Thanks for writing all that @SidViscous. Very informative.
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I do my best to try to pass along the information Iâve picked up. Seems like a more than fair trade to exchange knowledge about refrigeration (a subject that has tons and tons of accessible literature) in exchange for all the cutting edge secrets developed for the first time by the fine people of this forum.
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Yes its very much appreciated. Im sure I can get it working, but understanding more fully can only help.
So looking at the performance data sheet for the awa2464zxdxc, what size of txv would you chose to optimally run at -40, a 1/5 or 1/4 ton to match the -40 rating/data, or a half ton for its -10 ânominalâ range rating?
I am way over thinking it mainly because I would like to eventually get into cascade or autocascade usage, primarily because I would like to inject for extraction at a temp colder than -40, even -50 would be awesome, so Im trying to understand if its possible to âoverclockâ this Tecumseh unit to achieve lower temps than -40.
I am leaning towards a direct expansion application vs a plate or other exchanger. I am thinking of ordering a 6"x54" tube, with a wall thickness of 4mm which should have a collapse pressure of over 450. double jacket it. Roughly there would be 10sqft of evaporator surface area and near 1200cc of evap volume!
(obviously not the safe manner of thinking but the collapse pressure will be bolstered by the internal pressure which should rise pretty equally if using a propane dom mix as a solvent) Basically a dual permanent storage freezer/working vessel for the solvent.
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Do it! We can do the math to make that safe. I donât recommend placing any value on the internal pressure because leaks happen and then, well, yeah.
The biggest thing to look at is the compression ratio. -40 is right on the edge of what you can do with r404a. If you have to compress the vapor more than 10:1 itâs not going to work well. You can get up to 15:1with liquid or vapor injection but thatâs a different compressor than youâre looking at.
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Hereâs the saturation table for 404:
R404A (1).pdf (43.6 KB)
At -45C youâre at 14.9 psia. To condense at 43C, you need to be at 283 psia. Thatâs almost 20:1. I would suggest some sort of water cooled condenser to get your range down to a lower condensing temp.
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I read on some other site that 404a in freezer applications the typical range is 6:1 - 13:1 which the awa2464 is a 13:1 @ -40evap and 90f condensing temps, so was only mildly concerned.
Heres a updated performance data sheet for the unit, https://www.tecumseh.com/globalassets/media/drawing-data/north-america/cu-data-sheets/2t3224-2-awa2464zxdxc_a.pdf it shows the performance at 80f ambient temps as well now. It also has a new parameter âCond Tâ which im going to have to look up.
Whats with the higher btu capacity at 80F vs 90F but the watts goes down? typo?
Anyway, average temp at my location is very cold, I get maybe 4 or 5 days over 85f, average yearly temp is 1c. I will have a harder time keeping it above 40f than not for most of the time its in use.
Is there a sweet spot? To cold of ambient not good?
Maybe I should not be so concerned with a âpre builtâ condensing unit and source a compressor that can utilize a more suitable refrigerant? The amount of stuff on the schematic that is not a compressor and condenser does daunt me if I had to recreate all that.
⌠also what size TXV ya figure?
This week is ordering week!
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Iâd probably run an EFSE-1 (1 ton nominal) with an SX charge. Youâre probably not going to find a better single stage refrigerant than 404a, just beware the issue. There is no such thing as too cold an environment, you basically just translate all the parameters down.
Iâm used to sizing systems with the assumption that theyâre going to be in a hot ass mechanical room. If you can keep the condenser on the colder side you can probably make it work. Just watch the discharge temp on the compressor, that high compression ratio will make it hot and if it gets over 200C it will start to burn oil.
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Waiting on some quotes on the unit and hopefully expansion valve. Might have a hard time getting that one. Think I found the condensing unit for $1k though.
Got one price for the dx storage tank just using a simple design, not sure if it needs more consideration, should be okay with the intake and outake being opposite each other? I upped my diameter from 6" to 8" to lower the height and went with a 5mm wall thickness for the inner tank. Should hold 30lbs of propane.
These sites have some cool stuff:
https://refresearch.com/
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Some progress.
Picked up a used condensing unit locally for a couple hundred: a Copeland C8AL-0151-TAC-001. Its a âreceiver baseâ condensing unit. Will have to figure out the phase conversion though.
Heres some specs on the compressor it uses if anyone is interested: Copelametic EADA-020E-TAC (6000btu and 1.1KW cooling capacity)
Also picked up a keep rite freezer evaporator which doesnt have a name plate, but pretty sure it was paired with the condensing unit I picked up(restaurant auction)
The evap has a Danfoss TUAE valve rated to -40. I couldnt find a valve rated for lower than -40 at least without paying out the ass for a new one(over 500cad wtf)
Key items left:
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Still havent decided on the DX tubing size but am getting it done up local vs china, looks like itâll be around $1000cad for a 60-100lb pipe/tank.
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3phase converter.
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Been a couple days since you posted this but I had a couple questions/points (other than nice score on the unit, looks like it should do well):
When you talk about DX coil what did you have in mind, just a straight up wort chiller style coil in the tank? You may have issues with liquid holdup in the evaporator unless you use run multiple coils through a distributor. That storage tank looks like it might work well in a âflooded evaporatorâ style (basically a giant suction accumulator) although youâre going to want a lot of insulation on the outside (vac jacket would of course be ideal but money is a thing lol).
$500 for a TXV is insane, that nearly the cost of an EEV and controller. Hereâs an ERZE for $150 and Iâm sure a better deal could be have: https://www.supplyhouse.com/Sporlan-168784-ERZE-1-1-2-GA-3-8-x-1-2-ODF-Thermal-Expansion-Valve-w-60-Capillary-1-1-2-Ton
Disclaimer: Iâve never used danfoss components since they told me to get bent so that part may be totally suitable but I honestly didnât look for a cross
Lastly, whatcha gonna do with that evaporator if youâre DXing? Fun fact, most refrigeration components are either rated for 450psig or 700psig so you could probably work it in as additional condenser area if you needed it.
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It was a nice score, I could also pick up a used 4hp tecumseh for around $1000, so anyone watching, do some searching for used/refurbed units, unfortunately a lot of restaurants are going under so freezer units are around.
The DX style is the latter of your guesses, like a big suction accumulator, or a 6inch(or 8") double jacket one end closed material spool.
I was going to use sch 5 pipe for the jackets, but cant source it locally so far. If I cant source it I will probably use Sch 10 for both the inner storage pipe, and the dx first jacket. For the outter vac jacket I will probably get some ghetto tek going and use a few kitchen stock pots with ends cut off and welded together as a outer pipe to avoid a 10 or 12 inch sch 10 weight and cost.
I still cant find the collapse pressure for 8" pipes so if I go with that size for the inside storage pipe I will opt for sch 40, which the only reason I hesitate on that is the thermal transfer hit with the thickness increase, but I dont think a 7 foot tall 6" pipe is ideal compared to a 5 foot 8" pipe.
Im 95% sure im going to use swagelok pipe adapters to plumb everything. If I could find flexable line set for 404a with low ambient temp rating Id use that too, but havnt found it yet, not sure if swagelok can make something up or what.
The reason for the high price on the TXV is the extreme or ultra cold charges, the SX and ZZC for the Sporlan and Emerson. Regular -40 type valves are all over for around $100
I picked up the walk-in evaporator because I thought I could scavenge the expansion valve off of it as it was cheaper than purchasing the valve on its own. Also we have wanted a walk in freezer for processing storage as well, so will pick up a replacement valve for it or buy a different one for the DX pipe.
Im not sure Iâd need that much condensing power its very large compared to the condenser utilized by the unit. Its 8 or 10 foot long, youve kinda blown my mind with this prospect.
Honestly you probably wonât have an issue with hunting in your application which is what those specialty charges are for. Sounds like youâre basically going to be fully loaded above design temp until you reach design temp and then if your vessel does have a vac jacket, you wonât need much capacity to maintain your cooling. That means your TXV is going to be pretty fully open most of the time. I think you can probably get away with a regular LT charge.
As far as fabbing up the vessel, I definitely think vac jacket is the way to go if you can swing it. Youâll also probably find it much more economical to have someone roll plate for you than to use pipe. Thatâs a pretty standard vessel design, and pretty easy with a backing strip on the outer and middle wall. You will probably want to find/design around the torispherical heads. Flat heads even at these pressures/diameters will butcher your wall thickness calculations I think.
Lastly, hoses/fittings: there should be a plethora of options for hoses rated for -60 or so but they wonât be cheap. You may want to honestly consider hard piping; how often do you really move your rack? The only thing I will say is that youâll hate your life if you let a single pipe thread on the refrigerant system. I would have JIC flare fittings welded on personally.
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