r22 replacement issue -emergent

[Lc_shi]

Hi sirs
Our country will phase out r22 ahead of schedule,so it's becoming an emergent issue. As I know, there're following refrigerants can used as substitute:
1) 407c
2)134a
3)410a
4)417a
5)404a
6)natural

which is best for r22 replacement.:confused:

hope a detailed discussion

regards
LC

[Andy]

Hi sirs
Our country will phase out r22 ahead of schedule,so it's becoming an emergent issue. As I know, there're following refrigerants can used as substitute:
1) 407c
2)134a
3)410a
4)417a
5)404a
6)natural

which is best for r22 replacement.:confused:

hope a detailed discussion

regards
LC

Hi LC:)

that would be the problem, nobody knows:o

The 4 series are all mixtures, which need ester oil and tend to fractionate when they leak, the like of 407c has some serious glide, but is reasonably efficient at airconditioning duties.

R134a is a pure refrigerant, but some countries are talking about banning it:confused: Although at low compression ratios it can be very efficient, (such as water cooled chillers)

Natural is best, but will either poison you or blow you up. Co2 is just about possible, good for heating water, not yet fully developed (flooded systems, transcritical with expander cycle would be my guess, but expensive to develop and hard for the average engineer to work on).

Ammonia is the best and should be considered, very efficient on low speed recip compressors, however it has been tried on secondary systems in the UK within supermarkets, but in my mind the systems used were not suitable, a lot more developement need (such as intergral case/condensing units with water cooled condensers and water suspression in the event of a leak).

Just my thoughts.

Kind Regards Andy:)

[Lc_shi]

Hi Andy
Thanks for your good comment.

What is the meaning of mid-point 407c and dew-point 407c? what difference?

regards
LC

[Argus]

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Bubble and Dew point are both defined in various standards and are largely self-explanatory.

The Bubble Point is defined as the temperature at which the liquid blend in the correct proportions begins to show bubbles prior to evaporating.

The Dew Point is defined as the temperature at which the superheated gas begins to condense.

Glide is expressed as the temperature difference between the two in degrees K.

Some like to think of it as the first component to boil / condense, that’s not exactly true, but near enough.

In blends with a moderately high glide, such as R 407 C, (about 6.5 C at normal operating temperatures) the glide is derived from the subtraction of the Bubble Point from the Dew Point.

The problem arises with heat exchangers (usually finned tubes with this blend as it does not perform well in flooded vessels). There is no such thing as a fixed evaporating temperature within the glide, because it is changing constantly throughout the heat exchanger and it is very difficult to predict, so the evaporating temperature is expressed as the mean temperature between Bubble and Dew points throughout the coil. Arithmetically this becomes the mid-point.

Europe began plans to phase out R22 almost 10 years ago and R 407 C was used extensively in Europe as a short term first generation replacement for R 22 in small split type air conditioners. R22 is almost phased out here now. R 407 C is not necessarily a drop in for R 22 - there are other refrigerants for that. In recent years, manufacturers are replacing it with R 410 A.

If you have the choice - I'd recommend that you avoid it.

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