NO770371L - HEAT INSULATION MASSES. - Google Patents

Abstract

Thermal insulation compound

Description

To improve the thermal insulation in buildings, it is common

to place so-called heat barrier plates to thereby greatly reduce set the heat bypass. In new buildings, such heat<p>erre-

plates or thermal insulation plates are installed inside the walls, but it is then usually necessary to use an aluminum foil to protect against moisture. In recent times, thermal insulation boards have been developed which can be placed on the outside of existing buildings. However, due to the fact that the facades can be designed in very different ways, adaptation and attachment present major difficulties.

If the existing layer of plaster is replaced with thermal insulation boards of the same thickness, the existing window members, and especially the fastening devices for these, can be retained. In this case, calculations have shown that half and up to two-thirds of the through-heat can be saved, and the repayment period at the currently applicable heating oil prices is approx. 8-10 years.

The invention relates to a new heat-blocking mass of a hardenable binder which is initially liquid, and evenly distributed insulating bodies that are tightly packed in the binder, and the heat-blocking mass is characterized by the fact that the insulating bodies are hollow bodies with a gas-tight casing and are filled with a gas with a lower thermal conductivity than air, in that the ratio between the casing thickness of the hole covers and the diameter of the hole covers is at most 0.1:1.

The present mass can be used as plaster. The volume proportion of the hollow cores must be as large as possible in relation to the volume proportion of the binder, i.e. the hollow cores must be thoroughly shaken and evenly mixed with the binder. Hollow bodies made of glass are particularly suitable, but also plaster, e.g. molding resins and thermoplastics can be used.

Theoretical and experimental investigations have shown that by using spheres a packing density of up to 0.65 can be achieved and with small cylinders a packing density of up to 0.75, while the packing density for Raschig rings is 0.38.

The invention will be described in more detail with reference to the drawing, where

fig. 1 is a section through a calculation model for the thermal insulation mass according to the invention, and

fig. 2 is a section through the present thermal insulation mass according to an application example thereof.

The below calculated estimate provides a first starting point for the thermal properties of the thermal insulation material in question.

As used below means:

0.85 W/mK the thermal conductivity of concrete

^s = 0.024 " " " air ^g = 0.7 " " " glass ^so the effective thermal conductivity of the mass

d the internal diameter of the spheres =v 2r.

For a thin-walled, air-filled glass sphere 1 surrounded by a concrete replacement cylinder 2 with wall thickness r (Fig. 1), a first approximation yields a k-number of

and thus an effective thermal conductivity for the mass of For a plate with the thickness & = nr becomes

The wall thickness s for thin-walled hollow spheres then becomes

Of d Fo^ r = mu4 r0 s00 té- n 8 e0 r 00 p kpa /c= m 220. 0 M- ed 30m0 idkdp/eclm ve2r, dmieenne s ffoar sblyglas is If Ar is chosen = s, becomes

Thereby obtained

XsQ= \ + 0.08 X= 0.024 + 0.08 0.85 = 0.09 W/mk.

Compared to this, concrete has a thermal conductivity of

0.85 W/mK, i.e. an approximately ten times greater value.

A confirmation of this first estimate can be found in the theoretical-experimental investigation by P. Zehner from which the dimensionless thermal conductivity ratio ASQ/A ^an is derived as a function of X s</\>

For air-filled, spherical cavities in concrete are available

an effective ratio without consideration of convection and radiation of

i.e. a value that is greater by a factor of 1.1 than the approximately calculated value of 0.09.

Attempts have already been made to reduce the thermal conductivity of concrete by mixing particles with poor thermal conductivity into the concrete or by creating artificial porosity in the concrete.

It then turned out that when large quantities were mixed in or when a large porosity was formed, the thermal conductivity was indeed lower, but the mechanical strength was, on the other hand, greatly impaired. Nor can a packing density of 0.6-0.7 be achieved with such artificially formed pores. In contrast, small hollow spheres or hollow cylinders closed on all sides, as shown, have a high compressive strength, so that e.g. a plaster of a mixture of concrete and hollow cores has approximately the same strength as concrete. In order to improve the adhesion between the hollow cores and the binder, it can be beneficial to roughen the outer surface of the hollow cores. This mixture can therefore also be used to make masonry and ceiling tiles, coverings, pipework shelves and similar items. Such stones and slabs will be particularly suitable for new buildings. If pipes, e.g. for heat transfer from thermal power plants, is produced directly from the heat-insulating mass according to the invention, no further heat insulation is needed, and this leads to both space savings and cost savings.

In fig. 2 shows a heat-insulating pipe 3 which consists of the material according to the invention. The glass balls 1 are tightly packed and evenly distributed in the already hardened binder 4

and thereby forms a simple heat-insulating pipe body in which the heat flow moves in the direction of the arrow 5 without major losses.

However, if existing buildings are to be provided with better thermal insulation, the plastering will primarily be carried out with this composite material, and this will be as simple as applying a normal plaster.

As the casing of the small spheres or cylinders is gas-tight, it is also possible to fill them with a gas that has a lower thermal conductivity than air, e.g. krypton or xenon which has a thermal conductivity three or four times as poor as air. Moisture cannot penetrate either, and this implies a significant improvement compared to ordinary concrete. It is also an advantage that no convection takes place inside the plaster between the balls and that the radiation is strongly suppressed. If the holes are filled with gas under overpressure, the compressive strength will increase due to the resulting bias.

Claims (7)

1. Heat-insulating mass of a hardenable binder which is initially liquid and in which uniformly distributed insulating bodies are tightly packed, characterized in that the insulating bodies are hollow bodies with gas-tight casing and are filled with a gas with poorer thermal conductivity than air, as the ratio between the casing thickness for the hole blocks and the diameter of the hole blocks is at most 0.1. 2. Mass according to claim 1, characterized in that the holes consist of glass. 3. Mass according to claim 1, characterized in that the holes consist of plastic. 4. Mass according to claim 1, characterized in that the holes are spherical or cylindrical. 5. Mass according to claims 1-4, characterized in that the holes are filled with xenon. 6. Mass according to claim 1, characterized in that the outer surface of the hollow cores is roughened. 7. Use of the thermal insulation mass according to claim 1 as plaster.