sized per line size. The pressure drop may have been fine on that size of pipe if a muffler had not been added.
Regards. Andy:confused:

Prof Sporlan
29-09-2002, 03:17 PM
1.5 meters of discharge line isn't very long. The Prof would also be concerned about the muffler

29-09-2002, 05:17 PM
Thank all u.
2 circuits have same symptoms, so i think not muffler or sevice valve fail.
I would rather believe designer's neglect. it's unwise for money reson to undersize pipe.

30-09-2002, 01:07 AM
Symptom implies a problem. The overriding question is whether the pressure drop is normal for the muffler.

15-10-2002, 09:00 AM
The discharge pipe od is 1-5/8".
capacity is 112kw with 30C cooling water in and 7C chilled water out.

16-10-2002, 02:22 AM
from "Coolpack" calculated results, the pressure loss in pipe is only 0.16bar. So the muffler mayber a problem.

How to get info. about muffler's structure?