CA1116107A - Low emissivity liquid nitrogen dewar - Google Patents
Low emissivity liquid nitrogen dewarInfo
- Publication number
- CA1116107A CA1116107A CA321,939A CA321939A CA1116107A CA 1116107 A CA1116107 A CA 1116107A CA 321939 A CA321939 A CA 321939A CA 1116107 A CA1116107 A CA 1116107A
- Authority
- CA
- Canada
- Prior art keywords
- shell
- free
- dewar
- liquid
- aluminum
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C3/00—Vessels not under pressure
- F17C3/02—Vessels not under pressure with provision for thermal insulation
- F17C3/08—Vessels not under pressure with provision for thermal insulation by vacuum spaces, e.g. Dewar flask
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
- C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
- C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
- C23G1/12—Light metals
- C23G1/125—Light metals aluminium
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2203/00—Vessel construction, in particular walls or details thereof
- F17C2203/03—Thermal insulations
- F17C2203/0304—Thermal insulations by solid means
- F17C2203/0308—Radiation shield
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2203/00—Vessel construction, in particular walls or details thereof
- F17C2203/06—Materials for walls or layers thereof; Properties or structures of walls or their materials
- F17C2203/0602—Wall structures; Special features thereof
- F17C2203/0612—Wall structures
- F17C2203/0626—Multiple walls
- F17C2203/0629—Two walls
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2203/00—Vessel construction, in particular walls or details thereof
- F17C2203/06—Materials for walls or layers thereof; Properties or structures of walls or their materials
- F17C2203/0634—Materials for walls or layers thereof
- F17C2203/0636—Metals
- F17C2203/0646—Aluminium
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2203/00—Vessel construction, in particular walls or details thereof
- F17C2203/06—Materials for walls or layers thereof; Properties or structures of walls or their materials
- F17C2203/0634—Materials for walls or layers thereof
- F17C2203/0636—Metals
- F17C2203/0648—Alloys or compositions of metals
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2221/00—Handled fluid, in particular type of fluid
- F17C2221/01—Pure fluids
- F17C2221/014—Nitrogen
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2223/00—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel
- F17C2223/01—Handled fluid before transfer, i.e. state of fluid when stored in the vessel or before transfer from the vessel characterised by the phase
- F17C2223/0146—Two-phase
- F17C2223/0153—Liquefied gas, e.g. LPG, GPL
- F17C2223/0161—Liquefied gas, e.g. LPG, GPL cryogenic, e.g. LNG, GNL, PLNG
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17C—VESSELS FOR CONTAINING OR STORING COMPRESSED, LIQUEFIED OR SOLIDIFIED GASES; FIXED-CAPACITY GAS-HOLDERS; FILLING VESSELS WITH, OR DISCHARGING FROM VESSELS, COMPRESSED, LIQUEFIED, OR SOLIDIFIED GASES
- F17C2270/00—Applications
- F17C2270/05—Applications for industrial use
- F17C2270/0509—"Dewar" vessels
Abstract
PATENT APPLICATION
of GEORGE D. KNEIP, JR., GEORGE CHMYZ
and MARVIN H. ANDERSON
for LOW EMISSIVITY LIQUID NITROGEN DEWAR
FOR CRYOGENIC LIQUIDS
Abstract of the Disclosure A Dewar for liquified gases includes a spun can for the liquified gas, which spun can is surrounded by an exterior shell. Between the exterior shell and the can is an evacuated space containing a second shell that functions as a radiation shield. The can and both shells are formed of an aluminum alloy havng a very high percentage of aluminum. The exterior can surface, interior surface of the exterior shell, and both surfaces of the second shell have clean, non-pitted, smooth, matted, smut free and etched appearances free from discoloration and stains so that these surfaces have low radiation emissivity properties and there is a minimum amount of radiant energy transmitted from the exterior shell to the can and reduced heating of the liquid nitrogen in the can. Each of the surfaces is initially polished, either mechanically, electrochemically or chemically, and then chemically treated with an etchant of nitric acid and hydro-fluoric acid for a sufficient duration to achieve the desired appearance.
of GEORGE D. KNEIP, JR., GEORGE CHMYZ
and MARVIN H. ANDERSON
for LOW EMISSIVITY LIQUID NITROGEN DEWAR
FOR CRYOGENIC LIQUIDS
Abstract of the Disclosure A Dewar for liquified gases includes a spun can for the liquified gas, which spun can is surrounded by an exterior shell. Between the exterior shell and the can is an evacuated space containing a second shell that functions as a radiation shield. The can and both shells are formed of an aluminum alloy havng a very high percentage of aluminum. The exterior can surface, interior surface of the exterior shell, and both surfaces of the second shell have clean, non-pitted, smooth, matted, smut free and etched appearances free from discoloration and stains so that these surfaces have low radiation emissivity properties and there is a minimum amount of radiant energy transmitted from the exterior shell to the can and reduced heating of the liquid nitrogen in the can. Each of the surfaces is initially polished, either mechanically, electrochemically or chemically, and then chemically treated with an etchant of nitric acid and hydro-fluoric acid for a sufficient duration to achieve the desired appearance.
Description
Field of Invention The present invention relates generally to Dewars for li~uified gases and to a method of fabricatlng samc, and more particularly, to a liquid nitrogen De~ar having low radiation emissivity surfaces with clean, non-pitted, smooth, matted, smut free and etched appearances free from discoloration and stains as a result of being chemically treated by an etchant of nitric acid and hydrofluoric acid.
Back~round of the _vention Containers or Dewars for maintaining nitrogen or helium in a liquid, cryogenic condition are usually formed as a metal can in which the liquid gas i~loaded; the can is usuall~ ~
surrounded by a shell. The volume between the can and shell is evacuated to decrease the heat conduction from outside of the shell to the interior of .he can. In addition, it is usually desired to minimize the transmission of radiant energy from outside of the shell to the exterior surface of the can. For the purposes of this appliCation r~ference to li~uid nitrogen apparatus will be understood to apply to liquid helium apparatus where it is also understood that the respective boiling points of these liquids under standard condi~ions are 77K and 4.2K.
In the prior art, relatively lo~ amounts of radiation have been transmitted between the shell and exterior of the can by forming both the can and the shell of an aluminum alloy having a very high percentage, such as 99~, of aluminum. The interior of the shell and exterior of the can are usually mechanically polished to a lustrious high-gloss, an OperatiQn that also substantially removes tool marks applied to the shell and can buring the machining of these parts. After t~e ~an and shell have been ~y f2nically ,/
1~161n7 polished, they are vapor degreased to remove filings, dirt and other foreign materials from the C2SI and shell surfaces so these surfaces have relatively low radiant energy emissivities of approxi.mately 0.024 at the temperature of liquid nitrogen, 77 K. Radi~nt. ~neray emissivitv is defin~d in the usual 1 manner, i.e., as the ratio of radiation emitted by a surface
Back~round of the _vention Containers or Dewars for maintaining nitrogen or helium in a liquid, cryogenic condition are usually formed as a metal can in which the liquid gas i~loaded; the can is usuall~ ~
surrounded by a shell. The volume between the can and shell is evacuated to decrease the heat conduction from outside of the shell to the interior of .he can. In addition, it is usually desired to minimize the transmission of radiant energy from outside of the shell to the exterior surface of the can. For the purposes of this appliCation r~ference to li~uid nitrogen apparatus will be understood to apply to liquid helium apparatus where it is also understood that the respective boiling points of these liquids under standard condi~ions are 77K and 4.2K.
In the prior art, relatively lo~ amounts of radiation have been transmitted between the shell and exterior of the can by forming both the can and the shell of an aluminum alloy having a very high percentage, such as 99~, of aluminum. The interior of the shell and exterior of the can are usually mechanically polished to a lustrious high-gloss, an OperatiQn that also substantially removes tool marks applied to the shell and can buring the machining of these parts. After t~e ~an and shell have been ~y f2nically ,/
1~161n7 polished, they are vapor degreased to remove filings, dirt and other foreign materials from the C2SI and shell surfaces so these surfaces have relatively low radiant energy emissivities of approxi.mately 0.024 at the temperature of liquid nitrogen, 77 K. Radi~nt. ~neray emissivitv is defin~d in the usual 1 manner, i.e., as the ratio of radiation emitted by a surface
2 to the radiation emitted by a perfect black body radiator
3 at the same temperature.
4 While the prior art techniques for reducing the emissivity of the shell and can are satisfactory for many purposes, 6 the emissivity was not sufficiently reduced for other purposes.
7 In particular, if it is desired to maintain the nitrogen 8 in a liquid state for a prolonged duration, such as three 9 months, the emissivity of the prior art can and shell are excessively high if the aluminum is only polished.
11 Brief Description of the Invention 12 In accordance with the present invention, there is a 13 substantial reduction in the radiation emissivity of spun 14 cans and shells formed of sheet aluminum alloy utilized in Dewars for liquid nitrogen. The reduction in emissivity 16 is attained because the interior shell and exterior can 17 surfaces have clean, non-pitted, smooth, matted, smut free 18 and etched appearances free from discloration and stains 19 resulting from the polished surfaces being chemically treated with an etchant of nitric acid and hydrofloric acid. (The 21 term ~smut free" is well known to those skilled in the aluminum 22 processing art and means that the surface is not gray or 23 black.) The surfaces are chemically treated by the etchant 24 for between 15 and 45 seconds, until the desired appearances are attained, which usually occurs when one mil has been 26 removed. If the surface is treated for less than an adequate 27 time, it is not sufficiently cleaned, matted or smut free 28 and may be discolored or stained. If the surface is treated 29 for an excessive duration, it becomes pitted and is not 3 smooth. In either situation, the emissivity of the surface 31 is increased compared to the emissivity for the proper treat-32 ment duration. Tests conducted on Dewars with surfaces made ~. . '-., 2 in accordance with the present invention indicate approximately a 35~ reduction in emissivlty compared to the peior ar~.
3. The aluminum sheet can b~ polished either mechanically, 4 ¦ electrochemically or chemically. If a mechanical means are 5I employed, the procedure is identical with the prior art.
61 Electrochemical, i.e., electrolytic, polishing is achieved I in an 85 F, bath of fluoboric acid (2.5% by weight), at 8¦ a cùrrent density of 10 to ~0 amperes per square foot and 9 voltages of 15 to 30 volts, for 5 to 10 minutes, as described in U.S. patent 2,10~,603. If chemical polishing is employed, 11¦ the polishing is with an aqueous bath of phosphoric and 12 nitric acids, as disclosed in U.S. patent 2,729,551, or 131 in a bath of phosphoric, acetic and nitric acids, as dis-14 closed in U.S. patent 2,650,157.
lS While it is realized that aluminum surPaces have 16 been previously treated with an etchant of nitric acid 17 and hydrofluoric acid after having been mechanically 18 polished, the prior art procedures have generally been in connection with the manufacture of vacuum devices where radiation emissivity is not a factor. The present invention 221 utilizes the prior art technique to achieve the unexpected ¦ result of reduced radiation emissivity to assist in maintaining 23 a cryogenic Dewar at liquid nitrogen temperat-res.
In accordance with another aspect of the present 2 invention, the evacuated space between the can for liquid 2 nitrogen and the exterior shell of the Dewar includes a second shell of spun aluminum alloy having opposite faces 2 with the same low emissivity characteristics ~s the shell 0 interior and can exterior surfaces. Thereby the exterior 31 s~rface of ~he second shell absorbs a small percentage of the radiation emitted from the interior surface of the first 1~161{~
.
1 a small amount of radiant energy in the direction of the 2 can.
It is, accordingly, an object of the present invention 4 to provide a new and improved liquid nitrogen Dewar and to a method of forming same.
6 Another object of the present invention is to provide 7 a liquid nitrogen Dewar having reduced radiant energy 8 emissivity, and to a method of forming same.
9 Another object of the invention is to provide a new and improved liquid nitrogen ~ewar capable of storing liquid ll nitrogen for extremely long time intervals, such as 90 days, 12 and to a method of making such a Dewar.
13 The above and further objects and features, as well as 14 advantages, of the invention will become apparent from the following description of the drawing.
16 Brief Description of the Drawing 17 The sole figure is a cross-sectional view of a Dewar 18 manufactured in accordance with the present invention.
19 Detailed Description of the Drawing Reference is now made to the single figure of the drawing 21 wherein Dewar 10 is illustrated as being utilized in connection 22 with a nuclear magnetic resonance (NMR) spectrometer, including 23 a superconducting solenoid coil 11 that supplies a relatively 24 high intensity magnetic field Ho longitudinally of the coil through a sample 12 that is located in vial 13. Sample 26 13 is excited to nuclear magnetic resonance by rf energy 2 supplied to coils 14 by rf pulse source 15. Coils 14 are 2 wound so that the axes thereof are at right angles to field 2 H O . A pick-up coil 16, located in proximity to sample 13 and responsive to energy radiated from the sample, supplies 3 a suitable signal to rf receiver 17. Coil 16 is disposed 3 so that its A~is is at right angles to ~he axes of coils AL/RBNl2678 - 5 - 78-09 1~16:1~7 1 14, as well as to the direction of field Ho . Receiver 17 2 ¦ may include suitable Fourier analysis equipment for deriving 3 ¦ an output which is supplied to X - Y recorder 18, that plots 4 ¦ the spectral response of sample 13 to different frequencies
7 In particular, if it is desired to maintain the nitrogen 8 in a liquid state for a prolonged duration, such as three 9 months, the emissivity of the prior art can and shell are excessively high if the aluminum is only polished.
11 Brief Description of the Invention 12 In accordance with the present invention, there is a 13 substantial reduction in the radiation emissivity of spun 14 cans and shells formed of sheet aluminum alloy utilized in Dewars for liquid nitrogen. The reduction in emissivity 16 is attained because the interior shell and exterior can 17 surfaces have clean, non-pitted, smooth, matted, smut free 18 and etched appearances free from discloration and stains 19 resulting from the polished surfaces being chemically treated with an etchant of nitric acid and hydrofloric acid. (The 21 term ~smut free" is well known to those skilled in the aluminum 22 processing art and means that the surface is not gray or 23 black.) The surfaces are chemically treated by the etchant 24 for between 15 and 45 seconds, until the desired appearances are attained, which usually occurs when one mil has been 26 removed. If the surface is treated for less than an adequate 27 time, it is not sufficiently cleaned, matted or smut free 28 and may be discolored or stained. If the surface is treated 29 for an excessive duration, it becomes pitted and is not 3 smooth. In either situation, the emissivity of the surface 31 is increased compared to the emissivity for the proper treat-32 ment duration. Tests conducted on Dewars with surfaces made ~. . '-., 2 in accordance with the present invention indicate approximately a 35~ reduction in emissivlty compared to the peior ar~.
3. The aluminum sheet can b~ polished either mechanically, 4 ¦ electrochemically or chemically. If a mechanical means are 5I employed, the procedure is identical with the prior art.
61 Electrochemical, i.e., electrolytic, polishing is achieved I in an 85 F, bath of fluoboric acid (2.5% by weight), at 8¦ a cùrrent density of 10 to ~0 amperes per square foot and 9 voltages of 15 to 30 volts, for 5 to 10 minutes, as described in U.S. patent 2,10~,603. If chemical polishing is employed, 11¦ the polishing is with an aqueous bath of phosphoric and 12 nitric acids, as disclosed in U.S. patent 2,729,551, or 131 in a bath of phosphoric, acetic and nitric acids, as dis-14 closed in U.S. patent 2,650,157.
lS While it is realized that aluminum surPaces have 16 been previously treated with an etchant of nitric acid 17 and hydrofluoric acid after having been mechanically 18 polished, the prior art procedures have generally been in connection with the manufacture of vacuum devices where radiation emissivity is not a factor. The present invention 221 utilizes the prior art technique to achieve the unexpected ¦ result of reduced radiation emissivity to assist in maintaining 23 a cryogenic Dewar at liquid nitrogen temperat-res.
In accordance with another aspect of the present 2 invention, the evacuated space between the can for liquid 2 nitrogen and the exterior shell of the Dewar includes a second shell of spun aluminum alloy having opposite faces 2 with the same low emissivity characteristics ~s the shell 0 interior and can exterior surfaces. Thereby the exterior 31 s~rface of ~he second shell absorbs a small percentage of the radiation emitted from the interior surface of the first 1~161{~
.
1 a small amount of radiant energy in the direction of the 2 can.
It is, accordingly, an object of the present invention 4 to provide a new and improved liquid nitrogen Dewar and to a method of forming same.
6 Another object of the present invention is to provide 7 a liquid nitrogen Dewar having reduced radiant energy 8 emissivity, and to a method of forming same.
9 Another object of the invention is to provide a new and improved liquid nitrogen ~ewar capable of storing liquid ll nitrogen for extremely long time intervals, such as 90 days, 12 and to a method of making such a Dewar.
13 The above and further objects and features, as well as 14 advantages, of the invention will become apparent from the following description of the drawing.
16 Brief Description of the Drawing 17 The sole figure is a cross-sectional view of a Dewar 18 manufactured in accordance with the present invention.
19 Detailed Description of the Drawing Reference is now made to the single figure of the drawing 21 wherein Dewar 10 is illustrated as being utilized in connection 22 with a nuclear magnetic resonance (NMR) spectrometer, including 23 a superconducting solenoid coil 11 that supplies a relatively 24 high intensity magnetic field Ho longitudinally of the coil through a sample 12 that is located in vial 13. Sample 26 13 is excited to nuclear magnetic resonance by rf energy 2 supplied to coils 14 by rf pulse source 15. Coils 14 are 2 wound so that the axes thereof are at right angles to field 2 H O . A pick-up coil 16, located in proximity to sample 13 and responsive to energy radiated from the sample, supplies 3 a suitable signal to rf receiver 17. Coil 16 is disposed 3 so that its A~is is at right angles to ~he axes of coils AL/RBNl2678 - 5 - 78-09 1~16:1~7 1 14, as well as to the direction of field Ho . Receiver 17 2 ¦ may include suitable Fourier analysis equipment for deriving 3 ¦ an output which is supplied to X - Y recorder 18, that plots 4 ¦ the spectral response of sample 13 to different frequencies
5 ¦ of transmitter 15. Power is initially supplied to coil
6 11 by a DC power supply 18, which is disconnected from the
7 coil when it is operatin~ in the persistent, superconductor
8 mode.
9 ¦ Coil 11 is maintained at a superconducting state, at the temperature of liquid helium (4.2 K~ because it is 11¦ located in cylinder 21, which in turn is surrounded by a 12 liquid helium reservoir 23 that is contained in can 24.
13 Can 23 is below a liquid nitrogen reservoir formed by can 14 25. Cans 24 and 25 are inside of shell 26 that forms the exterior of the Dewar. Between the exterior of can 24 and 16 the interior of shell 26 is an evacuated volume, except for 17 the region where can 25 is located. In the evacuated volume 18 are thermal shields 27, 28 and 29. Shield 27 is located 19 between the exterior surface of can 24 and the interior surface of shield 28, as well as between floor 31 of can 25 21 and the exterior of can 24. Shield 29 is positioned between 22 the exterior wall of shield 28 and the interior wall of 23 shell 26, as well as between side wall 32 and roof 33 of 24 can 25 and the interior surface of shell 26.
Each of cans 24 and 25, as well as shell 26 and shields 2 27, 28 and 29 is a substantially isothermal surface formed 2 of spun sheets of aluminum alloy having a very high percentage of aluminum. Preferably, the aluminum alloy is 1100-0, 2 an alloy that is readily available from many manufacturers, 3 such as Reynolds or Alcoa. The alloy has an aluminum content 31 of at least 99%, a maximum iron and silicon content of 1~, 3 a maximum copper content of 0.2%, a maximum manganese content AL/~BN12678 - 6 - 78-09 1~ 7 1 of 0.05~ and a maximum zinc content nO greater than 0.1%.
2 To minimize radiant energy transfer between the interlor 3 surface of shell 26 and the extecior surface of can 25, 4 the interior surface of the shell, the exte~ior surace of the can, and both surfaces of shield 29 have low thermal 6 emissi~ity because they are specially processed to have 7 clean, non-pitted, smooth, matted, smut free and etched 8 appearances free from discoloration and stains. All of these 9 surfaces are processed in the same way to achieve the desired results.
11 After can 25, shell 26 and shield 29 have been spun, 12 they are polished, either mechanically, electrolytically 13 or chemically. Mechanical polishing involves the usual buffing 14 operations so that the surface of interest has a lustrous, high gloss and which results in removal of substantially 16 all tool marks from the spinning operation. Electrolytic 17 or chemical polishing, which are much less expensive and 18 therefore more desirable than mechanicaL polishing, can be 19 achieved as discussed supra. After the surface has been polished, the part is vapor degreased in a bath of li~uid 21 trichylorethelyne that emits vapors to remove dirt, filings 22 and other foreign materials. The part is then cleaned with 23 a detergent, such as Oakite*27, which is removed from the 24 part with a hot tap water rinse.
The surface of interest is then chemically treated 2 with an etchant solution of approximately 20%, by volume, 2 of nitric acid, 4%, by volume, of hydrofluoric acid and 2 the remainder of de-ionized water. ~he etchant attacks the 2 surface for between 15 and 4S seconds, so that approximately 3 1 mil is removed, whereby phosphates or chromates that may 3 have adhered to the surface during the chemica~ polishing 3 are removed, and the surface has the desired non-pitted, * Trade Mark 1~161n7 1 smooth, matted, smut free and etched appearance that is 1 free from discoloration and stains. Ir.itially, the etchant 3 ¦ bath has the stated proportions. After the etchant bath i has been used for a while, the proportions change somewhat.
The acid content is controlled in response to periodic testing 6 ¦ of specific gravity and chemical analysis. If these tests 8 indicate a substantial change in the acid percentages, e.g.
¦ decreases of about one-fourth in the percentages, additional 9 ¦ acid is added or a tank holding the bath is cleaned and a new mixture is employed.
11 The part is then rinsed with cold tap water, and then 12 twice rinsed with deionized water. Following the second 13 deionized water rinse, the part is dried in a suitable tunnel, 14 cooled and then inserted into a polyethelyne bag for protection purposes.
16 The Dewar is assemblied by suitably bonding the various 17 parts together, as illusteated in the Figure. Then, a vacuum 18 is drawn on the entire Dewar 10 through port 35 in shell 26 19 so all of the regions between the various cans and shields are evacuated to approximately 10-5 torr. Can 25 is then 21 illed with liquid nitrogen through port 36, causing can 222 23 to be ultimately lowered to the temperature of the liquid 31 nitrogen. Then, can 23 is filled with liquid helium through 24 a port ~not shown) to lower the temperature of superconducting 25 ¦ solenoid 11 to the temperature of liquid helium, 4.2 K.
26 The surfaces of shell 26, can 25 and shield 29 which 27 wese prepared in accordance with the present invention have 28 been found to have radiant energy emissivities considerably 2~ less than the prior art. Prior art spun aluminum surfaces fabricated from the same alloy as used to fabricate can 31 25, shell 2~ and shield 29 that were mechanically, electro-32 che~ic~lly or ch~mlcally polished, hut whiçh have n~t been ~ AL/RBN21478 - 8 - 78-09 lil61n7 1 etched with the nitric acid and hydrofluoric acid mixture, 2 ¦ have generally had radiant energy emissivities of approximately 3 1 0.024 at 77 K. In contrast, the surfaces which were chemically i ¦ treated by the nitric acid and hydrofluoric-acid etchant had 5 ¦ radiant energy emissivities of approximately 0.016 at 77 K.
6 From the foregoing, there is approximately a 35% improvement .
7 I in the emissivity characteristics of the very pure 1100-0 8 ¦ spun sheet aluminum alloy parts treated with the nitric 9 acid and hydrofluoric acid bath of the present invention.
It is to be understood that many changes may be made 11 in the specifically described embodiment without departing 12 from the true spirit and scope of the invention and that 13 the invention is to be determined from the scope of the 14 following claims, and not limited to the specifically ~¦ described mbodiment.
. 32 Ar.~RsN12678 - 9 - 78-09
13 Can 23 is below a liquid nitrogen reservoir formed by can 14 25. Cans 24 and 25 are inside of shell 26 that forms the exterior of the Dewar. Between the exterior of can 24 and 16 the interior of shell 26 is an evacuated volume, except for 17 the region where can 25 is located. In the evacuated volume 18 are thermal shields 27, 28 and 29. Shield 27 is located 19 between the exterior surface of can 24 and the interior surface of shield 28, as well as between floor 31 of can 25 21 and the exterior of can 24. Shield 29 is positioned between 22 the exterior wall of shield 28 and the interior wall of 23 shell 26, as well as between side wall 32 and roof 33 of 24 can 25 and the interior surface of shell 26.
Each of cans 24 and 25, as well as shell 26 and shields 2 27, 28 and 29 is a substantially isothermal surface formed 2 of spun sheets of aluminum alloy having a very high percentage of aluminum. Preferably, the aluminum alloy is 1100-0, 2 an alloy that is readily available from many manufacturers, 3 such as Reynolds or Alcoa. The alloy has an aluminum content 31 of at least 99%, a maximum iron and silicon content of 1~, 3 a maximum copper content of 0.2%, a maximum manganese content AL/~BN12678 - 6 - 78-09 1~ 7 1 of 0.05~ and a maximum zinc content nO greater than 0.1%.
2 To minimize radiant energy transfer between the interlor 3 surface of shell 26 and the extecior surface of can 25, 4 the interior surface of the shell, the exte~ior surace of the can, and both surfaces of shield 29 have low thermal 6 emissi~ity because they are specially processed to have 7 clean, non-pitted, smooth, matted, smut free and etched 8 appearances free from discoloration and stains. All of these 9 surfaces are processed in the same way to achieve the desired results.
11 After can 25, shell 26 and shield 29 have been spun, 12 they are polished, either mechanically, electrolytically 13 or chemically. Mechanical polishing involves the usual buffing 14 operations so that the surface of interest has a lustrous, high gloss and which results in removal of substantially 16 all tool marks from the spinning operation. Electrolytic 17 or chemical polishing, which are much less expensive and 18 therefore more desirable than mechanicaL polishing, can be 19 achieved as discussed supra. After the surface has been polished, the part is vapor degreased in a bath of li~uid 21 trichylorethelyne that emits vapors to remove dirt, filings 22 and other foreign materials. The part is then cleaned with 23 a detergent, such as Oakite*27, which is removed from the 24 part with a hot tap water rinse.
The surface of interest is then chemically treated 2 with an etchant solution of approximately 20%, by volume, 2 of nitric acid, 4%, by volume, of hydrofluoric acid and 2 the remainder of de-ionized water. ~he etchant attacks the 2 surface for between 15 and 4S seconds, so that approximately 3 1 mil is removed, whereby phosphates or chromates that may 3 have adhered to the surface during the chemica~ polishing 3 are removed, and the surface has the desired non-pitted, * Trade Mark 1~161n7 1 smooth, matted, smut free and etched appearance that is 1 free from discoloration and stains. Ir.itially, the etchant 3 ¦ bath has the stated proportions. After the etchant bath i has been used for a while, the proportions change somewhat.
The acid content is controlled in response to periodic testing 6 ¦ of specific gravity and chemical analysis. If these tests 8 indicate a substantial change in the acid percentages, e.g.
¦ decreases of about one-fourth in the percentages, additional 9 ¦ acid is added or a tank holding the bath is cleaned and a new mixture is employed.
11 The part is then rinsed with cold tap water, and then 12 twice rinsed with deionized water. Following the second 13 deionized water rinse, the part is dried in a suitable tunnel, 14 cooled and then inserted into a polyethelyne bag for protection purposes.
16 The Dewar is assemblied by suitably bonding the various 17 parts together, as illusteated in the Figure. Then, a vacuum 18 is drawn on the entire Dewar 10 through port 35 in shell 26 19 so all of the regions between the various cans and shields are evacuated to approximately 10-5 torr. Can 25 is then 21 illed with liquid nitrogen through port 36, causing can 222 23 to be ultimately lowered to the temperature of the liquid 31 nitrogen. Then, can 23 is filled with liquid helium through 24 a port ~not shown) to lower the temperature of superconducting 25 ¦ solenoid 11 to the temperature of liquid helium, 4.2 K.
26 The surfaces of shell 26, can 25 and shield 29 which 27 wese prepared in accordance with the present invention have 28 been found to have radiant energy emissivities considerably 2~ less than the prior art. Prior art spun aluminum surfaces fabricated from the same alloy as used to fabricate can 31 25, shell 2~ and shield 29 that were mechanically, electro-32 che~ic~lly or ch~mlcally polished, hut whiçh have n~t been ~ AL/RBN21478 - 8 - 78-09 lil61n7 1 etched with the nitric acid and hydrofluoric acid mixture, 2 ¦ have generally had radiant energy emissivities of approximately 3 1 0.024 at 77 K. In contrast, the surfaces which were chemically i ¦ treated by the nitric acid and hydrofluoric-acid etchant had 5 ¦ radiant energy emissivities of approximately 0.016 at 77 K.
6 From the foregoing, there is approximately a 35% improvement .
7 I in the emissivity characteristics of the very pure 1100-0 8 ¦ spun sheet aluminum alloy parts treated with the nitric 9 acid and hydrofluoric acid bath of the present invention.
It is to be understood that many changes may be made 11 in the specifically described embodiment without departing 12 from the true spirit and scope of the invention and that 13 the invention is to be determined from the scope of the 14 following claims, and not limited to the specifically ~¦ described mbodiment.
. 32 Ar.~RsN12678 - 9 - 78-09
Claims (19)
1. A Dewar for maintaining a liquid at cryogenic temperatures comprising a spun can of an aluminum alloy having a very high percentage of aluminum for the liquid, a spun shell of an aluminum alloy having a very high percentage of aluminum surrounding the can, said shell having an interior surface facing an exterior surface of the can, a vacuum being maintained between said surfaces, both of said surfaces having clean, non-pitted, smooth, matted, smut free, and etched appearances free from dis-coloration and stains, and reduced radiation emissivity whereby there are substantial reductions in the radiant energy radiated from the interior surface toward the ex-terior surface and there is a reduction in the heat absorb-ed by the exterior surface with a resulting reduction in heat conducted through the reservoir to the liquid nitro-gen.
2. The Dewar of claim 1 wherein both of said surfaces have a radiant energy emissivity of approximately 0.016.
3. The Dewar of claim 1 further including a radiation shield having one surface facing and surrounding the can and a second surface facing and being surrounded by the shell, said shield being of spun aluminum alloy having a very high percentage of aluminum, both of the surfaces of the shield having clean, non-pitted, smooth, matted, smut free and etched appearances free from discoloration and stains.
4. The Dewar of claim 3 wherein all of said surfaces have a radiant energy emissivity of approximately 0.016.
5. The Dewar of claim 3 wherein the spun aluminum is mechanically polished to a lustrous high gloss to remove substantially all tool marks.
6.The Dewar of claim 5 wherein all of said surfaces are polished and then chemically treated with a liquid etchant of nitric acid and hydrofluoric acid.
7. The Dewar of claim 6 wherein all of said surfaces have a radiant energy emissivity of approximately 0.016 at 77°K.
8. The Dewar of claim 5 wherein the spun aluminum is chemically polished to a lustrous high gloss to remove substantially all tool marks and the etchant removes any of the chemicals deposited on the surfaces by the chemical polishing.
9. The Dewar of claim 8 wherein all of said surfaces have a radiant energy emissivity of approximately 0.016 at 77°K.
10. A method of manufacturing a container for a liquid maintained at cryogenic temperatures from a can of spun sheet aluminum alloy having a very high percentage of aluminum and from a shell of spun sheet aluminum alloy having a very high percentage of aluminum, the exterior surface of the can being polished to a lustrous high gloss so that substantially all tool marks are removed therefrom, the interior surface of the shell being polished to a lustrous high gloss so that substantially all tool marks are removed therefrom, the method comprising the steps of: chemically treating the exterior surface of the can with a liquid etchant of nitric acid and hydrofluoric acid until the can exterior has a non-pitted, smooth, matted, smut free and etched appearance that is free from discoloration and stains, chemically treating the interior surface of the shell with a liquid etchant of nitric acid and hydrofluoric acid until the shell interior surface has a non-pitted, smooth, matted, smut free and etched appearance that is free from discoloration and stains, then assemblying the Dewar so that the shell surrounds the can, evacuating the space between the shell and the can, and then filling the can with the liquid.
11. The method of claim 10 wherein the etchant is approximately 4 percent by volume of hydrofluoric acid, approximately 20 percent by volume of nitric acid, and the remainder is de-ionized water.
12. The method of claim 11 wherein the surface is treated for between 15 and 45 seconds by the etchant.
13. A method of manufacturing a cryogenic liquid Dewar from a can of spun sheet aluminum alloy having a very percentage of aluminum and from a shell of spun sheet aluminum having a very high percentage of aluminum comprising polishing the exterior surface of the can to a lustrous high gloss to substantially remove all tool marks, polishing the interior surface of the shell to a lustrous high gloss to substantially remove all tool marks, chemically treating the exterior surface of the can with a liquid etchant of nitric acid and hydrofluoric acid until the can exterior surface has a non-pitted, smooth, matted, smut free and etched appearance that is free from discoloration and stains, chemically treating the interior surface of the shell with a liquid etchant of nitric acid and hydrofluoric acid until the shell interior surface has a non-pitted, smooth, matted, smut free and etched appearance that is free from discoloration and stains, then assemblying the Dewar so that the shell surrounds the can, evacuating the space between the shell and the can, and then filling the can with liquid nitrogen.
14. The method of claim 13 wherein the surfaces are mechanically polished.
15. A method of claim 13 wherein the surfaces are chemically polished and the etchant removes any of the chemicals deposited on the surface by the chemical polishing.
16. The method of claim 13 wherein the surfaces are electrochemically polished.
17. The method of claim 13 wherein the etchant is approximately 4 percent by volume of hydrofluoric acid and 20 percent by volume of nitric acid.
18. The method of claim 17 wherein the surface is treated by the etchant for between 15 and 45 seconds.
19. A method of manufacturing a Dewar for a liquid maintained at cryogenic temperatures from a can of spun sheet aluminum alloy having a very high percentage of aluminum, from a first shell of spun sheet aluminum alloy having a very high percentage of aluminum, and from a second shell of spun sheet aluminum alloy having a very high percentage of aluminum, the second shell being dimensioned so that it can fit inside of the first shell, the exterior surface of the can being polished to a lustrous high gloss so it is substantially free of all tool marks, the interior surface of the first shell being polished to a lustrous high gloss so that substantially all tool marks are removed therefrom, and both surfaces of the second shell being polished to a lustrous high gloss so that substantially all tool marks are removed therefrom, said method comprising: chemically treating the exterior surface of the can with a liquid etchant of nitric acid and hydrofluoric acid until the can exterior surface has a non-pitted, smooth, matted, smut free and etched appearance that is free from discoloration and stains, treating the interior surface of the first shell with a liquid etchant of nitric acid and hydrofluoric acid until the interior surface of the first shell has a non-pittted, smooth, matted, smut free and etched appearance that is free from discoloration and. stains, treating both the surfaces of the second shell with a liquid etchant of nitric acid and hydrogen fluoride until both surfaces of the second shell have non-pitted, smooth, bright, and etched appearances that are free from discoloration and stains, then assemblying the Dewar so that the second shell surrounds the can, and the first shell surrounds the second shell, evacuating the space between the first shell and the can, and then filling the can with the liquid.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US87929078A | 1978-02-21 | 1978-02-21 | |
| US879,290 | 1978-02-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1116107A true CA1116107A (en) | 1982-01-12 |
Family
ID=25373827
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA321,939A Expired CA1116107A (en) | 1978-02-21 | 1979-02-20 | Low emissivity liquid nitrogen dewar |
Country Status (6)
| Country | Link |
|---|---|
| JP (2) | JPS54128821A (en) |
| CA (1) | CA1116107A (en) |
| CH (1) | CH639744A5 (en) |
| DE (1) | DE2906075A1 (en) |
| FR (1) | FR2417719A1 (en) |
| GB (1) | GB2015720B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4350017A (en) * | 1980-11-10 | 1982-09-21 | Varian Associates, Inc. | Cryostat structure |
| GB2129117B (en) * | 1982-08-25 | 1985-12-18 | Zojirushi Vacuum Bottle Co | Stainless steel vacuum bottle and its production |
| US5417819A (en) * | 1994-01-21 | 1995-05-23 | Aluminum Company Of America | Method for desmutting aluminum alloys having a highly reflective surface |
| JP2003068520A (en) * | 2001-08-23 | 2003-03-07 | Sumitomo Heavy Ind Ltd | Freezer cooling type of superconductive magnet device |
| CN106939964A (en) * | 2017-03-04 | 2017-07-11 | 杭州医学院 | A kind of thermos bottle type liquid nitrogen container and inner bag replacement method |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB814207A (en) * | 1956-08-03 | 1959-06-03 | Aro Equipment Corp | Vacuum insulated vessels |
| US2541083A (en) * | 1945-08-25 | 1951-02-13 | Sperry Corp | Electroplating on aluminum |
| US2643022A (en) * | 1947-08-15 | 1953-06-23 | Union Carbide & Carbon Corp | Radiation shield supports in vacuum insulated containers |
| FR1029818A (en) * | 1949-08-08 | 1953-06-08 | Vaw Ver Aluminium Werke Ag | Chemical process for obtaining high gloss surfaces on aluminum and aluminum alloys |
| US2719781A (en) * | 1952-04-09 | 1955-10-04 | Kaiser Aluminium Chem Corp | Composition and method for treating aluminum and aluminum alloys |
| US2729551A (en) * | 1954-01-18 | 1956-01-03 | Samuel L Cohn | Surface treatment of aluminum and its alloys |
| US2776069A (en) * | 1955-06-30 | 1957-01-01 | Little Inc A | Container for liquefied gas |
| FR2036463A5 (en) * | 1969-03-14 | 1970-12-24 | Air Liquide | Insulating cryogenic fluid containers |
-
1979
- 1979-02-15 GB GB7905461A patent/GB2015720B/en not_active Expired
- 1979-02-16 DE DE19792906075 patent/DE2906075A1/en active Granted
- 1979-02-19 FR FR7904112A patent/FR2417719A1/en active Granted
- 1979-02-20 CH CH165079A patent/CH639744A5/en not_active IP Right Cessation
- 1979-02-20 CA CA321,939A patent/CA1116107A/en not_active Expired
- 1979-02-21 JP JP1856279A patent/JPS54128821A/en active Granted
-
1988
- 1988-12-28 JP JP63329579A patent/JPH01251677A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2417719B1 (en) | 1984-01-20 |
| FR2417719A1 (en) | 1979-09-14 |
| JPH01251677A (en) | 1989-10-06 |
| GB2015720B (en) | 1982-10-13 |
| GB2015720A (en) | 1979-09-12 |
| DE2906075C2 (en) | 1987-03-12 |
| JPH0260584B2 (en) | 1990-12-17 |
| JPS54128821A (en) | 1979-10-05 |
| DE2906075A1 (en) | 1979-08-30 |
| CH639744A5 (en) | 1983-11-30 |
| JPH0432555B2 (en) | 1992-05-29 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Kneisel et al. | On surface preparation and measurement of niobium used in high‐frequency cavities | |
| Ciovati et al. | High field Q slope and the baking effect: Review of recent experimental results and new data on Nb heat treatments | |
| CA1116107A (en) | Low emissivity liquid nitrogen dewar | |
| US5063651A (en) | Method of manufacturing a low emissivity liquid nitrogen dewar | |
| Ciovati et al. | Measurement of the high-field Q drop in a high-purity large-grain niobium cavity for different oxidation processes | |
| EP1132501B1 (en) | Anodized cryogenically treated aluminum | |
| Dhakal et al. | Surface characterization of nitrogen-doped high purity niobium coupons compared with superconducting rf cavity performance | |
| US4127452A (en) | Method for the manufacture of a superconductive Nb3 Sn layer on a niobium surface for high frequency applications | |
| Bruynseraede et al. | Surface-resistance measurements in TE011-mode cavities of superconducting indium, lead and an indium-lead alloy at low and high RF magnetic fields | |
| US5510144A (en) | Process for preventing heavy metal migration in crystal articles | |
| US4105512A (en) | Method for the manufacture of a superconductive Nb3 Sn layer on a niobium surface for high frequency applications | |
| Kumagai et al. | NMR Study on the Coexistence of Superconductivity and Ferromagnetism in (Ce1-x Gd x) Ru2 | |
| CN111800933B (en) | Medium-temperature annealing method for superconducting cavity | |
| Ciovati et al. | Measurement of the high-field Q drop in the TM 010 and TE 011 modes in a niobium cavity | |
| US3212939A (en) | Method of lowering the surface recombination velocity of indium antimonide crystals | |
| Dhakal | Recent development on nitrogen infusion work towards high Q and high gradient | |
| Banerjee et al. | Origin of luminescence in porous silicon | |
| Lilje | Experimental investigations on superconducting niobium cavities at highest radiofrequency fields | |
| Maple | Magnetic ordering in (La, Gd) Al2 alloys | |
| Kako et al. | Cavity performance in the 1.3 GHz Saclay/KEK Nb cavities | |
| Lengeler et al. | Superconducting niobium cavities of improved thermal conductivity | |
| US4330344A (en) | Selective absorber of solar energy and process for producing same | |
| JPH06208841A (en) | Cryogenic device for scanning electron microscope | |
| Grasselino et al. | High q0 in superconducting niobium cavities: Progress at fnal and future plans | |
| O'Hanlon | Factors Affecting the Growth Rate of Plasma A nodi zed Al2 O 3 |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |