Results 51 to 100 of 102
Thread: Carbon Dioxide Refrigeration
-
05-10-2006, 05:55 PM #51
Re: Carbon Dioxide Refrigeration
Since I am not much aware of the CO2/NH3 system and I am yet to come accross one which has been and in operation in our country, I would like to ask a (maybe a stupid) question. But as I have said earlier, that I have no experience in these systems as I have been handling mostly halocarbons.
My question is that could the CO2 in the lower stage be used as a DX system with suitable TEV and Air Cooling Unit for maintaining the desired temperature in the rooms or we have to chill the brine solution and circulate the same through Coils?
From the Forum it appears that a lot of work in this field are being done in Europe and USA.
With best wishes.
-
06-10-2006, 01:13 AM #52
Re: Carbon Dioxide Refrigeration
Originally Posted by Samarjit Sen
However, like any other refrigerant you can only apply it within the guidelines of safety and equipment limitations.
If you tried to use CO2 at normal refrigeration or AC conditions of say, -30C to +4.4C you would expect to see very high pressures. These higher pressures have to be contained by the components and piping.
On the other hand, if you were to use CO2 as we normally use common refrigerants you would find very low temperatures until you get to the triple point of CO2, which is about -67F (-55C).
Using air or liquid depends on the cooling process. In either case, air or liquid/brine are secondary refrigerants. The primary refrigerant would be CO2.
-
06-10-2006, 03:03 AM #53
Re: Carbon Dioxide Refrigeration
Thank you US Iceman. We propose to use CO2 in the lower stage and NH3 in the higher stage. The CO2 temperatures required are to be -45 Deg. C Te and -5 Deg. C Tc. There shall be three rooms. One to be maintained at - 40 Deg. C, and the other two at - 30 Deg. C. I would prefer to use a DX system as I am more aquainted with this . If you advice flooded we can also go for it.
Further you and Andy has been repeatedly emphasising on the maintaing the safety norms and controlling the pressure and temperatures. Could you please elaborate on this point, and as to how does one control the temperature of CO2 at the initial stage of commissioning and also at the idle stage.
With best wishes and thanks a lot for the guidance.Last edited by Samarjit Sen; 06-10-2006 at 03:05 AM.
-
06-10-2006, 02:37 PM #54
Re: Carbon Dioxide Refrigeration
Originally Posted by Samarjit Sen
1) You can use a smaller, separate refrigeration to coil the main CO2 vessel. This is verysimilar to the CO2 storage tanks commonly found. A small heat exchanger is installed in the CO2 tank. As this little refrigeration system operates it keeps the CO2 pressure down by condensing the CO2 vapor in this vessel.
2) You can use what we call fade-out vessels (sometimes called an expansion tank). In this example you have to provide sufficient additional volume in the CO2 system. When the system is idle, the liquid CO2 will evaporate. This causes th epressure to increase. By adding sufficient volume to the CO2 system you can limit the pressure rise so that it stays within acceptable limits (of the pressure vessels and safety relief valves).
For start up or initial commisioning you have to have the high stage system in operation first. This is the same on a two-stage compression system. You have to pull the temperature down before starting the low stage.
-
06-10-2006, 05:22 PM #55
Re: Carbon Dioxide Refrigeration
Dear US Iceman,
Thank you for advice. What now I understand that as in a R 404A/R 23 cascade system we provide an expansion tank the same process has to be adopted.
I have been enquiring in our country, and it appears that there are no CO2/NH3 Cascade plants installed as yet. Now what I would like to know that cost wise if you compare with a two stage reciprocating compressor using R 404A, what would be the position. The running cost will be lower but one must have an expert technician who has handled such plant available, which unfortunately there are none. It is the capital cost that matters. Will it be worth while to install CO2/NH3 cascade system of 130 Kw capacity in our country considering the points that I have stated above.
With best wishes,
-
06-10-2006, 11:10 PM #56
Re: Carbon Dioxide Refrigeration
Hi, Samarjit Sen
In your case I will go to your proposal (R404a) or to use 2 stage ammonia.
Down to -40C ammonia is the best one for sure even as 2 stage system, for capacity less then 750 kW!
Originally Posted by Web page
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
07-10-2006, 01:16 AM #57
Re: Carbon Dioxide Refrigeration
I'm going to agree with Josip and suggest the R-404a or two-stage ammonia system. Yes, there are some trade-offs between efficiencies and installed costs.
However, if the system is more complicated than the service people have experience with an efficienct cascade system does the owner no good. It's also probably much safer to provide a system close the experience level of the service technicians.
Josip, where did you find that web page?
Thanks my friend.
-
07-10-2006, 02:44 AM #58
Re: Carbon Dioxide Refrigeration
Dear Josip,
Thank you for the clear picture put up by you . The total refrigeration load of the system for all the three rooms is 130 kw.
Regarding the comparison of cost of the two system, it is still not clear. Could you please let me know as to the cost of whish system would be cheaper.
With best wishes,
-
08-10-2006, 10:04 AM #59
Re: Carbon Dioxide Refrigeration
Hi, US Iceman
I can agree for ***** plants, but for ammonia!?
Check this standard:
http://www.ari.org/NR/rdonlyres/193A...18/0/51093.pdf
maybe is too old, or...
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
08-10-2006, 10:35 AM #60
Re: Carbon Dioxide Refrigeration
Hi, Samarjit Sen
It is not clear for me either, but coming into new field with so many safety units, electronic devices, and so on; for me is clear: CO2/NH3 must be more expensive then the good old way: double stage R404a or ammonia.
From my previous post you can see they made comparison with two plants 750kW and 1500kW, what is about 6 to 12 times bigger then your plant i.e. under 750kW it is maybe too expensive, even to start to think about .
You can ask for an budget offer from Sabroe (http://www.sabroe.com/Information/CO2/index.html), or Gea-Grasso (http://www.grasso-global.com/Applications.14.0.html) or ask Andy for some help.
Maybe I am not right , but other guys will come with some better info...
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
08-10-2006, 06:26 PM #61
Re: Carbon Dioxide Refrigeration
The evaporative condenser project I saw was used on ***** systems for condensing temperatures about 48.8C (120F). From what I was able to learn Carrier tried this back in the 1950's & 60's. Unfortunately the condensers were never maintained and in a short time the condenser was converted into a solid block of concrete. Needless to say the condensers did not work well when that happened.
The 40C condensing for the NH3/CO2 system may have been due to higher supply water temperatures for some reason.
Or then again, someone may have tried to save money on the water cooling system with regard to the impact to the refrigeration system power use.
-
08-10-2006, 06:32 PM #62
Re: Carbon Dioxide Refrigeration
Hi Josip,
I just looked at the ARI standard you posted. This standard applies to the actual process used for rating the compressor performance and the tolerance for capacity & power deviation from published to test data.
It is not an actual design document for ammonia refrigeration systems.
You might see some ammonia systems using air-cooled condensers on some facilities such as atmospheric ammonia storage. In those examples, the condensing temperature are quite higher than 35C.
-
08-10-2006, 08:56 PM #63
Re: Carbon Dioxide Refrigeration
Hi, US Iceman
Agree 100%, it is not actual design document, what I was trying to said, it is possible to start design with CT at 35C, 13.5Bar i.e. lower energy consumption. If we have too hot water or too high temp with high humidty (some part of the year, in some part of the world) we will have, for short time higher CT.
With design of EC to work with CT at 35C, there should be more capacity in hard weather condition, then if design is for CT at 40C.
In another hand I was working with ammonia air condensers (CT=50C, 20Bar) in Saudi Arabia (still in use because there is not water available) but it is very hard for compressors and you need a lot of money for el.power .
To design a low energy consumption plant for sure is not to start with high condensing temp/press.
Of course there were and there are some facilities with condensing temp higher of 35C, due to process request but that is another story.
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
08-10-2006, 09:12 PM #64
Re: Carbon Dioxide Refrigeration
Hi Josip,
I agree 100% with what you mentioned.
I would like to know the reasoning behind th euse of 40C CT on ammonia for the NH3/CO2 system you posted earlier.
I normally use 35C CT as the starting point in the design, but also include greater allowances for higher entering wet bulb temperatures.
Most of the weather data I've seen for the US is of course based on the ASHRAE data. Then we have to select the percentage factors for the actual design conditions.
I prefer to use the accumulated weather data that shows the actual values. As you know, the weather is always hotter or more humid for some period of the year than what the weather data suggests.
For HVAC purposes this data is probably OK. However, for process requirements I would rather have the equipment sized to run in the extreme cases.
If we save money on the installation and equipment costs, this is a small portion of what the "real costs" are for production cooling.
The way I look at this is... It might be cheaper to use the "design conditions", but if the refrigeration system has to run at partial capacity due to high discharge pressures, who looses?
I can certainly understand the logic in using AC condensers in Saudia Arabia at first glance. But, is the quantity of water that might be needed for the evaporative condensers really that limited?
What do they do for all of those large HVAC chillers? Are they AC also?
-
08-10-2006, 10:02 PM #65
Re: Carbon Dioxide Refrigeration
Hi, US Iceman
It seems we are coming back to another question again:
-first cost or running cost
Agree with you to use design conditions for HVAC units but for refrigeration we have to use extreme conditions and try to design refrigeration plant to work with max COP even with partial load in extreme conditions.
All AC in SA are quite old and nowdays they start to change them with EC for ammonia plants.
HVAC chillers still today are with AC, because EC is more expensive. ***** is another story because we cannot beat them with the prices but you know that very well.
They approach with; we have green *****, not harmful, extra effective almost good as clear air you need for breathing and all that story to make a profit (and they are good in that). Another problem is a lack of knowledge about ammonia
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
08-10-2006, 11:47 PM #66
Re: Carbon Dioxide Refrigeration
Hi Josip,
Here is some information you can use with your next discussion of R-22 with the HVAC people.
This information comes from the Material Safety Data Sheets (MSDS) for R-22. I found this for another discussion taking place with some other gentlemen.
“Flash Point: Will not burn
Auto-decomposition: 632 C (1170 F)
Other burning materials may cause "*****" 22 to burn weakly. Chlorodifluoromethane is not flammable at ambient temperatures and atmospheric pressure. However, chlorodifluoromethane has been shown in tests to be combustible at pressures as low as 60 psig at ambient temperature when mixed with air at concentrations of 65 volume % air. Experimental data have also been reported which indicate combustibility of "*****" 22 in the presence of certain concentrations of chlorine.”
This does not even include the comments about disrupting the heart rate, potenital oxygen deprivation, or other fun things that can happen.
-
09-10-2006, 06:44 AM #67
Re: Carbon Dioxide Refrigeration
Dear Freinds,
Although I have hardly done any projects with NH3 and none involving CO2, but after seeing the datas that you all have provided and the details taught to me, I am really facinated with this refrigerant. You people have been a tremendous help to me and I wish some of my coleagues in our country could take advantage and learn a lot of things from this thread. I am now very keen to execute some contracts in CO2/NH3, and would request you all to please provide me some more technical details on the same.
Regarding the Condensing temperature of 40 Deg. C, we use it at places where the ambient are very high which are generally in the part of Northern side of our country. There are a number of projects where Condensing is taken as 35 deg. C. The ambient conditions in our country vary very much.
With all the best,
Samarjit
-
09-10-2006, 04:38 PM #68
Re: Carbon Dioxide Refrigeration
One of the items I tend to use for designing systems is an upper limit for condensing temperature on ammonia systems of 33.8C (93F).
35C (95F) is the normal "design" temperature commonly used, but I seem to remember some factors that can be minimized by a slightly lower condensing temperature when evaporative condenser are used.
It has to do with water quality and the chemical treatment of the recirculated water. It has nothing to do with Legionella bacteria, only scale formation.
I'll have to do a little research to refresh my memory. I will add these comments later.
-
09-10-2006, 09:48 PM #69
Re: Carbon Dioxide Refrigeration
Hi, US Iceman
You are right, I remember the past time when we design EC with desuperheater section (above water eliminator) where the inlet gas temperature were reduced to prevent extraction of calcium carbonate from cooling water. In that time water was treated only with NaCl to be soft, no other chemicals were added.
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
09-10-2006, 11:18 PM #70
Re: Carbon Dioxide Refrigeration
Originally Posted by Josip
The desuperheaters do accumulate some very small amounts of scale. But since they are in a humid air, rather than complete liquid water this makes a big difference.
I think it is a combination of discharge temperature in the tubes and the actual water temperature. Where both are high, the scale formation is much worse.
This makes another good example of why we should keep condensing temperatures/discharge pressures lower.
-
19-10-2006, 06:16 AM #71
Re: Carbon Dioxide Refrigeration
hi,everyone
i am a new engineer, and now working on designing co2 liquifier, could someone help me especially on calculating the co2 condensation heat transfer coefficients in-tube? and more information on the shell and tube exchanger design? thanks a lot!
best regards
-
19-10-2006, 09:02 PM #72
Re: Carbon Dioxide Refrigeration
Another plus for desuperheaters is that in winter the airflow leaving the condenser is slightly heated away from the saturation curve so that when mixed with the lower temperature ambient air it is kept clear of fogging conditions. Hence reducing the annoying (to some) plume of steam.
mick
-
12-11-2006, 08:39 PM #73
Re: Carbon Dioxide Refrigeration
hi i'm new at this forum but i was sent to a co2/r410a system becase of high pressure alarm in the r410a system.After 3,5 hours of checking i got a bit frustated and opened a liquid service valve for 2 seconds and all i saw was snow .Reason was a leaking heat exchanger(co2 condensor/r410a evaperator).Now when you try to recover 2500 kg r410a when it's mixed with co2 you will find enorm pressure in the tank All in all all the oil changed cleaned the inst. with n2 new ***** and co2(4000kg) and 60 hours later with 3 engineers inst. was up and running.
Just to point out one of the riscs
-
12-11-2006, 08:53 PM #74
-
17-11-2006, 03:54 AM #75
Re: Carbon Dioxide Refrigeration
hi,all.
Long long long time no see!
I am missing in the nh3/co2.
sagittarius
-
22-06-2007, 11:29 AM #76
Re: Carbon Dioxide Refrigeration
HAI, iam refrigeration engineer in uae .please send me a
drawing digrem in co2 and ammonia pumping
"xxxxxxxxxxxxxxx".Last edited by US Iceman; 22-06-2007 at 03:22 PM. Reason: removed email address to prevent spam email. Please use the private message system for sending and receiving information.
-
12-08-2007, 01:24 PM #77
Re: Carbon Dioxide Refrigeration
Hi fellows
I am interested for Co2 / NH4 Cacade Refrigeration cycle. If any body have a case study with system details for any existing refrigeration plant please let me know.
-
12-08-2007, 06:30 PM #78
Re: Carbon Dioxide Refrigeration
Hi Kawaljeet Singh,
It is very difficult much information on CO2/NH3 at present. However for your information a portal has been opened in Germany very recently. You may visit the same at www.co2refrigeration.com . Further Danfoss and Bock have done and are still working on this application. Just for your information the cascade system is just like anyothe cascade system. Here the NH3 is used in the High Stage and CO2 is used in Low Stage. CO2 has the pressure of building up a very high pressure at a higher temperature and as such to control the pressure is important. If you study this thread from the begining you will get a lot of reply to your questions.
-
23-09-2007, 11:04 PM #79
Re: Carbon Dioxide Refrigeration
I would be interested in the drawings for the cascade system. Please send them to me. I do not know how to email you directly. Can you find me?
Last edited by Buckiesr; 23-09-2007 at 11:45 PM. Reason: Please use the private messaging system so spammers do not get your email
-
23-09-2007, 11:09 PM #80
Re: Carbon Dioxide Refrigeration
Our plant manager is terrified of NH3, he says it all has to go. he wants all co2. I surmise that in the long run, more deaths will be attributed to co2 deaths than ammonia. (due to sensory properties.)
So he asked me, can we put smell in it like they do natural gas? I don't have a clue if it can be or is done or if anyone ever tried. I suggested maybe we should try color, then when you see purple haze you vacate.
WM
-
23-09-2007, 11:15 PM #81
Re: Carbon Dioxide Refrigeration
Hi Buckiesr,
Welcome to the RE forums.
The manager is using some of the most convoluted logic I have heard yet.
Get rid of the smelly refrigerant, spend several million dollars, use a different refrigerant and then make that refrigerant stink???
That has got to be one of the strangest arguments I have ever seen.If all else fails, ask for help.
-
23-09-2007, 11:50 PM #82
Re: Carbon Dioxide Refrigeration
Once people get ideas in their head they are closed to reason. I think that co2 will indeed be regulated jsut as much as other refrigerants because the real issue is about money, not so much environment. I usually, "it is because someone's brother-in-law needs a job!" (i.e. it is really about money.)
When
-
23-09-2007, 11:56 PM #83
Re: Carbon Dioxide Refrigeration
When the industry lowers the use of the other highly regulated refrigerants, then they will go after the others. co2 is a big issue in emmisions and might be in other industries except for the fact that production of biofuels are producing the greatest ammounts of co2, and they are funded by the biggest money holders who also have the most connected lobiest. Laws will be stimed until the lobiests stand down. Not to soon I suppose that would mean. But before long they will go after co2 also.
WM
-
24-09-2007, 12:06 AM #84
Re: Carbon Dioxide Refrigeration
Iceman, you are in the US, the plant manager has discounted my observation that nearly all of the knowledge with co2 has been acquired in Europe. He says we now know this is not true and that there is substantual project development in the US. He says they are building tons of new facilities in the US using only co2 systems. Much safer, much cheaper, much more effecient. I know he is being fed a lot of stuff from a company that wants to contract the new quick freezer facility we would like to add to our existing ammonia refrigerated plant. I can't seem to even get anyone to think about how we could design the new freezer in such a way that it would help the existing system and solve some of the existing complications. When we met on this issue the other day the IRR numbers were mostly in the red. the one option that was not in the red was pretty low. how many total co2 plants do you know of in the US currently? I keep telling him it is to stinkin cold for what we need. I just consult, I am not the decision maker. but I will inherit whatever we install.
WM
-
24-09-2007, 12:27 AM #85
Re: Carbon Dioxide Refrigeration
Check out this one companies idea on the "future"
http://www.gartner-refrig.com/whatsnew/index.asp
-
24-09-2007, 01:16 AM #86
Re: Carbon Dioxide Refrigeration
Buckiesr,
All of the reasons you are stating from your manager are the typical marketing BS used by everyone who wants to sell against ammonia.
Refrigeration systems are as safe as they are designed, maintained, and operated. The refrigerant is only a small portion of the selection process.
Efficiency is one of those over-used words that people throw out when they want to get someones attention.
My guess is there is not more than several dozen large CO2 systems installed right now. There are some benefits to using this, but I think the best selling point is the use of CO2 reduces the total ammonia charge.
People tend to think this is a good thing if it allows them to get out of a PSM or RMP program. Those are the same people who would not fix or maintain a refrigeration system until it blew up too.
Originally Posted by Buckiesr
Is IRR who I think it is?If all else fails, ask for help.
-
24-09-2007, 01:49 AM #87
Re: Carbon Dioxide Refrigeration
IRR = Internal Rate of Return This is one method for calculating the return on an investment. Not the most accurate way in my opinion. It is really easy to make mistakes and arrive at a false return. There can be multiple IRRs for the same input. The ROI (return on investment) is normally used and is how long will it take for the savings on the project to pay for the investment, including taxes, depreciation cost for the firm to borrow the investment money. By comparing what the end result ends up compared to what they are paying their investors, and/ or what they calculate they could make by investing in some other opportunity. (this is called Opportunity Cost). I bet you already knew all of that I wanted to see if I can remember it still.
WM
-
24-09-2007, 04:52 AM #88
Re: Carbon Dioxide Refrigeration
Sorry, I didn't mean to turn that into a memory test. You did OK though.
It would be interesting to see the actual power input differences between the NH3 and CO2 systems. It can't be too much if the economic costs were in the red.If all else fails, ask for help.
-
24-09-2007, 08:23 PM #89
-
24-09-2007, 11:03 PM #90
Re: Carbon Dioxide Refrigeration
Hi, Buckiesr
Welcome to RE
I am so sorry about you having that type of person for manager, your life must be very complicated... I must ask is he/she younger or older of you?
.....agree with you about accidents with CO2...for me is normal if lot of people use something (electricity, gas, cars...etc) there should be more accidents relating to that -whatever is...
I assume that you have an old ammonia plant with many problems due to bad design, maintenance, installation, etc (maybe I am wrong), but that is not and must not be a reason to not use ammonia especially in industrial area....
Coming back to CO2....
Originally Posted by Buckiesr
Originally Posted by Buckiesr
Originally Posted by US Iceman
Originally Posted by Buckiesr
but to install one "safe, cheap, efficient" plant using too much energy to run it, we must burn more fossil fuel and produce much more CO2 and release it in atmosphere, is that logical - safe, cheap or efficient???
Best regards, Josip
It's impossible to make anything foolproof because fools are so ingenious...
Don't ever underestimate the power of stupid people when they are in large groups.
Please, don't teach me how to be stupid....
No job is as important as to jeopardize the safety of you or those that you work with.
-
25-09-2007, 12:02 AM #91
Re: Carbon Dioxide Refrigeration
Originally Posted by Josip
The few adverts I have seen for CO2 systems have not provided very much raw data. I'm sure you realize any numbers provided may be suspect, because someone is trying to sell something.If all else fails, ask for help.
-
25-09-2007, 12:44 PM #92
Re: Carbon Dioxide Refrigeration
I am so sorry about you having that type of person for manager, your life must be very complicated... I must ask is he/she younger or older of you?
.....agree with you about accidents with CO2...for me is normal if lot of people use something (electricity, gas, cars...etc) there should be more accidents relating to that -whatever is...
RE: Josip. I assume that you have an old ammonia plant with many problems due to bad design, maintenance, installation, etc (maybe I am wrong), but that is not and must not be a reason to not use ammonia especially in industrial area....
My system is nearing 50 years old. But We have retrofitted many things to keep it up. I keep fining ways to gain effeciencies. To answer your question. The manager is near my age. I think older but not positive. He has read about bad things with ammonia. He is inherently fearful of it that is all. Ignorance can cause great anxiety in people of great responsability. We have had several deaths in the industry in the US this past several years. His fears are partly due to this. sales people like to play on fear if they detect it. They lead him along but now they are promoting a seald ***** or ammonia system for the new freezer and not co2. The other day one of my co-managers made a comment in a business meeting concerning the Engine Room here. he said that he has seldom ever walked through an engin room for an ammonia system and not been able to detect the slightest smell of ammonia but our is the exception. "that has to testify to our Engineer" I liked that comment. I try to keep the Engin Room as nice as I can, even at 50+ years old.
WM
-
25-09-2007, 01:09 PM #93
Re: Carbon Dioxide Refrigeration
Jesip
If you can know what the costs will be innitionally, and future costs, as well as the returns, then you can do an IRR. However when your guessing, it is tough. You sell your idea to the investor by showing what the return on his investment will be. it is like saying: If you give me this ammount of money to invest in my project, I will give you a return on that investment of ??% which will get all of your investment back in you hands in this much time, and then you will make all profit after that for the life of the project. Projects have a set ammount of time to depreciate completly out. companies set that time. ours is set for 7 years. My projects need to pay back the investment in 5 years or less to look good. calculating the IRR is the method of showing them how much this project is worth to them. If I set up the figures and add future costs to the project I can show more than one IRR. If you only used money you already have there is no IRR. Every time there is a sign change (putting in money-a cost- that is a minus, when you get money back- that is a plus. if you put in more money, that is what a sign change is; going from taking out to putting in.) I buy a flashlight for 5.00; -5.00, I save .50 on each candle I don't have to buy because I am using the flashlight for light. But after 10 candles worth of light, the batteries run down. Now I have to buy new batteries at 3.00. so -5.00 buy flashlight, +.50X10saved not buying candles, -3.00 new batteries. that is a sign change. Every time you have to add investment money to keep it going the IRR for the project would change. My point was that I can actually arrive at the number I want to show by playing with the numbers. I was saying this is why it is not the best method for calculating the return on an investment. I recomend that the ROI be used to demonstrate the value, present and furture, of a project.
I hope that helps you understand what I was saying.
WM
-
30-09-2007, 04:12 AM #94
Re: Carbon Dioxide Refrigeration
I'm sorry if I messed up sight. No posts since my last?
WM
-
14-10-2007, 10:44 AM #95
Re: Carbon Dioxide Refrigeration
Incressed the co2 pressure to 40 barg and use the glycol oil cooling system via heat exchanger to incress the temp to get around 20 to 30 deg C and we defrost the coolers.
-
05-11-2007, 06:42 PM #96
Re: Carbon Dioxide Refrigeration
I want to design a small co2 cooling system and I don t know how to start, I need to select all the equipement.
Can some help me !
-
11-11-2007, 05:52 PM #97
Re: Carbon Dioxide Refrigeration
what is the application? evap temp? capacity in kw?
-
05-03-2008, 02:20 PM #98
-
27-05-2008, 11:22 PM #99
Re: Carbon Dioxide Refrigeration
Andy, I have some questions, because a customer said in USA existing plant for precool with CO2 or N2 the fruit that enter to the IQF. You have some experience with that??.
-
06-06-2008, 10:26 AM #100
Re: Carbon Dioxide Refrigeration
Sorry to interrupt your technical discussion, but this is absolutely worth to be mentioned here: Have you seen the major announcement by the Coca-Cola CEO, that Coke will use 100,000 CO2 beverage coolers by 2010? He said, CO2 is safe, reliable, and more efficient than HFC. I am not allowed to post direct URLs yet but the story is quite good: r744.com/article.view.php?Id=666&latest=1
Sounds like a real commitment this time... Let's see if others get moving soon.
Similar Threads
-
advanced refrigeration technology
By Lc_shi in forum FundamentalsReplies: 10Last Post: 16-02-2011, 05:22 PM