View Full Version : Extra liquid pump in DX system

05-06-2011, 12:03 PM
Hi all.
I have came with idea to make a DX system with a extra pomp after liquid reciver.
What i want to do is to get with condensing temperature to a very low value even by the cost of no subcooling. This will make a compressor to have a lighter work (less power consuption, more cooling power). But TXV dont like small pressure different between suction and discharg line. So i'm thinking of putting a pomp with which i will rise the pressure of the liquid between pump and TXV also giving it some subcooling .

Sorry for my english, i'm from Poland :)
Any comments if someone have allready try such a thing? is it possible to work fine? does it have any sens?

Thanks for all opinions!

05-06-2011, 12:18 PM
Hi Crocens,

I think this might be what you are after.


05-06-2011, 01:07 PM
yes, this is exacly what i need. THANKS. But i have another problem with taking right pump... does anybody know how to choose the right size of such a pomp? Are there any equations about how much pressure i will gain after using such pomp?

05-06-2011, 04:42 PM
Pump curves will give you pressures and capacities.
Lowering condensing pressure is good energy saving measure. However, some other issues can arise. Hot gas defrosting, oil carry over...

05-06-2011, 09:40 PM
What pressure do you want to achieve & what refrigerant are you using?

You may be able to use a Hermetic liquid pump if Hysave is not big enough.

06-06-2011, 04:44 AM
I have R-404a, 4 compressors - each 25,57 m3/h, evaporating temp -10*C.
Pressure at inlet to the pomp will be floating from 9 to 18bars depending on weather. I want after the pomp about 16bars.

06-06-2011, 10:30 AM
Maybe you should try Hysave & see what they can recommend you anything.

I think Danfoss electronic expansion valves would be best option.

They can control over a much bigger range, I think down to 10%.

Correct selection for low & high discharge pressures should be achievable.

This is more accurate than conventional TX valves.

How many valves do you have?

06-06-2011, 04:36 PM
I have 10 evaporators, i thought that this pomp will give me constant 16bar at inlet of EVs. But i will concider puting EEV for another reasons. I have allready send a question to Hysave, we will see what they think about that.

Thanks for replay.