Cryogenic processor with Perlite insulation

[harsh234]

I am designing a cryogenic processor for size of 300x300x600mm rectangular with maximum efficiency.

Foam insulation will be very inefficient and other MLI and High vacuum insulation will be very costly.
So i was thinking of using 150mm thick insulation (annular section filled with expanded perlite. just my concern is whether vacuum is needed after loosely filled perlite inside the section or air tight section is fine.

or any other option for insulation.

 

[EdStainless]

Taking the air out is the primary insulation. You need to pull as good of a vacuum as you can.
Of course square is a very structurally inefficient shape for vacuum service.
Using vacuum as insulation is very inexpensive, just build a good shell and pump it down.
The filler helps the insulation when it acts to block radiant heat transfer in the vacuum space.

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[georgeverghese]

The cold box for the air separations plant ( double column operating at -160 to -195degC) I worked in in my younger days was perlite powder filled and kept blanketed with N2 at a very low positive pressure to keep wet air out.

Thermal conductivity values and total heat transfer coefficients for perlite powder in vacuum and slight N2 pressure my be found in Perry Chem Engg Handbook in the subsection for cryogenic insulation.

 

[harsh234]

Thank you EdStainless, do you have any idea, what level vacuum is prefered for square section?? i mean to ask, what sheet thickness of SS i should take for tank to sustain that much vacuum??
any engineering references for designing this type of box or vessel in cryogenics.

Below link is of Cryocart from Chart, i want something similar.

https://www.princetoncryo.com/cryocart.html

Thanks in advance.

 

[DSB123]

Expanded perlite is used between the inner and outer tank of LNG storage tanks. The "atmosphere" above the perlite is basically devoid of moisture laden air and is in fact methane/nitrogen under a small positive pressure.

 

[IRstuff]

?? Your vacuum should already be dictated by your "cryogenic" processing requirements. Nevertheless, you might wish to rethink using perlite in a vacuum chamber, as its surface area will cause a slow-down in pump-down time

TTFN (ta ta for now)
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