EP0691440A1 - Building block with insulating hollow spaces - Google Patents

Abstract

The brick or tile with inner hollow zones > 8 mm wide, has a heat reflective coating on the inner surfaces of the hollow zones (2). <IMAGE>

Description

The invention relates to a cuboid block with heat-insulating inner cavities that are more than 8 mm wide. A brick of this type can also be a brick. It is used to create heat-insulating walls and is walled up with adhesive, thin-bed, medium-bed or a fiber-containing mortar that does not fall into the cavities. The cavities can run vertically parallel to the wall surface, as with so-called perforated bricks, or horizontally.

In the case of conventional insulating building blocks, such as perforated bricks, gas concrete blocks and building blocks made of cement-bound lightweight building materials, attempts are made to optimize the thermal insulation capacity by using the lightest possible building material. That is why heavily porous clay is used for bricks, foamed concrete, pumice, pearlite or the like. However, this technology has its limits in the limited compressive strength of the lightweight materials.

Furthermore, it is state of the art to improve the heat insulation capacity by cleverly arranging air slots which pass completely or at least for the most part transversely to the heat flow direction from one component side to the other. In particular, slot-shaped cavities aligned in the longitudinal direction of the stone and offset with respect to one another transversely to the direction of heat flow improve the thermal insulation capacity. However, the elongated cavities that are produced in the extrusion process of bricks and therefore continuous weaken the cohesion, in particular the transverse tensile strength of the insulating blocks. Therefore, a minimum cross-sectional area of heat-conducting webs in the heat flow direction cannot be undershot.

It is known that for a given thickness of the longitudinal webs running transversely to the direction of heat flow, the optimal average slot width or the average number of successive slot holes in the direction of heat flow can be calculated (Swiss Patents 476 181, 482 882 and 516 057). The mean slot width is the cross-sectional area of a generally elongated cavity divided by its greatest extent transverse to the direction of heat flow. The number of slotted holes is averaged over a large number of cuts through the brick in the direction of heat flow. It corresponds to a more common parameter, namely the number of rows of slots. The cross sections of the cavities generally have elongated shapes such as ellipses, rectangles, trapezoids, cuboids, triangles, etc., transverse to the direction of heat flow. The cavities can also have square, round, pentagonal, hexagonal and polygonal shapes.

For blocks made of fired clay, web thicknesses of 6 mm and more are common. If the web thickness is reduced, for example to 4 or 2 mm, then increases based on the top mentioned patents very strongly on the optimal number of slotted holes, so that bricks with the theoretically determined optimal number of slotted rows can no longer be produced, since the extrusion of the clay masses results in excessively high pressures. For example, for a 30 cm thick brick with a web thickness of 2 mm according to Leitner (so-called CH-PS 516 057) or Amrein (so-called CH-PS 476 181), the slit hole width should be 3.5 mm. This would require more than 50 rows of slotted holes in order to approximately reach the theoretically determined maximum. Today 30 cm thick bricks usually have 17 rows of slots, a maximum of 21 rows. 30 rows of holes may currently represent a borderline case of producibility.

Another way of producing heat-insulating blocks is to create the block with several larger cavities and, in order to limit the heat loss in the cavities, to subsequently fill them with insulating inserts made from a wide variety of materials, but this is a complex operation.

Conventional insulation modules, which have been optimized with these methods, achieve thermal conductivity values of 0.12 W / mK or less, at best 0.15 W / mK for bricks.

The invention has for its object to provide insulating blocks that are statically loadable to a conventional extent, but have a much better thermal insulation than previously known, and are easier to produce.

Starting from a module of the type described in the introduction, this object is achieved by the characterizing feature of claim 1 and by the claimed method features.

The heat transport in an insulating module of the type mentioned takes place on the one hand by heat conduction in the base material, i. H. in the walkways, and on the other hand by convection, conduction and radiation in the cavities. Recent findings have shown that the share of heat transport through the air-filled dark cavities in the total heat transport is considerable, particularly in the case of building blocks with thin webs. Furthermore, the heat transport in the cavities by radiation is surprisingly high. This outweighs the share of heat transport by conduction in the air and by convection. The heat transfer by convection is small in slot holes with a height of 25 cm up to a slot width of approx. 3 cm next to the radiation component and also smaller than the heat transport through the heat conduction in the air. The large theoretical number of webs of a block optimized according to the above-mentioned script is basically only necessary because the webs, like screens, repeatedly interrupt the heat radiation. The same happens with known building blocks, the cavities of which are filled with insulating materials. For cavities that are considerably wider than 3 cm, the insulated inserts prevent convection, but for all filled cavities, especially those with a width of 3 cm and smaller, the insulated inserts primarily cause an interruption of the heat radiation. The still air alone would be an optimal insulator without convection and radiation.

It is generally known to provide heat-reflecting surfaces on the objects to be protected from thermal radiation for insulation purposes, especially at high temperatures and against solar radiation. Based on the above-mentioned knowledge that the heat radiation in the cavities has a surprisingly high influence even at room temperature, the invention proposes this possibility of reducing the heat radiation by heat-reflecting surfaces in the cavities of insulating modules use. It should be noted that in the interest of the maximum benefit of the coating the optimal number of rows of holes must be redefined.

Fortunately, it was found that building blocks with heat-reflective coated inner cavities can be provided with wider cavities than if the cavities are uncoated. It is therefore proposed, in contrast to the formulas according to the Swiss patents mentioned at the beginning, to provide fewer and wider rows of slotted holes. This means that further heat-conducting webs can be saved and the thermal insulation capacity of the module can be further increased. These wide internal cavities not only bring additional insulation gain, but also improve the producibility of the module.

The coated inner cavities do not need to be provided with additional insulating inserts because the coating of the cavities sufficiently reduces the heat exchange by radiation between the opposing webs delimiting the cavity. However, the most favorable thermal conductivity values are realized with cavity widths below 3 cm, because otherwise convection currents can arise in the cavity. For the same reason, the height of the cavity should be limited to a stone height of generally 25 cm and care should be taken that the cavities do not connect to channels during bricking, but are separated from one another by a layer of mortar. This can be achieved in particular in that a building block with large cavities up to three centimeters wide also has small cavities in addition to these, which are closed during bricking by the mortar used and cover the large cavities. In any case, it must be ensured that not too much mortar falls into the cavities, soiling them, partially filling them, and thus the insulation behavior lowers. In particular, it makes sense to coat handle holes in a heat-reflecting manner and to arrange them in such a way that they do not overlap in the usual offset during bricking. Advantageously, such building blocks are bricked up in the immersion process, that is, they are dipped only a few millimeters into the mortar and mixed with the mortar adhering to the stone.

By largely suppressing the heat radiation in the cavities, it is possible to reduce the total heat transport in the cavities by more than half at the usual climatic temperatures in the cavities. For example, the thermal conductivity for internally coated slot holes with a width of approx. 2 cm is less than 0.05 W / mK instead of over 0.11 W / mK for uncoated cavities.

When this technique is used on good insulating blocks, which are made from lightweight materials using the traditional method and which take the heat-reflecting coating into account with regard to the hole width and number of holes, it is possible to produce blocks for statically loadable insulating walls without additional insulation with thermal conductivities below 0.10 W / mK.

In a further development of the invention, it is proposed that, in addition to the cavities, the abutting sides of the insulating modules are also coated with heat reflecting properties. This applies in particular to building blocks that have recesses on the joint sides, which, when attached to a next stone in the same position, combine with the recesses to form closed cavities. These cavities are then also coated on their inner surfaces.

The heat reflective layer may contain aluminum or a similar heat reflective component. Various oxides such as zirconium oxide, titanium oxide, magnesium oxide etc. are also suitable. The heat-reflecting component can be in the Clay, embedded in a glaze, a varnish or any top layer or bonded with an adhesive layer.

A preferred method for applying the heat-reflecting layer is that it is evaporated or sprayed onto the traditionally produced insulating module. In the case of bricks in particular, it is proposed that, if a smooth surface is necessary, a glaze is applied as a base for the heat-reflecting layer before the latter is applied. This forms a hard, smooth surface on which z. B. aluminum can be evaporated or sprayed on. Instead of vapor deposition, special ceramic or inorganic masses can be sprayed on, which are then baked on.

The cavities can also be coated by spraying on a synthetic resin lacquer with reflective components, since the coating is not exposed to high temperatures.

Another method of coating the surfaces of insulating modules, in particular bricks, is to add water-soluble products with a low emission coefficient to the mass to be molded or the clay. During the drying and firing process, these migrate to the surfaces of the blank and coat it evenly. If this coating is undesirable on the wall-parallel outer surfaces, it can be brushed off or sanded down.

Another possibility of coating is that a glaze containing the heat reflecting component is co-extruded with the molding. The glaze is pressed onto the cores of the mouthpiece with great pressure.

The effectiveness of a heat-reflecting coating can be stated numerically by the so-called emission coefficient ε. It is 0.93 for fired clay or cement-bound lightweight building materials without coating, but only 0.05 for aluminum-coated surfaces. Paintings with aluminum bronze have an emission coefficient ε of around 0.20 and are therefore perfectly suitable for coating the cavities.

Fig. 1

die Draufsicht eines Bruchstücks eines Hochlochziegels mit wabenförmig angeordneten sechseckigen Hohlräumen (Wabenziegel),

Fig. 2

die entsprechende Draufsicht eines Hochlochziegels mit versetzten rechteckigen Hohlräumen (Schlitzlochziegel),

Fig. 3

die entsprechende Draufsicht eines Hochlochziegels mit elliptischen Hohlräumen,

Fig. 4

die Draufsicht eines ganzen Ziegels mit Grifflöchern im kleineren Maßstab,

Fig. 5

ein Kurvenschaubild, das bei einem Hochlochziegel bestimmter Abmessungen unter bestimmten Voraussetzungen die rechnerische Abhängigkeit des Wärmedurchlaßwiderstandes R von der Anzahl n der Lochreihen darstellt, und

Fig. 6 und 7

entsprechende Kurvenschaubilder, bei denen andere Parameter gelten.

Exemplary embodiments of insulating modules in which the invention is implemented are described below with reference to the drawing. This also shows some arithmetically obtained graphs that underline the importance of the invention. In detail shows

Fig. 1

the top view of a fragment of a perforated brick with honeycomb-shaped hexagonal cavities (honeycomb brick),

Fig. 2

the corresponding top view of a perforated brick with offset rectangular cavities (slotted perforated brick),

Fig. 3

the corresponding top view of a perforated brick with elliptical cavities,

Fig. 4

the top view of an entire brick with handle holes on a smaller scale,

Fig. 5

a graph showing the mathematical dependence of the thermal resistance R on the number n of rows of holes in a perforated brick of certain dimensions under certain conditions, and

6 and 7

Corresponding graphs where other parameters apply.

In the figures 1 to 3, a neighboring tile is indicated by dash-dotted lines. The cavities are coated with heat reflecting on their wall surfaces. A corresponding coating is of course possible for any shape of the cavities.

At the abutting surfaces 1, these bricks are designed in such a way that the adjacent ends of the bricks complement the respective hole pattern. Accordingly, not only are the inner surfaces of the cross-sectionally differently shaped holes 2 running perpendicular to the bearing surface of the brick heat reflectively coated, but also the abutting surfaces 1 in order to also capture the inner surfaces of the trapezoidal, rectangular or wedge-shaped grooves, in which after the bricks have been assembled heat transfer by radiation also takes place. On the visible sides 3, the wall thickness of the brick was chosen to be 6 mm. The wall thickness of the inner webs is 3 mm.

1 has 15 rows of holes. Masonry created with such bricks achieves a wall thickness of 30 cm unplastered, taking into account the standardized heat transfer coefficients and with a thermal conductivity of the cullet material of 0.30 W / mK for non-reflecting inner surfaces a k-value of 0.38 W / m²K. The emission coefficient is Clay surface 0.93. If the surfaces are reflective with an emission coefficient ε = 0.1, a k-value of 0.25 W / m²K is achieved instead of 0.38 W / m²K.

In the brick shown in Fig. 4, the honeycomb pattern is refined again. The brick floor plan measures 30 x 27 cm. There are 21 rows of holes in the heat flow direction. Another special feature of this brick are two embedded handle holes 4 and a half-cavity 5 on the butt sides. These half-cavities complement each other when a further brick is added to form a whole cavity. Of course, as in the previous examples, all cavities and the butt sides can be coated in a heat-reflecting manner. A very favorable influence can also be expected if only the grip holes 4 and the half-cavities 5 are coated accordingly. On a butt side, this brick has four vertical springs 6, each containing a hexagonal cavity, which engage in corresponding grooves 7 of the neighboring brick.

5, 6 and 7, the influence of a heat-reflecting coating of the cavities on the thermal resistance R and on the theoretically optimal number n of rows of slots of a 30 cm wide and 25 cm high building block with different web widths is shown graphically. These representations apply under the following conditions: The thermal conductivity of the body is 0.30 W / mK, the two outer edge webs on the visible surfaces are twice as thick as the inner webs. Thermally conductive crossbars made of clay are neglected, as is heat transfer by convection currents, which means that the validity of the diagrams is limited to a maximum hole width of 3 cm. In general, the thermal resistance R of the brick increases with increasing quality of the coating and the optimal number n of rows of slots decreases, the slots being wider will. The emission ratio ε, which was changed between 0.05 and 0.9 with three intermediate stages in this calculation, is shown in FIG. 5 for the individual curves. It can be seen that with increasing quality of the heat-reflecting coating, ie with a smaller emission ratio ε, the thermal resistance R not only becomes fundamentally greater, but the curve shape changes in such a way that a maximum becomes visible at all. This is particularly clear in FIG. 7 (web thickness 6 mm).

It can be seen that in the case of modules with coated cavities, if there are more than 25 rows of slots, the thermal resistance R at web thicknesses of 4 mm and 6 mm decreases very strongly and even at 2 mm. It is therefore not sensible to coat the cavities of building blocks with slot widths below 8 mm in a heat-reflecting manner.

Claims (10)

Building block with heat-insulating empty inner cavities that are more than 8 mm wide, characterized in that the inner surfaces of the cavities (2) are coated with heat reflecting. Building block according to claim 1, characterized in that the abutting surfaces (1) are also coated in a heat-reflecting manner. Building block according to claim 1, characterized in that larger cavities such as grip holes (4) are coated with heat reflection and are arranged in such a way that the cavities do not lie directly one above the other when the building blocks are bricked up. Building block according to claim 1, characterized in that the heat-reflecting layer contains aluminum or a similar heat-reflecting component as other metals or oxides. Masonry, created with building blocks according to one of claims 1 to 4, which are walled with adhesive, thin-bed, medium-bed or fibrous mortar, so that the cavities do not fill with mortar or become dirty. Process for the production of building blocks according to one of the preceding claims, characterized in that the heat-reflecting layer is vapor-deposited or sprayed on or glued on as a thin film. A method according to claim 6, characterized in that the heat reflecting layer is baked. A method according to claim 7, characterized in that the heat-reflecting layer is applied to bricks before firing by spraying, co-extrusion or brushing. Process for the production of building blocks, in particular bricks, according to one of the preceding claims, characterized in that a glaze is applied as a base for the heat-reflecting layer before the latter is applied. Process for the production of building blocks, in particular bricks, according to one of the preceding claims, characterized in that a water-soluble, heat-reflecting component is added to the raw material clay, which migrates to the surface of the cavities during the drying and firing process and coats them.

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