Thermosiphon use (free-cooling)

[Dutchman]

The same post can also be found in "Controls"
It was a suggestion of the moderator to post it here also!

I am investigating to use 19XR (5 MW) chillers in free-cooling mode. (thermosiphon)

Open the guide vanes and control the chilled water temperature by controlling the cooling water 3-way valve.
(To be used on cruise ships)

Has anybody any experience with this?

Some questions:
- How can i open the guide vanes without going into the controls test? In other words > how can I perform this through automation?
- Does the chiller accepts this without alarms?
- Is there any problem known with oil loss during free-cooling?
- What cooling capacity can be obtained in the free-cooling mode?

Dutchman.

[nyrb]

Can't tell you if it's possible to automatically open the vanes but I highly doubt it. I have attempted this with York YK's and I can tell you that you are limited in capacity due to restricted refrigerant flow through the wheel.

Chillers intended for free cooling using "Refrigerant Migration" usually come a large refrigerant crossover pipe from the top of the evap to the top of the condenser equipped and an automated valve that opens when in free cooling mode.

With a properly designed free cooling cycle up to 40% capacity can be achieved according to most manufacturers.

See Also
http://hvac-talk.com/vbb/showthread.php?t=474812

[Dutchman]

Nyrb,

Thanks for your reply!
I appreciate that you gave me the link to the other thread.
It seems that there are very few people having experience with this kind of operation.
It is only mentioned briefly in some manufacturers documentation.
However nobody responded with longer experience.
I thought that especially in cold climates this should be applied more often, but apparently not.
It seems that I have to re-invent the wheel!
However as this is for cruiseships sailing in cold waters, I must be sure that it can work without having problems while commissioning and/or later on.

Dutchman.

[triggerhappy]

Trane makes a free cooling in a CVHE and CVHF. You should be able to check out the control stratagy\mech. sequence on them, all you have to do externally is close a set or contacts.

I realize that you were not asking about a Trane and I do not know about converting your Carrier. As you said you might have to reinvent the wheel for the Carrier or you could buy a Trane and be off to the races.

We have quite a few free cooling machines in my area which is in the mid atlantic area.

[pecmsg]

The guide vanes can be manually opened from the local controller. (I would have to look in the manual for the procedure) The problem is if this unit receives a START command with the vanes open and flow switches closed.

Is there space for a simple heat exchanger sea water / chilled water?

[AExYorkTech]

Be very careful. If enough differential can be developed the impeller could rotate the compressor without lubrication. I have done this on (2) 1600 ton York YK's.

[deux]

I um, ah, fried a 600v oil heater by running the free cooling at a wery wery low ambient temps once. Sucked the oil some where and left the heater dry.

Clean up was a B*%$h! A lesson learned.