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AndrOvr
19-08-2002, 08:05 PM
What temps show I expect from a 1/4hp and 1/8hp compressors in a cascade system ... w R409a?

Gary
19-08-2002, 10:43 PM
I hardly know where to start on this question. There are various temperatures at various points in each system, and all of these depend upon a great many variables. The question is impossible to answer.

aenigma
20-08-2002, 01:23 AM
Probably cold :)
My dual phase cascade system got below -60f.
But with a load it doesnt work nearly good enough for the noise/cost, not reliable and is huge.
But mine isnt just cascade...just a cascade system would probably work good,hundekot(carrion) is working on his cascade system.You should wait till he is done to see what kind of temps it gets.

AndrOvr
20-08-2002, 02:39 AM
I want -50c w load :)
lol.... harD? (this w r409a...)

aenigma
20-08-2002, 10:07 AM
Originally posted by AndrOvr
I want -50c w load :)
lol.... harD? (this w r409a...)
hahaha good luck getting that cold :p

AndrOvr
20-08-2002, 07:34 PM
Damn!...
Some guys have their R134a w a 1/2hp comp. runing at -40c (evap.) w load...
and w a cascade system.... It will not give me any better than -45c or loweR?!?!

What is the best... Cascade systems or dual phase?

Dual phase like this:
http://subz3ro.net/dually/bigimages/dcp_5392.jpg

Compressors conectected each other...hmmm Good?

Gary
20-08-2002, 09:37 PM
There are cascade systems capable of -150F.

AndrOvr
20-08-2002, 09:58 PM
Nice... BUT I only want one that does -50c w load :)
I want to know what is the best way to reach it...
Cascade system... or the dual phase (the 2 compressors working together...)

Gary
20-08-2002, 10:43 PM
I'm not sure you know what a cascade system is, and I have no idea what "dual phase" means. Phase, in our industry refers to electricity.

AndrOvr
20-08-2002, 10:52 PM
Well... one compressor cools down the cond. of the onther... while the other compre. cools down at very low temp... Rite? :rolleyes:

Gary
21-08-2002, 12:22 AM
yes, that's a cascade system. :)

Prof Sporlan
21-08-2002, 01:50 AM
If the Prof may add his two cents worth.... :)

A two circuit cascade system entails two separate refrigeration systems connected by a heat exchanger which serves as the evaporator of the high stage, and the condenser for the low stage. As he recalls, the term "interstage heat exchanger" is often used here. Appropriate refrigerants are selected for each circuit to achieve desired low temperatures. Common low stage refrigerants used in the past have been R-13 and R-503, both CFCs. R-23 has been in recent use, an HFC, though it has problems with high discharge temperatures. R-170 (ethane) has also been used, though for obvious reasons its use hasn't been universal. R-508B (SUVA 95) is current a favorite with many cascade system manufacturers.

Using a two-stage compressor is a simpler approach, though it is not as effective at reaching low temps as a cascade system. Here, a single refrigeration circuit is used, and the compressor has separate cylinders to take low pressure refrigerant to an interstage pressure, and interstage pressure refrigerant to condensing pressure. A means of desuperheating the interstage refrigerant is needed.

The photo seems to detail what the Prof would call a "compound" compressor system, though the term "two-stage" would still apply here, though not to confuse it with a two-stage compressor. Here we seem to have one compressor pumping into another. The low stage compressor is often referred to as a "booster" compressor, and the function is effectively identical to a two-stage compressor.

aenigma
21-08-2002, 02:04 AM
what he said :)
Yeah that is my dual staged/dual phase system.What ever you wish to call it,gary was telling me it is dual phase,now he is saying he doesnt know what dual phase is :rolleyes: :p
Yes there are cascade system that get extremely low temps by utilising 2 types of refrigerant and phase seperators and all that fun stuff that isnt really easy to get :)
But a basic cascade system,I am not sure if it will give you the temps you want.It might.
But dont build a dual phase cascade,that is just a headache to work on :eek:

You could try going with a dually or cascade.If you made a nice heat exchanger you could probably get the cascade system pretty small.My heat exchanger was a coaxial pipe I made.
Pretty big too.

Now if I could have got my hands on some good refrigerant for cascade system,that thing would have worked great.But I only use R290....

Good luck....

Gary
21-08-2002, 04:44 AM
Call things what you will, but we can't see it from here. We can only see the system through the description and the temperature measurements.

Overclockers seem to have their own refrigeration terminology, and that's fine, but it doesn't describe the system to those in the refrigeration trade.

I gather that what we would call a change of state is a 'phase change' in overclocker speak.

Cascade means something specific to me, as does two stage.

Air conditioning (aka high temp system) describes a specific temperature range, as does medium temp, low temp, ultralow temp, and cryogenic.

Supercooling describes nothing that I'm aware of. Dually is also meaningless to me, as is dual phase.

It's easier to communicate if we speak the same language. I'll keep trying to pierce the veil, but I find it extremely difficult. Even within our trade it is sometimes difficult, as the terminology is less than universal.

It's hard enough just converting Centigrade to Fahrenheit when trying to evaluate the data. :)

Gary
21-08-2002, 04:50 AM
Prof, I wonder if R410A would be effective as a low stage refrigerant?

aenigma
21-08-2002, 08:20 AM
Originally posted by Gary
Call things what you will, but we can't see it from here. We can only see the system through the description and the temperature measurements.

Overclockers seem to have their own refrigeration terminology, and that's fine, but it doesn't describe the system to those in the refrigeration trade.

I gather that what we would call a change of state is a 'phase change' in overclocker speak.

Cascade means something specific to me, as does two stage.

Air conditioning (aka high temp system) describes a specific temperature range, as does medium temp, low temp, ultralow temp, and cryogenic.

Supercooling describes nothing that I'm aware of. Dually is also meaningless to me, as is dual phase.

It's easier to communicate if we speak the same language. I'll keep trying to pierce the veil, but I find it extremely difficult. Even within our trade it is sometimes difficult, as the terminology is less than universal.

It's hard enough just converting Centigrade to Fahrenheit when trying to evaluate the data. :)
Yeah I usually use Farenheit also.

It is just a dual compressor system....
I was just saying awhile ago when I called the system dual staged,you said it was dual phase,so i called it that instead.
But you just said you dont know what im talking about when I referred to it as a dual phase system, so i thought that was strange ;)

What do you call a dual compressor system,besides just dual compressor?

Cascade also means something specific to me.
So does dual stage/dual phase.

I guess I could call it a dual compressor refrigeration unit configured for low temps to aid in overclocking my cpu :)

Actually I dont do it just for overclocking,I just love refrigeration...

Oh by the way Androvr I would go with a dual compressor setup.It is working great for me other than the smaller 1/2hp compressor being extremely hot...About 152.6f as we speak :eek:
Even with a 235cfm fan blowing on it....
The 1hp isnt too warm though....

This thing gets cold enough to gel the antifreeze,ack i hate antifreeze..
Evap gets below -60f(all my temp probe will read)

Gary
21-08-2002, 03:03 PM
What I would call a system with two compressors would depend on how they are piped.

I don't recall ever calling a system dual phase and I'm too lazy to dig back through all of my posts... LOL

More likely, I was just agreeing with you, being the agreeable kinda guy that I am. :)

Prof Sporlan
21-08-2002, 04:16 PM
Prof, I wonder if R410A would be effective as a low stage refrigerant?

R-410A has been promoted as a R-13B1 replacement, which has typically been used with single stage refrigeration systems to achieve operating evap temperatures down to about -60F. In fact, Sporlan has manufactured a few low temp R-410A TEVs for this purpose. BTW, R-13B1 (aka halon 1301) was also used for fire suppression before its production was banned with all the other CFCs.

As for a refrigerant in the low stage of a cascade system, there are apparently better choices available.

Gary
21-08-2002, 05:06 PM
As for a refrigerant in the low stage of a cascade system, there are apparently better choices available.

No doubt. I was thinking in terms of price and availability, although R410A is probably not a good choice for DIYers.

It seems like R22 might be capable of respectable temperatures also, especially as a low stage refrigerant.

AndrOvr
21-08-2002, 07:47 PM
What about R409a?
Its the only one I can get here :(

aenigma
22-08-2002, 06:53 AM
Originally posted by Gary
What I would call a system with two compressors would depend on how they are piped.

I don't recall ever calling a system dual phase and I'm too lazy to dig back through all of my posts... LOL

More likely, I was just agreeing with you, being the agreeable kinda guy that I am. :)

Doh I re-read it you didnt say dual phase.
I was calling it dual staged,then you said something about there being 2 stage compressors.So I just called it dual phase. :)

So what would you call my system?
2 compressors in series,1/2hp discharge 1hp suction.

aenigma
22-08-2002, 07:16 AM
Originally posted by AndrOvr
What about R409a?
Its the only one I can get here :(

R409a will probably get you the temps you want.
What does it boil at anyways?

Gary
22-08-2002, 07:44 AM
If the refrigerant being discharged from the first compressor enters the suction of the second compressor, it is a two stage system.

It is also possible to do this with a single two (or more) cylinder compressor, the output of one cylinder entering the suction of the other. This would be called a two stage compressor.

Two stages will usually have a de-superheater between them to help cool the high stage.

If the two compressor's refrigerant piping forms two separate loops, with heat exchanged between them (one cooling the other), but not actually sharing refrigerant, then it is a cascade system.

Gary
22-08-2002, 07:58 AM
The boiling point of any liquid depends upon it's pressure. For example, put water in a pressurized container and it will boil at a much higher temperature than 212F. Then call it a pressure cooker. :)

superheat
22-08-2002, 03:47 PM
I could not see why someone would make a 409 cascade system. I have never seen a R12 cascade system either.

I have a man who wants to restore a very old water cooled cascade system. 502 high stage and 170 low stage. It might be too old to retrofit. I have not looked too hard for 170 (ethane I think). What refrigerant could I possably use for the 170 part.
This man want to try retrofit first before replacing compressors.

aenigma
23-08-2002, 01:24 AM
Originally posted by Gary
If the refrigerant being discharged from the first compressor enters the suction of the second compressor, it is a two stage system.

It is also possible to do this with a single two (or more) cylinder compressor, the output of one cylinder entering the suction of the other. This would be called a two stage compressor.

Two stages will usually have a de-superheater between them to help cool the high stage.

If the two compressor's refrigerant piping forms two separate loops, with heat exchanged between them (one cooling the other), but not actually sharing refrigerant, then it is a cascade system.
Ok cool,we call it the same thing then :)
I called it a dual stage system also,same thing as saying 2 stage.

Oh btw I know how pressure affects boiling point and everything,I was just wondering what the average boiling point of R409a is.Like at atmospheric pressure.

Gary
23-08-2002, 01:48 AM
Oh btw I know how pressure affects boiling point and everything,I was just wondering what the average boiling point of R409a is.Like at atmospheric pressure.


Roughly -16F.

Pressure/Temperature charts for all of the common refrigerants are available wherever refrigerants are sold. They come in handy. :)

aenigma
23-08-2002, 06:47 AM
Originally posted by Gary


Roughly -16F.

Pressure/Temperature charts for all of the common refrigerants are available wherever refrigerants are sold. They come in handy. :)

Yep,I am just lazy haha

Thanks :)

Gary
23-08-2002, 09:20 AM
I'm thinking your two stage system would perform better if the smaller compressor were the low stage and the larger compressor the high stage. :)

aenigma
23-08-2002, 09:42 AM
Low stage=low side right?Just making sure.
If so,then that is the way my system is.
1HP is the suction side while the 1/2hp is discharge.
My last one with dual compressor was set up the other way,bigger compressor for discharge and smaller for suction,I didnt get much of a vaccum on low side and it never did work right.
This current system well get the liquid well below -60f with no load easy.
With the computer running it stays around -40f or -50f.
But that little 1/2hp compressor is getting pretty warm,and I might just put a 3/4 in its place when I actually get something to braze with.