Morphing Air Conditioner into Autocascade System

[kang-China]

I found this forum last year ,and look your AC-2,and AC-3.so,I don't understand this .

I have not your experience,so I ask some question to you .

so I say sorry to your

[n00b 0f l337]

Where'd you get the butane from this time around Michael?
I keep making the calls and everyone either doesn't have or considers its so specialty they want more than the cost of R14 for it.

[mytekcontrols]

kang-China no reason to say your sorry, and I hope you don't think you need to from our discussion. It is just very difficult for me to provide better answers then what I have given thus far.

Nol...

Where'd you get the butane from this time around Michael?

I got it from UltraLow. he had some extra from a Sanyo chiller that he was charging, and in exchange for some consulting, he sent me about 10lbs of the stuff in a cylinder that I provided.

I think I've gone through about half of it, if not slightly more. Perhaps we can make arrangements to get some out to you. How much do you need?

Also check with UltraLow, because he might be closer to you, thus saving on the shipping, assuming he still has some available. It is high purity refrigeration grade stuff.

[n00b 0f l337]

Not more than a pound I don't think.
I'll have to ask where he got it from, I don't mind paying, just not $45 a pound.

[mytekcontrols]

Nol...

I'll have to ask where he got it from, I don't mind paying, just not $45 a pound.

Yeah pretty pricey stuff, and almost impossible to get in small quantities. Let me know what happens (send me an email if you like), and if UltraLow can't do it, then I'm sure we can work something out. I'll just need shipping covered, the 1lb of butane you can have for free. But you gotta promise me that you'll post the results of whatever it gets used in.

[n00b 0f l337]

But you gotta promise me that you'll post the results of whatever it gets used in.

Ha of course, I'll let you know, and thanks as always.

[kang-China]

hi guy,
I didn't know, about your AC-2,or AC-3, what's refrigeration in the lastest evaporator to work,
Ar or R14 ?

please answer to me

refrigerant pressure/temperature chart I had looked

The Ar critical temp is -122.4℃,

In the lastest evaporator to used Ar lique, so R14 evaporation temperature

is about -128℃,



what do you think?

[n00b 0f l337]

He is not attempting to condense argon.

[mytekcontrols]

kang-China...

In the lastest evaporator to used Ar lique, so R14 evaporation temperature is about -128℃

Unfortunately I think we are having a language translation problem

As Nol just stated: the Argon is not condensed.

But in order to have the evaporator get colder then -128C, especially when the evaporator pressure is above 0 psi, Argon is required. However due to the critical point of Argon, no amount of pressure would be able to condense it.

So what does the Argon do if it can not be condensed?

The exact mechanism is unknown, but as I stated in an earlier posted answer to your question, it is felt that two possibilities exist. The first one having to do with "Partial Pressure", where the presence of Argon in the evaporator, creates an effect on the evaporating R14, of being evaporated into a lower pressure than reality.

The use of Argon to create a "Partial Pressure" on the R14 is the same principle as used in Absorption Refrigeration Systems, and is best described by this excerpt from this WorldLingo article (for our scenario, substitute R14 for the Ammonia, and Argon for the Hydrogen)...

The cooling cycle starts at the evaporator, where liquefied anhydrous ammonia enters. (Anhydrous means there is no water in the ammonia, which is critical for exploiting its sub-zero boiling point.) The "evaporator" contains another gas (in this case, hydrogen), whose presence lowers the partial pressure of the ammonia in that part of the system. The total pressure in the system is still the same, but now not all of the pressure is being exerted by ammonia, as much of it is due to the pressure of the hydrogen. Ammonia doesn't react with hydrogen - the hydrogen is there solely to take up space - creating a void that still has the same pressure as the rest of the system, but not in the form of ammonia. Per Dalton's law, the ammonia behaves only in response to the proportion of the pressure represented by the ammonia, as if there was a vacuum and the hydrogen wasn't there. Because a substance's boiling point changes with pressure, the lowered partial pressure of ammonia changes the ammonia's boiling point, bringing it low enough that it can now boil below room temperature, as though it wasn't under the pressure of the system in the first place. When it boils, it takes some heat away with it from the evaporator - which produces the "cold" desired in the refrigerator.

The 2nd possibility of what happens with the Argon and R14 mixture, is that the Argon gas will dissolve to a small degree into the condensed R14, thereby causing the R14 to evaporate at a temperature below it's norm when later expanded. The degree of Argon that goes into solution with the R14, is wholly dependent on the temperature of the condensed R14. So as it gets colder, and goes into a subcooled state, more Argon will tend to dissolve into it, thus the R14/Argon solution will evaporate even colder. This effect will continue until such time that an equilibrium is obtained, where the physical constraints of heat load versus evaporating pressure exert themselves (determined by limits of pressure drop through heat exchangers, and pumping ability of the compressor).

It is my belief that both of these theories are in effect with the R14/Argon mixture within an AutoC.

[kang-China]

hi guy,metek
in your AC-2,AC-3

I don't know the area
each cascade condenser

common temp about -20or-30 ,figure out the area is very easy.
But your AC-2,OR AC-3, condenser area is very very difficulty!

so you are a marvelous guy

could you tell about this '

[n00b 0f l337]

I believe it's in the thread here.

[kang-China]

Hi,mytek in you AC-2

To buffer valve in the phase separator#1 is not very well
I think in the lastest phase separator is best,

and you say that in your AC-2(buffered 4 times within the first 15 minutes)

if to To buffer valve in the lastest phase separator i think is better

[n00b 0f l337]

Based on what? That seems rather unfounded. Have you considered the temperature that the solenoid valve would then have to deal with?

[mytekcontrols]

kang-China...

To buffer valve in the phase separator#1 is not very well
I think in the lastest phase separator is best

Theoretically you are correct, but in actual practice nothing is really gained in moving the Buffer gas source to the last Phase Separator (I've run tests both ways). Remember that in an ideal set-up, where the Buffer/Expansion Tank is sized so that the static balance pressure is <=175 psig, the need to buffer will only occur once soon after start-up. In my unit I was limited to using a rather small tank, hence the need to buffer several times.

Another factor that needs to be considered, is the added pressure drop when moving the Buffer gas source near the end of the system. This pressure drop can be detrimental to the response time in lowering the discharge pressure, which kinda defeats your buffering to some degree.

And Nol brings up a good point about the operation of the valve using a potentially much colder gas stream, although I think this would only be an issue if the buffer valve were to open much later in the run time, such as when encountering a high heat load late in the game.

[kang-China]

hi mytek
in your AC-2,AC-3

I don't know the area
each cascade condenser

common temp about -20or-30 ,figure out the area is very easy.
But your AC-2,OR AC-3, condenser area is very very difficulty!

so you are a marvelous guy

could you tell about this '

[mytekcontrols]

Yes calculating the areas for the discharge and/or suction circuit of each Cascade Condenser (as well as the Auxiliary Condenser) does get a little tricky, especially with the dual 3/16" tubes inside of the 1/2". But it is doable by using the area of the circles, subtracting the wall thicknesses, and then factoring in the overall length. But I'll leave this for someone else to do, since it wasn't a great concern for me when I built the AC-2 (I made an educated guess when designing the heat exchangers). Although my design might not be optimized, it did work pretty well.

[kang-China]

hi ,mytek

what about the captube in your AC-2 OR NEW machine AC-C

why ,the 2#,3#,4# in the same length,

and i think, it use the different Refrigeration ,so the captube is different

length.

[n00b 0f l337]

Again he's working out of experience, more tweaking the charge than the capillary tubing. Part of this process is simply making the most of expansion, and if a refrigerant isn't boiled at one HX it will be boiled off at the next and pass back through the first.

[Sgrios]

Michael, If I may have a moment of your time.. I'm not sure what kind of run time the Polycold units were subjected to (IE. 24 hours, seven days a week), but how did the Polycold cope with oil migration and clogging of the evaporator over extended run time at these temperatures? Defrost cycles?

[n00b 0f l337]

I can answer that I believe,
Defrost cycles and often times, parallel high end oil separators. Some of them went as far as being upgraded to serial 905 Temprites, but more then a few I've seen with parallel 902's that boast 99.95% oil removal.

[Sgrios]

I can answer that I believe,
Defrost cycles and often times, parallel high end oil separators. Some of them went as far as being upgraded to serial 905 Temprites, but more then a few I've seen with parallel 902's that boast 99.95% oil removal.

Thank you, Adam. I'm modifying my 'standard' cascade design in which it will be able to cope with 24/7 operation. This is due to a customer request.

This should get me headed in the right direction.

[n00b 0f l337]

http://cgi.ebay.com/TEMPRITE-902-ODS...ht_2162wt_1139
or
http://cgi.ebay.com/TEMPRITE-905-1-3...ht_2429wt_1139

both are half price

[Sgrios]

http://cgi.ebay.com/TEMPRITE-902-ODS...ht_2162wt_1139
or
http://cgi.ebay.com/TEMPRITE-905-1-3...ht_2429wt_1139

both are half price

Thanks, Adam. I have a 902 in my run of the mill cascade and I'm not sure if it's enough at -103c loaded for 24x7 operation.

[n00b 0f l337]

I would say it is most likely enough. I used one in a 3 stager.

[Sgrios]

I would say it is most likely enough. I used one in a 3 stager.

I guess there is one way to find out. =].
Thanks again, Adam.