DE2151467A1 - Insulation to reduce the heat transfer between a surface and a liquid - Google Patents

Description

Patent attorneys

Dr.-Ing. Wilhelm Reichel Dipl.-Ing. Woligtmg Reichel

6 Frankfurt a. M. 1
Park street 13

6847

KARTIiT EARIEITA CORPORATΙΟΙ, Denver, USA

Insulation to reduce heat transfer between a surface and a liquid

The present invention relates to insulation for reduction the heat transfer between a surface and a liquid or a theraic insulation for liquids with low temperature or coolants.

In the German patent application P 21 28 720.7 (honeycomb freezing) describes a thermal insulation for liquids that have a cellular structure having separate or individual cells, which a Contains insulating gas. The structure is attached to the inside of a liquid container, and a capillary cover with one or more openings per cell is attached to the liquid side of the structure. One stable or stable gas-liquid interface, which acts as a stretched or stretched membrane,

209817/0941

is formed at each opening, thereby preventing the entry of the liquid into the cells. The gas and the liquid are in a state of equilibrium at the interface , if the liquid is supercooled at the interface (ie the liquid is cooler than the saturation or boiling temperature), the gas condenses in the cells and the liquid Leak-through tends to develop, with the fluid alternately entering and vaporizing the cells and then bubbling back into the main body of the fluid through the capillary orifice.

According to the present invention, a container for a created supercooled liquid, which is characterized by thermal insulation on its inner surface, wherein the insulation has a cellular structure with a plurality of separate cells which contain an insulating gas, a capillary opening that extends between each cell and extending to the interior space below the container, uneven, stable or stable gas-liquid capillary interface between the gas in the cells and the liquid, and by a device that the! liquid next to the Zv / ischenflache at its boiling point.

The invention will now be described in detail with reference to the accompanying schematic drawings, all of which are taken from the description and the details or features shown in the figures for solving the problem within the meaning of the invention can contribute and were included in the application with the intention of being patented. Show it:

../3 209817 / 09At

BATH ORIGINAL

215H67

Figure 1 shows a perspective view of the insulation according to the invention;

liigur 2 shows a section on an enlarged scale the line 2-2 of Figure 1 and

FIG. 3 shows a section on a further enlarged scale, namely of part 3 in FIG. 2.

The insulation 10 shown in the drawings is used for long-term storage of supercooled liquids with a low boiling point, such as liquefied natural gas or liquid nitrogen, oxygen, hydrogen etc. The insulation 10 is on a support surface 12, uv.-ockaäfiig the inner surface of a can or other Fixed container in which the liquid is to be stored or kept.

The insulation 10 has a cellular structure 14-, which is formed from a number of strips 16, which are assembled on edge and at a distance from one another lying positions are connected. Each strip has a corrugated shape, with adjacent strips work together to form single or separate cells 18 therebetween. The edges of the strips form one another opposing generally flat surfaces, one of the surfaces being attached to surface 12.

The cells 18 are on the liquid side of the structure 14-through a capillary cover 20 which extends across each of the cells 18 and is substantially closed

..A 209817/0941

BADORIQJNAL

215H67

-A-

z. B. is attached to the structure 14 by an adhesive bond. The cord of the cover over each cell 18 can be arched or concave, as shown in FIG

of the German patent application ·. "Isolation for

Reducing heat transfer between a surface and a liquid "(stress reliever). The cover 20 contains numerous capillary openings 22, with at least one opening per cell. These openings create a communication between the Inside the cells 18 and the liquid stored in the container. A gas column is erected in every cell, to isolate the stored liquid from surface 12, and a stable or persistent gas-liquid interface or membrane 24 is formed on all openings 22. The cellular structure 14, the capillary cover 20 and the manner in which the gas column is erected or produced are detailed in the German patent application P 21 28 720.7 (honeycomb freezing) described. If the. G-a column is built, the pressure of the gas can be slightly greater than the pressure in the neighboring liquid, because of the capillary compressive forces, and it is important that the fluid the saturation temperature immediately next to the membrane at this pressure. Kit in other words, it is known that the boiling temperature of the liquid is below the present pressure conditions at the interface must be present.

When the liquid becomes hypothermic and the temperature is below the boiling temperature of the liquid on the membranes 24, the membranes 24 are destroyed and it occurs the leakage process described above.

209817/0941

BAD ORlQiNM.

■ 215H67

To eliminate the leakage process becomes a thermal one Barrier switched on between the capillary cover 20 and the body of liquid a layer 30 of insulating material on the capillary cover 20 is placed or arranged. The layer 30 consists, for example, of cork or a foamed material. the The function of the layer 30 is to isolate the membrane 24 from the main body of the liquid, but not segregate. The layer 30 therefore only needs to be fastened to the extent that it is above the cover 20 in the installed position is held. The layer 30 is not intended to be sealed to the cover and it will preferably be a relatively porous one Material is used for the layer 30 so that the liquid can pass through the layer 30 to form the membranes 24 to train. If the material forming the layer 30 is not. is itself porous, perforations or openings are machined in the material so that the liquid can pass through can. By allowing the liquid to pass unimpeded through the layer 30, pressure differentials are created across this position and therefore no structural or structural load is generated within the insulation. If a porous material is used for the layer 30, the liquid layer is next to the cover 20 "still or stationary", i.e., the layer 30 prevents free convection currents from developing in the liquid will. The stationary or resting liquid layer forms a thermal resistance that is sufficient to generate the necessary temperature difference between the cover 20 and the main body of liquid.

As shown in Figure 2, the sheet 30 is in direct contact with the cover 20, with a smaller one Gap 32 between the concave parts of the cover 20 and the layer 30 is present. However, the layer 30 can also be in a small distance from the cover 20 can be arranged.

209817/0941 "^{# / 6}

219H97

The composition of the layer 30, as well as its thickness, can vary depending on many factors including the minimal heat flow associated with the insulation used v / should be grounded, and the degree of hypothermia of the change stored liquid. In general, it can be said that the layer 30 must be such that a temperature stratification is created, with a minimal work heat flow through the insulation system, which, measured across layer 30, a temperature difference which is equal to the difference between the boiling temperatures and mass temperatures of the liquid. Referring to Figures 2 and 3, it is thus established that the mass temperature of the body of liquid L-g, rather remote from the membranes, is the supercooled Temperature corresponds, while the temperature of the liquid Lj next to the membranes 24 corresponds to the boiling temperature or saturation temperature. This temperature difference is shown in mainly maintained by the layer 30, as well as by the natural transfer of some heat-from the Walls of the container from inside. However, when designing a system for subcooled liquids, the insulation layer 30 in such a way takes into account that at the minimum allowable heat flow of the insulation the temperature difference across layer 30 is such that the liquid Iy is kept at the boiling point

If the heat transfer to the liquid L _{1 increases} above the minimum value calculated in the design, a certain boiling of the liquid in the gap 32 can occur. However, this boiling does not adversely affect the insulating function of the insulation, since it merely causes the membrane 24 to move away from the capillary openings 22 intermittently. However, finds

../7 209817/0941

in this case no liquid entry through the openings 22 in the cells 1L ötatt. "If the temperature in this Range, then returns to the boiling temperature value, the liquid also returns to the area between the layer 30 and the capillary cover 20, and the Membrane 24 is immediately formed again in the capillary openings 22.

The isolation described in detail can be converted into a relatively large tank or container are used, in which the hydrostatic pressure at the container bottom is significant is larger than, for example, at a position in the upper area of the container. This pressure difference leads to a Difference in the boiling temperature of the liquid at the bottom ■ of the container compared to the boiling temperature of the liquid at the top of the container. Since the hydrostatic Pressure increases with depth in the container, and consequently the boiling temperature also increases with depth, it grows Extent of subcooling of the liquid body with the depth in the container. The layer 30 can therefore be on the ground of the container but are omitted in the upper parts of the container. Ia alternative case can A layer 30 can be used throughout the container, but of greater thickness in the lower part of the container than ir; upper part. Different insulating materials can also be used use to form the layer 30 along different parts of the insulation. So you can on the ground of the container use a certain insulation material, while at the top of the container a different one Material used.

As an alternative to creating layer 30, hypothermia can be used Liquids are stored by controlling the vapor pressure within the cells and thus

../8 209817/0941

215H97

the boiling point of the liquid. If the cells with a gas other than the vapor of the stored liquid, s.B. Helium, partially filled, corresponds to the saturation pressure of the stored liquid at the Membranes the partial pressure of the vapor phase of the enclosed liquid that is present within the cells. Of the Vapor pressure within the cells and thus the boiling temperature of the liquid are reduced accordingly. By The partial pressure of the Steam within the cells can be influenced or controlled. However, over a longer period of time the helium or other gas is absorbed by the liquid or through continuous bubbles and when filling of the cells due to fluctuations in pressure or fluid level. A supercooled liquid can therefore only be stored for relatively short periods of time using this method.

209817 / 09Λ1

Claims (1)

6847 claims Insulation to reduce heat transfer between a surface and a liquid, characterized in that the insulation has a plurality of cells which are arranged to extend between the surface and the liquid and contain a gas to a Form a gas layer between the surface and the liquid that a cover the liquid side of the Closes cells and has an opening in communication with each cell in order to ensure a stable or loaded ' permanent gas-liquid interface between the gas layer and to form the liquid, and that a device is provided which the thermo-dynamic relationship controlled between the liquid next to the cells and the vapor of the liquid trapped in the cells, to ensure that the liquid is not below its boiling point, thereby the formation to control the interface. 2 «insulation according to claim 1,
characterized in that the means for controlling the thermodynamic relationship comprises means for thermally isolating the interface from the liquid remote from the interface. ../10 209817/0941 215U67 2. Isolation according to claims 2, characterized in that the means for isolating the interface is a thermal barrier that have a difference between the temperature of the liquid remote from the interfacial surface and the temperature of the Generates fluid on the thigh surface. 4. Insulation according to claim 3, characterized in that that the temperature difference is the difference between the Boiling temperature of the liquid at the interfacial surface and corresponds to the temperature of the liquid that is remote from the interfacial surface. 5. Insulation according to claim 3 or claim 4, characterized in that that the thermal barrier is a material layer with a low thermal conductivity to v / eist between the Intermediate surface and the liquid main body is arranged, and that the material layer is designed so that the liquid from the side of the material that is remote from the interface, through the material against the Side can pass through, which is located nefcen the toe surface. 6. Isolation according to claim 3 »characterized in that that the thermal barrier is a layer of porous material which liquid can absorb and store in a relatively stationary or stationary layer to reduce free convection within the material layer. ../11 209817/0941 7. Isolation according to claim 5 or 6, characterized by u> r ch, that the material layer is arranged over the cover. 3. Isolation according to claim 1,
characterized in that the means for controlling the rm ο dynamic ratio contain a gas in the cells which differs from the vapor of the liquid. 9. Isolation to reduce Y / heat transfer between the surface of a container and a liquid contained in it, which has a low boiling point on v / eist, characterized in that the insulation has a cellular structure with a Has a large number of cells in order to create numerous gas columns between the liquid to be stored and the surface of the 3ehälters that a capillary device forms a stable capillary intermediate surface between the Columns of gas and the liquid generated, and that a device has a thermodynamic s relationship between the Liquid next to each cell and the vapor of the liquid contained in the cells forms in order to ensure that the liquid is not below its boiling point. 10. Isolation according to claim 9 s
characterized in that the device has a gas in the cells which differs from the vapor of the liquid, so that the vapor pressure of the liquid in the cells has a partial pressure of the total pressure in the cells. ../12 209817/0941 BATH 215U67 ■ 11. Container for a supercooled liquid, marked d u r; c h a thermal insulation on its inner surface, the Insulation has a cellular structure with a multiplicity of separate cells which "contain an insulating gas, a capillary opening extending between each cell and the interior space below the container, around a stable or stable gas-liquid capillary interface between the gas in the cells and the liquid, and by a device that keeps the liquid next to the interface at its boiling temperature. 12. Method of isolating the surface of a container for the purpose of storing a liquid with a low Boiling temperature in the container, characterized in that the method comprises the steps of: forming a plurality of gas columns between the liquid to be stored and the container surface and creating a stable capillary interface between the gas columns and the liquid, while the temperature at the interface increases to the boiling temperature of the liquid for the Case is set that the liquid would otherwise be undercooled at the interface. 13. The method according to claim 12,
characterized in that the temperature at the intermediate surface is set or maintained at the boiling point of the liquid in that the liquid next to the intermediate surface is thermally insulated from the liquid which is remote from the intermediate surface. 209817 / (1941 ^: 215H67 14. Procedure according to. Claim 12,
characterized in that the gas columns are held in the cells and the • temperature at the interface is brought to the boiling point of the liquid by additionally introducing a gas into the cells that differs from the vapor of the liquid, so that the The vapor pressure of the liquid in the cells is a partial pressure of the total pressure in the cells. Re /]? U / Gr _# 209817/0941 Blank page