FR3001278A1 - Method for assembly of materials for increasing thermal resistance of thermal path by multiplier effect, involves replacing length of tube by homogeneous volume, and providing thermal resistance multiplier effect according to specific ratio - Google Patents

Abstract

The method involves providing two volumes (A1, A2) of a solid material that defines two outer sides surfaces (S) between which energy is exchanged by heat flow. A tube (B) provided with reinforcements (C) made of the solid material is arranged with a thin peripheral wall thickness that connects the two volumes. A length of the tube is replaced by homogeneous volume of same solid material, and an energy heat transferring surface is provided for the tube. A thermal resistance multiplier effect is provided according to a specific ratio and length of the tube.

Description

The present invention relates primarily to the field of devices and methods of construction for the building, especially for the realization of insulating walls. It relates more particularly to an assembly of materials for increasing the thermal resistance of the thermal path traversed by a heat flux between two opposite faces outside said assembly. For the record, the materials have a physical quantity called "thermal conductivity": LAMBDA (X) expressed in W m'1 K-1 for 1 m2. It is possible to calculate a "thermal resistance" Rth expressed in K W1 with the formula: Rth = (1 / X) * (L / S) where L is the length of the material in the direction of heat exchange, expressed in meters , and S is the area through which the flow of heat flows, expressed in m2. In the current state of the art, the search for the highest possible thermal resistance between two opposite outer faces can be done by one of the six means mentioned below. According to a first means, the choice is made of solid solid materials. At the highest thermal resistance corresponds the lowest thermal conductivity. In the present state of the known materials, polystyrene with X = 0.04 is commonly used and some materials are given for slightly weaker ones.

In a second way, the air is trapped in a fibrous system. It is noted that the air has a very low X. This fibrous system will avoid the transport of energy by convection of air, which in addition to the conduction decreases the thermal resistance. The method has its limits because the fibrous system itself, composed of solid fibers, brings a conduction which decreases the thermal resistance. With I air = 0.025 and X fiber = 1, isolations with global X are carried out around 0.030 to 0.040.

According to a third means, it is also possible to trap air in a network of microbubbles. It falls on the same problem as the second way because we use so-called plastic materials with a plastic around 0.15. Even taking care to stop the radiation with surfaces that reflect the thermal radiation, the final result, global X, remains around 0.030 to 0.040. According to a fourth means, it is also possible to trap the air in aerogels. With aerogels you can get very close to the X of the air.

In general, we can approach the X air but we can not go below. It has also been noticed that vacuum allows neither conduction nor convection, only thermal radiation propagating in a vacuum. According to a fifth means, it has been created a bottle lined with another, the two together at the neck. The space between the two bottles is lined with a material that reflects the thermal radiation and the vacuum is made between the two bottles. This gives very good results but between the inside of a bottle and the outside of the other. This is not suitable for use in the construction of a building.

According to the sixth means, structures adapted to the construction are proposed forming vacuum insulating panels. They give very good results in terms of a ,. It is possible to produce thin panels. It seems that the life of these structures is limited because the envelopes of these panels are not perfectly impervious to air. The object of the invention is to propose a device and a method which make it possible to obtain improved thermal insulation between the two faces of a wall, in particular between the inside and the outside of the building.

According to the invention, such a device is formed of a thermally insulating construction element characterized in that it comprises: - two side walls each comprising an outer surface spaced from each other along an axis; a tube connecting said walls to each other in a substantially gas-tight manner; - At least one reflector for thermal radiation, disposed in the tube, substantially transverse to the axis, having a reflective surface substantially vis-à-vis one or other of said side walls; said side walls and the tube together forming a vacuum volume. At least one reflector, among the reflectors, may be arranged against one of the side walls vis-à-vis the other side wall.

At least one reflector, among the reflectors, is advantageously an intermediate reflector disposed at a distance from the side walls. This intermediate reflector may comprise two reflecting surfaces, each vis-à-vis a respective side wall. It may furthermore constitute a means of transverse reinforcement for the tube. It can also be pierced with a hole to circulate the air during the evacuation. The tube may further comprise at least one reinforcing rib extending longitudinally along one of its inner faces or at an angle. Preferably, the reflector is in contact with the tube substantially over a whole peripheral edge of said reflector, said peripheral edge preferably being beveled.

The invention also relates to a method of constructing an insulating wall, characterized in that it comprises the use of construction elements according to the invention.

The present invention thus proposes a device forming building bricks and a method for assembling materials between two opposing planes, by constructing a thermal resistance multiplier, which makes it possible to produce such solid bricks, which are not very fragile, of standardized size. , which can be produced in series. The construction of these bricks can be achieved with technologies currently known and controlled. Several embodiments of the invention will be described hereinafter, by way of non-limiting examples, with reference to the accompanying drawings, in which: FIG. 1 schematically illustrates, in section and in elevation, a brick device according to FIG. invention and the principle of its assembly; Figure 2 illustrates four different sectional shapes for a tube used to form a brick according to the invention; Figure 3 illustrates, in section, two embodiments for a tube section, one hexagonal, the other square, each comprising ribs, and for each, a corresponding reflector / reinforcement; FIG. 4 illustrates an example of arrangement for reflectors / reinforcements in a tube and a detail of contact between this tube and a reflector / reinforcement; and, Figure 5 illustrates schematically, in section, an embodiment for a brick according to the invention, in its position in a partition. FIG. 1 illustrates a device of the type of building brick 1. In the example illustrated, the brick 1 has an elongation direction along an axis of symmetry X1. Brick 1 comprises two volumes of a solid material each forming a side wall 2,3, each defining a respective lateral face 4,5 of the brick, substantially transverse to the axis X1; the brick extends in the direction defined by the axis X1 between the two lateral faces 4,5. In a building, the brick 1 is provided to be arranged so that energy exchanges are mainly between the side faces 4,5, substantially along the axis X1. For example, one of the lateral faces 4,5 may be in contact with the external environment of the building, the other face being in contact with the interior environment of this building. The brick further comprises a tube 6 of solid material interconnecting the two side walls 2, 3. The tube is formed of one or more peripheral walls 7 of thickness e. The thickness e is chosen to be small in order to limit thermal exchanges by conduction between the two side walls 2,3. The surface of the solid section of thickness e, measured transversely to the peripheral walls 7 is denoted Sb.

In the illustrated example, the section of the tube 6 and the thickness e, measured perpendicular to the axis X1 are substantially constant, the walls 7 of the tube 6 extend substantially perpendicularly to the side walls 2, 3, and the walls peripherals 7 are connected to each side wall along a peripheral edge of said side wall. Thus, the outer dimensions of the brick 1, measured transverse to the axis X1, are substantially constant from one face 4.5 to the other. The various elements forming the side walls 2, 3 and the tube 6 are rigidly and airtightly connected to one another; thus, the connection C between each of the two volumes of the side walls 2, 3 and the tube 6 is solid and watertight. The internal volume V defined between the side walls and the tube is advantageously placed under vacuum. The materials of the side walls and of the tube are sufficiently sealed to limit the introduction of air or steam for a sufficiently long time, compatible with the use of the assembly; for example, for a brick according to the example, we will consider the life of the construction in which it is planned to integrate. Such an arrangement makes it possible to limit the convective exchanges inside the volume V, in particular between the side walls 2, 3. Advantageously, to limit the radiative heat exchange between the two side walls, directly or indirectly, one or more reflectors 8, 9 are arranged in the volume V, between the side walls. The reflectors each occupy a section of the tube 6, i.e. they extend between the walls of the tube occupying the entire corresponding tube section. Optionally, some reflectors may be arranged against the inside of the side walls. In the example shown, the brick 1 comprises two intermediate reflectors 8, spaced apart from the side walls, and two end reflectors 9, each attached to the inside of a respective side wall 2,3; all four extend substantially perpendicular to the axis X1. The energy of the heat flow which circulates between the two surfaces S of the lateral faces 4,5 is constrained to pass through the surface sB formed by the solid section of the tube 6 (see FIG. 2). The energy of this heat flow can not pass through the S-sB surface for three reasons: - there is no conduction, since there is no liquid or gas in the interior volume V ; there is no convection, for there is neither liquid nor gas in the interior volume V; the thermal radiation is almost completely stopped by the reflectors 8,9. Considering on the one hand the assembly described, comprising the tube 6 whose solid section is sB and made with a material of thermal conductivity X, the thermal resistance of this tube is: Rth (tube 6) = (1 / k) x (L6 / sB) where L is the length of the tube 6 and sB is the solid section of the tube 6. Considering also the above-mentioned assembly, and assuming that the tube 6 is replaced by a homogeneous volume of the same material and the same external section, the thermal resistance of this volume would be: Rth (homogeneous volume) = (1 / X) x (L6 / S) where L is the length of the assembly, between the two surfaces exchange 4.5. There is a multiplying effect of the thermal resistance in the ratio: Rth (homogeneous volume) / Rth (tube B) = S / sB. The assembly must be made with a solid material on the one hand and low X on the other hand. Referring to Figure 2, the different shapes of the tube 6 may be: a circle, a hexagon, a square, a triangle or other shapes as needed. Depending on the shape, for the same surface S and for the same ratio S / sB, the thickness of the peripheral wall of the tube varies as well as the peripheral length of the tube 6. -8 Examples for different forms: Table of dimensions in the assumption of a ratio S / sB = 10, for example for a surface of 1 m2.

Shape Surface Area Outside Radius Tube Thickness B External Perimeter Length S sB Circle 1 m2 0.1 m2 0.564 m 0.029 m 3.54 m Outside Length Length Hexagon 1 m2 0.1 m2 0.623 m 0.028 m 3.73 m Square 1 m2 0.1 m2 1 m 0.026 m 4 m Equilateral triangle 1 m2 0.1 m2 1.52 m 0.022 m 4.56 m The circular shape is mechanically the best. But the juxtaposition of circles does not completely cover a flat wall of large area.

The interstices must be filled with a common material, which reduces the total thermal resistance of the wall. The circular shape can be used for special cases. The hexagonal shape and the square shape, which are juxtaposed, make it possible to form large insulating flat surfaces; The triangular shape which is less advantageous can be the subject of particular applications. In all cases, the tube 6 must withstand a pressure of S / sB atmospheres in the direction of the axis in length.

Example for a plastic material (X plastic = 0,15) and if one assumes to arrive at X, = 0,015 the ratio multiplier S / sB in this example must be of 10. In the hypothesis of this ratio, the tube must withstand 10 atmospheres in the direction of its axis, ie 10 kg / cm2. The compressive strength of a plastic (material taken as an example) among the least solid is 1.5 daN / mm 2 is 150 kg / cm2. The pressure to bear in the example is 15 times smaller than the least solid plastics (most plastics have a compressive strength greater than 6 daN / mm2).

The tube 6 is subjected to atmospheric pressure on its periphery; combined with compression, these forces can cause buckling. To reduce the risk of buckling, the reflectors 8 are used as reinforcement discs, each disc substantially conforming to the inner shape of the tube 6. The reinforcing discs may also not be reflectors. As illustrated in FIG. 3, the mechanical strength and the buckling resistance can be improved by arranging ribs 11 inside the tube 6, substantially parallel to the axis X1. These ribs, which increase the surface sB must be optimized because they reduce the thermal resistance. Figure 3 shows two examples of ribbed tubes with the ribs 11 and the complementary shape of the corresponding reflectors / reinforcements 11. One of the tubes is of substantially hexagonal section and the second of substantially square section, the ribs being arranged in each of the angles of the hexagon or square, respectively. The ribs can be supplemented or replaced by local extra thicknesses. The materials used for the reflectors / reinforcements 8 may be metal with the thermally reflective surfaces or any other mechanically resistant material with one or two surfaces rendered thermally reflective. In the examples illustrated in FIG. 3, the reflectors / reinforcements 8 are provided with a hole 12 to ensure the vacuum throughout the tube 6. The number of the reflectors / reinforcements 8 is optimized according to the risk of buckling and the Efficiency of the thermal barrier. FIG. 4 shows a possible arrangement of the reflectors / reinforcements 8 in the tube 6. Their distribution, close to the lateral walls and more spaced in the middle of the tube 6, results from the distribution of the mechanical stresses. along the tube 6. An enlarged detail shows a contact 13 between a wall of the tube 6 and one of the reflectors / reinforcements 8. This contact 13 should preferably remain as small as possible to limit the formation of a thermal bridge. In the illustrated example, the edge of the reflector is bevelled, so that the contact is along a strip narrower than the reflector is thick.

The internal volume V defines by the two side walls 2,3 and the tube 6 is placed under vacuum and this vacuum must be kept long enough in comparison with the expected use time. In the case of using porous materials, the assembly can be sealed: either by surface treatment, or by adding non-porous materials, or both simultaneously. The brick shape with flat surfaces lends itself well to these three possibilities. The tube 6 may then consist of two or more materials, at least one of which is non-porous. We then consider the 2 of each of the materials and we identify a global 2. The mechanical strength becomes that of the two or more materials assembled given their method of assembly. The plastic (material taken for example), which is porous in both air and water requires to be sealed by the means mentioned above. By way of example, the following possibilities can be mentioned: - With a plastic material (X plastic = 0.15) and another glass material (X, glass = 1). If the thickness of the glass is 0.2 mm, the glass is the equivalent of 1.33 mm of the plastic. Assuming the table of dimensions above, and in the case of the shape of the square, then there is a tube 6 consisting of 24.67 mm of plastic and 0.2 mm of glass. 2- With a plastic material (I plastic = 0.15) and the other material which is a metal layer nikel / chrome or invar (X metal alloy at 23 ° C = 13). If the thickness of the metal is 0.1 mm, it is the equivalent of 8 min of the plastic. Assuming the table of dimensions above, and in the case of the shape of the square, then there is a tube 6 composed of 18 mm of plastic and 0.1 mm of metal. 3- With a plastic material (X plastic = 0.15) and the other material which is a layer obtained by electroplating (X metal = 90). If the thickness of the metal is 0.01 mm, it is the equivalent of 6 mm of the plastic. Assuming the table of dimensions above, and in the case of the shape of the square, then there is a tube 6 composed of 20 mm of plastic and 0.01 mm of metal. It can be seen in the three examples above that the thermal resistance is maintained and that the mechanical strength can always be ensured with a plastic material. The two volumes of the solid material 2,3 forming the side walls and defining the two faces 4,5 between which the energy is exchanged are provided strong enough to withstand the atmospheric pressure and transmit the resultant force on the tube 6. In the In the case of large surfaces, one or more spacers may be added between the two side walls, but these spacers will reduce the thermal resistance of the assembly. The thermal resistance of the two side walls is a value which corresponds to the path of the heat flow in this volume. The path of the heat flow crosses on one side the surface 2, 3 of a wall and on the other side the surface sB corresponding to the contact of said wall with the tube 6. The flow of heat circulating therefore mainly radially, c ' that is to say transversely to the axis X1, in the illustrated example. The influence of the two side walls on the total thermal resistance is not preponderant but if the material has a low 2 'these two volumes can add a significant thermal resistance. In practice, the thermal resistance of the assembly is counted on the total length Lt along the axis X1: Rth (assembly) = Rth (wall 2) + ((1 / X) * (L / S) * (S / sB)) + Rth (wall 3) One of the two side walls 2, 3 is advantageously equipped with a connection system for evacuating. This connection system allows a tight closure.

The assembly method has the characteristic of having two material size transitions. The transmission of acoustic vibrations presents in these places a strong reflection by acoustic impedance break. Moreover, the void does not transmit sounds. As a result, the assembly has a high attenuation for acoustic waves, excluding resonances. In the example illustrated in FIG. 5, the tube 6 is of square section; it is made of plastic and the side walls 2,3 are made of steel. In the figure, no stiffener or reflector is shown, for simplification. In order to absorb the differences in expansion between steel and plastic, for example PVC, each side wall 2,3 is connected to the tube 6 by a respective elastic seal 20. Each of the four walls of the tube 6 is lined with a respective glass plate 21.

Each side wall 2,3 forms a bowl 22 having a concavity facing outwardly of the brick 1. In each of the cups is housed a bung 25,26 engaged with the interior volume V of the brick. A first bung 25 makes it possible to measure the pressure in the volume V. This first bung comprises a chip of the RFID type 27, so that the pressure can be controlled remotely when the brick is in place in a construction. The second bung 26 is intended to evacuate the volume V, initially during the manufacture of the brick, and then when the brick is in the construction. Indeed, the plastic being generally breathable, it may be necessary to remake the vacuum in the volume V at regular intervals, for example every twenty years, or at least when control using the RFID chip 27 indicates insufficient vacuum to provide a desired thermal insulation. The second bung comprises a tubing 28 for connecting the internal volume V to a vacuum pump and a valve 29 to isolate and volume V when the pump is not in use. Preferably, several pipes, or all the pipes of the same wall or of several walls are connected together and to a same pump. In Figure 5, the brick 1 is shown in a partition of a construction.

Typically, this construction is made of a timber frame. The bricks, which do not have in this case a carrier function, are stacked (only one is shown in Figure 5) in the intervals between the elements of the framework. Cladding panels 41, 42 are disposed on either side of the stack of bricks with a respective clearance J1, J2, typically of 10 millimeters. Of course, the invention is not limited to the examples which have just been described. Thus, instead of two bungs only one can be provided on each brick, combining the functions of pressure taking and vacuum. In addition, all or part of the tube can be made in one piece with one of the side walls, before assembly of the brick.

Claims (10)

REVENDICATIONS1. Thermally insulating building element (1), characterized in that it comprises: two side walls (2,3) each comprising an outer surface (4,5) spaced from each other along an axis (X1); a tube (6) connecting said walls to each other in a substantially gas-tight manner; at least one reflector (8, 9) for thermal radiation disposed in the tube, substantially transverse to the axis (X1), having a reflective surface substantially facing one or the other of said walls; lateral, said side walls (2,3) and the tube (6) together forming a volume (V) under vacuum. 2. Construction element according to claim 1, characterized in that a reflector (9) at least among the reflectors is disposed against one of the side walls (2,3) vis-à-vis the other wall lateral (3,2). 3. Construction element according to one of claims 1 or 2, characterized in that an intermediate reflector (8) at least among the reflectors is disposed at a distance from the side walls (2,3). 4. Construction element according to claim 3, characterized in that the intermediate reflector (8) comprises two reflective surfaces, each vis-à-vis a respective side wall. 5. Construction element according to one of claims 3 or 4, characterized in that the intermediate reflector is a transverse reinforcement means for the tube (6) .- 16- 6. Construction element according to one of claims 3 to 5, characterized in that the reflector is pierced with a hole (12). 7. Building element according to one of claims 1 to 6, characterized in that the tube (6) further comprises at least one reinforcing rib (11) extending longitudinally along one of its inner faces. 8. Construction element according to one of claims 1 to 7, characterized in that the reflector is in contact with the tube substantially on the whole of a peripheral edge (13) of said reflector, said peripheral edge preferably being bevelled. 9. Construction element according to one of claims 1 to 7, characterized in that it comprises at least one plug (25,26) comprising means (28,29) for making or remaking the vacuum in the volume (V ) and / or means (27) for measuring the pressure in said volume. 10. A method of constructing an insulating partition, characterized in that it comprises the use of building elements according to one of the preceding claims.