R23 Cascade

[Brian_UK]

I think that I am going to be the lucky one who does a refrigerant change on an old Fison environmental chamber in the new year.

It's currently running on R502 and R13 but will be changing over to R23 and I think we are using R408A on the 1st stage.

Originally I thought 'this could be interesting' and then I realised where the job was.....the chamber is in a room that is about 2.5 times the size of itself, the compressors etc are all at floor level (and at the back of course!).

The normal aggravation with changing the compressor oil pales into insignifigance when I saw the location of the oil separators

Anyone out there used R23 and have any input would be welcomed.

[Prof Sporlan]

R-23 was perhaps the first proposed HFC alternative to R-13 and R-503. The problem you have with R-23 is it runs very high discharge temperatures, and desuperheating the return gas to the compressor is almost a necessity to prevent compressor overheating. The Prof isn't aware of any cascade environmental chamber OEMs using R-23 at this time.

DuPont has promoted R-508B which runs much lower discharge temps, which is an azeotropic blend of R-23 and R-116 (46/54 percent by weight). You might check this option before proceeding with the retrofit.

If you don't mind using a flammable refrigerant, ethane (R-170) would work well as a substitute for R-13.

[vspiteri]

The old chambers were on R13 - R13B1 and R13 - R503 and a few years ago we changed them to R23 and R22 -

Years ago too, parallel to the introduction of the R23 several tests were being done on new blends (R22 circuit) due to environmental laws.

Brian - has anybody mentioned of adding 100CC of R11 to the POE of the R 23 circuit - How did you charge the R23 - Statically or dynamically ?

If you need any help pls advise and I see if I can contribute

victor

[dwallan]

I would be more concerned with the high stage. Converting to R408a creates a performance drop which will cause problems in the low stage. What we are finding is in systems operating in an ambient over 24'C the low stage is dropping out intermittently.

[Brian_UK]

Thanks for the early input guys, we haven't finalised the gases to be used yet but at least I have some more ammunition as to which way it could go, and why.

[shaun spencer]

did insalls for russells technical products. they are (were been 10 months) using R404 in high stage. R23 in low stage.
have done many retros using R23 as it the price is so much better than suva95. with Carlysle compressor being the norm, i go back to old style valve plates (better discharge temp) a t/c and a watlow control to monitor discharge temps.
Thermotron advocates the use of an extra expansion tank with R23 - a money grab IMHO. Have done over 100 retros to R23 and exisiting expansion tank with no problem.i have a apreferance for R507 (AZ50) as it doesnt have the glide problems associated with R404 (HP62) in high stage

[dwallan]

Could you expand on the expansion tank idea, how do you size the vessel etc.

David

[shaun spencer]

The expansion tank works same (sort of) as a reciever.
It holds the whole charge of refrigerant in the vapour state, no liquid , due to pressures associated with ultra low temp, high pressure refrigerants

[shaun spencer]

also during pulldown the refrigerant is 'dumped' into expansion tank and bled back into suction

[johndavies]

anyone know best way to reclaim this r23

[Brian_UK]

Originally posted by johndavies
anyone know best way to reclaim this r23

You need a specialist recovery unit and, of course, a high pressure bottle. Remeber that the charge is normally quite small in relation to more normal temperature refrigerants.

[David Gethsame]

I am in the process of designing a cascade refrigeration system for a freezer chamber of -70 deg.C, using R-23 as first stage and R404a as second stage. can anyone gimme tech advices.

[TXiceman]

Do a search for previous discussions on a fade out tank or receiver for the R-23 side. As for R408B, check the compressor out for use on R507. It is an azetrop and you do not have the glide problems and charging problems of a 400 series blend.

Cascade systems can be tricky and do require some special considerations.

Ken

[Peter_1]

Some questions: room size, type of room panels, panel thickness, type of door, temperature outside the room, heat load in the room, application, distance between room and compressors, door heatings, run time, what compressers do you think you will use, what type of evaporator, ....

Your question is to common to give you some help. Provide first some more info becuase this isn't that simple. This is very real refrigeration and you will have to understand the basics very well.

Oh BTW..., nice introduction here on RE David.

[shanes696]

[QUOTE=shaun spencer]The expansion tank works same (sort of) as a reciever.
It holds the whole charge of refrigerant in the vapour state, no liquid , due to pressures associated with ultra low temp, high pressure refrigerants[/QU
I worked for the U.K. branch of Thermotron back in the late 80's. The expansion tanks are just that -for expansion. When the system is shut down the first stage is not cooling the second stage & so the second stage gas temperasture rises & the pressure rises with it -you need somewhere for all that pressure to go. Also they act as a kind of buffer in the delivery circuit allowing some expansion of the gas of the discharge line while the first stage cooling catches up when the system is called for.

[shanes696]

also during pulldown the refrigerant is 'dumped' into expansion tank and bled back into suction

On the outlet of the expansion tank is a solenoid valve connected to the suction. It's a bypass circuit; the (de-superheated) discharge gas which has lost it's energy in the expansion tank is dumped into the suction (through a restricting valve). When the test chamber has reached setpoint it cycles between the bypass valve & the liquid line sol. valve to achieve close control.

[shanes696]

I think that I am going to be the lucky one who does a refrigerant change on an old Fison environmental chamber in the new year.

It's currently running on R502 and R13 but will be changing over to R23 and I think we are using R408A on the 1st stage.

Originally I thought 'this could be interesting' and then I realised where the job was.....the chamber is in a room that is about 2.5 times the size of itself, the compressors etc are all at floor level (and at the back of course!).

The normal aggravation with changing the compressor oil pales into insignifigance when I saw the location of the oil separators

Anyone out there used R23 and have any input would be welcomed.

As well as Thermotron I used to work for Fisons too (although the company was called Sanyo Gallenkamp when I was working for them). Yep, the refrigerants you are using are perfectly O.K., that's what we used to retro-fit.

[shanes696]

R-23 was perhaps the first proposed HFC alternative to R-13 and R-503. The problem you have with R-23 is it runs very high discharge temperatures, and desuperheating the return gas to the compressor is almost a necessity to prevent compressor overheating. The Prof isn't aware of any cascade environmental chamber OEMs using R-23 at this time.

DuPont has promoted R-508B which runs much lower discharge temps, which is an azeotropic blend of R-23 and R-116 (46/54 percent by weight). You might check this option before proceeding with the retrofit.

If you don't mind using a flammable refrigerant, ethane (R-170) would work well as a substitute for R-13.

What I don't get is that R23 is the envirionmentally better alternative to R13 & R503, yet R23 is a 50:50 blend of R13 & R503. Go figure

[shanes696]

anyone know best way to reclaim this r23

There are no commercially available refrigerant reclaim units that I'm aware of for R23. The way we used to do it was to cool the cylinder you are using for the reclaiming in the chamber first down to say -50 deg. C & then take the liquid out from a suitable point on the 2nd. stage (we sometimes had to solder schreader stubs in before-hand) & the liquid is half-pumped/migrates into the reclaim cylinder.

[shanes696]

The old chambers were on R13 - R13B1 and R13 - R503 and a few years ago we changed them to R23 and R22 -

Years ago too, parallel to the introduction of the R23 several tests were being done on new blends (R22 circuit) due to environmental laws.

Brian - has anybody mentioned of adding 100CC of R11 to the POE of the R 23 circuit - How did you charge the R23 - Statically or dynamically ?

If you need any help pls advise and I see if I can contribute

victor

R13B1 was one of the first refrigerants to be banned back in about '92 as it had something like a hundred-times more ozone-depleting potential than R22. There was no commercially available alternative at the time, but the director of the environmental chamber manufacturing company that I was employed by at the time did some detective work & found out that R13B1 was exactly the same as Halon 1301 which is (was?) used in aircraft engine fire-extinguishing systems. I was despatched to a company near Heathrow where they reclaimed it from aircraft & loaded my Nissan Bluebird Estate (back seat folded down, cylinders loaded right up to the head-lining & in every available space) so that we had a stockpile until an alternative was available. I still have memories of the rear tyres rubbing on the wheel arches with all that weight on the back, christ wouldn't dream of doing that now

[David Gethsame]

i have a apreferance for R507 (AZ50) as it doesnt have the glide problems associated with R404 (HP62) in high stage

Whats a 'glide problem'

[Brian_UK]

Whats a 'glide problem'

Glide is the temperature difference (slope) between the different components of the refrigerant concerned. Generally when the refrigerant is condensing or evaporating.

Try this link for more info http://www.suva.dupont.ca/H45938-3.pdf

[TXiceman]

also during pulldown the refrigerant is 'dumped' into expansion tank and bled back into suction

Say what??? The fade out tank is generally piped into the suction with a tee connection. It is also generally tied to the high side via a inlet pressure valve to bleed excessive pressure (during stand by) until all of the liquid on the high side has gone to vapor. The volume is calculated from the gas laws once you have the toal refrigernat voume and run down to the lower pressure, usually 300 to 350 PSIG DWP.

I do not see how it is dumped during pul down. WHenyou start the compressor, and start pull down, yuo are simply reducing the pressure on the suctionand expansion tank, and condensingliquid in the cascade condenser. You bring the system into equilibrum with the normal high side and low side pressures.

Ken

Ken

[slingblade]

On the outlet of the expansion tank is a solenoid valve connected to the suction. It's a bypass circuit; the (de-superheated) discharge gas which has lost it's energy in the expansion tank is dumped into the suction (through a restricting valve). When the test chamber has reached setpoint it cycles between the bypass valve & the liquid line sol. valve to achieve close control.

Last one i worked on was a Lawler twin evap. forced air test cabinet, R508. the return from the expansion tank (looks a bit like an oil sep. ?) was a capillary tube. there was no sol. valve, but close control of air temp. was done via two electronic controls and electric air heaters. i did not see an l.p. or h.p. on either the high or low side. first one like this i have seen, is this common?

[shanes696]

Say what??? The fade out tank is generally piped into the suction with a tee connection. It is also generally tied to the high side via a inlet pressure valve to bleed excessive pressure (during stand by) until all of the liquid on the high side has gone to vapor. The volume is calculated from the gas laws once you have the toal refrigernat voume and run down to the lower pressure, usually 300 to 350 PSIG DWP.

I do not see how it is dumped during pul down. WHenyou start the compressor, and start pull down, yuo are simply reducing the pressure on the suctionand expansion tank, and condensingliquid in the cascade condenser. You bring the system into equilibrum with the normal high side and low side pressures.

Ken

Ken

I think what he means is that expansion tank pressure is dumped into the suction when the chamber temperature is nearing setpoint. Although it's not actually 'dumped', it's usually bled via some sort of restrictor such as an orifice or similar. It acts as a bypass to keep the 2nd stage compressor from cutting out on LP & when setpoint is reached & the temp. controller cycles between the liq. sol. valve & the bypass (expansion tank to suction) to gain close control (usually + or - 0.1 deg.C). Although I've also seen on some designs the expansion tank 'dumping' into the suction on pulldown to keep the high side pressure down, controlled by an extra HP switch.

[shanes696]

Last one i worked on was a Lawler twin evap. forced air test cabinet, R508. the return from the expansion tank (looks a bit like an oil sep. ?) was a capillary tube. there was no sol. valve, but close control of air temp. was done via two electronic controls and electric air heaters. i did not see an l.p. or h.p. on either the high or low side. first one like this i have seen, is this common?

Must've been a very small test chamber? I've seen bench top test chambers with capillaries being used as the expansion device on both the 1st & 2nd stages. Using heaters is another method of close control, the chamber pulls down on the refrigeration, the refrigeration stays on at full kilter & then the heaters (sized to have more output than the fridge) are pulsed by the controller to maintain setpoint. Quite wasteful from an energy consumption point of view.

[slingblade]

Must've been a very small test chamber?

Yes it was a benchtop.

[shanes696]

I also remember converting an American bench top chamber (can't remember what make) from R502 & R13 to R22 & R23 about 10 years ago. On the 2nd stage it had an R12 expansion valve permanently tee'd into the suction line with the phial attached on the suction near the compressor. They were using it as a liquid injection to save the compressor windings when pulling down from elevated temps. & because of the different working band of the R12 TEV it would be wide open as it pulled down from higher temps & then close down to a tiny trickle as the the suction temp. came down to acceptable levels. A clever simple solution I thought.

[TXiceman]

The size of the fad-out drum is not that diffucut to calculate. You have to calculate the total volume of the system, than calculate the toal volume of refrigerant in the sytem at full charge. Now determine the total vapor volume of the refrigerant chage at fade-out conditions. The vapor will follow the standard gas laws at this point so you can calculate the total required volume to have all of the refigerant volume at 300 PSIG of you have a 350 PSIG DWO|P on the system. The fade-out drum is sized such that the volume of the sytrem plus the drum will be slightly larger than the calculared fade-out volume at the 250 PSIG and ambient temperature.

This is the type system that will get you in a lot of trouble if you do not understand what you are doing.

One thing that is often over looked is the lower suction temperature limit of the compressor. You may have to add a liquid/suction exchange to get the compressor suction superheat up so that you are over the compressor minimum suction temperature.

At these low temperatures you need to watch the oil and refigerant properties and make sure you can return the oil from the evaporator.

Ken

Ken

[coolit24]

Hey! You best give that very strange guy (Craig Tom) a call at thermotron UK, He will do his very best to fill you with total CR*P. What a profesional ?? will condem your chamber in seconds! or fire it.

[Peter_1]

The size of the fad-out drum is not that diffucut to calculate. You have to calculate the total volume of the system, than calculate the toal volume of refrigerant in the sytem at full charge. ....

That's what is now so difficult, calculating the total refrigerant in the system.
How much refrigerant will be in the evaporator, in the condensor..??
If you miscalculate 100 gr with R23, then the stabilising pressure will be something completely different.

We once made some cascades for a Meissner coil (vacuum chambers) and we did it with with a simple trial and error test which lasted onlmy some minutes: we just connected small empty refrigerant cilinders to the service port of the compressor till the equalising pressure was what we needed.
It was much faster then calculating it and we were sure that it was also correct, whatever the calculations should have say.

[shanes696]

Hey! You best give that very strange guy (Craig Tom) a call at thermotron UK, He will do his very best to fill you with total CR*P. What a profesional ?? will condem your chamber in seconds! or fire it.

I take it that Craig Tom is one of their service engineers? I'm not familiar with that name as I left Thermotron UK in '89 but I do know that George Dane is still working for them as I saw & spoke to him a couple of years ago while stocking up from NRS in Maidstone.

[hundred]

Now.I finding cascade diagram of Bock compressor.I had new project desing IQF .I want overall knowlege of equipment to choose for assembly.The system want TE - 60 c.Pls.send to at sdd_888@hotmail.com
Thank you....

[5inatribe]

It has been along time since I have heard of anyone using R-11 in the low stage. Some manufacturers are using Pentane. and that is mainly with R-13 and R-503. SUVA 95 (R-508b) does not usually require it but a High Effeciency oil seperator is a must.

[hundred]

What brand oil is suitable with R 23 .I am not sure my customer used Zerol 150.

[hundred]

About additive in low stage .Am I need fill n-pentene mix with r 23.
pls,tell me.
Thank you