DE102010061741A1 - Suspension containing phase change material and graphite particles and container with suspension - Google Patents

Abstract

The present invention relates to a suspension (1) which contains a phase change material (PCM) and graphite particles. According to the invention, the graphite particles contain expanded graphite and / or natural graphite, with essentially no PCM being present within the expanded graphite and within the natural graphite.

Description

The invention relates to a suspension of phase change material and graphite particles and a container containing a suspension of phase change material and graphite particles.

Phase change materials (PCMs) can store heat energy in the form of latent heat due to their phase transformation. Due to their low thermal conductivity loading and unloading of heat storage tanks with PCM are very slow. Therefore, it has been proven to add PCM to increase the thermal conductivity of carbon, in particular expanded graphite.

In the DE 102 50 249 A1 describes mixtures with phase change material and particulate expanded graphite, PCM in the solid state and graphite are mixed and pressed into shaped bodies.

The EP 1 598 406 describes a composite material in which, in particular by means of extruder and kneader, an intensive mixture of graphite flakes and PCM is achieved.

All materials have proven in their use for heat storage However, the disadvantage is the poor recoverability of the individual components of the composite materials, since graphite and PCM can be badly separated from each other.

The object of the present invention is to avoid the abovementioned disadvantages, in particular to provide a mixture which is readily recyclable, which can be used flexibly, is easy to produce and has good thermal conductivity and thermal storage capacity.

The object is achieved with a suspension according to claim 1. A suspension according to the invention contains phase change material (hereinafter also called PCM for short) and graphite particles, the graphite particles containing expanded graphite and / or natural graphite, wherein essentially no PCM is present within the expanded graphite and substantially no PCM is present within the natural graphite. In other words, the graphite particles may be either expanded graphite or natural graphite or a mixture of both. In the context of the invention, however, essentially no PCM is present in both types of graphite, regardless of their proportion.

Surprisingly, in contrast to conventional mixtures, a problem-free separation of the two components graphite particles and PCM is possible with the present suspension according to the invention. Until now, it was not known that a lack of penetration of PCM into graphite favored a separation of the components.

Separation can be done mechanically, for example by simply pouring or scarfing through a sieve, whereby the PCM drains off and leaves the expanded graphite and / or natural graphite at most with a certain surface wetting.

In conventional blends of PCM and graphite particles, on the other hand, PCM forms an intimate bond with graphite, for example a composite material, since the PCM is present inside the particles. Due in part to capillary and surface forces, this PCM can not be removed from the graphite at all or at great expense.

Under the feature that no PCM is present within the expanded graphite and / or natural graphite of the graphite particles, it is understood in the context of the invention that the PCM is present at most in a region near the surface in expanded graphite and / or natural graphite. This surface area near the surface is at most a quarter of the diameter, in particular at most a quarter of the radius. The substantially lack of presence of the PCM according to the invention can also be defined by the fact that PCM is at most 30% by volume, in particular at most 15% by volume, in the porosity of the graphite particles.

The term "suspension" underlines in the invention the lack of penetration of the PCM into the respective graphite. In the case of a suspension, there is a boundary between the liquid (here the PCM) and the graphite particles.

Advantageously, the expanded graphite of the graphite particles contains graphite expandate and / or powder obtained by crushing compressed graphite expandate, granules or chaff, chips, strips or the like. The term "expanded graphite" thus advantageously represents a generic term of all types of at least partially expanded graphite, which either can not be treated at all or can be further treated in various ways. Their production. and properties are known in the art and are therefore not explained in detail here. The production of Graphitexpandat is for example from the US 3 404 061 known Graphitexpandat is in the form of worm or accordion-like aggregates. Compacted graphite expandate can advantageously be present as graphite foil, which in turn can be comminuted as explained above.

For example, these types of expanded graphite may also be combined with each other such that chopped shreds obtained by crushing expanded graphite expandate, for example, are present side by side in the PCM.

Preferably, a lack of PCM in the expanded graphite is caused by the expanded graphite of the graphite particles having a mean pore size and a pore size distribution formed such that the PCM does not substantially penetrate the expanded graphite and / or the natural graphite at normal pressure ,

A mean pore size and a pore size distribution, which cause no infiltration of the PCM is given in the graphite particles, can be relatively easily adjusted on the production process of the graphite particles. Known parameters, such as calendering parameters in the production of graphite foil as a possible expanded graphite, can be easily adjusted conventionally, so that by means of such parameters the penetration behavior of PCM in the expanded graphite can be targeted. In this case, average pore size and pore size distribution can be adjusted so that, depending on the PCM, penetration into the expanded graphite is optimized. Since different phase change materials differ with regard to melting point, viscosity, surface tension, wetting behavior and other properties essential for penetration into expanded graphite, the average pore size and pore size distribution are to be set specifically with respect to this variant of the invention.

Depending on the deposit and the selected treatment stage of the graphite ore mined for the production of natural graphite, a natural graphite with specific porosities and / or densities can be obtained.

Advantageously, the graphite particles are mixed with the PCM without generating pressure, such as occurs by intensive use of mixing tools or by negative pressure. At normal pressure, the PCM in the liquid state penetrates into the expanded graphite and / or natural graphite according to the invention, in particular with a specifically set pore size distribution, essentially not.

The non-pressurized mixing is advantageously carried out by placing the graphite particles as a loose bed in a container and filling the container with the PCM. Since this requires no special technical precautions, a suspension according to the invention can be easily produced on site, for example on a construction site.

Preferably, the bulk density of the expanded graphite (without PCM) in the case of graphite expandate is between 0.002 and 0.015 g / cm ³ , in the case of chaff, chips, granules, between 0.01 g / cm ³ and 2.0 g / cm ³ , in the case of powder or regrind between 0.10 g / cm ³ and 1.0 g / cm ³ .

This bulk density range has proved to be particularly advantageous for producing a suspension according to the invention. Expanded graphite in these bulk densities is particularly easy to mix with PCM without PCM penetrating the expanded graphite.

Advantageously in the suspension fins, d. H. at least one fin introduced, which has a high thermal conductivity in the plane, in particular of more than 5 W / mK, in particular of more than 25 W / mK, more particularly of more than 50 W / mK, most particularly more than 100 W / mK.

Such fins can advantageously contribute to transporting heat and / or cold into and out of the suspension. The graphite particles of the suspension itself already contribute to a good thermal conduction, but a fin, which is a one-piece heat conductor that does not consist of a plurality of individual graphite particles that need to transfer via contact points heat / cold, suitable, heat and / or cold to transport directly into the interior of the suspension.

Advantageously, the at least one fin comprises compressed expanded graphite Such fins have on the one hand a particularly good thermal conductivity, on the other hand, their anisotropy is particularly high, because when compressing expanded. Graphite particles are aligned in the plane direction, which greatly increases the thermal conductivity in the plane direction. Thermally conductive fins with graphite allow the suspension according to the invention to work particularly well, since warmth and / or cooling is particularly effective in the suspension and out of it. Fins with graphite preferably have a thermal conductivity of more than 25 W / mK, in particular more than 50 W / mK, in particular more than 100 W / mK.

Advantageously, the at least one fin contains graphite foil, in particular it is made of graphite foil. Graphite foil has a particularly good thermal conductivity and, moreover, is mechanically quite stable and thus easy to handle, and furthermore commercially available.

Alternatively or in combination with the mentioned graphite-containing fins, however, metal fines can also be used. Due to their high conductivity and low density, aluminum or an Al alloy can be used as metal However, other metals are also conceivable, in particular with a correspondingly small thickness of the fins, such as copper or a Cu alloy, such as brass. Copper can have a thermal conductivity of over 250 W / mK, in particular over 350 W / mK. However, metal fins made of steel with a thermal conductivity of up to 60 W / mK or of stainless steel, which are particularly resistant chemically, or of noble metals whose thermal conductivity can be up to more than 450 W / mK, in particular up to 600 W / mK, are also conceivable ,

Advantageously, a plurality of fins is connected to each other, in particular by nesting, and forms a 2- and / or 3-dimensional structure.

This advantageously ensures that heat and / or cold can be introduced over a large area into the suspension and distributed over the suspension. Furthermore, interconnected fins stabilize each other mechanically. Since, in particular, graphite foil can be machined easily, for example, by cutting, in particular joining by nesting is a preferred variant. The nesting is accomplished, for example, with fins having correspondingly provided recesses, such as slots, wherein the recesses of two fins are inserted into each other. This allows a fixation of two fins to each other. By repeating this process, even more complex structures, such as lattice-like structures, can be produced from a plurality of fins.

Advantageously, the at least one fin is fixed in position by the suspension.

This is advantageously possible because the viscosity of the suspension is set such that the fin (s), which advantageously have a low density and a large surface area, are fixed without this having to be done by conventional means. In particular, no mechanical aids such as clamps, screws or the like are necessary. The fins can be placed in the suspension without any attachment and remain in an original position within the suspension even over several years. Graphite foil is particularly well fixed by the suspension in its position with a low density at the corresponding large surface of the fins.

The at least one fin can be fixed horizontally, vertically, or at any angle by the suspension in its position. Also, a plurality of fins may form a so-called random position, that is, the fins may be randomly disposed within the suspension. This can contribute to a very uniform, homogeneous heat conduction over the entirety of the suspension.

The graphite particles are preferably distributed uniformly throughout the suspension, which leads to a homogeneous heat conduction of the suspension. However, the invention also includes that the lower portion of the suspension is somewhat depleted of graphite particles relative to the remainder of the suspension. Preferably, in a lower region of the suspension, there are so many graphite particles and / or additional graphite that the overall thermal conductivity of the lower region is at most 50%, in particular at most 30% less than the total thermal conductivity of the suspension in the remaining region of the suspension, in particular of this essentially does not differ.

The lower area means the area of the suspension which, with respect to a container in which the suspension is located, faces a bottom of the container. In this case, the lower region is the region which transfers heat and / or cold to the ground. If, as in the prior art, the lower region is free of particles of high thermal conductivity, the lower region acts as an insulator, which thermally isolates the remaining region of the suspension from the bottom of the container. The preferred embodiment of the suspension according to the invention solves this problem.

The hardly or hardly lowered thermal conductivity of the lower region can be advantageously achieved in that the interaction of the density of the PCM and the proportions of graphite and PCM, the graphite does not float in the PCM Conventionally, such a floating occurs in suspensions of PCM and expanded graphite, because expanded Graphite has a low density. Especially with salt hydrate as PCM there is a risk of floating of expanded graphite. According to the advantageous variant of the invention, the proportion of PCM in the suspension is so low that a cloud of expanded graphite, which would tend to float in a larger amount of PCM, is located directly above a bottom of a container. Conventionally, there is a distance of the cloud to the ground, forming an area of PCM free of graphite, so that this area conventionally provides high thermal insulation.

By virtue of the high conductivity in the lower region of the suspension according to the variant of the invention, it is advantageously achieved that the suspension according to the invention can be applied in a container to objects to be cooled or heated from above. As in the lower part of the suspension no insulating PCM layer forms, the corresponding object can be cooled or heated particularly well. For example, the container can be placed on a heating medium-carrying tubes.

Advantageously, the suspension in addition to the. Particles of expanded graphite and / or natural graphite contain an additional graphite, wherein the additional graphite synthetic graphite and / or additional natural graphite and / or carbon black and / or carbon fibers or a mixture containing at least one of these components.

In particular, synthetic graphite and additional natural graphite can help prevent floating of graphite particles containing expanded graphite. This can be explained by the fact that the graphite particles containing expanded graphite are weighted down by the additional graphite and pushed down so that they remain suspended instead of ascending.

This is a surprising effect that was unexpected. Conventionally, particles of higher density slip down to lower density particles. In the present embodiment of the invention, there appears to be an effect which prevents such segregation. It is believed that particles of expanded graphite and / or natural graphite form a structure that is so mechanically stable that higher density particles can not penetrate them. Due to comparison experiments with other materials, which do not have this effect of building up a "self-blocking" structure, it is believed that the particles block and / or get stuck together mainly because of the molecular structure of graphite. Advantageously flat or needle-shaped particles form a kartenhausartige structure, which has a high mechanical stability. Particles of expanded graphite with a high surface area are therefore particularly suitable. Likewise, a needle-like structure is advantageous in natural graphite Advantageously, particles of expanded graphite and / or natural graphite are not so far mechanically processed, z. B. by grinding, that they have a more spherical shape. In such a case, training a card house-like structure would not be possible.

The construction of a self-blocking structure is also possible with graphite particles, as described above, without a lack of penetration of PCM. Therefore, here also a suspension is considered to be described, which has all the features of the description, the claims and the figures, but in which there is a penetration of PCM in the graphite particles.

In particular, horizontally present in the suspension fins can reinforce the effect described that additional graphite does not sink through graphite particles with expanded graphite and / or natural graphite. The fins, in addition to the self-blocking effect, inhibit particles from sinking, presumably in particular by preventing vertical flows.

Depending on the density of the PCM used and the density of the expanded graphite used or after preparation and density of the natural graphite used, a corresponding amount of synthetic and / or additional natural graphite can advantageously be used. The same applies to the grain size. For example, a proportion of more than 90% by weight of the graphite grains may be less than 0.4 mm. But it can also be a proportion of 65 wt .-% between 0.8 and 1.25 mm. The quantity and the particle size distribution can be optimized by the person skilled in the art depending on the PCM density, the density of the expanded graphite and the grain size of the expanded graphite without having to be inventive. In particular, with salt hydrate as PCM having a density in the range of 1.05 to 2.0 g / cm ³ and above, expanded graphite has a strong buoyancy, which would result in floating of the graphite particles. It should be emphasized again at this point that the suspension can have natural graphite both as graphite particles, so also fulfill as additional graphite natural graphite the task of obstructing by floating a floating of the graphite particles, it is called exclusively "additional graphite". The additional graphite must fulfill other properties for this task in terms of grain size and possibly also particle shape and density. Both the natural graphite of the graphite particles of the suspension and the additional natural graphite can, as explained above, be obtained from various deposits, processed differently and thus obtain corresponding grain sizes, residual impurities, densities and porosities. It is also possible to use different particle shapes, such as needles or flat particles, specifically for achieving the described effects.

According to a variant of the invention, the suspension may contain, in addition to the graphite particles, metal particles, such as aluminum particles, but also copper, brass and / or steel particles. Depending on the corrosive behavior of the PCM used, the type of metal particles will be selected accordingly. For example, it is advisable to use steel particles instead of aluminum particles in the case of highly corrosive PCM.

Thus, on the one hand metal waste can advantageously be recycled, on the other hand it can also prevent the floating of graphite particles, as already mentioned above additional graphite described. Due to the higher density of metal particles than of graphite particles, the particle size of the metal particles is deliberately set so small that the self-blocking structure still bears its weight in that the graphite particles are printed downwards without the metal particles sinking past the graphite particles. However, if the metal particles sink downwards and come to rest in the lower region, for example due to a specifically set larger particle size, this can also be advantageous, because a possibly present lower thermal conductivity of the suspension in this region is due to floating of the expanded graphite in the PCM balanced by the metal particles.

Floating can also advantageously be prevented by using non-metallic particles in addition to or instead of metallic particles. These may advantageously be mineral particles, such as calcium carbonate, kaolin or chalk, glass powder, plastic powder and similar particles. In this case, the ratio of the density of the particles to the density of the PCM and the graphite particles must be taken into account so that the floating can be prevented.

An advantageous PCM can be at least one PCM from the group comprising paraffins, sugar alcohols, gas hydrates, water, aqueous salt solutions, salt water eutectics, salt hydrates, mixtures of salt hydrates, salts and eutectic mixtures of salts, alkali metal hydroxides and mixtures of salts and alkali metal Hydroxides or a mixture of at least one PCM from this group.

Preferably, the ratio of additional graphite and expanded graphite or natural graphite may be set such that the expanded graphite and / or natural graphite is prevented from floating up the PCM by the additional graphite such that the total thermal conductivity of the lower region is at most 50%, in particular at most 30% less than the total thermal conductivity of the suspension in the remaining area of the suspension, in particular of this substantially does not deviate.

Incidentally, such a suspension is also encompassed by the present invention when PCM has penetrated to a large extent into the expanded graphite. In this case, all optional features for a suspension according to claim 1 mentioned in the description, the exemplary embodiments, the claims and the figures are also intended together with such a suspension with penetrated PCM apply as disclosed.

Advantageously used metal particles can also sink into the lower region of the PCM so that a possibly present lower thermal conductivity of the suspension in this region is compensated by the floating up of the expanded graphite in the PCM by the metal particles.

According to a variant of the invention, a container is filled with a suspension according to the invention. Such a container can be handled well and used for example for air conditioning, such as buildings. Preferably, the container has a thermally highly conductive outer wall, such as a metal foil, which may be mechanically reinforced with a plastic film. Advantageously, the container has a flexible, adaptable outer shell. Such a container lends itself particularly well to hang up on irregularly shaped, to be cooled objects, such as a heating or cooling pipe hang a climate ceiling. The use of PCM-filled containers with a flexible, adaptable outer shell is detailed in the EP 1 371 915 B1 described and all features, which concern this container with PCM are hereby by reference to the EP 1 371 915 B1 added. When filled with a suspension according to the invention, such containers can absorb and / or give off heat and / or cold much faster than in the prior art.

In such containers with a flexible outer shell comes another advantage of fins containing compressed expanded graphite, to advantage. In contrast to metal fins, there is no risk of graphite fines damaging the outer shell due to sharp edges. Advantageously, the fins may even partially cling to them in mechanical contact with the outer shell, so that a particularly good heat coupling of fins in the outer shell and thus in an object to be tempered is possible.

But it may also be advantageous that the outer shell is rigid. In particular for placing on straight surfaces or for self-supporting modules a rigid container is advantageous. It may be formed, for example, as a flat container.

Preferably, the graphite particles are uniformly distributed throughout the suspension, resulting in a homogeneous heat conduction of the suspension and thus also to a good transfer of heat and / or cold to the bottom of the container. However, the invention also includes that the lower portion of the suspension is somewhat depleted of graphite particles relative to the remainder of the suspension. Preferably located in one lower area of the suspension so many graphite particles and / or additional graphite and / or metal particles that the total thermal conductivity of the underside of the container area is at most 50% lower than the total thermal conductivity of the suspension in the remaining area of the suspension, in particular by at most 30% in particular, it does not substantially deviate from the total thermal conductivity in the remaining area.

A climate device may preferably contain a suspension according to the invention, in particular with a container according to the invention. Such an air conditioning device can be used as an element of an air conditioner that stores and releases heat and / or cold.

Preferably, the container may be in contact with at least one thermally conductive sheet. The term sheet metal is used here for each sheet-like heat-conducting element, that is, it can also consist of or contain graphite.

The at least one metal sheet can be formed from a closed-surface metal sheet, a perforated metal sheet, a grid, a net or from fixing rods.

Advantageously, the container is held between two sheets, which are arranged, for example, parallel to each other or v-shaped to each other. In particular, a container with a flexible outer shell is advantageous in this case, because such a bag-like container nestles very well on the sheets, so that a heat transfer from the suspension can be done directly on the sheet without disturbing air cushion.

The object is further achieved by a method according to claim 25. According to the invention it is provided to produce a suspension of PCM and graphite particles in that the graphite particles containing expanded graphite and / or natural graphite are mixed with the PCM in liquid form, without PCM penetrates the expanded graphite and natural graphite.

This can advantageously be achieved by placing the graphite particles in a container as a loose filling and filling the container with the PCM. It is thereby achieved that without generating pressure, mechanical, tensions or strong flows, mixing takes place avoiding the penetration of PCM into the expanded graphite and natural graphite.

It may be advantageous first to mix the proportions of expanded graphite and natural graphite, in particular dry, and then to proceed as described above. In the presence of additional graphite, it may be advantageous to mix the proportions of expanded graphite and / or natural graphite with the additional graphite and then perform mixing with the PCM.

It may also be advantageous to first mix expanded graphite and / or natural graphite with PCM and then add the additional graphite. Since the additional graphite is used to weight the possibly floating graphite particles, it may be advantageous for the additional graphite to be as high as possible. Even if the additional graphite should slide down through the expanded graphite and / or natural graphite due to greater density and / or larger particle size, the "starting position" of the additional graphite above the expanded graphite and / or natural graphite achieves that the Graphite particles is obstructed.

The suspension of the invention can be solidified by lowering the temperature below the melting point of the PCM. In this state, it can be crushed and transported the resulting grains and poured for the particular purpose, for example, in a container.

In the following, the invention will be described in more detail for explanation with reference to a concrete embodiment and with reference to some figures. This embodiment is not restrictive.

Show in detail

1a FIG. 4 is a top view of a measurement setup for determining the heat storage and heat conduction properties of suspensions. FIG.

1b : a sectional side view of the measurement setup of 2a .

2 : Temperature profiles of suspensions according to the invention during a heating process compared to conventional PCM materials,

3 : Temperature profiles of suspensions according to the invention during a cooling process compared to conventional PCM materials,

4a : a fin for introduction into the suspension according to the invention,

4b a structure of nested fins,

5a FIG. 2: a perspective view of a container according to the invention with a partially cutaway main surface, FIG.

5b : the container of 5a in a longitudinal section and

6 : A perspective view of an air conditioning device with a container according to the invention.

According to the embodiment, 477 g of graphite powder (specification: particle size distribution d ₀ : 1000-1400 microns, bulk density after DIN 51705 : 160-210 g / l) and 1691 g paraffin with a melting point of 21 ° C (specification: heat capacity 134 kJ / kg, density fixed 0.88 kg / l, density liquid 0.77 kg / l, thermal conductivity 0.2 W / (m.K) is mixed with a hand mixer without further stirring, the resulting suspension 1 in flat bags 2 as containers 2 with a flexible, adaptable outer shell 3 filled, the dimensions of 2.5 cm in this example, 30 cm wide, 30 cm in length have. The bag 2 owns as outer shell 3 a metal-coated plastic film or a plastic-coated metal foil.

Will the bag 2 on one of its two main surfaces 4 . 5 lying fills, there is the possibility of some Finns from above 6 use of graphite foil. The second main area 5 of the bag 2 can then from the top, for example, by conventional film welding with the rest of the bag 2 connected and the bag 2 thus be closed. The bag 2 can be transported with the PCM in the liquid state, but can also be cooled to temperatures below the melting point of paraffin to the suspension 1 into the solid state of aggregation.

The bag 2 becomes a measuring apparatus 7 used as they are in 1a and 1b you can see. A first wall 8th high thermal conductivity and a second wall 9 low thermal conductivity (here Plexiglas) limit together with lateral elements 9a low thermal conductivity (here Plexiglas) a measuring space 10 into the bag 2 can be introduced. Above the melting point of the PCM, in this case at 21 ° C, the bag nestles 2 due to the flexible, adaptable outer shell 3 on both walls 8th . 9 and the lateral elements 9a at. A heat source 11 , which could also be called a source of cold, is with the first wall 8th thermally connected. As a heat / cold source here is a conventional thermostat 11 used that over hoses 12 . 13 with the first wall 8th connected is. On the bag 2 are first temperature sensors 14 arranged the temperature of the bag 2 on his the first wall 8th facing side and second temperature sensor 15 that the temperature of the bag 2 on his the second wall 9 measure facing side. An insulating wall 16 made of plastic foam, for example, adjacent to the second wall 9 additionally contributes to the fact that the measurement is not falsified by heat losses. The two walls 8th . 9 with the measuring room 10 are in an insulated container 17 introduced with thermally highly insulating walls, as they are commonly used for example in insulation technology.

For a first measurement of the temperature control is the with the suspension of the invention 1 filled bags 2 heated from 10 ° C to 40 ° C and measured the evolution of temperature over time.

Trace A in 2 shows the course of the temperature of the thermostat itself curve B shows the course of the temperature at the sensors 14 between the first wall 8th and the bag 2 , Curve C shows the course of the temperature at the probes 15 between the second wall 9 and the bag 2 , where the bag 2 initially filled for comparison with pure paraffin as PCM without graphite particles. It can be seen that both curves B, C lag far behind the thermostat curve A in time. This demonstrates the inertia of conventional PCM tempering systems. In particular, the temperature range falls between 20 and 35 ° C, in which is stored by the phase transformation during melting latent heat in the PCM, the so-called latent phase. Due to the poor thermal conductivity of pure PCM, this storage takes almost two hours. It is noticeable that curve C lags even behind curve B behind. This shows even more the low thermal conductivity of the pure PCM.

Trace D shows the course of the temperature at the probes 14 between the first wall 8th and the bag 2 , Trace E shows the course of the temperature at the probes 15 between the second wall 9 and the bag 2 , where the bag 2 now with the suspension according to the invention 1 whose preparation is described above, is filled. Both curves have a significantly shorter time interval from the thermostatic curve A. In particular, the phase of storing latent heat is much shorter due to the very good thermal conductivity of the suspension 1 Heat gets very fast over the entire PCM of the bag 2 distributed and stored therein in the form of latent heat. The small time interval between curve D and E also shows this. The temperature of the suspension then further increases according to the temperature set by the thermostat.

3 : shows a cooling process of the same two bags 2 as for the heating process, in 2 is reproduced. The curves are marked accordingly with A to E. Again, the very low inertia of the suspension 1 to recognize according to the invention in comparison to pure PCM. The solidification of the pure PCM takes much longer than with the suspension.

The 2 and 3 make it clear overall how fast an inventive bag 2 can be thermally charged and discharged.

After the measurement, the bag became 2 sliced and poured at temperatures above the melting point, the suspension in a sieve of mesh size 0.1 mm.

Due to the lack of PCM in the graphite particles, almost the same starting weight amounts of PCM and graphite particles were obtained as were originally used to prepare the suspension 1 weighed in wounds.

In a second embodiment, in the suspension as in 5a and 5b shown in the bag 2 Finns 6 used from graphite foil. Because of the high viscosity of the suspension 1 These retain their position without mechanical attachment.

The bag 2 is used in air conditioning units. Here are in an in 6 schematically illustrated climatic device 18 walls 19 in front, the first and second walls 8th . 9 the experimental setup 7 However, both of which consist of good heat conducting materials, in this case perforated plates made of conventional steel. The of the suspension 1 stored heat or cold is applied to the perforated sheets 19 directed and discharged from there by means of fans (not shown) to a room air to be conditioned.

When using the bag 2 with a suspension according to the invention for air conditioning devices 18 makes this noticeable by very fast storage and provision of heat or cold. This demonstrates the practical utility of the invention.

In another embodiment, salt hydrate is used as the PCM instead of paraffin, with the major component of the salt hydrate being calcium chloride hexahydrate.

As in the salt hydrate (specification: heat capacity 134 kJ / kg, density solid 1.6 kg / l, density liquid 1.5 kg / l, thermal conductivity fixed 1.2 w / mK, thermal conductivity liquid 0.6 w / mK) with A high density of graphite particles in this case 1.6 g / cm ³ tend to float strongly, are used in this embodiment, the milled graphite films with particle sizes of d: 1000-1400 microns (bulk density after DIN 51705 : 160-210 g / l) and the graphite expander mixed with a density of 1.0 g / cm ³ with synthetic graphite, placed in a stirred tank and doused with liquid salt hydrate at 30 ° C, ie above the melting point of salt hydrate. The synthetic graphite has the following specification: bulk density 1.67-1.91 g / cm ³ , bulk density according to DIN 51705 : ≤ 1 g / cm ³ , grain size distribution in% after DIN 51938 : 5% ≙ 0-0.4 mm; 90% ≙ 0.4 0.8 mm; 5% ≙> 0.8 mm. The resulting suspension 1 becomes as described above in the first embodiment in flat bag 2 filled.

With this suspension 1 becomes a bag 2 filled and welded. It is placed horizontally on leads in a climatic ceiling through which a heat medium is conducted.

Due to the fact that the synthetic graphite contains the expanded graphite in the suspension 1 in a lower area of the bag 2 no insulating pure PCM area forms near the bottom of the bag 2 heat and cold are in the bag at high speed 2 saved and returned.

The suspension according to the invention 1 can be used advantageously wherever heat and / or cold should be stored and released again. Advantageously, it can be used in a container, such as a tank, for storing heat generated in a power plant, such as solar heat, domestic hot water, process heat, heat from combined heat and power plants, night refrigeration, ice storage, food, such as Cooling and / or warming food, as well as in the storage and transport of food, such as in warehouses or refrigerated counters or in the installation of refrigerated trucks or refrigerated containers.

Preferably, the suspension can be used for lost-wax core processes in mold making. The wax can be melted faster with the graphite particles and poured into the mold. After forming and curing the component around the wax core, the core can be melted out of the component more quickly.

Advantageously, the suspension according to the invention, in particular in a bag according to the invention with a flexible outer shell, in the medical field, such as a cooling bag for the treatment of wounds or for cooling of grafts applicable.

Another preferred use of a suspension according to the invention is in the vehicle air conditioning, in particular the air conditioning electrically powered vehicles, the cooling of electrochemical storage systems, such as stationary batteries and batteries, such as in electric vehicles. Not only in normal operation, the suspension is used advantageously, but also in case of damage of a battery (eg in case of damage due to penetration of metal parts or deformation by accident). Then the suspension according to the invention can absorb the released thermal energy and prevent a chain reaction of the battery or at least slow it down.

In addition, the suspension according to the invention can be used, for example, as a heat accumulator for engine preheating in vehicle technology in order to reduce pollutant emissions during a cold start.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10250249 A1 [0003]
• EP 1598406 [0004]
• US 3404061 [0013]
• EP 1371915 B1 [0049, 0049]

Cited non-patent literature

• DIN 51705 [0073]
• DIN 51705 [0087]
• DIN 51705 [0087]
• DIN 51938 [0087]

Claims (31)

Suspension (suspension) 1 containing phase change material (PCM) and graphite particles, characterized in that the graphite particles contain expanded graphite and / or natural graphite, wherein there is substantially no PCM within the expanded graphite and within the natural graphite. Suspension (suspension) 1 ) according to claim 1, characterized in that based on the total amount of expanded graphite and natural graphite, the amount of expanded graphite between 0 and 100 wt .-% and the amount of natural graphite is between 0 and 100%. Suspension (suspension) 1 ) according to claim 1 or 2, characterized in that the expanded graphite and the natural graphite have a mean pore size and a pore size distribution, which are formed such that the PCM at normal pressure substantially does not penetrate into the expanded graphite and the natural graphite. Suspension (suspension) 1 ) according to one or more of claims 1 to 3, characterized in that the expanded graphite graphite expandate and / or obtained by crushing compressed graphite expandate powder or chaff and / or obtained by crushing graphite expanded powder. Suspension (suspension) 1 ) according to one or more of claims 1 to 4, characterized in that the bulk density of the expanded graphite (without PCM) in the case of Graphitexpandat between 0.002 and 0.015 g / cm ³ , in the case of chaff, chips, strips or granules between 0 , 01 g / cm ³ and 2.0 g / cm ³ , in the case of powder or regrind is between 0.10 g / cm ³ and 1.0 g / cm ³ . Suspension (suspension) 1 ) according to one or more of claims 1 to 5, characterized in that in the suspension at least one fin ( 6 ) is introduced, which has a high thermal conductivity in the plane, in particular of more 25 W / mK, in particular more than 100 W / mK. Suspension (suspension) 1 ) according to claim 6, characterized in that the at least one fin ( 6 ) comprises compressed expanded graphite. Suspension (suspension) 1 ) according to claim 6 or 7, characterized in that the at least one fin ( 6 ) Contains graphite foil, in particular made of graphite foil is constructed. Suspension (suspension) 1 ) according to one or more of claims 6 to 8, characterized in that a plurality of fins ( 6 ) is connected to each other, in particular by nesting, and forms a 2- and / or 3-dimensional structure. Suspension (suspension) 1 ) according to one or more of claims 6 to 9, characterized in that the at least one fin ( 6 ) through the suspension ( 1 ) is fixed in position. Suspension (suspension) 1 ) according to claim 10, characterized in that the at least one fin ( 6 ) horizontally, vertically or at any angle through the suspension ( 1 ) is fixed in position. Suspension (suspension) 1 ) according to one or more of the preceding claims, characterized in that are located in a lower portion of the suspension graphite particles and / or additional graphite, so that the total thermal conductivity of the lower region is at most 50%, in particular at most 30% lower than that Total thermal conductivity of the suspension ( 1 ) in the remaining area of the suspension ( 1 ). Suspension (suspension) 1 ) according to one or more of the preceding claims, characterized in that the suspension ( 1 ) contains an additional graphite, wherein the additional graphite contains synthetic graphite and / or additional natural graphite and / or carbon black and / or carbon fibers or a mixture of at least one of these components. Suspension (suspension) 1 ) according to one or more of the preceding claims, characterized in that the suspension ( 1 ) Contains metal particles, such as aluminum particles, copper, brass and / or steel particles. Suspension (suspension) 1 ) according to one or more of the preceding claims, characterized in that the PCM at least one PCM from the group comprising paraffins, sugar alcohols, gas hydrates, water, aqueous salt solutions, salt water eutectics, salt hydrates, mixtures of salt hydrates, salts and eutectic mixtures of Salts, alkali metal hydroxides and mixtures of salts and alkali metal hydroxides or a mixture of at least one PCM from this group contains. Suspension (suspension) 1 ) according to one or more of the preceding claims, characterized in that the ratio of additional graphite and expanded graphite and / or natural graphite is adjusted so that the expanded graphite and / or the natural graphite is prevented by the additional graphite from floating in the PCM, so that the total thermal conductivity of the lower region is at most 50%, in particular at most 30% lower than that Total thermal conductivity of the suspension ( 1 ) in the remaining area of the suspension ( 1 ), in particular not substantially deviates from this. Container ( 2 ) filled with a suspension ( 1 containing graphite and PCM, in particular according to one of claims 1 to 16, characterized in that it has a flexible, adaptable outer shell ( 3 ) having. Container ( 2 ) filled with a suspension ( 1 containing graphite and PCM, in particular according to one of claims 1 to 16, characterized in that it has a rigid outer shell ( 3 ) having. Container ( 2 ) according to claim 17 or 18, characterized in that in a bottom of the container ( 2 ) facing the suspension ( 1 ) Graphite particles and / or metal particles are located, so that the total thermal conductivity of the underside of the container ( 2 ) is at most 50% less than the total thermal conductivity of the suspension ( 1 ) in the remaining area of the suspension ( 1 ). Container ( 2 ) according to one or more of claims 17 to 19, characterized in that the outer shell ( 3 ) contains a metal layer. Climate device ( 18 ), characterized in that it contains a suspension ( 1 ) according to one or more of claims 1 to 16 and / or a container ( 3 ) according to one or more of claims 17 to 20. Climate device ( 18 ) according to claim 21, characterized in that the container ( 2 ) with at least one heat-conducting sheet ( 19 ) is in thermal contact. Climate device ( 18 ) according to claim 22, characterized in that the at least one sheet ( 19 ) is formed from a closed-surface sheet metal, a perforated plate, a grid, a net or by fixing rods. Climate device ( 18 ) according to claim 21 or 22, characterized in that the container ( 2 ) between two sheets ( 19 ), which are arranged parallel to each other or V-shaped to each other. Process for the preparation of a suspension ( 1 ) of PCM and graphite particles, characterized in that the graphite particles contain expanded graphite and / or natural graphite and the graphite particles are mixed with the PCM in liquid form without PCM penetrating into the expanded graphite and / or the natural graphite. A method according to claim 25, characterized in that the graphite particles are mixed with the PCM in that the graphite particles are added as a loose bed in a container and the container is filled with the PCM. Method for equipping a ceiling to be conditioned, in particular to a subsequent equipment, characterized in that at least one container ( 2 ) according to one or more of claims 17 to 20, in particular filled with a suspension ( 1 ) is introduced according to one or more of claims 1 to 16 in the ceiling. Use of a suspension ( 1 ) according to one or more of claims 1 to 16 in a container, such as a tank, for storing heat generated in a power plant, such as solar heat, hot water heat, process heat, heat from cogeneration plants, night cold, for ice storage, im Food sector, such as for cooling and / or warming food. Use of a suspension ( 1 ) according to one or more of claims 1 to 16 for lost-core methods. Use of a suspension ( 1 ) according to one or more of claims 1 to 16, in particular in a container ( 2 ) with a flexible outer shell ( 3 ) according to one or more of claims 17, 19 and 20, in the medical field, such as a cooling bag for the treatment of wounds or for the cooling of transplants. Use of a suspension ( 1 ) according to one or more of claims 1 to 16 for vehicle air conditioning, for cooling of electrochemical storage systems, such as batteries, or for the air conditioning of electrically powered vehicles.

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