TXV for Ethylene

[NoL]

I'm starting to work on a new build for computer cooling, three stage cascade.
R507a, r1150, r14+r740 (with subcooler)
Aims for -125C or colder.
Right now looking to use a TXV on first and 2nd stages. The first two compressors are 3/4hp tecumseh rotarys, while the third is a 1.125hp tecumseh rotary compressor.
What sort of TXV should I use for working with something like liquid ethylene, which will be around -30 to -40C into the TXV, and -80 to -100C outlet from the TXV into the second plate heat exchanger.
Or should I just swap to capillary?

[NoL]

Anyone?
I cant find anything.

[US Iceman]

If you want to use a TXV on ethylene call Sporlan Valve. They will not have a catalog number for the TXV, but can probably select one for you.

Since you are using ethylene for the low-stage, what are you planning on doing if the power goes out? At ambient temperatures the pressure of ethylene is pretty high.

[norseman]

Why are you using the bigger compressor for
the 3. stage? Normally are the cascades made with
smaller and smaller compressors through the stages down. Anyway, I was into some test chambers making +200c down to -80c. The TXV used in this
two stage system had as mostly seen a high MOP to
prevent to much stress on the compressor. The bad with such valves is that the inlet get may be -40c and the bulb stay high in the start up and every on.
The MOP use a partially liquid filling and the main problem is that the liquid migrate to the head and
stay there. I ended up often to a unit which almost
did not cool since the liquid kept the valve closed.
The good thing with a capillary is that by start up,
the refrigerant boil in the capillary so the compressor do not have to "eat" too much in the beginning. If you want to have as low as possible static charge to
prevent the high discharge those systems create, you can put on a tank on the 3. suction side and a normally open valve over a short cap. Make a sensor
on the eva. An associated controller to drop the power to the valve the at -60c or so. The extra charge will then pop in to make some more capacity.

[NoL]

Both the second stage and the third stage will be having expansion tanks, the extra volume being created by 4" diameter 11" tall accumulators attached to the low side via capillary (probably 3' of .031" for each). Might end up using more then one per to keep the pressures sub 250 psi with static and ambient hx's. The largest compressor is happening upon the third stage due to the higher cfm that I want to get the most out of r14 with argon saturation.
I'm going to use a Sporlan 3/4 Ton internal equalized; EGV-3/4-Z (21953) for the first stage, but I'm starting to consider a capillary line for the second stage simply due to the hassle and seemingly problems created with using a TXV past the HX of the first stage.
The first stage will have more then enough compressor cooling, and all will have 250-300cfm of aircooling upon them if not more, the 2nd and 3rd stage will have an autocascading oil separation stage featuring a slight amount of r290 used to break the vacuum of the unit, combined with the temprite 3 series oil separators and captube should have very efficient oil separation.

[Rob S]

This is not going to work well. I've seen the guys use A/C rotory comps in cascades before. After about 50hrs of run time the oil is now a brownish sludge. Prob with those rotory comps is the way the gas cools it's motor windings. Its discharge gas not suction. Thats just my two cents...

Anyway... use a EBFS-AA-Z valve for the 404A stage with the 1.125hp. A EGW-1/8-GP for the 1170.. But you'll have to use a captube or Auto-expantion valve for your 3rd stage. Because there is no way you'll get much more than a 1/16th of a ton from it.

[Peter_1]

We have a 2-stage ethylene running (production machine) but with a capillary.
Or you can use an AEV instead of a TEV.

[Rob S]

Peter...
Are you talking about using R1150 in a cascade or in a compound 2stage system?
Because I dont see how you can 2stage ethylene. With out say a -40C chilling loop cooling the condensor.

[Peter_1]

Casaced, 1st stage propylene, 2nd ethylene.
Given the pressures, a compound is technical impossible.