Heat exchange – Regenerator – Heat collector
Reexamination Certificate
2000-03-31
2003-09-09
Bennett, Henry (Department: 3743)
Heat exchange
Regenerator
Heat collector
C428S304400
Reexamination Certificate
active
06615906
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a latent heat body with paraffin-based latent heat storage material accommodated in a carrier material which has capillary-like holding spaces, the carrier material comprising an organic plastics material or natural material.
From German Utility Model 84 08 966, there is known a porous foam material as the carrier material. However, with this foam material it is impossible to achieve the structural strength desired even when the latent heat storage material is in the heated state. Moreover, the porous foam material cannot readily be impregnated with the latent heat storage material. Special measures, such as squeezing, have to be taken.
working on this basis, the invention deals with the technical problem of providing a latent heat body which, while being easy to produce, is highly efficient, i.e. has a high heat storage capacity and, at the same time, exhibits sufficient structural strength even in the heated state. It is also desired for the carrier material to be filled with or suck up the latent heat storage material automatically, as far as possible. It is also important to achieve a high retention capacity with regard to the latent heat storage material by means of the properties of the carrier material alone.
SUMMARY OF THE INVENTION
These technical problems are initially and substantially solved by assembling the carrier material from individual carrier-material elements which are inherently structurally strong or, when combined with the latent heat storage material, lead to the appropriate structural strength, for example by adhesive bonding. For the invention, it is important for the carrier-material elements to be held cohesively together even in the absence of latent heat storage material, and consequently the carrier material is one or more structures each comprising a multiplicity of combined carrier-material elements. According to the invention, the carrier-material elements are assembled in such a way that capillary holding spaces for the latent heat storage material are formed between them, which spaces may be in the form of a crack. The capillary holding spaces described above, due to their capillary action on a fluid, allow the carrier material to be filled with or to suck up the fluid in a substantially automatic manner and provide the carrier material with a high retention capacity. This action is used to good effect for the latent heat body according to the invention in that the proposed paraffin-based latent heat storage material to which individual additives, or a plurality of the additives, cited in this application may be added, is liquefied by heating to a sufficient extent for the automatic suction action to be observed. Preferably, the latent heat storage material can be heated up to a temperature which is above the highest melting point of the individual paraffins and additives contained therein. The latent heat storage material is in this way liquefied to such an extent that it can be taken up automatically by the carrier material until the latter is completely saturated. This procedure results in the advantage that it is possible to dispense with complex and therefore expensive technological process steps which involve a high input of in particular mechanical energy.
The assembly procedure which leads to a fixed bond between the carrier-material elements is at the same time suitable for setting the size of the holding spaces which remain between the carrier-material elements and for influencing the desired structural strength.
By virtue of the adjustability of the size of the holding spaces, there exists furthermore the possibility of establishing, as a function of the boundary or surface tension of the latent heat storage material, a size of the holding spaces which is optimized with regard to a maximum possible holding capacity and, at the same time, a sufficiently high capillary action.
Suitable carrier materials are organic materials such as plastics or cellulose. It is also preferable for a carrier-material element to have its own capillarity. An example is a cellulose fibre, such as a wood fibre, which inherently forms a considerably finer capillary space than the capillarity formed between two fibres. It is also important for the latent heat storage material itself to form homogeneously distributed hollow structures. These structures are of particular importance for the performance or response of the latent heat body. Firstly, such hollow structures provide yielding spaces as the volume changes during heating or cooling. This volume change may generally be of the order of 10% of the volume. As carrier-material elements, there may furthermore be used fibres of very different lengths and diameters. Suitable elements are in particular also ceramic fibres, mineral wool, plastics fibres and other suitable fibres, such as for example cotton or wool. Ceramic fibres used preferably substantially comprise Al
2
O
3
, Si
2
, ZrO
2
and organic additions, and the quantities in which the components are present may vary considerably. Depending on the proportions selected, the density of the ceramic fibres fluctuates, preferably within a range from 150 to 400 kg/m
3
. With regard to the mineral wool, preference is given to using rock wool with or without the addition of thermosetting synthetic resins, and the wool may furthermore contain glass fibres. The density fluctuates as a function of the composition selected for the individual case and preferably lies in a range between 200 and 300 g/m
3
. Plastic fibres which are suitable as carrier-aterial elements preferably contain base materials such as polyester, polyamide, polyurethane, polyacrylonitrile or polyolefins. In this regard, it is particularly preferable for the latent heat storage material to be a paraffin as described in DE-A-43 07 065. The entire contents of this prior publication are hereby incorporated into the disclosure of this application, also for the purpose of including features of this prior publication in claims of the present application.
In the solidified state, such a paraffin has crystal structures which are modified by a structural additive, preferably so as to create hollow structures, such as for example hollow cones. This makes it possible to significantly improve the response of the latent heat storage material when heat is introduced. As a result, the latent heat storage material, such as paraffin, adopts, as it were, a porous structure. When heat is introduced, constituents of the latent heat storage material which melt more easily can flow through the hollow structures provided in the material itself. A type of micro-convection is able to establish itself, if appropriate also with regard to air inclusions which are present. The result is a highly efficient mixing together. There is a further advantage with regard to the abovementioned expansion behaviour in the event of a phase change. The structural additive is preferably dissolved homogeneously in the latent heat storage material. In detail, structural additives such as those based on polyalkyl methacrylates (PA-MA) and polyalkyl acrylates (PAA) have proven suitable as individual components or in combination. Their crystal-modifying effect is brought about by the fact that the polymer molecules are incorporated into the growing paraffin crystals and prevent this crystal shape from growing further. Because of the presence of the polymer molecules even in associated form in the homogeneous solution in paraffin, paraffins may grow on the special supranuclear assemblies. Hollow cones which are no longer able to form networks are formed. Due to the synergistic action of this structural additive on the crystallization behaviour of the paraffins, cavities are formed and therefore the ease with which the heat storage medium paraffin can flow through (for example for air or water vapour which is included in the latent heat storage body or for liquefied phases of the latent heat storage material, i.e. of the paraffin itself) is improved compared to paraffins which h
Fieback Klaus
Haberschuss Toni
Matthäi Michael
Bennett Henry
Duong Tho V
Farber Martin A.
Schümann Sasol GmbH & Co. KG
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