I think this thread should be added to the guides and or stickied, maybe a cleanup of the stickies is in order.
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I think this thread should be added to the guides and or stickied, maybe a cleanup of the stickies is in order.
Opps! I forgot to list the R23, which I have now corrected on my original post.
Nol -- Yep the R236fa/R125 combo is aimed at creating an R114 look-alike. And this along with the other components selected, was intended to be a conforming non-CFC/HCFC charge that would also be non-flammable. To this end, they have indeed succeeded.
But as you and Walt have observed, oil can be quite a problem with this charge.
BTW; R125 is one of the primary ingredients in several of the new alternative refrigerants, including R410a.
Thanks Walt :)Quote:
I realized that, and it was a great build and informative.
Oh so still r23, okay that makes a great deal of sense. Must be a very small r125 charge then I'd imagine. Maybe 2 phase seps in that system Michael?
Actually it has 3 phase seps. Pretty much the same as my latest AC-2 system, but done with much larger, multiple inner tube coaxial heat exchangers, and of course very large oil seps following the compressor discharge.
I'd imagine, but then again thats probably not a half horse compressor ;)
Hey Michael,
After looking at your new schematic I was interested in your cap tube sizing, adding up the flow factors from all your cap tubes excluding the one that feeds the subcooler comes to 0.556 according to the flow factor chart, which puts you at the mass flow of the compressor you have.
But your captube that feeds the subcooler would supply about 0.04-0.03 approx, since 192" of 0.026 isnt listed on the chart, so im assuming its beneficial to allow slightly more flow then whats being produced by the compressor?
Also when I asked about R290 instead of R22 I was meaning it would go in combination with R123, I asked this cause in talking to adam he has found it results in lower pressures then R22.
Or would the fact R290 is a HC mean that it won't combine quite as well with R123 as R22 does?
oh i also wanted to ask if using 3/16 in 3/8 would be ok for the subcooler HX instead of 1/8 in 1/4?
Raadster -- You are correct on the fact that I have exceeded the compressor's mass flow abilities with my captube selection. It was a compromise I made, because I really didn't want to resize all the captubes at this point, and for the temperature/wattage requirements I knew it wasn't going to be an issue. Also keep in mind that the captube flow rate specs are based on a constant liquid seal at the entrance of the captube, something that it is difficult to achieve in the later stages of an autocascade, especially under load.
On the sizing of the Sub-Cooler HX; remember that as compared to the other HX's, the mass flow is very low. For the system I built; 1/8" inside of 1/4" was quite sufficient. If you are building a bigger system, then the next logical size would be 3/16" inside of 5/16", although in a pinch, 3/8" would probably work.
Yeah you really want something incredibly tight with the subcooler. Plus 1/8 in 1/4 has gotta be the easiest to bend HX ever ;)
This is most likely going to be my final charge for the newly configured AC-2 unit. Although I might need to tweak it when I get the HMS Cold Probe attached, and run it in a vacuum.
6oz R123
3oz R22
62psi R170
75psi R14
42psi Argon
Being air-cooled, it likes a much higher ratio on the R123 vs. the R22. Also a larger amount of R14 vs. R170 seemed to yield better results for low temps when the load is minimal (which is the case for the HMS application). And as you can see, there is a substantial amount of Argon being used, which is why we can go down to -140C, while still having a suction pressure of 27 psi.
Beautifuly informative as always Michael! I was actually looking at some of your patent info the other day.
Might actually try out the "Zero Gravity Separation" ;) ;)
Hey Adam --- when do you anticipate releasing some more info on your AutoC project? :slobber:
Yeah the "Zero Gravity" system was very easy to fabricate, but being partial separation kinda makes it imperative to add an oil separator even with AB oil, and will also require considerably more separation points for temperatures below -100C.
I did participate in some discussions with Cryo-Tek about this in the AutoC Drawings thread. You might want to check it out. :)
The S.S. Destroyer is in tuning and insulating phase, doing a triple evac to very low microns, thus working on the Window AC Cascade.Quote:
Hey Adam --- when do you anticipate releasing some more info on your AutoC project?
Hey don't give it away! :P And yep I am thinking of going with a 3 captube approach within the HX's, then one to Evap. R600/R290/R1150 is the goal. Probably going to use a 5600 btuh roto and some condensers I have vs a window AC this time though, since I'll want to keep it small.Quote:
Yeah the "Zero Gravity" system was very easy to fabricate, but being partial separation kinda makes it imperative to add an oil separator even with AB oil, and will also require considerably more separation points for temperatures below -100C.
I did participate in some discussions with Cryo-Tek about this in the AutoC Drawings thread. You might want to check it out.
Oh and I think I'll replace oil with Zerol 150, don't expect final temps in the -100C range.
I forgot to answer this question by Raadster:
Although I haven't tried combining R290 (as a substitute for R22) with R123, I would imagine that it should work. As for how well an HC will combine with an HCFC, I really couldn't say. Any chemists out there care to venture a guess?Quote:
Also when I asked about R290 instead of R22 I was meaning it would go in combination with R123, I asked this cause in talking to adam he has found it results in lower pressures then R22.
Or would the fact R290 is a HC mean that it won't combine quite as well with R123 as R22 does?
R290 is CH3CH2CH3, or three carbons long, saturated with hydrogen. This results in a mid to low level dispersion force.
R123 is CHCl2CF3, or two carbons, one saturated th Flourine, and one with two Chlorine and a Hydrogen. Flourine results in a very tiny dispersion cloud, thus results in mid to low level dispersion force (and weak intermolecular bonds, thus R14 is such a low boiling point). However it's other end has Chlorine, a very high dispersion force item, which is resulting in very strong intermolecular bonds on that one side, only slightly balanced by the hydrogen there. That is why R123 boils so warm. I would say that your mixing will not be as devastatingly amazing as two Hydrocarbons, however saturation will still be very high as R123 has an irregular shape and electron cloud, which propane will (being very small) attempt to fit into. Should work just fine.
The main difference between the HC's and the others, is the higher oil miscibility, and the lower mass. I've found they like about a 10-20% longer captube.
Now Mytek, got another Q for you. What happens if your captube flow is less then that of the compressor, and what if it's more, like in your case. What is the side effect.
Adam -- Wow! Great explanation of chemical properties of the refrigerants and their inter-relationship. I'll have to read it a couple more times to let it all sink in.
Captube sizing in AutoC is not much different then single stage as far as affect. Less flow = higher differential pressures and vice-versa. And higher differential pressures mean lower evaporating temperature on suction side, or in other words lower temperatures overall.
Oh almost forgot; higher differential pressure also equates to less mass flow, and of course lower mass flow means that we can't pull as many watts out of the system.
It's rather simple,
Like attracts like, and such.
The farther up and right you go on the periodic table, the smaller the electron cloud due to what is called Zeff factor, or the pull of the nucleus on the outer electrons. Very small molecules like to be with other small molecules, but more so they want to be with similar. Non-polar's will not mix with polar molecules well or easily, if at all. The problem with R290 and R123 is that R123 by most standards is probably polar, however "at one end", the Chlorine and Carbon bond is polar, and there going to be pulling electrons to the Chlorine and causing a disturbence there, and effecting the dispersion force (sort of like inner vibrational force of electrons, as they sway back and forth in a sense).
So they will mix, but not the best. The R290 will most likely try and stay on the CF' side of the molecule, where dispersion is still low, polar is still happening however more then likely slightly canceling out across the molecule.
Just my guess though ;)
Really when it comes down to it, most of these refrigerants will mix about the same, and it's more a matter of increasing saturation via lower temperature then anything. And of course the higher temperature refrigerants are normally bigger with more intermolecular forces, so are prone to pull in the little ones ;)
Hey Michael, looking over your patent info for Patent # 4,689,964, and though I understand the crimp and plant technique of the captube, I don't see how its a physical possibilty using 3/16 in 3/8. A .031" captube almost perfectly uses up all available space within a 3/16" tube, with no crimp.
The main reason I ask about the potential for R290 to combine with R123 rather then with R22 is that its been shown as ive come to discover that there are substantial gains to be had by using a SLHX with R290.
Conversely, R22 shows to have a decrease in COP and Capacity when a SLHX is used.
The reason is when we use a SLHX 2 essential factors are conflicting with each other:
1. Theres a gain in capacity by the liquid being subcooled, resulting in greater capacity.
2. We add superheat to the saturated vapor resulting in greater volume of the vapour and since compressors work by a standard volume per unit time we inevitably have less mass being circulated each stroke and thus ultimately have less mass flow overall. Obviously resulting in less capacity.
Thus if we can combine refrigerants which have been shown to result in COP and capacity gains from using SLHX, which in an Auto-cascade obviously can't be avoided, then we can have ultimately better loads for the same temps.
On a side note, since we are essentially never working with pure refrigerants at any stage in a Auto-c you may dismiss the following proposition presented above since there will be a "pseudo refrigerant", and thus the effects would be mellowed by the combination of other refrigerants. I personally think that any time your combining 2 things that you will come to a foreground between the 2 in terms of the good and bad properties of each. Thus to me personally I would think that although the negative effects of COP and capacity that R22 suffers from using a SLHX may be minimised, they are ultimately present.
NB: the gains in COP and capacity of using a SLHX with R290 are shown to be in the 5-15% region while R22 suffers by -5%.
I thought you guys might be interested in what the actual Sub-Cooler looked like, and where I had to cram it in (not kidding about that, starting to run out of room). In the image you can also see most of the 16 foot .026 ID captube residing inside the coils of the Sub-Cooler.
Haha sorta as I pictured it. Looks nice, I love watching you dig in the foam :P
With 3/16" tubing, and .031 ID captube, no crimping required. As you said, it practically takes up all the space inside. Instead; drill into the 3/16" at an extreme angle, so that when the captube is inserted, it will tend to lay flat against the tubing. Basically what you are trying to achieve is to create a highly restrictive area where the captube enters the discharge tubing. This will create a turbulent area around the entrance of the captube, and thereby cause some liquid to feed it. Crimping the tubing would only be required for a higher mass flow system that uses larger discharge side tubing.Quote:
Hey Michael, looking over your patent info for Patent # 4,689,964, and though I understand the crimp and plant technique of the captube, I don't see how its a physical possibilty using 3/16 in 3/8. A .031" captube almost perfectly uses up all available space within a 3/16" tube, with no crimp.
I was thinking on that all day actually Mike, and yep came to that conclusion. It would result in almost a capillary effect around the capillary, restriction indeed. That will let the gas slip by as it would fit through easier, probably due to "surface" tension on the liquid at least in some part, and the liquid would be forced into the evap.
Hopefully If I have time before school in Sept, I will get to that.
50ft of 3/8" on the way though, have 3/16 ;)