ultra-low temperature freezer

Hi everyone, i am fresh here, brief self-introduction, from China, 23, male, engineer, my jod is to design and develop ultra-low temperature freezer in my company, my major is english in college. so i hope to discuss with you in english, of course, if you want to learn Chinese or culture of China, just tell me and i can help you. I have to say sorry because i can't log in facebook or youtube because of some political reasons, but at here, we can talk about refrigeration technology and clutures, and i am waiting for your reply;)

Albiet not the correct forum for this, how ever excellently written introduction, and thusly welcome!

Pleasure to meet you.

Now for ultra low temp stuff do you use conventional cascade systems or auto cascade? I personaly was thinking of building an autocascade due to runing efficiency and faverable compressor temps.

Attachment 10601Thank you for reply, actually, it's conventional cascade, it can reach -86℃to -150℃ with only one compressor, and it's efficient. The key point is refrigeration fluid, it is mixed(not just one), do you have some suggestions to develop my products? Because this kind freezer is used in storage of blood and marrow or some scientific research fields, i hope it can be more efficient and reliable, thank you!

Ah then this is called an auto cascade in these parts! very good system.

The bigest point is for the compressor cooling, some good work has been don in pure hydrocarbon blends with R-600 replacing the R-123

Other big advantage of the hydrocarbons is lowe compression ratios yeilding power savings.

http://www.xtremesystems.org/forums/...cascade-System

A hobby forum but with a very skilled engineer, be an interesting thing to view through a different set of eyes, may give you some neat ideas!

It's cool, but R600 is not safe, right? It may explode when meet fire, the forum is quite nice, thank you.Ah the pic shows my system, quite easy, right?Attachment 10602Attachment 10603

R600 - like all HC working fluids - will combust quite easily.

I'm curious - what type of compressor and oil are you using in that system? -104ºC is some pretty low stuff if you're using oil lubricated compressors...

So do the oils in any refrigeration system, but unlike the typical halogen based refrigerents HC's won't burn your lungs out of your body when they do burn! which makes the HCs much more safe in my books & with HC's you need a smaller charge often.

Another great benifit is excellent oil transport, will stop allot of oil logging issues and when blended with HFC's it reduces the lower flammibility limmit if not removing it all togeather. A pure HC blend would be the ultimate goal as this would make you able to claim a very eco friendly unit while retaining excellent temps.

yup real easy if we ignore the 30 to 40 feet of coaxial copper heat exchanger lol!

hi johnzx, have worked on a few auto cascade systems ,never mixed refrigerates myself but lots of $$$ required in charging an auto cascade,
in storage of blood/plasma only -40c needed, marrow/bone -80c,in most cases liquid nitro drums are used for below that,,auto cascade systems are great when working ,,costly to repair good luck :)

sorry to reply you so late, we just use traditional compressor, it's brand is Danfoss, the key point is about refrigeration fluid, it is mixed, more than 3 kinds. I want to improve my product, do you have some good suggestions?

need more detail info, do you have pic?

Read through from the hobby forum I gave the fellow there goes into great detail on how to design and mix a charge. some them guys been building cascades that go below -180C I won't quote em on longevity but they have don it.

Great, i have tried many ways, but the lowest is about -150, and it's not quite stable. By the way, where to find the details?

read the whole thread in that forum, the guy whent very deep into the charge detailes and heat exchanger desine.

http://www.xtremesystems.org/forums/...cascade-System in this one? and could you kindly to tell me your email please? mine is johnzx001@hotmail.com

Hi,

We are looking for a paid consultant who can help us out in Thermal Regulation of a Thermal Vacuum Chamber. A secondary heat transport fluid (limonene) is used for the thermal regulation of copper shroud. The fluid is thermally regulated by Cascade Refrigeration (R23/R404A) for cooling and Electric Resistance Heater for heating.

Temperature range: -70C to +150C
Cooling capacity (including the load of the limonene, copper shroud, device under test and other factors): 15kW

Feel free to contact me directly at sydomr[at]ymail_dot_com

Regards,
BrightSide

If you're looking to achieve ultra a low temperatures you're best bet is surely running several individual systems in unison. Linking the systems together with cascade condensers/heat exchangers and using appropriate gas in each system will achieve what you're after with little effort.
This is fairly basic knowledge. With the position you claim to have I'm surprised you don't already know this basic method.