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garyb
11-04-2006, 01:11 PM
Does anyone have any experience with using the "new" refrigerants on flooded systems?

In Australasia (and probably elsewhere too) back in the late 80s and early 90s R22 was promoted as the way forward as a replacement for R502 for low temp systems in new systems for clients that weren't keen to go ammonia. Advertising with such memorable phrases as: "R22 - the green alternative" and "R22 - Part of the solution, not part of the problem" were common. Consequently a significant number of major low temp installations were done with R22 and guess what? We are back where we started when R502 was on its way out except now the issue is with R22. Personally I won't be sad to see the back of LT R22 and all the hassles that came with it - high discharge temperatures, oil recovery from flooded separators etc. Trouble is a lot of these systems were big (for non NH3 systems) up to 5000kg of refrigerant and while I'd be happy to sell them ammonia, 30 or so replacment coils and re-run all the copper in steel there are other issues; Ammonia that gets contaminated by HCFC creates some seriously corrosive and dangerous compounds, production plant down time is not an option and the cost would be enormous.

And so to my question - has anyone used R404a, R407c or R507 on flooded applications?? An aozetrope fluid like R507 would be my pick but I have not found anyone thats done it before.

Any comments appreciated.

Argus
11-04-2006, 01:46 PM
Gary, Thanks for the interesting post.





In Australasia (and probably elsewhere too) back in the late 80s and early 90s R22 was promoted as the way forward as a replacement for R502 for low temp systems in new systems for clients that weren't keen to go ammonia. Advertising with such memorable phrases as: "R22 - the green alternative" and "R22 - Part of the solution, not part of the problem" were common.

I know what you mean. In the early 80?s HCFCs were actually promoted in the Montreal Protocol as ?transitional substances?, to be used while a replacement was found for CFCs.

But from my limited experience, R22 was never any good for low temperature work. Fraught with high temperature discharge problems.





And so to my question - has anyone used R404a, R407c or R507 on flooded applications?? An aozetrope fluid like R507 would be my pick but I have not found anyone thats done it before.




But the short answer to your question about flooded systems is, if it?s got a glide (Zeotropic) - don?t.
Especially R407C.

You will end up with an odd-ball mixture in the low side and God-knows-what elsewhere.

Additionally, go into it with your eyes open as far as oil scavenging at low capacity is concerned.

.
________
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US Iceman
11-04-2006, 02:13 PM
As Argus stated, I would not recommend the refrigerants with a glide. Too many potential problems.

If you use an azeotrope, the system will not be much different than the flooded R-22 systems. Oil recovery will still be a concern as will the potential for discharge temperatures of the compressors.

If the specific heat ratio of the replacement refrigerant is lower than that of R-22, the discharge temperature will reduce somewhat. But perhaps not significantly.


...but I have not found anyone that's done it before

There will be a lot of this because of the new refrigerants and phase out of the older ones. I think you are asking all of the right questions. The way you are approaching this is very reasonable.

The refrigerant changeover might present some unknown issues that you should make the owners aware of. After all you are venturing into somewhat unknown territory and they should be advised that some unknown issue may present itself at the least convenient time.

NoNickName
11-04-2006, 02:14 PM
Condensing and evaporating are not distilling.
So R407c is always in the right proportion provided SC and SH specifications are respectfully followed. Nonetheless, it's not suitable for low temperature, for Te lower than -10C.
R404a has a too low discharge temperature, so I would suggest R507

Johnny Rod
11-04-2006, 02:41 PM
As Argus says, you can't use a zeotrope (400 series) in a flooded system - it fractionates. They're only for DX systems. Probably have someone on here any minute who has used R404A in something as it fractionates less than 407, or for low temp perhaps you could use R410A as it is high pressure and again near-azeotrope, but I doubt these would be good for large systems. We only really have one R22 replacement for large flooded systems which is called RS52, I don't know a lot about it though, but it is being trialled in a large pumped liquid type system. Otherwise you could always use propane aka R290/Care40 if you can use a hydrocarbon. There are a number of big systems using propane, if it's an industrial site it may not be a problem.

NoNickName
11-04-2006, 02:57 PM
Yes R404a is also a quasi-azeotropic, but it has got a small glide of 0.7K.

US Iceman
11-04-2006, 03:02 PM
So R407c is always in the right proportion provided SC and SH specifications are respectfully followed

Which reinforces what Johnny Rod stated. In a flooded system there is no superheat at the evaporator.


...RS52, I don't know a lot about it though, but it is being trialled in a large pumped liquid type system

I would be interested to hear how this develops.

Andy
11-04-2006, 07:40 PM
Hi Garyb:)

never tried it but I would consider R404a an option, very small glide, no real oil return problems in DX systems.

Try a small plant first.

Er forget R407c it's not a very good refrigerant for anything and responsible for bursting a fair few water chillers:(

Kind Regards. Andy:)

NoNickName
11-04-2006, 08:07 PM
R407c is commonly and satisfactorily used for chillers and heat pumps all over Europe, for chillers and air conditioners in medium to high temperature range.
We have a number of applications dating back to the late 90s that are working nicely.
R404a is instead a bitch, with a low discharge temperature which causes oil dilution.
Your mileage may vary.

Argus
11-04-2006, 08:16 PM
.

I think that oil behaves completely differently in a DX system that is subjected to continuously higher velocities in smaller pipes than in a flooded system.

It is also very difficult to return oil adequately in prolonged low-load situations, hence some of the elaborate return systems put in place on flooded evaporators.

Added to this is the uncertain results of dropping in a 'drop-in' replacement.

In many R22 systems of uncertain age, the ecconomics of conversion may not add up.

.
________
star craft replays (http://screplays.com/)

Johnny Rod
12-04-2006, 11:27 AM
R407C is used in lots of applications, true, feel free to find a flooded system with it in and let us know how it is getting on.

I think the RS52 trial is still ongoing, will have to find out the latest. It isn't cheap though so as you say looking at the total cost of sorting out the problem opens up some interesting arguements.

NoNickName
12-04-2006, 12:12 PM
My objection was on the assertion that "R407c is not a good refrigerant". Still think this is not necessarily true.

For flooded system, I will refrain from argueing.

garyb
19-04-2006, 06:36 AM
Thanks for the feedback,

I share your concerns of trying to run 400 series refrigerants flooded with issues of fractionation and glide. Oil return/recovery is always an issue for non ammonia systems so no suprises there.

The reference to propane is interesting but I imagine there would be substantial resistance to a highly flammable product and would require a lot of re-engineering of the operation, layout and electrical hardware.

The RS52 sounds interesting - is there information available for it?

I'm suprised no one has mentioned R507. I would have thought that being a 500 series that it would have been a much better option than the the 400s?

Johnny Rod
21-04-2006, 01:40 PM
propane - problems you have with flammability would depend on the environment in which the system runs. Nice idea but not always practical.

The only feedback I have had on RS52 so far is that the trial is ongoing, and so far so good. R507 should also be fine but RS52 is a drop-in replacement for R22 so would work with mineral oil -with R507 you'd have to convert to non-mineral oil. To be honest that's the limit of my knowledge on the application side, here is some more info:

http://www.refsols.com/RS-52.html

Tycho
21-04-2006, 09:48 PM
Some Years back... R-507 was hyped up to be the "new" R-22 and we hyped it up towards out customers how cost effective it would be and how much cheaper it would be compared to R-22 pricewise... so we designed, built and comissioned their plant, with R-507.

everything is identical to an R-22 plant (of our design, may be some variation to pipe size and such).

It's still in operation today, no problems...


Only thing is, as I said R-507 :) was hyped to be the new R-22 here in Norway, the price was redicoulusly(think I spelled that right, but you get my drift) low.
about a year or so, someone figured that R-507 wasnt so environmental friendly after all, so the government slapped on some (un)healthy tolls... and a 57Kg cylinder (125 ponds) now costs $143 (912 Norwegian kroner) for 2 ponds (1 kg) <-- price is in the ballpark.

Whilst R-22 is still at $13,37 (85 Nok) for a pound (1 kg).

US Iceman
21-04-2006, 10:02 PM
Hi Tycho,

You raise a very interesting argument. With the environmental aspects of refrigerants changing (it seems almost daily) how do you tell a customer anything without looking bad at a later date.

With the new refrigerants and those still being developed nothing is certain as it was with R-22, R-12, R-502.

The problem you described is one that concerns me when discussing these issues with clients. They (the clients) are sometimes not very forgiving when the situation does not work out as discussed the previous year.

How does everyone deal with this issue?