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  1. #1
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    Refrigerants and The Environment


    Economically sustainable - for mother nature

    The refrigeration and air conditioning industries effect the environment all over the world, both directly with emissions and indirectly with their power consumption. The use of ozone destructive CFC's is not permitted in the developed industrial countries and the fade out for HCFC's is already decided. The discussion about the global warming effecting HFC refrigerants, however, is still in progress. These so called replacement refrigerants, like bromine and chlorine free HFC's, do not harm the ozone layer but have unfavourably high global warming potential. For this reason, the 1997 Kyoto Protocol called for a worldwide reduction of these greenhouse gases. Even new alternative refrigerants and blends like R134a, R404A and R507, each of them being HFC's, are less attractive for forward looking applications due to their relatively high greenhouse effect.

    Against the backdrop of global efforts to protect the environment, natural refrigerants are the obvious choice as a sustainable and ecological alternative to HFC's. All natural refrigerants occur in nature's material cycle even without human interference. They do not contribute to the depletion of the ozone layer and have no significant influence to the greenhouse effect substantially less then synthetic refrigerants like HFC's. The natural refrigerant ammonia and carbon dioxide are highly important to the economy. Natural refrigerants have been used in food production and storage for more than 100 years. In recent times, technological progress and innovations have added new fields of application.

    For all these reasons we are convinced that the natural refrigerants ammonia and carbon dioxide will be the most important for the future....................
    Find this at http://www.grasso-global.com/Refrigerants.26.0.html

    coments



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    Re: Refrigerants and The Environment

    Natural refrigerants have been used in food production and storage for more than 100 years. In recent times, technological progress and innovations have added new fields of application.

    For all these reasons we are convinced that the natural refrigerants ammonia and carbon dioxide will be the most important for the future....................
    I could not have said this any better!
    It is very interesting to see CO2 returning to favor.

    I think what we will see is more CO2 systems being used for very low temperature applications as a cascade system. This would help to make the low-stage compressors smaller and probably more efficient.

    Then we can use the ammonia system for the cascade condenser and the remaining higher temperature loads.

    One question I am thinking about is how do we defrost coils when we use CO2? Water defrost???

    What have you guys seen?

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    Re: Refrigerants and The Environment

    Quote Originally Posted by US Iceman

    One question I am thinking about is how do we defrost coils when we use CO2? Water defrost???

    What have you guys seen?
    That is the secret that makes it all work.

    Star Refrigeration have a system using pumps to boost the R744 to a pressure several bar above the R744 condenser pressure, before they vapourize the liquid to produce the hot gas (I think patent pending is what they say)
    Others use electric heater, or a second coil in the evaporator with warm glycol defrost pumped in for defrosting

    Kind Regards. Andy

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    Re: Refrigerants and The Environment

    As you say, this is the hard part. The pumps would have to boost the pressure to a fairly high pressure, so that the flash gas formed during the expansion process would be able to provide defrost gas above 0C, right?

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    Re: Refrigerants and The Environment

    For higher temperature applications, could water be used as a refrigerant? Obviously, it'll be difficult to find a compatible oil, but it could work, right?

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    Re: Refrigerants and The Environment

    Hello,

    see this,

    www.airah.org.au/downloads/2002-06-02.pdf

    there are also some other systems like Andy said. Using CO2 people will find out how to make safety and cheap defrost

    Star882 can you explain what did you mean about water as refrigerant. Why you need compatible oil?

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    Re: Refrigerants and The Environment

    Couldn't water be used as the refrigerant in a medium/high temperature application? (I have heard about a very large A/C that used water as the refrigerant.) The problem with the oil is that common refrigeration oils react with water.

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    Re: Refrigerants and The Environment

    I theory there is no reason you couldn't use water as it has a high latent heat of vaporisation, but obviously the normal boiling point is high and there's the oil question. I think there is a design kicking about somewhere which I could look up, it's a bit different to usual, think it uses something resembling a big fan.
    It's a lovely day to pump some gas

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    Re: Refrigerants and The Environment

    Quote Originally Posted by star882
    Couldn't water be used as the refrigerant in a medium/high temperature application? (I have heard about a very large A/C that used water as the refrigerant.) The problem with the oil is that common refrigeration oils react with water.
    Quote Originally Posted by Johnny Rod
    I theory there is no reason you couldn't use water as it has a high latent heat of vaporisation, but obviously the normal boiling point is high and there's the oil question. I think there is a design kicking about somewhere which I could look up, it's a bit different to usual, think it uses something resembling a big fan.
    Very interesting new idea, realy working but.....

    http://st-div.web.cern.ch/st-div/wor...ogy/JacekK.pdf
    http://www.arti-research.org/researc...s/10080-es.pdf
    http://criepi.denken.or.jp/en/e_publ...03setsubi3.pdf

    So many pro&contra let's see

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    Re: Refrigerants and The Environment

    Water as a refrigerant???

    Why not? The evaporating temperature would have to be above 0C, but anything else above this temperature should be OK.

    For oil selection you would have to find an oil that works and is compatible with H2O for the operating conditions and meets the compressor viscosity requirements.

    Sounds a lot like a vacuum cooling system or a steam system.

    In both of these water is the primary refrigerant.
    Last edited by US Iceman; 09-03-2006 at 09:21 PM. Reason: spelling

  11. #11
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    Re: Refrigerants and The Environment

    Hello,

    Yes, I understand all of that but as you can see it is still under researching.

    Using turbocompressors (like with old R11) or huge vacuum pumps.... whole plant is quite huge and very expensive, yet.

    Maybe one day will be possible to use magnetic bearings for compressor and maybe some other improvments...

    For all temperatures around and above 0C sounds very good.

    Until that I prefer to do that on the old fashioned way .
    Definitely something what people can use in the near future.

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    Re: Refrigerants and The Environment

    I agree that using water would be a very expensive task.

    In principle it sounds very attractive, but in application it is a different story.

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    Re: Refrigerants and The Environment

    Hello

    At LEGO in denmark Sabroe+Soeby(now York koleteknik) have at large A/C system using H2O (R718)

    “A 2682 hp Refrigeration Plant Using Water as Refrigerant,”

    or se this:
    http://www.arti-research.org/researc...0010-final.pdf

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    Re: Refrigerants and The Environment

    Quote Originally Posted by US Iceman
    As you say, this is the hard part. The pumps would have to boost the pressure to a fairly high pressure, so that the flash gas formed during the expansion process would be able to provide defrost gas above 0C, right?
    Pressure is about 6 to 8 deg c from memory, although it is highly superheated, I suppose you could use a lower saturation pressure, say -5 deg c, but you would need very large volumes of highly superheated vapour to perform any sort of defrost.

    Kind Regards. Andy

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    Re: Refrigerants and The Environment

    Quote Originally Posted by kasperDK
    Hello

    At LEGO in denmark Sabroe+Soeby(now York koleteknik) have at large A/C system using H2O (R718)

    A 2682 hp Refrigeration Plant Using Water as Refrigerant,

    or se this:
    http://www.arti-research.org/researc...0010-final.pdf

    The worlds MAD I say MAD

    You would want a non corrosive compressor, otherwise the steam condensate would eat the compressor from the inside out. I suppose that goes for all the system components

    Kind Regards. Andy

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    Re: Refrigerants and The Environment

    Hi Andy,

    I suppose you could use a lower saturation pressure, say -5 deg c, but you would need very large volumes of highly superheated vapour to perform any sort of defrost
    How do you defrost the coil with -5C vapor condensing? This could certainly warm the coil up to -5C, but the frost is still solid, not liquid.

    Even with a lot of superheat at a -5C saturation pressure, the gas will still want to condense at -5C right?

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    Re: Refrigerants and The Environment

    You are right Ken - the liquid needs to be pressurised to about 45 bar before it is vaporised to create the "hot gas". For CO2 45 bar (about 675psig) is about 10C (50F) saturated, so the defrost works a treat. This seems to be much more efficient than a typical ammonia hot gas defrost, but I don't know why. Perhaps there is a lot less gas passing through the evaporator without condensing, so less dummy load on the compressor when CO2 is used?


    Cheers
    Andy P

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    Re: Refrigerants and The Environment

    Quote Originally Posted by Andy P
    This seems to be much more efficient than a typical ammonia hot gas defrost, but I don't know why.
    I think you answered your own question Andy.

    Perhaps there is a lot less gas passing through the evaporator without condensing, so less dummy load on the compressor when CO2 is used?
    I think the difference you may be seeing is due to how the condensate from defrost is allowed to pass. If a traditional pressure regulator were to be used on the CO2 system I suspect this would be similar to an ammonia system.

    However, if a liquid drainer was used to pass the defrost condensate, the false load back to the compressors would be much less than the regulator.

    I doubt the ammonia or CO2 are behaving much differently. I believe it is a function of the defrost system design.
    Last edited by US Iceman; 27-08-2006 at 09:22 PM. Reason: added minor text

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    Re: Refrigerants and The Environment

    SO water as refrigerant could only be on a very large scale?

    Why did the indunstry ever step back and re evaluate using CO2?

    Sorry for silly questions i'm a little new to the field.

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