Three-stages cascade [ designing ]

[Sk_rmouche]

Hello,

Let me introduce first : Vincent, I'm french, so excuse me in advance for bad english, I'll do my best to try not make my topic unreadable.
So I'm trying to make a three stage cascade, presently I'm still ( and for a long time ) in designing.

I will re-use my "box" of my old waterchiller :

http://img829.imageshack.us/img829/6277/27072011668.jpg

http://img861.imageshack.us/img861/4279/29032011567.jpg

Just for info, the first version with cap tube instead of a TXV, running with R507A gas.
So the box is empty now, ready for the cascade

Here is my idea of the potential staging :

First stage :

Some rotary compressor, something like 10 or 12 kbtu/h ( you will see why such a weak compressor a few sentences after ... )
R410A with TXV, orifice 00 or 01.
Condenser of ~ 3 kW @ 15k, with 10 ou 12 120 mm fan, digitally regulated by a circuit based on a PIC, built by me, and a PID regulator.
HX 10 or 20 plates.
HP pressure switch 25 bara.

Second stage :

Rotary compressor ~ 21 kbtu/h and 36cc displacement.
R23 with R23 TXV, orifice 00 or 01 ( I think 00 will just be fine ).
Big desuperheater
Home-made oil separator with manual valve.
Dead volumes for a medium static pressure.
HP pressure switch 25 bara.

Third stage :

SC21G, and if it not fit well with the power of the rotaries, a big rotary like the second stage.
CPEV Fach PZ from Piotres.
R14 ( the hardest things, it's strictly regulated here in France, as a perfluorocarbon, cost me about 1000 euros ( 1300$+ ) for 2 kilos of it with Air Liquide, freakin' expensive )...
Desuperheater like the second stage.
Home-made oil separator with manual valve.
Dead volumes home-made.

About the "little" rotary at first stage, I want to take a R407C compressor, then fill the circuit with R410A, and running it with a high BP, something like 2 bars, to get -30°C, in order to condense R23 at a reasonnable pressure ( not too high, but not to low ).
So I think if I take a biggest compressor, I'll flooding everything and have liquid return in excess... )

I hope I'll continue the project until the end

Ps : feel free to tell me if something's wrong, or tips

Thanks you for reading !

Vincent.

[SAE]

Primarily, welcome to XS.

And: I am looking forward to seeing your progress. It's nice to have some phase guys around here as it has been too "silent" in this section for the last months.

[Hondacity]

PIC programmers ftw

[teurorist]

N1 waiting for results

R170 in 2nd stage isn't a possibility for you ?

[n00b 0f l337]

Hey I don't get enough time to stop in here anymore, but I've PM'd you my email if you need to drop questions for quick answers, you're welcome to post them here as well.

[Sk_rmouche]

Thanks "n00b of 1337" !

And thanks to others guys too.

About the R170... shame on me but ... my father doesn't allow me using flammable gas, without that you could easily imagine that I'll go for a R410A/R1150/R1150-R50 cascade, R14 is so expensive ...

[teurorist]

then don't tell him ?

[Sk_rmouche]

You have to know that here in France, Air Liquide trust the market, and its gases aren't cheap as well. So for a bottle of R1150 and another one filled with R50, at high purity level, I don't think that I'll pay really less than a bottle of R14.

Otherwise, R14 is easier to condense, with no stressing compression rates, and it'll fits well with R23 I think. And I've already buy R23 TXV, so ...

[wdrzal]

About the R170... shame on me but ... my father doesn't allow me using flammable gas, without that you could easily imagine that I'll go for a R410A/R1150/R1150-R50 cascade, R14 is so expensive ...

Someone needs to read the MSDS sheet on ethylene (R1150). Explosive in air LFL 2.7% to UFL 36%.

UNUSUAL FIRE AND EXPLOSION HAZARDS:
Spontaneously explosive when combined with chlorine in sunlight. Forms explosive mixtures with air and oxidizing agents. Heat of fire can build pressure in cylinder and cause it to rupture. No part of a cylinder should be subjected to a temperature higher than 125°F (52°C). Ethylene cylinders are equipped with a pressure relief device. (Exceptions may exist where authorized by DOT.) If venting or leaking product catches fire, do not extinguish flames. Flammable gas may spread from leak, creating an explosive reignition hazard. Vapors can be ignited by pilot lights, other flames, smoking, sparks, heaters, electrical equipment, static discharge, or other ignition sources at locations distant from product handling point. Explosive atmospheres may linger. Before entering area, especially confined areas, check atmosphere with an appropriate device

[Sk_rmouche]

I think we all knows about risks using flammable gas, just to tell, the acetylen of your welding torch is way more dangerous than propane or even ethylene ( which at least can be compressed, and is not instable ).

If I could, I will go for a 4 stager cascade, with R410a, R23, R1150 and finally R50, but I don't, not only because ethylene and methane, but I've not so much space in the box, despite its looking on pictures

[Sk_rmouche]

I received these days some parts of the cascade :





Cpev from Piotres, a FACH PZ

Last week I bought for something like 70$ an old HVAC, and I got a rotary compressor, and a big evaporator to make a dual desuperheater ( for second and third stage ) :




( sorry not good quality pictures, taken with my phone )
I didn't find datasheet for the compressor, it's a really "google-unknown"
I'll use it for first stage, only thing I could tell is it's a 1.5 HP compressor ( 1150W ) running with R407C.

I've also write a little table with estimated pressures rates, it's in french but i bet that it's not so hard to understand



Is anybody tried to run with a two-stages compressor ?

[Sk_rmouche]

Given the difficulties in the supply of R14, it is possible that eventually the cascade consists of a staging R134a/R410a/R23 or nitrous oxide, I'm not yet sure, but it's a possibility. In the mean time I'll see if nitrous oxyde is a reliable refrigerant ( R744a ). I've ordered some to make tests, related to his oxidizing state with oil.

With CPEV at final stage I could adjust precisely the evap' pressure to aim -88/89°C without reaching the melting point of nitrous oxyde.

[Patrickclouds]

i would say that is a 16,4ccm rotary.

http://pwcg.panasonic.cn/en/indoor/p...s=1041&pid=369
or page 2
http://acma.vn/admin/upload/download...d_benefits.pdf

[Sk_rmouche]

Oh thanks Patrick ! I've searched but didn't think about Matsuchita, the old name of Toshiba Company

So this is really a little compressor, more powerful than my danfoss SC21G, but tiny displacement

[Sk_rmouche]

Okay, I have one question : is someone knows about fluorocarbon oil ? Air Liquide says that N2O ( nitrous oxide ) is tolerated by this type of oil, unlike hydrocarbon one, can I found it easily ? I've never heard about it

[Sk_rmouche]

Hi dudes,

Some updates, I've got some R23 @ home, with R23 TXV by Danfoss, a new welding torch with quite big bottles



And prepared some parts, like desuperheater or 1/2 stages HX, down here :



Everything is ready for 1/2 stages. The third stage is on an awful way, damned R14, so hard to find at a good price, don't know how I will manage that yet, I make researches toward another gas, like NF3 ( nitrogen trifluoride ), but it is expensive too.

Maybe I'll go to R1150 for third stage if I got nothing...

[Kamil Grzbiecik]

When a further report from the building?
Good luck

[Sk_rmouche]

I might be able to give you some news within 2 weeks, at least I hope so ... :o

[mytekcontrols]

Given the difficulties in the supply of R14, it is possible that eventually the cascade consists of a staging R134a/R410a/R23 or nitrous oxide, I'm not yet sure, but it's a possibility. In the mean time I'll see if nitrous oxyde is a reliable refrigerant ( R744a ). I've ordered some to make tests, related to his oxidizing state with oil.

With CPEV at final stage I could adjust precisely the evap' pressure to aim -88/89°C without reaching the melting point of nitrous oxyde.

Maybe it's just me and perhaps I've watched too many Fast & Furious movies, but would Nitrous Oxide be a good idea in a cascade? How would it react with the oil under heat and compression?

I dunno

Just a thought.

[Charles Wirth]

Thanks update, looks similar to my brazed plate and valves. no cap tubes

[Sk_rmouche]

Maybe it's just me and perhaps I've watched too many Fast & Furious movies, but would Nitrous Oxide be a good idea in a cascade? How would it react with the oil under heat and compression?

From my readings, nitrous oxyde isn't an oxidizer as its initial state, it's the temperature which is the "trigger" ( sorry if I don't use the right words, I'm french ) to decompose N2O in O2 and 2N2 at something like 400°C, and > 250°C under pressure. Beside, I could eventually use perfluorinated oil to skip "flammable issues".

But I got my R23 bottle, so N2O isn't a problem any more

[mandolin hot]

Could a mixture of C02 and a lower pressure gas be a good option?

http://encyclopedia.airliquide.com/E...rPressureGraph

C02 would be "dry ice" after the ISHX, so it needs to float around in something else, maybe whatever gas is used for the 2nd stage (or first stage, even). It would be like a dry ice slush. The C02 crystals would be carried by the condensed lower pressure refrigerant. CO2 has good heat carrying capability, among other obvious cost benefits.

[Sk_rmouche]

Yeah why not, I've a CO2 tank @home for pressure test, and when I was looking for N2O I wanted to mix them.
What about a R23/Co2 mix ?

[n00b 0f l337]

If you have r23. Use r23. You won't be unhappy.

[Sk_rmouche]

I won't if I can have some NF3 or R14

You guys clearly use ethylene or methane instead, didn't see numerous cascade with R14.