Free Cooling - Refrigerant Migration
Just finished an 8 hour experiment at customer's request to see if we could get free cooling from their existing arrangement. I had read up on the subject but never had the opportunity to try it and I was surprised by the outcome.
Customer has large chiller room with 5 - 2000 ton YK's and 1-1000 ton YK. Upon arrival 1000 ton chiller running at no production winter load of 60%. Forced flow over multiple towers to drive condenser water temperature to low 40's and turned off chiller. Opened valves (chilled and condenser) on 2 idle 2000 ton machines, vanes and hotgas valves were manually driven 100% open and monitored operation. Condenser water continued to fall to 37 (28 ambient today) and chilled loop temp maintained 40f all day long, no tower fans and the same amount of pumps running.
Anybody else ever encounter this type of cooling just utilizing natural convection from refrigerant flow to condenser from evaporator and how much capacity were you able to attain? Quick calculations come to about 400 tons of free cooling and a power reduction of about 430 KW/hr.
Once the test was complete the owner wanted the chiller put back online, YK's never cease to amaze me. Started and ran with 38 entering tower water and didn't make any fuss.
The link shows in theory what we manged to accomplish with standard factory equipment.
Worked with free cooling on 2 or 3 occasions. Most notably, got 1300 tons out of an idle 4000 TR machine - pretty cool what you can do without technology or moving parts.
p.s. That's a pretty ugly wheel you got there.....
Out of curiousity was your 4000 TR machine equipped for free cooling with a equalizer line from top of the evap to the top of the condenser? I feel we have more capacity available here but wonder if we're limited by the volume we can get through a 3 inch hot gas line and the compessor wheel.
Originally Posted by klove
As far as the ugly wheel goes 120 degree tower water can kill a YK, especially without surge protection.
i have only encountered free cooling machines that were designed to be free cooling machines...they have valves that open automatically when in free cooling mode. you would get about 40% of machine rated capacity.
the only concern that i would have with your "more natural" set up is somebody make sure that you have your evaporator flow! we have had a "non free cooling" machine freeze up and bust a bunch of evaporator tubes when someone turned on the condensor pumps (closed loop glycol) without turning on the chiller in very cold weather...they estimated that they lost about 20,000 gallons of water through the rupture disk before anybody noticed.
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All of the machines that we actually left running in a free-cooling mode were designed and set up as such, with associated controls and full flow vent lines and valves. I've also shown some customers that it can be done by simply doing it the same way that you did. They each and every one were thoroughly impressed - not enough to spend a truckload of money to retrofit, but impressed none-the-less.
Originally Posted by nyrb
Have that where I'm at,along with heat exchangers.
The current way it's staged now per the engineer, is the free cooling (through the chillers) is used within about a 5 deg band based on OD temp and load, then if OD drops lower or load grows then its all on the heat exchangers.
This is the first place I have seen utilising both of these, and this is the first winter for it (new facility).
So far it's been good, with some tweaks.
Don't want to get too far off topic but that link is a pretty cool website.
Originally Posted by nyrb
All my leon freaked out!
I totally agree on that point because if you had a power failure or chiller trip on overloads or fuses you would freeze up your chiller barrel for sure.
Originally Posted by jayguy
I have a plant with 2 1200 YK's, without the free cooling vent line. I run them in make-shift free cooling some nights (shut down chiller, and open vanes and hot gas bypass), and am able to achieve about a 5 deg approach between Condensing Water supply, and Chilled Water Supply up to about 20% of the chiller's capacity. The savings, I find, are minimal, as the biggest load under these conditions are the condensing water pumps, and tower fans, regardless of whether the chiller is running or not. I'd be able to save a lot more if I could cool the chilled water directly with the outside air, and just shut down the towers entirely. It's nice to keep the runtime down on the chillers though, so there is at least some minimal savings there.