Do you have any experience with this system?

[lana]

Hi there,

Please have a look at the picture.

It is a some kind of liquid circulation system but without compressor.

From the condenser liquid R134a goes into the receiver then it's pumped through the evaporator. Mixture of liquid and gas comes out of the evaporator then goes in to the condenser.
Through the condenser 7°C cold water is circulated (from a chiller).

This system works and one of the Datacom colling system manufacturer introduced it into the market.

I would like to know experts opinion on the followings :
1- Efficiency (energy ...)
2- Advantages
3- Disadvantages

Thanks for your kind attention.

Cheers
LANA

[mad fridgie]

Almost a perfect system!

[chilliwilly]

Interesting, whereabouts did you get this drawing from? It looks like the kind of thing you would see in a multi choice exam, representing one of the incorrect answers.

Maybe that pump symbol does actually represent a compressor. But looking at the water cooled condenser, you would be increasing the risk of liquid slugging the compressor because of its position. Unless of course its a non recipricating type.

And judging by the fact that there's r134a in there, it would need a compressor in there, and not just a circulating pump. So maybe the symbol does represent a compressor. But the system efficiency is very poor.

Even a flooded evaporator has the condensor after the compressor. I once saw a very crude designed sweet water system set up similar to this, but it didn't work very well. Infact they took it out and put a proper one in.

[lana]

Interesting, whereabouts did you get this drawing from? It looks like the kind of thing you would see in a multi choice exam, representing one of the incorrect answers.

Maybe that pump symbol does actually represent a compressor. But looking at the water cooled condenser, you would be increasing the risk of liquid slugging the compressor because of its position. Unless of course its a non recipricating type.

And judging by the fact that there's r134a in there, it would need a compressor in there, and not just a circulating pump. So maybe the symbol does represent a compressor. But the system efficiency is very poor.

Even a flooded evaporator has the condensor after the compressor. I once saw a very crude designed sweet water system set up similar to this, but it didn't work very well. Infact they took it out and put a proper one in.

Thanks for the reply.

NO there is no Compressor.
The compressor is in the chiller which supplies the cold water for the condenser. The symbol is for the pump.

This system is in a Datacom center which supplies four evaporators.

I repeat : there is no compressor and the liquid is circulated by a pump.

Cheers

[desA]

There is little, or no cycle to speak of. Plot the operation out on a log(P)-h diagram to see this.

I would class it as a glorified heat-pipe arrangement, with forced circulation.

[desA]

[desA]

@Lana. If you have additional details on this working system, please share these with the forum.

[Paco villarreal]

Hello lana.
Ok, the concept is interesting, but honestly not see the case of such a system when you already have coold water to 7 ° C.
Efficiency: I don't think is very good R134 57Psi is 15.5 ° C temperature of evaporator.
The KW which the system is not spent them is spending the chiller. It could possibly be having more consumption of energy due to the consumption of the pump.
Example: If your system is 5TR. To the source of coold water to cool the condenser chiller you we are removing approximately the 5TR.
Advantages: no
Disadvantages: a system of that worry leakage and other matters, possibly more consumption kW.

Personally I would take better coold water to 7 ° C from chiller and install an air/water evaporator, to send coold water to him.
It is my point of view.

Best regards and Apologies that my English isn't very good.

[mad fridgie]

It is a high density sensible energy chiller, liquid over feed through the evap. (no need for superheat) Because it is a datacom centre, you do not want "water" any where near the electronics.
Slightly less efficient than a DX system, but gives a better control constant.

[Segei]

This is like second brine loop. You will have temperature difference between suction to water(chiller) and temperature difference between water to condensing temperature(this loop). This is double inefficiency.

[lana]

Thanks everybody for your comments.

As mentioned by others, It is interesting but still I don't get the point of using this system.
In datacom centers, DX systems are used and tell you, nowadays they use water as cooling medium, i.e. inside the coil water is circulated . So much for no water near the equipment.

As for the energy consumption I don't see any benefit, because energy is used in the chiller instead.
As for the initial cost it is much more expensive than a simple DX system.

Anyways, thanks guys for your ideas.

Cheers
LANA

[mad fridgie]

So what do you want leaking on your electronics, "water" or "refrigerant"!

[desA]

Folks - this is not a refrigeration system as you know it. There is no energy advantage at all. It is merely an energy transport device - hence the name - heat-pipe.

Essentially, the pump-around circuit mechanically forces the return liquid flow from the condenser back to the evaporator, rather than relying on a complex wick system.

I'm interested in understanding the pipe dimensions between evap & condenser. This is critical in terms of preventing sonic choke in this device.

[lana]

Hi there,

Whoever is interested have a look at the technical doc :
http://www.liebert.com/common/ViewDocument.aspx?id=1213

They call this system "XD system". The document name is:
"Technical Note : Key Points of Design, Installation and Maintenance for Configuring Liebert XD Systems"

Any more comments are welcome.

Cheers

[desA]

Excellent information. Thank you so much, Lana.

[Magoo]

Lana
Looks like a thermosyphon type system quite often used in food processing aplications, where the heat load is high and ambient wet buld is relatively low.
7 degrees would be a non event though, unless if the night time temps were nut cracking cold.

[lana]

Lana
Looks like a thermosyphon type system quite often used in food processing aplications, where the heat load is high and ambient wet buld is relatively low.
7 degrees would be a non event though, unless if the night time temps were nut cracking cold.

Hi Magoo,

I am not sure what you mean but thermosyphon does not have a pump, has it?

In the condenser cold water is required because entering pressure of R134a is not high enough (like compressor discharge) therefore, for condensation to occur we need colder medium.

Cheers

[Allrounder]

I think you will find the system is absorbing the heat coming off the servers (at above 30c) and then stopping that heat going into the room. This is a far more efficient way of cooling, the room will then need much less conventional cooling. The unit will also run 100% sensible again making it more efficient.
Its a very clever arrangement.