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Post by elec573 on Feb 17, 2018 2:28:14 GMT
How were the drs on the heat ?How did the R124 work in compairson with the so2 as far as the high heat in the dome ? Just a thought I believe this is why a lot of drs fail
do to the heat breaking down the electrical insulation on the motor and other components. Maybe another test for another time. Buy comparison look at the wiring on the outside
its a wonder any of them are still working.
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Post by Travis on Feb 17, 2018 2:53:14 GMT
Herb,
I would doubt they operate much cooler. The system is still a high side dome with an 80 something year old motor.
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Post by blackhorse on Feb 17, 2018 4:54:57 GMT
Physics would say a bit cooler, SO2 has notoriously high superheat.
From a practical standpoint?
I agree, it would be enlightening to take side-by-side, top-of-the-dome readings in about 100F ambient.
In about 6 months. Or ship them to Aus--
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Post by Travis on Feb 17, 2018 5:01:13 GMT
True,
I think we're running out of DR's that still have so2. I am not going to force one of my babies to run in a 100 degree room. That's just looking for another casualty.
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Post by elec573 on Feb 17, 2018 5:05:25 GMT
Well I’m sure cable hack would love to have some drs as guests. Although he might have to expand his house . Drs I know of at least 2 looking for homes .
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Post by blackhorse on Feb 17, 2018 5:21:43 GMT
Yeah there's that; maybe 90F then.
They would need to be as closely matched as possible; some fascinating recent research indicates the earlier compressors didn't have the internal fans that the later ones had. That would no doubt make at least as much difference in dome temperature as the refrigerant.
Which in itself merits measurement. I wonder how different the top of the dome temp is in the later ones compared to the earlier ones.
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Post by elec573 on Feb 17, 2018 6:10:04 GMT
Well maybe for the next test that could be done. I want to thank coldspaces for all his work.
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Post by birkie on Feb 17, 2018 14:28:48 GMT
How were the drs on the heat ?How did the R124 work in compairson with the so2 as far as the high heat in the dome ? Just a thought I believe this is why a lot of drs fail do to the heat breaking down the electrical insulation on the motor and other components. Maybe another test for another time. Buy comparison look at the wiring on the outside its a wonder any of them are still working. ran them in some summer heat. If I recall correctly, there was no obvious difference between the SO2 and R124 dome temps (they'd both get up to similar temps), but that wasn't something specifically monitored as part of the experiment. One would really need a data logger to do that effectively; it's really labor intensive for something so esoteric otherwise. I agree, it would be enlightening to take side-by-side, top-of-the-dome readings in about 100F ambient. There are a lot of nerdy questions I have regarding dome temps in general, like being able to understand how long (in normal cycling) the dome temps are low enough to allow condensation or refrigerant inside the dome; how ambient temperatures affect these dynamics, etc. For that, I think something like this data logger, this pressure sensor, and some thermistors would be necessary. I'm aiming to set up something like that in my garage in the mid-to-late summer time frame, if the stars alinn correctly. |
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Post by CCL2F2 on Nov 19, 2019 7:29:06 GMT
It wouldn’t let me post in the other thread for some reason and the first post seems to have disappeared? I suspect part of the problem with using higher pressure refrigerants in dr units is that increased capacity causes the condenser to warm up faster than heat can make it down to the bottom of the compressor. The latest unit started with hot oil and a cold room and it worked fine. Also perhaps the higher discharge temperature of so2 is why it works ok with a smaller heater.
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Post by coldspaces on Nov 20, 2019 5:02:44 GMT
I suspect part of the problem with using higher pressure refrigerants in dr units is that increased capacity causes the condenser to warm up faster than heat can make it down to the bottom of the compressor. The latest unit started with hot oil and a cold room and it worked fine. Also perhaps the higher discharge temperature of so2 is why it works ok with a smaller heater. Interesting possibilities! I believe a lot of the work I did with 152a was when my garage was cold. I have been rereading my work, I do so much in a year its hard to remember all the details. I really looks like the cold sump is the root of all the 152a issues I saw. A hotter oil heater may be all that is really needed to solve it. I ended up with a 40 watt in the NJ DR3 with R124. Didn't try that much heat when testing 152a. I don't remember if 152a has a lower btu per Lb than so2 and 124. If so that would account for it condensing easier, less btu's would be needed per lb to make it condense in the cold sump. |
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Post by coldspaces on Nov 20, 2019 5:05:23 GMT
An update: A few of us have been communicating regarding logistics of pairing guinea pig machines with refrigerants. In that conversation, Gill mentioned that he and Travis once talked about trying R124 too. It's an HCFC (so it's going to eventually be banned), but it looks like some production of it might be allowed up to 2030. They're not sharply scaling it back like they're doing to R22. Anyway, it's available at reasonable prices through wholesalers as a refrigerant. I ran some calculations on it and ... WOW! R124 is also a very close match SO2 as well! It looks like it's very weakly miscible in mineral oil; practically immiscible below 114F. That's promising for oil return. Here's it's data sheet www.chemours.com/Refrigerants/en_US/assets/downloads/h62445_hcfc124_push.pdf Here's how it compares with SO2, R227ea, R1234ze, R134a, R152a as a drop-in replacement in the same hypothetically ideal compressor, with 15F low-side and 100F high-side saturation temperatures: Power Draw (relative) ------- SO2: 1 R124: 0.92 R227ea: 0.97
R1234ze: 1.12 R152a: 1.41 R134a: 1.52 Capacity (relative) -------- SO2: 1 R124: 0.99 R227ea: 1.18 R1234ze: 1.29 R152a: 1.55 R134a: 1.73 COP ----- SO2: 5.62 R124: 6.47 R227ea: 6.80 R1234ze: 6.50 R152a: 6.19 R134a: 6.40 Head pressure differential (relative) ---------- SO2: 1 R124: .92 R227ea: 1.08 R1234ze: 1.17 R152a: 1.41 R134a: 1.55 Mass flow (relative) ----------- SO2: 1 R124: 2.35 R227ea: 3.57
R1234ze: 2.65 R152a: 1.91 R134a: 3.28 Molar flow (relative) ------------ SO2: 1 R124: 1.10 R227ea: 1.35
R1234ze: 1.49 R152a: 1.85 R134a: 2.05 So I'd say it's an even closer match than R227ea by a hair, and it's more "normal" as far as density. In any case, we now have two outstanding contenders for the DR drop-in replacement challenge! Appendix: Here's a little p/t comparison chart.
| SO2 | R124 | R227ea | R1234ze | R152a | R134a | | -5 F | 11.6" vacuum | 9.3" vacuum | 5.1" vacuum | 2" vacuum | 2.4 psig | 4.1 psig | | 5 F | 6.1" vacuum | 3.6" vacuum | 0.9 psig | 2.7 psig | 6.9 psig | 9.1 psig | | 15 F | 0.4 psig | 1.6 psig | 4.9 psig | 7.2 psig | 12.2 psig | 15.0 psig | | 85 F | 51.1 psig | 48.8 psig | 61.0 psig | 67.8 psig | 83.8 psig | 95.2 psig | | 95 F | 63.8 psig | 60.1 psig | 72.9 psig | 82.1 psig | 100.4 psig | 114.0 psig | | 105 F | 78.3 psig | 72.7 psig | 88.8 psig | 98.1 psig | 119.2 psig | 135.0 psig |
Here is Birkie's work that shows R124 was about as close as anything we have found to replace so2. |
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Post by elec573 on Dec 14, 2019 4:23:19 GMT
Nice work and very informative.
Thanks for posting.
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Post by perryhahn on Aug 12, 2020 7:56:59 GMT
I was considering using r227 for a monitor top. Doing the calculations for the compression cycle, I assumed an intake temperature of 263K, or 14 degrees F, saturated vapor. I also assumed that the end pressure would be the same as that of the saturated liquid entering the float valve, which would be 6.085 MPa at 308K (95 degrees F). Assuming an isotropic process, the entropy would stay at s=1.4480J/g*K. Now, generally this compression process takes a saturated vapor into superheat. However, the Temperature-Entropy diagram for r227 is not shaped like normal substances. If you start on the edge of the saturated vapor curve, and go vertically along a constant entropy line, you don't end up in superheat territory unless you go way up beyond anything that a refrigerator would encounter. Instead, you end up with a combination of liquid and vapor. In this case, the compression cycle takes you to 90% vapor and 10% liquid. Since this requires it to be at saturation pressure, the temperature doesn't go beyond the 308K of the line leading to the float valve.
The upshot of all of this is that if my reasoning is correct, the compression process is dumping a considerable amount of liquid r227 directly into the oil reservoir in the dome, where it sinks below the lighter mineral oil and probably stays there. This may result in a seeming loss of refrigerant. To fix the problem, someone may keep adding refrigerant over several servicing sessions, until the oil sump is sucking up r227 instead of oil, lubricating a 90 year old machine with a liquid that has less viscosity than gasoline.
Can someone find a flaw in my calculations or reasoning? Has anyone had this problem with r227?
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Post by turbokinetic on Aug 17, 2020 0:54:38 GMT
I was considering using r227 for a monitor top. Doing the calculations for the compression cycle, I assumed an intake temperature of 263K, or 14 degrees F, saturated vapor. I also assumed that the end pressure would be the same as that of the saturated liquid entering the float valve, which would be 6.085 MPa at 308K (95 degrees F). Assuming an isotropic process, the entropy would stay at s=1.4480J/g*K. Now, generally this compression process takes a saturated vapor into superheat. However, the Temperature-Entropy diagram for r227 is not shaped like normal substances. If you start on the edge of the saturated vapor curve, and go vertically along a constant entropy line, you don't end up in superheat territory unless you go way up beyond anything that a refrigerator would encounter. Instead, you end up with a combination of liquid and vapor. In this case, the compression cycle takes you to 90% vapor and 10% liquid. Since this requires it to be at saturation pressure, the temperature doesn't go beyond the 308K of the line leading to the float valve. The upshot of all of this is that if my reasoning is correct, the compression process is dumping a considerable amount of liquid r227 directly into the oil reservoir in the dome, where it sinks below the lighter mineral oil and probably stays there. This may result in a seeming loss of refrigerant. To fix the problem, someone may keep adding refrigerant over several servicing sessions, until the oil sump is sucking up r227 instead of oil, lubricating a 90 year old machine with a liquid that has less viscosity than gasoline. Can someone find a flaw in my calculations or reasoning? Has anyone had this problem with r227? Thanks for the post and glad you've joined up! Several of us have considered R277 / FM200 but the high cost and low availability has dissuaded us from using it. There are so many factors at play in these systems that purely theoretical numbers rarely work out in reality. These compressors are designed for dry vapor on the suction side, with significant superheat; as well as a refrigerant which maintains a superheat through the compression process, thereby discharging dry vapor. Any condensation in the cylinder would be harmful in that it would displace the oil from the cylinder walls and piston. When it comes to units originally designed for SO2, there are primarily two alternatives which many of us have used. The first choice was R124, which has been around a long time and proven in many systems. A newer choice is R152A which has been used quite a bit in the last decade or so. They both have proven working records in the CK machines. Pluses of R124 are that it has been in use longer and more professionals are familiar with it; also it runs at a lower pressure similar to SO2. Some minuses to it are that it is a phase-out refrigerant and is very costly due to taxes. Also, it will blend with the lube oil in these systems, which is not how they were originally designed to operate. This blending and solvent action can stir up sludge and cause issues when it is introduced to old systems which have not been fully dismantled and cleaned. With R152A, pluses are that it is not highly soluble in the oil and will perform similarly to SO2 in this manner. It is not a phase-out refrigerant and is not expensive. Possible minuses are that it is not well known outside of the automotive A/C and antique circles and few current professionals are familiar with it. It provides a capacity increase over SO2, due to a slightly higher operating pressure, so this could be a concern if you are trying to minimize any change from factory ratings. Lastly, liquid spills of this refrigerant can be ignited; although this is the case for several of the newer refrigerants. Both R124 and R152A are proven. There is a new one which has been experimented with lately, called R1234ZE. It is a hydrofluoroolefin gas operating at a pressure in between R124 and R152A. There are only a handful of machines running this refrigerant and as far as I know, none of them have had any failures. It's somewhat hard to obtain and more costly than most refrigerants, but it is touted as 0% flammable in any form, and is the latest in environmentally safe refrigerants. Here is a short video on this one https://youtu.be/to99qC6pafUMost of us are all about learning how new gases work in these units! If you have access to R277, by all means try it! I would love to see how this works. I am familiar with it from fire suppression systems but have not had any opportunity to obtain any for my own use. Sincerely, David |
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Post by perryhahn on Aug 30, 2020 8:15:31 GMT
Your reply has escaped my notice until now. Thanks. I guess I have not yet learned how to navigate on these forums.
I have no access to r227, and based on my figures I don't want to be the guinea pig. One would need 24 degrees F of superheat at the compressor inlet to keep from dumping liquid refrigerant into the dome, so I don't want to try this. I brought up the topic because I know that some people are using it for an SO2 replacement in monitor tops. I even saw a You-tube video of someone doing this. My figures raised some alarm bells, and I was wondering if my thinking is wrong. If not, then anyone considering r227 should be warned.
Aren't you the same guy who does videos on replacing SO2 in monitor tops with r152a? I learned a lot from these videos, and r152a is also one of my refrigerants of choice. However, Coldspaces here has had mixed results with his experiments with r152a. Have you seen his posts? Have you had trouble with rattling or stuck float valves?
I'd really rather use the factory recommended refrigerant, if I can get it anywhere. I would probably keep the refrigerator on the porch anyway, so I'm not so worried about a sulfur dioxide leak.
Perry Hahn
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