DE102014225620A1 - Latent heat storage - Google Patents

Abstract

A latent heat store (1) for storing latent heat is proposed which comprises at least two graphite plates (2) and a guide device (8) with a longitudinal axis (100). According to the invention, each graphite plate (2) has a recess (12) through which the guide device (8) extends, wherein the graphite plates (2) are spaced apart by a gap (6) along the longitudinal axis (100) of the guide device (8) and the gap (6) comprises a phase change material (4). The invention further relates to a method for producing a latent heat accumulator (1).

Description

The invention relates to a latent heat accumulator comprising a phase change material and a method for producing a latent heat accumulator.

According to the prior art, latent heat accumulators, which comprise a phase change material, are used as thermal energy stores. This latent heat storage have the advantage that they heat energy, that is heat, hidden and low-loss with many Wiederholzyklen over a longer period of time. For the latent storage of the heat of a heat source, the latent heat storage, typically via a contact surface, is thermally coupled to the heat source.

Particularly in the case of a short-term absorption of heat, the latent heat accumulators known from the prior art have the disadvantage that the phase change material of the latent heat accumulator melts only at the contact surface. This is the case because typically the internal thermal conductivity of the latent heat storage is not sufficient. In particular, when storing electrical heat loss, for example in cyclically loaded electronic components, this is disadvantageous.

The incorporation of graphite powder or metal particles in the latent heat storage, the internal thermal conductivity of the latent heat storage can be improved. However, an improvement of the internal thermal conductivity above 20 W / (m · K) is typically not possible.

Furthermore, it is known to embed a porous metal or a graphite foam in the phase change material. As a result, the internal thermal conductivity of the latent heat accumulator can typically be increased to 100 W / (m · K). However, the production of such a latent heat storage, especially when using porous Graphitschäumen, technically complex.

The present invention has for its object to provide a latent heat storage, which has a high internal thermal conductivity and improved production.

The object is achieved by a latent heat storage with the features of independent claim 1 and by a method having the features of independent claim 12. In the dependent claims advantageous refinements and developments of the invention are given.

The latent heat storage device according to the invention for storing latent heat comprises at least two graphite plates and a guide device. According to the invention, each graphite plate has a recess through which the guide device extends, wherein the graphite plates are spaced apart by a gap along a longitudinal axis of the guide device and the gap comprises a phase change material (abbreviated PCM).

As a graphite plate in this case a plate is referred to, which comprises at least graphite. Furthermore, the term graphite plate comprises plates which have a coating of graphite and graphite foils.

According to the invention, the latent heat store comprises at least two, that is, a plurality of graphite plates. The graphite plates are stacked through the gap along the longitudinal axis of the guide device. The gap which lies between the two graphite plates, in particular between two adjacent graphite plates, is intended for filling with the phase change material. According to the invention, the internal thermal conductivity of the latent heat accumulator is improved by the stacked and spaced arranged graphite plates. Especially with a short-term and / or cyclic storage of heat is ensured by the introduced graphite plates, that arranged in the space phase change material almost completely melts.

The guiding device of the latent heat accumulator is preferably thermally coupled with a heat source whose thermal energy, that is to say its heat, is to be stored at least partially by means of the latent heat accumulator. The thermal energy of the heat source is transmitted to the phase change material by means of the guide device. Advantageously, a uniform transfer of heat to the phase change material arranged in the intermediate space is made possible by the stacked arrangement of the graphite plates. This results in a spatially approximately uniform melting of the phase change material. In addition, the thermal contact area between the heat source and the phase change material is increased by the latent heat storage device according to the invention.

A further advantage of the latent heat accumulator according to the invention is that it allows a technically efficient and cost-saving production process by the stacked arrangement of the graphite plates along the longitudinal axis of the guide device.

Particularly preferred are graphite plates which have an anisotropic thermal conductivity. Thus, it is advantageous if the thermal conductivity within the graphite plate plane, that is perpendicular to the longitudinal axis of the guide device, is increased. The use of graphite plates, which have an approximately isotropic thermal conductivity is conceivable. In general, for example, a thermal conductivity of at least 50 W / (m · K), in particular at least 1000 W / (m · K), is advantageous.

According to the invention, a method for producing a latent heat accumulator is proposed in which at least two graphite plates and a guide device having a longitudinal axis are provided, in which the graphite plates are cut onto the guide device by recesses of the graphite plates in such a way that the guide device extends along its longitudinal axis extends the recesses and in which a gap between the two graphite plates is at least partially filled with a phase change material.

According to the invention, the method enables a technically efficient and cost-saving production of a latent heat accumulator, in which the graphite plates are arranged stacked along the longitudinal axis of the guide device. The space between two adjacently arranged graphite plates is filled with the phase change material. This advantageously simplifies the production of the latent heat accumulator and in particular improves the thermal properties and the mechanical stability of the latent heat accumulator.

Furthermore, similar and equivalent advantages of the method according to the invention arise for the already mentioned latent heat store.

According to an advantageous embodiment of the invention, at least one of the recesses is formed as a punched recess.

As a punching recess, a recess is referred to, which has been produced or formed by means of a stamping process. Advantageously, the production of the latent heat accumulator can be further improved by punching the one recess. In particular, standardized graphite plates can thus be used to produce the latent heat accumulator. This advantageously enables a cost-saving and effective mass production manufacturing process of the latent heat storage. Particularly preferred here are previously standardized graphite plates used. Furthermore, the recesses and the graphite plates can be produced by means of a stamping process.

Preferably, in this case at least one of the recesses on a burr, wherein the graphite plates are spaced apart by means of the punching burr.

In other words, the recess is punched while maintaining its production-related burr. In this case, the burr is referred to as the burr, which results from the production of the blank when punching the recess. Advantageously, the punching burr, which protrudes from the graphite plate in the direction of the longitudinal axis of the guide device, is used as a spacer for the graphite plates. This advantageously further improves the manufacturing process of the latent heat accumulator.

Furthermore, a thermal coupling between the two graphite plates is effected by the punching burr, so that the heat introduced into the latent heat store is distributed in an improved manner within the latent heat store, in particular between the two graphite plates.

According to an advantageous embodiment of the invention, at least one of the recesses is formed as a bore, wherein the bore extends through the entire thickness of the respective graphite plate.

In this case, the recess which is formed as a bore can be formed by means of a stamping process or drilling process. As a bore, an opening of the graphite plate is designated, whose side surfaces are completely formed by the graphite plate and which extends through the entire thickness of said graphite plate. In contrast to a bore, the side surfaces of a recess may be only partially formed by the graphite plate.

The at least one graphite plate may be pierced by a drilling process, with the guide device extending through the bore. As a result, the at least one graphite plate can be placed on the guide device and arranged at a distance from the further graphite plates. Advantageously, this results in a cost-saving and effective production of the latent heat storage.

Preferably, the guide device is designed as a tube.

As a result, advantageously designed as a pipe guide device through the holes of the graphite plates, for example, positively inserted. Furthermore, to transfer the heat from the heat source to the latent heat storage a heat transfer medium may be provided, through the pipe, that is through the guide device, flows. As a result, a uniform and thermally efficient heat transfer from the heat source to the latent heat accumulator, in particular to the phase change material arranged within the latent heat accumulator, is advantageously made possible.

In a further advantageous embodiment of the invention, the guide device has a thread.

Advantageously, a nut can be arranged on the guide device by the thread, which mechanically engages or braces the graphite plates. This advantageously improves the mechanical stability of the latent heat accumulator. Furthermore, the nut screwed onto the thread can be provided as a spacer for the graphite plates.

According to a particularly preferred embodiment of the invention, the latent heat storage comprises at least one clamping plate, which is arranged in an end region of the guide device and provided for the mechanical clamping of the graphite plates.

As a result, the stacked graphite plates are advantageously further mechanically stabilized. In this case, the clamping plate may comprise a mechanically stable material, for example aluminum. Furthermore, the mechanically stable material should be chemically resistant to the phase change material.

Preferably, a clamping plate is arranged in each end region of the guide device. As a result, a mechanical tensioning of the graphite plates and the phase change material arranged between the graphite plates is advantageously made possible. The graphite plates and the phase change material are thereby further mechanically stabilized and held together. Another advantage is that can be increased by the mechanical strain of the fill factor of the latent heat storage.

Preferably, the clamping plate has a recess or a bore through which the guide device extends.

As a result, advantageously, the clamping plate can be attached to the guide device. In other words, results in a layered or stacked structure of the latent heat storage, in which preferably first a clamping plate, then subsequently at least two graphite plates and another clamping plate are attached to the guide device. In the space between the two plugged graphite plates turn the phase change material is arranged. Advantageously, this enables mechanical stabilization of the graphite plates and the phase change material.

In a further advantageous embodiment of the invention, the phase change material is embedded in a fluid-tight sheath.

As a result, leakage of liquefied phase change material is advantageously prevented.

Furthermore, a fluid-tight encapsulation of the phase change material is conceivable. This prevents leakage of the phase change material, for example from the intermediate space and / or from the graphite plates. Preferably, the encapsulation is effected by means of a metal housing, wherein the clamping plates form an axial end of the metal housing. Here, the metal housing may comprise aluminum and be thermally and / or chemically resistant to the phase change material. The encapsulation can take place cohesively by means of a welding process, which comprises plastic films, by means of potting in a potting material and / or by means of painting.

According to a particularly preferred embodiment of the invention, the graphite plates are at least partially porous.

As a result, a thermally particularly efficient latent heat accumulator with a particularly high internal thermal conductivity is advantageously made possible. In particular, for a short-term and / or cyclic storage of thermal energy of the latent heat storage is advantageous.

Most preferably, the porous or foamy graphite plates comprise the phase change material. Due to the porous structure of the graphite plates, the phase change material within the graphite plates, that is, in cavities formed by the porosity of the graphite plates can be arranged. The porosity of the graphite plates is preferably in the range of 10% to 90%, more preferably in the range of 10% to 75%.

Preferably, the phase change material is introduced by means of a vacuum infiltration process in the gap and / or in porous graphite plates.

In particular, when using porous graphite plates, the vacuum infiltration process is advantageous because the phase change material by the filling by means of the Vakuuminfiltrationsverfahrens penetrates into the cavities of the graphite plates, which cavities are present by the porosity of the graphite plates, and this almost completely fills. As a result, an advantageous and thermally optimized connection between the phase change material and the porous graphite plates is made possible.

Advantageously, the contact area between the graphite plates and the phase change material is further increased, whereby the uniform distribution of the heat is improved on the phase change material. Thus, advantageously, the internal thermal conductivity of the latent heat storage is increased and further improved.

Further advantages, features and details of the invention will become apparent from the embodiments described below and with reference to the drawings. Shown schematically:

1 a latent heat storage with a plurality of parallel stacked graphite plates;

2 a punched graphite plate of the latent heat storage 1 ;

3 two adjacently arranged graphite plates, each having a punched bore, wherein the punching burrs of the holes were left on the graphite plates;

4 a graphite plate having a plurality of bores and a plurality of threaded rods; and

5 a guide device which is formed as a tube and has a thread in each of its end regions.

Similar or equivalent elements may be provided with the same reference numerals in the figures.

1 shows a section of a latent heat storage 1 along a longitudinal axis 100 a guide device 8th , Here is the guide device 8th designed as a tube.

The latent heat storage 1 has two graphite plates 2 on. The graphite plates 2 are along the longitudinal axis 100 the guide device 8th arranged in parallel spaced. The guiding device 8th extends through a hole 12 (please refer 2 ) of the graphite plates 2 , The hole 12 is regarding the graphite plates 2 arranged approximately centrally.

Relative to the longitudinal axis 100 the guide device 8th is between each two adjacent graphite plates 2 a phase change material 4 arranged. In other words, the phase change material 4 in a gap 6 between each two adjacent graphite plates 2 brought in. As a result, a layered or stacked structure of the latent heat accumulator is advantageously realized, which is an efficient and cost-saving method of producing the latent heat accumulator 1 allows.

As axial termination of the latent heat storage 1 is in axial end areas 18 the guide device 8th one clamping plate each 10 intended. The relative term axial refers to the longitudinal axis 100 the guide device 8th , The clamping plates 10 clamp the graphite plates 2 as well as the phase change material 4 axially, whereby the mechanical stability of the latent heat accumulator 1 is ensured. Furthermore, a jacket of the phase change material 4 be provided, which is fluid-tight. As a result, advantageously, leakage of liquefied phase change material 4 prevented.

The guiding device 8th the latent heat storage 1 is designed as a tube, which is flowed through by a heat transfer medium. Here, the heat transfer medium is fluidly coupled to a heat source, not shown. In other words, the heat transfer medium flows through the latent heat storage 1 , As a result, advantageously, the heat or the thermal energy of the heat source to that within the latent heat storage 1 arranged phase change material 4 transfer. The heat of the heat source is thus to the heat transfer medium and by means of the guide device 8th to the latent heat storage 1 submitted and stored within this at least partially.

The graphite plates 2 can be porous. Are the graphite plates 2 porous or include this porous graphite, so is for the production of the latent heat storage 1 a vacuum infiltration process for filling the gap 6 and the porous graphite plates 2 with the phase change material 4 intended. This allows the graphite plates 2 at least partially with the phase change material 4 be filled. In other words, the phase change material 4 in the gap 6 and in the graphite plates 2 at least partially introduced.

In 2 is an example of a rectangular, in particular square, graphite plate 2 the latent heat storage 1 out 1 shown. Here is the graphite plate 2 along a section perpendicular to the longitudinal axis 100 the guide device 8th shown.

The graphite plate 2 has a hole arranged in its center 12 on. Here is a punching of the hole 12 while maintaining her burr 14 provided (see 3 ). It is further envisaged that the guiding device 8th out 1 through the hole 12 extends. This can advantageously the graphite plate 2 For example, in the production of the latent heat storage 1 , on the guide device 8th be plugged.

In 3 are two adjacently arranged arranged graphite plates 2 , each one a punched hole 12 have shown. The representation in 3 refers to a section of a section of the latent heat storage 1 along the longitudinal axis 100 the guide device 8th ,

The punching of the graphite plates 2 generated burrs 14 have been maintained. In other words, every hole has 12 a burr 14 on. The burrs 14 are here circular around the hole 12 arranged.

Advantageously, the punching burrs 14 as a spacer between adjacent graphite plates 2 be used. In other words, one of the two graphite plates lies 2 on the burr 14 the other graphite plate 2 on. As a result, advantageously, the gap 6 between the two graphite plates 2 educated. The gap 6 includes the phase change material 4 ,

The burrs 14 stand above the respective graphite plate 2 axially, that is in the direction of the longitudinal axis 100 the guide device 8th , forth. The burrs 14 thus form axial projections of the graphite plates 14 out. The supernatants of the graphite plates 2 are related to the longitudinal axis 100 Aligned so that all supernatants point in the same direction. In particular, each space comprises 6 exactly one burr 14 , The graphite plates 2 Consequently, based on their punching direction, equal within the latent heat storage 1 arranged.

In 4 is an example of a graphite plate 2 shown a plurality of holes 12 and a plurality of threaded rod 16 having.

The graphite plate 2 has at least five holes 12 on. Four of the holes 12 are each in a corner of the graphite plate 2 arranged. Another, fifth hole 12 is based on the graphite plate 2 arranged in the middle.

Through each hole 12 can become a guiding device 8th , in particular a pipe, extend. This advantageously the heat transfer from a heat source to the latent heat storage 1 as well as the internal thermal conductivity of the latent heat storage 1 improved. Furthermore, by the majority of the guide devices 8th the mechanical stability of the latent heat accumulator 1 elevated.

Through four openings of the graphite plate 2 each extends a threaded rod 16 , Every threaded rod 16 is between two of the holes 12 arranged. In particular, the threaded rods 16 around the central hole 12 the graphite plate 2 arranged symmetrically. The openings of the graphite plate 2 through which the threaded rods pass 16 extend, form the corners of a rectangle, in particular a square, which rectangle or square opposite the reckteckform the graphite plate 2 , in particular by an angle of 45 °, is rotated.

In 5 is a guide device 8th shown as a pipe 8th is formed and in each of its end regions 18 a thread 20 having. In other words, at each end of the pipe 8th an area 18 provided, which is intended for screwing a nut.

The graphite plates 2 can, as in 1 shown on the pipe 8th be plugged. Subsequently, be axial, from both ends of the tube 8th starting, two mechanically stable clamping plates 10 attached. On every thread 20 Subsequently, at least one nut, not shown, is screwed on, the clamping plates 10 and the graphite plates 2 braced against each other and / or pressed. As a result, advantageously, an efficient and cost-saving production of the latent heat storage 1 allows. In particular, in the manufacture of the latent heat storage 1 standardized components, in particular standardized graphite plates 2 , standardized clamping plates 10 and / or standardized guiding devices 8th , in particular standardized pipes 8th , be used.

Although the invention has been further illustrated and described in detail by the preferred embodiments, the invention is not limited by the disclosed examples, or other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (16)

Latent heat storage ( 1 ) for storing latent heat comprising at least two graphite plates ( 2 ) and a guiding device ( 8th ) with a longitudinal axis ( 100 ), characterized in that each graphite plate ( 2 ) a recess ( 12 ) through which the guiding device ( 8th ), wherein the graphite plates ( 2 ) through a gap ( 6 ) spaced along the Longitudinal axis ( 100 ) of the guiding device ( 8th ) are arranged and the space ( 6 ) a phase change material ( 4 ). Latent heat storage ( 1 ) according to claim 1, characterized in that at least one of the recesses ( 12 ) as a punching recess ( 12 ) is trained. Latent heat storage ( 1 ) according to claim 2, characterized in that at least one of the recesses ( 12 ) a punching burr ( 14 ), wherein the graphite plates ( 2 ) by means of the burr ( 14 ) are spaced from each other. Latent heat storage ( 1 ) according to one of the preceding claims, characterized in that at least one of the recess ( 12 ) as a bore ( 12 ) is formed, wherein the bore ( 12 ) through the entire thickness of the respective graphite plate ( 2 ). Latent heat storage ( 1 ) according to one of the preceding claims, characterized in that the guiding device ( 8th ) as a pipe ( 8th ) is trained. Latent heat storage ( 1 ) according to one of the preceding claims, characterized in that the guiding device ( 8th ) a thread ( 20 ) having. Latent heat storage ( 1 ) according to one of the preceding claims, with at least one clamping plate ( 10 ), which are in an end region ( 18 ) of the guiding device ( 8th ) and for the mechanical strain of the graphite plates ( 2 ) is provided. Latent heat storage ( 1 ) according to claim 7, characterized in that the clamping plate ( 10 ) has a recess or bore through which the guide device ( 8th ). Latent heat storage ( 1 ) according to one of the preceding claims, characterized in that the phase change material ( 4 ) is embedded in a fluid-tight sheath. Latent heat storage ( 1 ) according to one of the preceding claims, characterized in that the graphite plates ( 2 ) are at least partially porous. Latent heat storage ( 1 ) according to claim 10, characterized in that the at least partially porous graphite plates ( 2 ) a phase change material ( 4 ). Method for producing a latent heat accumulator ( 1 ), in which at least two graphite plates ( 2 ) and a guiding device ( 8th ), which has a longitudinal axis ( 100 ), in which the graphite plates ( 2 ) by means of recesses ( 12 ) of the graphite plates ( 2 ) in such a way on the guide device ( 8th ) are attached, that the guiding device ( 8th ) along its longitudinal axis ( 100 ) through the recesses ( 12 ) and in which a gap ( 6 ) between the two graphite plates ( 2 ) at least partially with a phase change material ( 4 ) is filled. Process according to claim 12, in which the phase change material ( 4 ) by means of a vacuum infiltration process into the space ( 6 ) and / or in porous graphite plates ( 2 ) is introduced. Method according to claim 12 or 13, wherein at least one of the recesses ( 12 ) while maintaining its production-related burr ( 14 ) is punched. Process according to one of Claims 12 to 14, in which the graphite plates ( 2 ) by means of at least one threaded rod ( 16 ) are braced against each other. Method according to one of Claims 12 to 15, in which a tube ( 8th ) as a guiding device ( 8th ) is used, wherein the pipe ( 8th ) at least in one of its end regions ( 18 ) a thread ( 20 ), and in which a nut for bracing the graphite plates ( 2 ) on the thread ( 20 ) is screwed.

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