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skhan855
21-06-2015, 11:47 AM
Hi

After having lot of problems with my cold store (leaking and highly inefficiency) I took charge of it and decided to replace old system/ upgrade with new ones. So I went for new condensers, addition of new evaporators and thicker insulations.

Also I planned to add new compressors of 290 KW instead of smaller 120 KW compressors I had to save electricity.


I was studying 2 diagrams of basic ammonia refrigeration and both shows presence of Low pressure liquid pumps which is just before low pressure liquid receiver.

http://www.rmtech.net/Copy_of_Refrigeration.jpg
http://www.coolpartners.dk/wp-content/uploads/2012/12/Tomorrows_Trouble_Free_Ammonia_System-Full.jpg


The problem is that I do not have these pumps installed since last many years and I called some people in same industry and they also confirmed or heard of such pumps.

Can some one help me by solving this question that
1) What is function of this Low pressure liquid pump
2) Is it required in refrigeration where temperature is required at +3.0 Degree C

Our store is meant to store fresh fruits.

Your help would be really appreciated.

Regards
Salman Khan

RANGER1
21-06-2015, 09:57 PM
Skhan,
Low pressure liquid pump system is very efficient system, but also most expensive.
Air coolers (evaporators)are flooded with ammonia & also have to be designed to suit.
Usually used on multiple evaporator system to justify installing it.

What type of system do you have now?

At 3 deg C temperature TX valves or electronic ones would be Ok
if evaporators specifically designed to suit as well as suction trap or slop pot in plant room with high pressure liquid line coil passing through it to boil off excess refrigerant returning from evaporators.

I think you should call expert company to sort this out

McFranklin
22-06-2015, 05:14 AM
To answer your questions:
1) The low pressure liquid pump provides the necessary increase in liquid pressure to allow it to be distributed throughout the low pressure side of the refrigeration system.
2) Without a diagram of your system I can not answer this question. There are designs that require pumps as well as designs that do not require pumps. With that being said it is possible your system is using high pressure liquid taken directly from the high pressure receiver to feed the evaporators.

Tycho
22-06-2015, 06:12 PM
Hi

After having lot of problems with my cold store (leaking and highly inefficiency) I took charge of it and decided to replace old system/ upgrade with new ones. So I went for new condensers, addition of new evaporators and thicker insulations.

Also I planned to add new compressors of 290 KW instead of smaller 120 KW compressors I had to save electricity.


I was studying 2 diagrams of basic ammonia refrigeration and both shows presence of Low pressure liquid pumps which is just before low pressure liquid receiver.

http://www.rmtech.net/Copy_of_Refrigeration.jpg
http://www.coolpartners.dk/wp-content/uploads/2012/12/Tomorrows_Trouble_Free_Ammonia_System-Full.jpg


The problem is that I do not have these pumps installed since last many years and I called some people in same industry and they also confirmed or heard of such pumps.

Can some one help me by solving this question that
1) What is function of this Low pressure liquid pump
2) Is it required in refrigeration where temperature is required at +3.0 Degree C

Our store is meant to store fresh fruits.

Your help would be really appreciated.

Regards
Salman Khan

Are you redesigning the whole system, or just replacing compressor, condenser and evaporators?

I've never seen liquid pumps on a system that runs at +3C

if your system is designed to run on cold storage where all the rooms are on +3C or if you also have rooms that run at -20, I would suggest using a danfoss solution for each of the evaporators, I would suggest the AK-CC 550 (http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/01/RI8LN902.pdf)

We have delivered many systems like this for fish factories in Norway, with one controller pr room it also enables you to run the system with different room temperatures.

the ones we have delivered has been for a -25C application, but we have had clients where we have changed the setpoint from -25C to +5C and the regulator has kept the temperature correct even with a suction pressure of -30.

These systems are very simple, step by step you need this flow:
Compressor - condenser - high pressure receiver - evaporator with AK-CC 550 regulator and valves - suction drum (needs to have room for the full ammonia amount) - compressor suction.

This is of course very simplified, all the components needs to be calculated to make sure you have an efficient system.

Hope this helps a little :)

RANGER1
22-06-2015, 08:29 PM
The most common system before the electronic expansion valve was a surge drum mounted directly above evaporator/s.
High pressure liquid from liquid receiver maintaining a level in "surge drum" above evaporator so, flooding coils with liquid ammonia.
Dry gas suction back to compressor, but still have suction trap in plant room to be on the safe side if any flood overs.
If you had say more than 6-7 of these surge drums, then probably instal ammonia pumps with one accumulator vessel in plant room replacing all them.
As Tyco says unusual for the temperature of 3 deg