US1969621A

US1969621A - Heat insulation

Info

Publication number: US1969621A
Application number: US718663A
Authority: US
Inventors: Munters Carl Georg
Original assignee: Individual
Current assignee: Individual
Priority date: 1931-03-03
Filing date: 1934-04-02
Publication date: 1934-08-07
Anticipated expiration: 1951-08-07
Also published as: GB417114A

Description

Aug. 7, 1934.

C. G. MUNTERS HEAT INSULATION l Filed April 2, 1954 MMM 39 laf isf Patented Aug. 7, 1934 lmAT INSULATION Carl Georg Munters, Stockholm, Sweden Application April z, 1934,'seria1 No. '316,666

In Sweden March 3, 1931 7 Claims. (Cl. 154-45) This application is in part la continuation of my copending application Serial No. 595,411

led February 26, 1932.

My invention relates to insulationand more particularly to insulation of the character employing a. relatively small amount of solid material arranged to form intervening spaces containing gaseous material.-

It has heretofore been proposed to form insu- 10 lation of sheets of solid material with intervening air spaces, said sheets in sc me Ainstances being of metal foil, as aluminum foil, to provide surfaces having lhigh heat-reecting characteristics. If the layers of air are on the order of one centimeter in thickness in the direction of heat transfer, the air in said layers is substantially dead and so far as reducing heat transfer by convection maximum efciency has been sub- .stantially obtained. gases have a lower heat conductivity than air and it might be expected that' insulation of the character above referred to could be improved by replacing the air by such a gas of lower heat conductivity. I

I have discovered, however, that such is not the case and the amount of heat transfer through insulation charged with a gas of lower heat conductivity may` in fa t be higher'than that for the same .insulation when charged with air. I/ have further discovered, on the other hand, that advantage may be taken of the lower heat conductivity -of such gases in insulating .structures of the type above referred to if the' gas layers arel made materially narrower than the critical spacing for preventing convection currents in intervening vertical layers of air, and although this involves an increase in the number of sheets or partitions, and thereby in the weight of solid material used, the total ad- 40 vantage derived from the use of the gas of lower heat conductivity results in insulation of materially higher elciency than the best heretofore obtained by use of stagnant layers of air ofwhatever thickness.

of layers into which the should be greater as the specific Weight of the gas employed increases, to the end that convection currents within said gas layers may be reduced to a minimum. Therefore, in accordance with my invention, I provide a hermetically sealed enclosure which is charged with a suitable gas of lower heat conductivity than air at a corresponding temperature and pressure and the gas space is subdivided gas lled space is subdivided;V by partitions of It` is known that certain' In accordance with my discovery the numberv sheet material which provide narrow gas spaces in the direction of heat transfer and which afford a minimum of conductive contacts or paths for conduction between said sheets or partitions.

As compared with the spacing heretofore used when stagnant air has been employed, the thick- .ness of the `gas layers in the direction of heat transfer bears an inverse relation` to the specific weight of` the lga Width of gas space in the direction of heat flow,

the heavier the gas the sheets partitions or s, whereby for a given total greater the number of which are employed.

Whereas 'a spacing of one centimeter or more is suitable for sheets between air layers, for an insulation of average heat drop,

the spacing ac- 76 cording to thepresent inventionwill be lessthan oneecentimeter, and preferably not exceeding about 5 mm.,

less than 5 mm.

Furthermore, to minimize or all of the partitions or` vided with bright surfaces and may be materially heat transier, some sheets may be proto reduce radiation,

and the members of the insulation in the direc` tion of heat flow are made heat conductivity.

of a material of low 80 'Ihe invention will be further described in the following specification of illustrative embodiments, though it will be clear that the invention is not limited to the embodiments specifically disclosed.

Of the accompanying drawing, which forms a part of this specification:

Fig. 1 is a sectional view, 1-1 of Fig. 2, through a embodying the invention;

Fig. 2 is a sectional 2-2 0f Fig. 1;

and

Fig. 4 is a ture.

The structure shown in taken lon the line slab of insulation view taken on the line View of part of the strucand 2,. on enlarged scale;

` sectional view of a modified struc- Figs. 1, 2 and 3 comprises a hermetically sealed casing including side walls 34 and end or transverse walls'35. The 100 slab is to act as a heat insulation between the spaces outsidek and adjacent walls 34. Consequently the line or direction of heat ow' is perpendicular to the planes of walls 34. Walls or plates 34 may be corrugated or otherwise formed 105 and are of such thickness as to give the insulating element sufficient strength and resistance to shocks. These walls may be made of aluminum, iron,- or other for the purpose.

gastight substance suitable 'Ihe walls should be able to 110 vmethane (CClzFz)-;

withstandV pressure uctuations of about 100 millimeters mercury due to variations in atmospheric pressure. The end walls 35 are made of material of low heat conductive capacity, such, for instance, as cellon lose and camphor or like plasticizers), celluloid, pollopas (an artificial mass obtained by condensation of urea or its derivatives and formaldehyde in the presence of bases) or the like, or a nickel-iron alloy, for example of Z5-35% nickel. Walls 35, as anged over the walls 34 and, when using one or more of the non-metallic substances, are pasted thereto by a suitable kind of paste, which, for instance, may consist of a mixture lof cellon'and vinepas (polymeric vinylacetate) dissolved in acetone.

Within the casing or element are a plurality of thin partitions 30 of sheet material spaced by frames 31 of felt, porous paper composition or like material having low heat conductive ca# pacity, which frames are made suiliciently rigid for handling during manufacture by means of similarly formed frames 32 of suitable material such as cardboard pasted to the felt or the like. The cardboard frames are also preferably pasted to the sheets 30. Sheet members 30 may be aluminum foils or the like. The sheets 30 are disposed transversely to the direction of flow of heat.

Within the frames`31 and between the sheet` members are spacinglmembers made of superimposed pieces of felt and cardboard pieces 33 similar to the material of

parts

31 and 32.

At least every other partition 30 preferably has bright heat reflecting Asurfaces in order to counteract heat transmission through the ele-4 -ment due to radiation.

The other partitions may consist of paper or the like having less heat reecting capacity, since` their principal purpose is to provide such narrow gas layers as to substantially prevent movement of gas in the` layers, and thus prevent heat transfer byl convection.

lThe interior of lthe casing, and consequently the spaces between the partitions 30 of sheet material are lled with a gas having a lower coeicient of heat conductivity than air at corresponding pressure and temperature. Thev preferred gases are sulfur hexailuoride (SFs): methyl chloride (CHsCl), dichlorodirluorosulfuryl fluoride (SOaFz): methyl bromide (CHaBr): and ethyliodide (02H51). All these gases are halogen compounds. Other suitable gases for certain insulations vare compounds of sulphur such as sulphur 'dioxide (SO2) and carbon disulphide (CS2). A mixture of two or more ofl said gases may be used. The gas or gas mixture which is made use of should have a boiling point lower than the lowest temperature prevailing where the heat insulator is to be used. The' gas chosen should be insoluble inthematerial of which the insulation is made and should not react with said material.

I have discovered that these heavy gases require a closer spacing than the critical spacing for air; and in general the spacing should be e1eser `the heavier the gas. with the gases above mentioned, theidistance between the partitions or foils is preferably less than 5 millimeters in order to prevent convection of the In order that the gas may enter all of the spaces between the partitions, the felt frames shown in Figs. 2 and 3, arev may be provided with small holes Vcommunicating with Athe narrow space 36 between the frames and the transverse walls verse walls may be made of a single strip secured and made tight by an overlapping corner piece 38. A filling hole 39 is provided which may be closed by a coverv pasted thereon.

When the insulation is made as shown in Figs. 1, 2, and 3, it is preferable, thoughnot essential, to use a gas pressure approximately the same as but slightly below atmospheric pressure, since, in suclr case, the preponderance of pressure acting on' the outside ofthe casing tends to maintain the separating members in place. Y

Fig. 4 shows a construction'permitting a higher pressure to prevail inside the insulation thanoutside. In this embodiment, the partitions are spaced by means of ring elements 40 placed around pins 41 of a material of low heat con'- ductivity, such, for instance, as baklite, to

35. The transwhich the outside walls or plates are secured by means of screws 42. A The gas may be introduced by evacuating and vfilling the insulation casing while 'wholly containedin a pressure vessel, so that the pressure inside and outside the insulationvcasing can be maintained the same.

In the foregoing, I have described-an insulating unit in which some of the partitions have bright surfaces, as when using. aluminum foil, backed or unbacked, or alternate foil and paper partitions.v The invention may be carried out without the use of reecting surfaces. For ex- In such case, the spacing should be still closer than hereinbefore indicated in order to obtain equivalent effect in preventing heat transfer by radiation. Paper may be used without special ample, the partitions may be entirely of paper. 110

frame members-by crumpling the paper so as to have a minimum contact. I have found an advantageous spacing of paper sheets tobe about 0.6 millimeter.

may pass through the vpaper partitions.

What I claim is:

l: A heat insulating structure comprising exterior c'onning walls, agas hermetically enclosed therein and having a lower heat conductivity than air at a corresponding pressure and temperature, and partitions formed of sheet material between said walls arranged transversely to the direction of heat transfer for counteracting heat transmission byl radiation and convec4 tion, said partitions forming intervening gaseous layers materially narrower than the critical .spacing for preventing convection currents in intervening vertical layers of air.

2. A heat insulating structure comprising ex terior confining walls, a gas hermetically enclosed therein and. having a lower heat conductivity than that of air at a corresponding pressure and temperature, said gas comprising a -gaseous compoundv of the group including sulphur hexauoride, methyl chloride, dichlorodiuoromethane, sulfuryl fluoride, methyl bromide and ethyliodide, and partitions formed of sheet material between said walls arranged transversely to the direction of heat transfer for counteracting heat transmission by radiation and coneous layers materially narrower than the critical spacing for preventing convection currents in intervening vertical layers of air.

Non-conductive` spacing pins 3. A. heat insulating structure comprising 150 spaced walls to be maintained at diiere'nt temvestion, said partitionsforming intervening gas- .145

perature, other walls forming with the first mentioned walls a hermetically sealed casing, a gas in said casing heavier than air, and a plurality of partitions ofsheet material per centimeter distance between the first-mentioned walls for dividing the gas into layers.

4. A heat insulating structure comprising exterior confining walls, a gas hermetically enclosed therein and having a lower heat conductivity than air at a corresponding pressure and temperature, and partitions formed of sheet material between said walls arranged transversely to the direction of heat transfer for counteracting heat transmission by`radiation and convection, said partitions forming intervening gaseous layers having a thickness in the direction of heat transfer not greater than 5 millimeters.

5. A heat insulating structure comprising exterior conining walls, a gas hermetically enclosed therein and having a lower heat conductivity than that of air at a corresponding pressure and temperature, said gas comprising a gaseous compound of the group including sul-4 phur dioxide and carbon bisulfide, and partitions formed of sheet material between said walls arranged transversely to ,the direction of heat transfer for counteracting heat transmission by radiation and convection, said partitions forming intervening gaseous layers materially narrower than the critical spacing for preventing convection currents in intervening vertical layers of air.

6. AL heat insulating structure comprising exteriorv confining walls, a gas heremetically enclosed therein and having a lower heat conductivity than air at a corresponding pressure and temperature, partitions formed of sheet material between said walls arranged transversely to the direction of heat transfer for counteracting heat transmission by radiation and convection. and pressure resisting members of low heat conductivity passing through the partitions.

7. A heat insulating structure comprising exterior confining walls, a gas hermetically enclosed therein and having a lower heat conductivity than air at a corresponding pressure and temperature, and partitions formed of sheet material between said walls arranged transversely to the direction of heat transfer for counteracting heat transmission by radiation and convection, said partitions forming intervening gaseous layers whose thickness in the direction of heat transfer is less than one centimeter and'of a thickness sufficient to substantially prevent convection currents in intervening vertical layers of