DE102014217394A1 - Latent heat storage, process for its production and use of containers produced by pressure forming or train forming for the encapsulation of phase change material - Google Patents

Abstract

The present invention relates to a latent heat accumulator made of a container made of a metal or a metal composite produced by pressure forming or train pressure forming, in which a phase change material (PCM) is encapsulated. Likewise, the present invention relates to a method for producing such latent heat storage and the use of a container made of a metal or a metal composite produced by pressure forming or Zugdruckumformen with at least one fluid-tight sealable opening for encapsulation of a phase change material.

Description

The present invention relates to a latent heat accumulator made of a container made of a metal or a metal composite produced by pressure forming or train pressure forming, in which a phase change material (PCM) is encapsulated. Likewise, the present invention relates to a method for producing such latent heat storage and the use of a container made of a metal or a metal composite produced by pressure forming or Zugdruckumformen with at least one fluid-tight sealable opening for encapsulation of a phase change material.

Latent storage materials, also referred to as PCM (Phase Change Materials) or phase change materials, store large amounts of heat compared to sensitive thermal storage materials through a phase change, for example from solid to liquid, with a small temperature change. Thus, PCM are suitable as a heat storage with high storage density and can be used due to the melting at a constant temperature for passive temperature stabilization. Since PCMs have a liquid phase depending on the application condition, it is generally necessary to provide a suitable container for encapsulation. Special requirements are placed on the encapsulation materials with regard to the physicochemical properties of different PCMs. For example, encapsulating materials are highly stressed over a wide temperature range and / or as a result of PCM corrosive properties. Furthermore, PCM can also have combustible properties, as it is the case for example with paraffins as PCM, so that in addition to the chemical / mechanical strength and a sufficient fluid tightness must be ensured that prevents the escape of PCM. In addition to the properties, such as tightness and chemical / mechanical stability, the encapsulation material should also have a sufficiently high thermal conductivity in order to achieve the highest possible heat transfer performance to the environment. Depending on the field of application, plastics, metals or composites of these materials are therefore used as the encapsulating material.

For the production of latent heat storage devices, a number of special processes and devices have already been developed. That's how it is DE 10 2007 010 104 A1 a method for encapsulation of PCM is known in which two polyolefin half-shells are joined together by laser welding technology. In particular, spherical PCM-containing capsules can be formed by this method. The necessity of a laser welding machine, however, represents a high cost factor.

In DE 10 2009 032 918 A1 A method of making a PCM capsule from a sheet material is described. In the method, a film tube is used, which is closed by filling with PCM at a first end before filling and after filling at one end in each case by pressure welding.

Another method of encapsulating PCM is out DE 10 2010 025 297 A1 known, in which a PCM capsule is made with a resilient plastic material. Due to the elasticity of the material, an expansion of the PCM is to be compensated for changes in the state of matter. In the process, a crystallized spherical PCM placed in a mold is half-wrapped by a half-shell of a capsule. By means of an injection molding process, the second plastic capsule half shell is formed and the PCM completely enveloped. However, the need for a special crystallized (solid) PCM molding makes the process expensive and therefore expensive.

A major disadvantage of known solutions for PCM encapsulation is that specially developed capsule systems are used, which are expensive and are produced in only small quantities. As a result, these PCM systems are expensive, which prevents widespread use. In addition, composite materials made of plastics (thermoplastics), metals and PCM are used, from which a low thermal conductivity and thus a low loading and unloading performance results. For phase change temperatures of PCM, which are in the range above the melting temperatures customarily usable thermoplastics, mainly metal materials are suitable as encapsulating material, which allow a corresponding temperature stability and due to their high thermal conductivity and high loading and unloading.

In DE 20 2005 015 393 U1 is a cuboid metallic PCM encapsulation described whose walls have structurings with which a mechanical stabilization is to be achieved. In this case, the encapsulation body is produced in such a way that two sheets lying one above the other are crimped or folded over at the edges. However, the full-circumference folding requires an increased manufacturing effort, which is therefore associated with increased manufacturing costs.

Compared to the prior art, the object of the invention is therefore to propose an encapsulation for PCM, the one safe handling of PCM is possible as well as simple and inexpensive to manufacture.

The object of the invention is achieved with a latent heat storage according to the features of claim 1 and a method for the production of latent heat storage according to claim 8. Claim 15 specifies a use according to the invention. Further developments and embodiments of the invention are set forth in the dependent claims.

The latent heat accumulator according to the invention is based on at least one phase change material (PCM), which is encapsulated in a container made of a metal or metal composite produced by pressure forming or Zugdruckumformen having at least one fluid-tight closed opening. In this case, the container has a wall thickness in the range of 90 to 300 microns.

The core of the present invention is the metallic container produced by pressure forming or draw-forming which, as a result of its production process, has a small wall thickness of 90 to 300 μm and thus low weight. Compared to plastics, which have significantly lower thermal conductivities, improved heat transfer capacities between the PCM and the environment can be achieved by the metallic material of the container. In this case, a heat transfer is also favored by the small wall thickness of the container, so that a reaction of the encapsulated PCM can be carried out as a result of a change in temperature with a small time constant.

The mechanical stability of the container can be achieved by a cylindrical shape. Thus, a can shape of the container, in particular with a diameter in the range of 40 mm to 70 mm and a longitudinal extent of 110 mm to 180 mm, is preferred. In the case of the cylindrical shaping, the at least one opening, which may be formed in the cover surfaces of the cylindrical container, can be screwed in a fluid-tight manner to a cover. In this case, a lid used for closing can have a self-separating thread. In another variant, it is also possible to provide covers which are crimped or welded to the at least one opening of the container.

As an alternative to the cylindrical shape, a further preferred embodiment provides that the container is realized in the form of a tube. The tube-shaped container preferably has a diameter in the range from 20 mm to 40 mm and a length in the range from 150 mm to 220 mm at its cylindrical head end. A fluid-tight closure of the at least one opening can be realized by a folding of the material of the container.

In the event that the container is formed from a cylindrical sleeve open on both sides, can be provided to close the openings on one side a fold and opposite to the closure with a threaded cover a thread. One or both openings can each be crimped fluid-tight with a lid. It is also possible that both openings are each sealed fluid-tight by a fold or weld.

In the stated variants for the fluid-tight closure of the opening of the container, it is advantageous that the fluid-tight seal is realized in each case in a simple manner by cold forming, force and / or positive locking, without requiring a structure-changing material bond is required.

The container preferably has a volume up to 500 ml, particularly preferably up to 350 ml.

The at least one encapsulated PCM may have a phase change temperature in the range of -50 ° C to 400 ° C, preferably in a range of 6 ° C to 350 ° C. Thus, for the present invention as PCM, at least one paraffin, a fatty acid, a salt hydrate, an alcohol, a salt or a mixture thereof may preferably be used.

For the use of the PCMs having a phase change temperature above 300 ° C, the container should be formed of a metal or metal composite material which is preferably selected from the group consisting of aluminum, steel sheet, tin coated steel sheet, stainless steel or composites thereof. Preferably, the metal or metal composite material has a temperature stability up to a temperature of 200 ° C, preferably 400 ° C and particularly preferably 600 ° C.

Further, at least the inner surface of the container may at least partially have a coating with anti-corrosion and / or anti-adhesion properties, so that the container is protected against corrosive wear that may be caused by the PCM. In the event that the latent heat storage is flowed around in a heat transfer fluid, it is also advantageous if the outer surface of the container has a coating with anti-corrosion and / or non-stick properties. Such a coating may be formed of epoxy resin, polytetrafluoroethylene (PTFE) or a ceramic material.

In the event that a lid is provided for fluid-tight closure of the opening / s of the container, this should also be formed primarily of the container material and have a material thickness less than or equal to 300 microns. At the same time, at least the cover side facing the interior of the container should also be provided with said coating.

According to the phase change characteristics of the PCM used, it may be provided that the container sealed in a fluid-tight manner with the PCM encapsulated therein has a space filled with a gas which serves to compensate volume expansions in the case of changes in state (solid / liquid, liquid / solid) of the PCM.

In the method according to the invention for the production of latent heat accumulators, the procedure is such that first of all a container having at least one opening and a wall thickness in the range of 90 μm to 300 μm is formed from a plate-shaped or strip-shaped metal or metal composite material by means of pressure forming or tensile pressure forming. The forming of the plate-shaped or strip-shaped metal or metal composite material can be achieved by deep drawing or extrusion - methods which are well known from the prior art - can be achieved. Preferably, the forming of the plate-shaped or strip-shaped metal or metal composite material can be achieved by ironing, wherein cylindrical containers are formed whose top surface relative to the lateral surface have a greater wall thickness. Forming by ironing is also state of the art and is used in particular in the production of beverage cans. The container thus produced is then filled through the opening (s) with at least one PCM. Finally, the opening (s) of the container are / are closed in a fluid-tight manner.

For forming the container, a plate or tape-shaped metal or metal composite material may be used, which is preferably selected from the group consisting of: aluminum, steel, tin-coated steel sheet (tinplate), stainless steel. It is preferred that a plate-shaped or band-shaped metal or metal composite material is used, at least on the inner surface of the container forming side a coating with anti-corrosion and / or non-stick properties, in particular epoxy resin, polytetrafluoroethylene (PTFE), a ceramic Material or combinations thereof, so that the formed inside of the container from corrosive wear can be protected by the PCM used. Alternatively, the coating may also be carried out after the manufacturing process of the container as an intermediate step before the PCM is filled in. The intermediate step for coating the container inner wall may necessitate further process steps, such as a drying step.

In the method according to the invention, it is particularly favorable that recourse can be made to already established methods (deep-drawing, ironing by drawing or extruding) for forming the encapsulation container, without the need for a constructive development effort for special devices.

The fluid-tight closing of the at least one opening of the container can be achieved by screwing with a lid, by crimping with a lid, by welding and / or by a folding of the material of the container. In particular, the closing of the opening by a folding of the material of the container can be realized easily and inexpensively, since no further parts (cover) necessary to complete the encapsulation. It is possible to carry out the essential process steps - molding the container, filling the container with PCM and closing the opening (s) of the container - in one go. In this way, large quantities of encapsulated PCM can be produced at high speed.

In one embodiment variant, it can be provided that threaded covers are used for the screwed closure of the openings. As a result, both a positive connection and a positive connection between the lid and container can be achieved. Used lids should preferably be formed from the container material and have a wall thickness which is in the range of 90 microns to 300 microns.

In the method according to the invention, it is also advantageous that in the proposed closure variants, a fluid-tight closure of the openings of the container by cold forming (folding) or screwing can be achieved without the use of a sealing material is necessary.

In order to give the PCM enough space for expansion after the fluid-tight closure of the opening (s) of the container during a phase change, the container is filled with only 80% to 95% of its available volume with the PCM, so that in the closed container with a Gas-filled open space is formed.

For simplified filling of the container with the PCM, it may be advantageous if a PCM is used, which is free-flowing or liquid. This can be a simplified application and Dosage, for example, be achieved by an applicator.

Alternatively, when filling the container with PCM and when closing the container, an ambient temperature and / or a temperature of the container can be maintained at which the PCM has a flowable state of aggregation in order to achieve optimum filling and dosing.

Care should also be taken that when the container is closed, a temperature below the recrystallization temperature of the container material used is maintained. With the method according to the invention PCM can be encapsulated having a phase change temperature in a temperature range of -50 ° C to 400 ° C, preferably in a temperature range of 6 ° C to 300 ° C. For encapsulation PCM can preferably be used: paraffin, alcohols, polymers, salt hydrates, salts.

The invention also provides the use of a container made of a metal or a metal composite produced by pressure forming or tensile pressure forming with at least one fluid-tight sealable opening for encapsulating a phase change material.

In this case, it is preferred that the metal or metal composite material is selected from the group consisting of aluminum, steel sheet, tin-coated steel sheet, stainless steel or bonded thereof, wherein the metal or metal composite material preferably up to a temperature of 200 ° C, preferably 400 ° C. and particularly preferably 600 ° C is temperature stable.

A further preferred embodiment provides that the inner and / or surface of the container at least partially has a coating with anti-corrosion and / or anti-adhesion properties, in particular of epoxy resin, polytetrafluoroethylene (PTFE), a ceramic material or combinations thereof.

The at least one opening of the container is preferably fluid-tight screwed with a lid or verschördelbar and / or fluid-tight manner by a folding of the material of the container.

Hereinafter, the latent heat storage according to the invention is explained in detail with reference to preferred embodiments.

Show it:

1a and 1b : an embodiment of a latent heat storage in tube form,

2a to 2d : various views of an embodiment of a can-shaped container for encapsulating PCM

3 : An embodiment of a bottle-shaped container with threaded opening

The 1a and 1b show in two different views ( 1b in partial view) a latent heat accumulator produced by pressure forming or train pressure forming, which is formed in a tube shape and has a filling with a PCM. The container 1 is made of anti-corrosion coated aluminum and has a wall thickness of 90 microns. Furthermore, the container is fluid-tightly sealed at two openings, wherein the closure on the cylindrical side with a threaded cover 3 made of aluminum and on the opposite side by a fold 2 the container material is realized.

The 2a to 2d show in various views / partial views of an embodiment of a can-shaped container for encapsulation of PCM. With the reference number 4 in each case flanged edges are marked on which the metallic container with a as in 2c partially illustrated cover 5 Can be closed fluid-tight by crimping. In the present case, it is a container made of aluminum with a wall thickness of 100 microns.

The in 2 illustrated container is formed in a bottle shape, wherein an opening has a thread for a screw cap.

In the method according to the invention for producing a latent heat accumulator, the procedure is such that a container having at least one opening and a wall thickness in the range from 90 μm to 300 μm is formed from a plate-shaped or strip-shaped metal or metal composite material by means of pressure forming or draw pressure forming. For the manufacturing process, for example, a tinplate or aluminum strip is wetted with an extender (lubricant) and cut out or punched out suitable washers, from which then the body (container) is pulled. First, a flat cup is formed, which is pushed in the ironing machine over a plunger through several, increasingly narrow Abziehringinge until the desired wall thickness is reached. The cup deforms to an increasingly longer and thinner walled container shape. At the end of the ironing process, the bottom is shaped by a punch. Subsequently, material supernatant is removed. In the further course of the process, a washing step may be provided in order to remove the extender.

Furthermore, prior to filling the container with PCM further intermediate steps may be provided to provide the container inside and / or outside with non-stick and / or anti-corrosion coatings.

Following this, the container is filled through the at least one opening with at least one PCM. In this case, a flowable PCM is used, wherein the ambient temperature during the filling and the temperature of the container formed kept constant in order to ensure the flowability of the PCM.

Finally, the opening is closed fluid-tight by a folding or welding of the container material.

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 102007010104 A1 [0003]
• DE 102009032918 A1 [0004]
• DE 102010025297 A1 [0005]
• DE 202005015393 U1 [0007]

Claims (20)

Latent heat accumulator containing at least one phase change material (PCM), which is encapsulated in a produced by pressure forming or Zugdruckumformen container made of a metal or a metal composite with at least one fluid-tight sealable opening, wherein the container has a wall thickness in the range of 90 to 300 microns. Latent heat store according to claim 1, characterized in that the container has a can shape or a tube shape. Latent heat store according to claims 1 or 2, characterized in that the container has a volume less than 500 ml, preferably less than 350 ml. Latent heat store according to one of claims 1 to 3, characterized in that the metal or metal composite material is selected from the group consisting of aluminum, steel sheet, tin-coated steel sheet, stainless steel or bonded thereof. Latent heat store according to one of claims 1 to 4, characterized in that the metal or metal composite material is temperature-stable up to a temperature of 200 ° C, preferably 400 ° C and particularly preferably 600 ° C. Latent heat store according to one of claims 1 to 5, characterized in that the inner and / or surface of the container at least partially a coating with anti-corrosion and / or anti-adhesion properties, in particular of epoxy resin, polytetrafluoroethylene (PTFE), a ceramic material or combinations thereof , Latent heat store according to one of claims 1 to 6, characterized in that the at least one opening of the container with a lid fluid-tight screwed or verschördelbar, welded and / or fluid-tightly closed by a folding of the material of the container. Latent heat store according to one of claims 1 to 7, characterized in that the at least one phase change material has a phase change temperature in a temperature range from -50 ° C to 400 ° C and in particular is selected from the group consisting of paraffins, fatty acids, salt hydrates, alcohols, salt or mixtures thereof. Process for producing a latent heat store, in which A container having at least one opening and a wall thickness in the range of 90 μm to 300 μm is formed from a plate-shaped or strip-shaped metal or metal composite material by means of pressure forming or draw-forming; - The container is filled through the at least one opening with at least one phase change material (PCM); and - The at least one opening is then closed fluid-tight. A method according to claim 9, characterized in that the container is formed by deep drawing, preferably by draw-drawing or by an extrusion molding process. Method according to one of claims 9 or 10, characterized in that the at least one opening of the container is screwed to a lid, crimped, welded and / or fluid-tightly sealed by a folding of the material of the container. Method according to one of claims 9 to 11, characterized in that the at least one phase change material has a phase change temperature in a temperature range from -50 ° C to 400 ° C and in particular is selected from the group consisting of paraffins, fatty acids, salt hydrates, alcohols, salt or mixtures thereof. Method according to one of claims 9 to 12, characterized in that a plate-shaped or band-shaped metal or metal composite material is used, which is selected from the group consisting of aluminum, steel sheet, tin-coated steel sheet, stainless steel or bonded thereof. Method according to one of claims 9 to 13, characterized in that a plate-shaped or band-shaped metal or metal composite material is used, at least on the inner surface of the container forming side of a coating with anti-corrosion and / or non-stick properties, in particular epoxy resin, Polytetrafluoroethylene (PTFE), a ceramic material or combinations thereof. Method according to one of claims 9 to 14, characterized in that at least one paraffin, a fatty acid, a salt hydrate, an alcohol, a salt or a mixture thereof is used as the phase change material. Use of a container made of a metal or a metal composite produced by pressure forming or by draw-forming at least one fluid-tight sealable opening for encapsulating a phase change material. Use according to claim 16, characterized in that the metal or metal composite material is selected from the group consisting of aluminum, steel sheet, tin-coated steel sheet, stainless steel or composites thereof, wherein the metal or metal composite material preferably up to a temperature of 200 ° C, preferably 400 ° C and particularly preferably 600 ° C is temperature stable. Use according to one of claims 16 or 17, characterized in that the inner and / or surface of the container at least partially a coating with anti-corrosion and / or anti-adhesion properties, in particular of epoxy resin, polytetrafluoroethylene (PTFE), a ceramic material or combinations thereof , Use according to one of claims 16 to 18, characterized in that the at least one opening of the container with a lid fluid-tight screwed or verschördelbar, welded and / or fluid-tightly closed by a fold of the material of the container. Use according to one of claims 16 to 19, characterized in that the at least one phase change material has a phase change temperature in a temperature range from -50 ° C to 400 ° C and is in particular selected from the group consisting of paraffins, fatty acids, salt hydrates, alcohols, salt or mixtures thereof.

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