Three-stages cascade system

[Sk_rmouche]

Hello everyone !

I'm new here, but read so much topics in this cat', we learn a lot !
Excuse me in advance if I make mistakes in English, I'm french

So my project consists in a cooling/heating chamber that I'm currently building, here's a picture :




On the paper I want to be able to bring down the internal T° to -130°C ( that's what I'm aiming to at least ... ). I already got my two first stages in run, but I'm stuck about R14, hard to get some, and expensive. Some people told me that I could use a blend of methane and ethylene instead; of course it'll be tacky to tune, but I'm seriously considering that option, what do you think guys ?

First stage run with R404a @ -40°C with R404a TXV Danfoss
Second stage run with R23 @ ~ -80°C with R23 TXV Danfoss
Third stage should run on CPEV, if it leaks I'll turn over to EEV with PID regulator, I think.

Thanks, and have a nice day !

Vincent.

[Sk_rmouche]

The inside of the chamber :