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US Iceman
18-05-2006, 07:06 PM
Something for your reading pleasure.:D

http://www.ept.ntnu.no/fag/tep32/Pensum/CO2.pdf

(2.5 MB)

sagittarius
23-05-2006, 10:52 AM
Hi, US Iceman. I know some about making CO2 liquid system.Because I have schemed some projects the system.One source is synthetic ammonia factory,fertilizer factory.Other source is beer,soft drink factory,fermenting process.

sagittarius
23-05-2006, 10:55 AM
I have downloaded the file and skimmed through.Maybe help me about my recently project -Nh3/Co2 refrigeration.Thankyou very much.

Andy
16-07-2006, 01:33 PM
I have downloaded the file and skimmed through.Maybe help me about my recently project -Nh3/Co2 refrigeration.Thankyou very much.

What size of a system are you designing:)

Trans or subcritcal system:confused:

Kind Regards Andy:)

Samarjit Sen
30-09-2006, 04:38 PM
Dear Sagittarius,

Could you please provide me some technical details of your NH3/CO2 projects. I require a system of 132 kw at -45 Deg. C Te. Your help shall be very much appreciated.

bruceboldy
02-10-2006, 12:15 AM
I was talking to a contractor last week who says
he is bidding a large co2 /ammonia sytem for USCOLD STORAGE IN calif they apparently have another one operating on the east coast
This cascade co2 / ammonia system design is starting to really take off it seems.

Pmap
17-04-2010, 06:41 PM
We are actually building a 170 TR CO2/NH3 system in Montreal, Canada. It is another interesting CO2 project.

GCAP CoolCast
09-11-2010, 03:05 PM
Garden City Ammonia Program's "CoolCast" (An Ammonia Refrigeration Podcast) has just released 2 episodes on CO2 cascade systems. we interviewed Greg Robinson from M&M Refrigeration.
its a pretty good episode and it talks alot about the money you can save by running a CO2 cascade system.

GCAP CoolCast
09-11-2010, 03:06 PM
i cant seem to post a link to our podcast website but you can search for us on google if you are so inclined.

Peter_1
09-11-2010, 10:54 PM
Garden City Ammonia Program's "CoolCast" (An Ammonia Refrigeration Podcast) has just released 2 episodes on CO2 cascade systems. we interviewed Greg Robinson from M&M Refrigeration.
its a pretty good episode and it talks alot about the money you can save by running a CO2 cascade system.

I seriously doubt you can save money by running a CO2 system but saving the environment, that's another story.
You have to do it for the environment and certainly not for the money.

GCAP CoolCast
10-11-2010, 01:22 PM
actually US Cold storage is showing 40% energy savings running CO2 cascade when at -40 degrees

Peter_1
10-11-2010, 03:52 PM
40%??!!:eek: We all have to change to CO2 now. Com'on be serious, this isn't true and it can't be, even not pure thermodynamical, so certainly not in a real life situation. Give us precise and real numbers and then we can talk again.
40% savings is peptalk for salesman.
I was at Atmosphere 2010, a very big congress about CO2 and there was another story heard.

GCAP CoolCast
10-11-2010, 04:41 PM
40%??!!:eek: We all have to change to CO2 now. Com'on be serious, this isn't true and it can't be, even not pure thermodynamical, so certainly not in a real life situation. Give us precise and real numbers and then we can talk again.
40% savings is peptalk for salesman.
I was at Atmosphere 2010, a very big congress about CO2 and there was another story heard.

http://mmrefrigeration.com/images/gogreen-diagram1.jpgI'm suprised that you will buy into the global warming with little or no tangible evidence but doubt energy savings of using CO2. I'll attempt to provide you with the necessary data to back up that claim.

I did make a mistake, -40 degree rooms see a 30% energy savings, you dont reach 40% untill you get below -50 degrees C

Compared with conventional two-stage or economized single-stage systems,
a CO₂ /NH₃ System uses significantly less power.

you can see some of this information at
http://mmrefrigeration.com/co2compressor.html

Also here is the PDF file M&M Refrigeration sent us containing actual data from a US Cold Storage plant they installed a CO2 system in.

http://www.gcapcoolcast.com/20101001101734532.pdf

I have spoken with the engineer of this facility before and he assures me that the savings are real.



http://mmrefrigeration.com/images/gogreen-diagram2.jpg
http://mmrefrigeration.com/images/gogreen-diagram2.jpg

GCAP CoolCast
10-11-2010, 05:05 PM
also here on slide #24 you can see they hold with the same stat of 40% savings

http://www.slideshare.net/ozonaction/1-shecco-unep-workshop-colombia-final-4665979

Segei
11-11-2010, 12:44 AM
http://mmrefrigeration.com/images/gogreen-diagram1.jpgI'm suprised that you will buy into the global warming with little or no tangible evidence but doubt energy savings of using CO2. I'll attempt to provide you with the necessary data to back up that claim.

I did make a mistake, -40 degree rooms see a 30% energy savings, you dont reach 40% untill you get below -50 degrees C

Compared with conventional two-stage or economized single-stage systems,
a CO₂ /NH₃ System uses significantly less power.

you can see some of this information at
http://mmrefrigeration.com/co2compressor.html

Also here is the PDF file M&M Refrigeration sent us containing actual data from a US Cold Storage plant they installed a CO2 system in.

http://www.gcapcoolcast.com/20101001101734532.pdf

I have spoken with the engineer of this facility before and he assures me that the savings are real.



http://mmrefrigeration.com/images/gogreen-diagram2.jpg
http://mmrefrigeration.com/images/gogreen-diagram2.jpg
Couple years ago at IIAR conference a technical paper was presented. It shown that there is no difference in efficiencies until -40F. I asked manager of US Cold Storage. Why does CO2 system has much better efficiency at part load then NH3 system? He didn't have a answer.

desA
11-11-2010, 04:51 AM
I was at Atmosphere 2010, a very big congress about CO2 and there was another story heard.

Can you perhaps tell us more, Peter?

GCAP CoolCast
11-11-2010, 01:56 PM
Couple years ago at IIAR conference a technical paper was presented. It shown that there is no difference in efficiencies until -40F. I asked manager of US Cold Storage. Why does CO2 system has much better efficiency at part load then NH3 system? He didn't have a answer.

yes that paper was written by Joe Phillis who if I remember correctly works for Frick or maybe Johnson Controls.

PG&E in california put out an 86 page report march 30 of 2009 using real world testing at a US Cold Storage facility that conflicts with Joe's report.

they did a 5 month study using flow meters, power meters, etc. they found that the CO2 cascade system using recips was at a much lower kW/Cube than a two stage ammonia system.

another independant study was done as well by Vacom Technologies. Their website is http://www.vacomtech.com/

also Greg Robinson from M&M refrigeration asked me to post his phone number so that anyone who had question or doubts about CO2's energy efficiency could give him a call for more information.

Greg Robinson
Email gregr@mmrefrigeration.com
Work 410-754-8005

Peter_1
11-11-2010, 05:42 PM
This smells more and more to hidden publicity, dressed up with nice graphs which you can make with Excel or Photoshop but no figures.
Again, it's impossible to prove this pure thermodynamically in a theoretical cycle, then how it can be done in real life with even more difficult conditions?

mad fridgie
11-11-2010, 07:31 PM
I do beleive CO2 as a broad band refrigerant is overrated, how ever, there are benefits in certain areas, the saving stated, are more likely to be achieved due to the practical aspects more than just a theorectical calculation.
For example at low temps, CO2 pipe work is much smaller than NH3, so non useful heat ingress would be reduced.
The data is raw and more than likely shows the best results.

Segei
11-11-2010, 11:38 PM
yes that paper was written by Joe Phillis who if I remember correctly works for Frick or maybe Johnson Controls.

PG&E in california put out an 86 page report march 30 of 2009 using real world testing at a US Cold Storage facility that conflicts with Joe's report.

they did a 5 month study using flow meters, power meters, etc. they found that the CO2 cascade system using recips was at a much lower kW/Cube than a two stage ammonia system.

another independant study was done as well by Vacom Technologies. Their website is http://www.vacomtech.com/

also Greg Robinson from M&M refrigeration asked me to post his phone number so that anyone who had question or doubts about CO2's energy efficiency could give him a call for more information.

Greg Robinson
Email gregr@mmrefrigeration.com
Work 410-754-8005
One end user, one contractor, one consultant. It looks like they work as a team.
I didn't see this report. However, to do it right they should compare apple and apple. It looks like CO2 recip. compressors were compared to NH3 screw compressors. Definitely, part load efficiency of recip. is better than part load of screw. However, if you put VFD for screw it will be close. Another issue is condensing pressure. NH3 system require hot gas defrost. Some people do defrost at 150 psig, others at 120 psig. I saw plant that was defrosted at 80 psig of condensing pressure. What pressure did they choose for this study? Probably, 180 psig for NH3 plant and 100 psig for CO2. In this case you will get 30% of energy savings. CO2 plant has electrical defrost. No limitation to the condensing pressure. However, they have to change elec. heaters very often.

Peter_1
12-11-2010, 11:16 AM
Segei, I agree with you, it all depends what figures you use to compare and you can prove everything and nothing with numbers. We have a quote in Belgium which says: numbers never lie but liars can count very well.

Segei
12-11-2010, 11:00 PM
I crunched some numbers to have look on 30 % improvement of efficiency for CO2 plant.
Example. 2 stages NH3 plant. Low stage: 1 compressor - 150HP. High stage: 2 compressors 125HP each(250HP stage). Total 400HP. Suction - 40F(-9"Hg), intermediate - 15F(28 psig), condensing 152 psig(85F). Assume that we install CO2 system for low side. CO2 compressor run suction and discharge the same as booster. Suction of high stage should be -6F at 9F TD. Lowering suction temp. by 1F reduce efficiency of high stage compressors by 2%. 9F - 18% or 250x0.18=45HP; CO2 compressor power is A. 30% energy savings is 400x0.3=120HP. Total for CO2 plant is 250+45+A+120=400. A=-15HP. It means that CO2 compressor should generate 15HP energy to get 30% energy savings.:eek: When load is 50%. TD is 6F. High stage power increase 250x0.12=30HP. Total CO2 plant 250+30+A+120=400. A=0. CO2 compressor doesn't use power at all. :rolleyes: This is real life refrigeration plant, these are real life numbers

sterl
01-03-2011, 02:32 AM
I know Chuck Toogood, Greg Robison and Joe Pillis quite well. They are all sincere and do not reagrd any of this as simply sales gamesmanship.

The key point on this discussion is not comparing one CS warehouse to another (unless you had a 50/50 arrangement in the same location) but comparing the performance of the CO2 cascade system with that of a well designed 2-stage R-717 plant....Because at the temperatures and scale of discussion that is the realistic competitor....

But typical cost realities does tip the balance somewhat to the CO2 system....Consider for Minus 40 Low Stage Evap, and something like 145 Psig Discharge as per Segei: the "other loads" tend to want about 20 to 22 Deg F as evap temp for docks and holding coolers....and the ideal compression ratio leads you to plus 15. To RAISE the ammonia circuit suction temp to 22 says ALL YOUR EVAPS get larger (maybe) but your compressors get smaller and more efficient.

Second we're comparing Screws functioning on Slide Valves for unloading with Recips....And boosters for Minus 40 loads R-717 are big-rotored machines. By contrast the CO2 machines are recips....And the Cost Temptation with screws it to put in as few, big machines as will carry the load without getting involved with special motors, starters and etc. For a cold storage/ Blast freezer type of application, carrying that load with a big single screw is going to leave it unloaded 99.9% of the time....And unloaded screws cost. Variable Vi and VFD drives have fixed that to some degree but the general market is still dominated currently by slide valve machines.

The part load perfromance of recips is better than screws but its also better with a low discharge superheat refrigerant..which CO2 definitely is. Further: The typical valve and similar "spring force" related pressure losses for either machine are a whole lot easier to tolerate for a compressor operating at 90 Psi Suction than one running at 11" HG...its also a simpler install; the machines are smaller therefore lighter, don't have external oil pumps or oil coolers and the corresponding plumbing, etc; and running 20 cylinders as an 8 and 2 6's gives lots of flexibility to match loads on a Coid Storage where the interior temperature is going to take 6-hours to respond to a 1-psi change in suction temperature....
But consider a pair of Spiral Freezers running near full out 16 hours a day...and then they are off....The application balance tends to tilt back toward 2-stage compression under those circumstances because you are just not going to spend much of those KWHR at 40% load so a big-rotored machine is more tolerable and the cascade HEX's temperature difference is not going to decline, which is the big player in the CO2-cascade getting better as plant loading decreases. Defrost in particular can be very different for the process scenario: those heaters for defrosting a spiral coil inside a tight enclosure get very interesting to service.... Go an additional 15 deg lower though and the economics will again point you toward the Cascade arrangement.

So its not just compressor characteristics or how good the sequencer works or how much cascade heat exchanger you can afford....but does the circuit, and its design for the initial investment, suit the entire load profile and cycle? It would certainly appear that CO2 suits the Cold Storage of a given scale..>That USCS plant in Bethlehem PA is something like 13.5 million cubic feet of storage with 54 operating truck doors and 10 rail car positions....Thats a big CSW!