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.
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