Multilayer Vacuum Insulation for Cryogenic Application

Try a google search for dewar vessel insulation material.

Vacuum is your friend. Leave the unknown material out of your "design", since you have no idea what it is and can't find it anyway. Use a few locator studs to keep things in place.

Or why not just buy an existing, properly designed tank.

I believe the idea behind the insulation in the evacuated region is to limit "cold loss" (i.e. heat gain) by radiation.

Of course you are right. Next time I'll give it more thought before I jump in.

Well, thank you for comments.

I have one variant of laying insulation, but my Boss said me there is a better insulating laying material, that allows radically reduce the vacuumizing procedure time.

Thank you!

Regards,

Vadim

In the US. Air Force tanks I maintained there was a blown in insulation between the inner and outer tank. The supports for the inner tank were all stainless steel to reduce thermal transfer to the inner tank. Unfortunately I am uncertain what the blown in beads were, but we should be able do deduce what they are by their function. They must have been something that blocked heat that could transfer through a vacuum.

Make sure you leave a method for pulling your vacuum again in the future, and installing a device to measure the vacuum will help monitor it also. I believe we used a thermocouple device that was calibrated to measure a pretty hard vacuum.

Also, you will get the best vacuum if your inner and outer tank are warm. I have had the best results when pulling a vacuum while purging the tank. If your design doesn't already incorperate a purge method you might install one. Purging is blowing hot air into the tank fill inlet and once the outlet (vent) reaches optimal temp, you cycle all the pressure build up and issue lines to evaporate any contaminates that may have accumulated. You have to be careful with Liquid Nitrogen (LIN) because it will precipitate oxygen out of the air which could leave you with a (fire) dangerous oxygen rich environment. Large puddles of LIN can gas off and displace oxygen in low lying areas so do not leave your tank in an unventilated area.

Sorry for all the additional safety information, I do not know your knowledge level and thought it appropriate to include it in this post.

Drew

what you need is called 'super insulation' in the trade.

They take a roll of very thin aluminized mylar and roll it around the object to be insulated and they allow a little fumed silica, called cabosil, to enter the nip so the mylar layers are tented apart by about 1/25" of an inch. It can also be laid on flat square plates, and other shapes to constitute a dewar shape. Then the container is assembled with inner and outer shell, rounded bottom and top, or any shape you like that conforms to what you want as long as you have many layers of thie aluminized mylar kept apart by cabosil.

The container is sealed with a perfect gas seal, with the exception of an evacuation nipple, evacuated to draw a hard vacuum and held at a vacuum while heated below the damage point of the mylar for some period of time until the vacum level is stable and there is no more outgassing. The nipple is then melted shut, and you have the super insulated vessel. lots if hints here.

I used to make this at a company when I was a student in 1964, stateof the art has not moved much since then

http://www.google.ca/#hl=en&q=superinsulation+%2Bmylar+&meta=&aq=f&oq=superinsulation+%2Bmylar+&fp=7310e1b076ed5f89

I agree to aurizon. Some years ago I worked in the military aviation field and this type of insulation, together with a vaccum jacket was used for the insulation of liqiud oxygen tanks used onboard aircraft. As the combination of silica and aluminum foil will reduce heat losses through radiation, the vacuum will help to keep losses though heat conduction low. One of the crucial points is to achive a high vacuum level. Therefor so called ion getter pumps are typically used in the last pumpnig step. Another thing, besides good sealing, is to maintain the vacuum even during the sealing process and after that. For this reason I often found that a small quantity of an ion getter material was put into the vaccum space to "capture" as many residual gas molecules as possible.

Regards nudnik

Hi,

any material between the 2 tanks is worse than no material.

Heat loss is by radiation, so outer surface of inner tank and inner surface of outer tank shall be as good reflecting as possible!

I Dewars silver or aluminum is used on glass.

You have chosen metallic tanks, so look at thermal conductivity of weldings: may be much more heat transporting into your tank than you would like.

Glass is a much better insulator than any metal.

Metals: titanium is much lower in thermal conductivity than stainless (a factor of 15 to 20!!!), so look to the bolts - if any - and to the welding: how much heat transport?

Look what in satellites is used for good and lightweight radiation-insulation: gold-coated mylar.

Aluminum is nearly as good (may be even better).

Reflectivity data are compiled in the book: Musicant, Optical Materials.

Most simple approach: crumbled aluminum foil, many turns. Good reflectivity, low heat conductance despite high conductivity as touching areas from one layer to the next are small and irregular. Make sure you do not get oil on the surface if to be operated above 100 °C.

RHABE

Dear questioner,

there are two insulating materials which we put in between two walls vessels of cryogenic liquid tanks.

1) thermal insulating material called perlite powder which is made of crusing of rock.it is easly available in india and saudi arbia(saudi perlite company)al

thanks

RCMANDAL

M-00971505962275

C.E.(INDIA)

Perlite beads!

That is the insulation I recall being blown into my Air Force 5000 gallon liquid nitrogen / oxygen tanks. I didn't think I could be remembering that name right, but you confirmed it for me.

As I mentioned above, vacuum, non-thermally conductive supports and perlite beads.

Drew

perlite, as described, is OK, if you can buy new liquid gas to recharge it as needed.

For deep cryo work you need the high vacuum, gettered, reflective mylar method.

The inner and outer are linked by sparse mechanical couplings that involve deep insulated ripples of this fiberglass sheet to provide a minimal conductive path.

It is highly evolved.

google linked terms, cryogenic +insulation +vacuum

Correct, but as the OP stated the question, I am not sure they will need such an elaborate system.

As far as I know we never did anything with the perlite. It was sealed within the vacuumed annular space and we would monitor the vacuum with an electronic gauge (thermister?) and pull vacuum during hot air purge when necessary.

Drew

Dear Engineers,

Finely I have found one manufacturer of multilayer vacuum insulation.

The link is:

http://www.lydallthermal.com/what/CryogenicProducts.shtml

Thank for every body who helped me by comments!

Kind Regards,

Vadim.

there must be many suppliers of this material.

a search gives these associated links. looking at each paper might show more suppliers.

http://www.google.ca/#hl=en&safe=off&q=%22multilayer+insulation+material+guidelines%22&meta=&aq=&aqi=&aql=&oq=%22multilayer+insulation+material+guidelines%22&gs_rfai=&fp=1e76ebc91b139a28

http://www.google.ca/#hl=en&safe=off&q=%22multilayer+vacuum+insulation%22&meta=&aq=f&aqi=&aql=&oq=%22multilayer+vacuum+insulation%22&gs_rfai=&fp=1e76ebc91b139a28

Dear Aurison, Thank you for your comment. I googled your links but found nothing useful. Seems, I have to visit some special Cryogenic Exhibitions. Thank you! Kind Regards, Vadim

HEY IT IS PERFECTLY OK TO USE PERLITE POWDER IN CRYOGENIC STORAGE TANKS.

FOR BUYING THIS KIND OF TANKS AT LOWEST COST AND RELIABLE ONES YOU CAN GO FOR BOC INDIA

I AM SURE THEY WILL HELP YOU OUT AND ALSO SUPPLY YOU THE TANK AT A LOWEST PRICE.

SUPRIYO