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haris
14-11-2014, 11:25 AM
Hi Everyone,

I heard from someone that they require a -90C cold room. I was wondering if it is possible and how? I have heard of freezers for bio medical applications running cryogenic temperatures, but entire rooms - this is a first? Any one knows of any such applications?

Thank you!

chillerman2006
14-11-2014, 12:07 PM
I heard from someone that you should not eat brown snow
Know not to eat yellow snow but maybe brown is ok
Does anyone know someone that eats brown snow
Where would you get brown snow
Maybe a cascade system would do

pcvh1976
14-11-2014, 12:15 PM
It would be probably a vacuum freezer they run on very low temps. -60C or -70C. But -90C is very low.

haris
15-11-2014, 02:01 PM
Yeah, I thought so too. As for chillerman2006.. yes a cascade system would do - but maintaining the room at -90C - even beats the yellow snow, brown snow dilemma ;)

Peter_1
20-11-2014, 02:34 PM
For -90C, you will need a triple cascade, in 2 stages impossible.
Or even better an autocascade.

mbc
20-11-2014, 04:55 PM
to reach for low temp. is possible ,
liquid N2 = about -180 -- 5 stage
liquid co2 = -78 --- 3 stage

up to -50 ( room temp. )) R-410 a is right

mich_vk
25-11-2014, 02:25 PM
You would have to use refrigerants that are not common for refrogeration, somethinf like Ethylene or methane. R23 is not enough. As for cascades: you should build a 3 stage if you do not mix refrigerants, or even autocascade if you do. But if do have brain it's not your choice. Blends are suitable for biofreesers only. Because a single leak will ruin the blend &... then you're in trouble

sphere478
26-11-2014, 08:42 AM
double post

sphere478
26-11-2014, 08:45 AM
I'm working on a similar project. subscribed. I'm interested to see what you come up with.

@mbc My experience with 410a has been that much more than -40c/f room temp on a single stage and the compressor acts like it's begining to starve for return gas to keep it cool. at that point, systems i've experamented with are starting to go into vacuum terratory. I gues you've seen 410a used colder than that? did you notice any longevity issues? where any other measures taken to keep the compressor cool? reciprocating? scroll? screw?

I do like 410a as a low temp first stage refrigerant the times i've used it. Though, I like r1270 even better! it seems to have better head pressures and i've been able to get slightly better results on evap temp. not to mention oil compatability being a hydrocarbon. with r1270 my test rigs have ran lower amperage aswell. only thing is it's flamable (like methane, ethylene) so i'd be weary of using it on a large system or on anything that i didn't personally own. :-( I get my 1270 from mapp/pro cans. (and run it through a series of filter driers for good measure while charging) i currently have a chest freezer expirement that has approached close to -50(f not c) room temp using r1270.

So you guys don't think he can get to -90c with a two stage setup?

http://www.xtremesystems.org/forums/showthread.php?165728-Xtreme-Phase-Hall-of-Fame there are a few two stage builds there in the sub -100c arena there. interesting reads, wish the pic links weren't broken :-(

mbc
28-11-2014, 05:17 AM
Hi sphere

also in 410a you have to use 2 stage .

use flammable gas needs more attention and especial equipment .

co2 is right gas for up to -75 c (( 3 stage))

Cofreth
28-11-2014, 09:04 AM
Long ago I have done on a chest type freezer which can pull down to -95C , cascade system using R-12 and R13B1,
not sure presently what ozone free refrigerant to take over R13B1.