Abstract:
A method for producing a latent heat accumulator may include filling a can body with a phase-change material in the liquid or solid aggregate state, and closing the can body filled with said solid or liquid phase-change material by flanging such that fluid cannot pass through.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a U.S. National Stage Application of International Application No. PCT/EP2015/058397 filed Apr. 17, 2015, which designates the United States of America, and claims priority to DE Application No. 10 2014 208 555.1 filed May 7, 2014, the contents of which are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a method for producing a latent heat storage device. 
       BACKGROUND 
       [0003]    According to the prior art, latent heat storage devices that comprise a phase-change material are used as thermal energy storage devices. In this context, latent heat storage devices have the advantage that they store thermal energy (heat) in a hidden and low-loss manner with multiple repeated cycles over a relatively long time. 
         [0004]    Production methods for latent heat storage devices can use jackets which accommodate the phase-change material of the latent heat storage device. Such a jacket is useful in particular in the liquid state of the phase-change material. Typically, coatings and/or polymers are used for the jacket. The prior art production methods for latent heat storage devices, in particular methods that coat and/or deposit a polymer onto the phase-change materials, are typically technically complex and cost-intensive. Consequently, they reduce the utility value of the thermal energy stored in the latent heat storage device. In particular for temperatures above 100° C. (373.15 K) known jackets, or known latent heat storage devices, cannot be used. 
       SUMMARY 
       [0005]    One embodiment provides a method for producing a latent heat storage device, wherein a phase-change material in the liquid or solid state is introduced into a can body, and wherein the can body filled with the solid or liquid phase-change material is closed in a fluid-tight manner by seam rolling. 
         [0006]    In one embodiment, the solid phase-change material and the can body are heated prior to filling, and wherein the heated can body is filled with the phase-change material that has been liquefied by heating. 
         [0007]    In one embodiment, the seam rolling is performed after solidification of the introduced liquefied phase-change material. 
         [0008]    In one embodiment, the can body is filled with a powdery phase-change material. 
         [0009]    In one embodiment, the can body is filled with a pelletized and/or molded phase-change material. 
         [0010]    In one embodiment, the can body is filled with a pelletized and/or molded phase-change material having a form fit with the can body. 
         [0011]    In one embodiment, the introduced phase-change material and/or the filled can body is/are heated prior to seam rolling, wherein said heating liquefies the introduced phase-change material. 
         [0012]    In one embodiment, the liquefied, introduced phase-change material and/or the filled can body are cooled prior to seam rolling, the liquefied, introduced phase-change material being re-solidified by said cooling. 
         [0013]    In one embodiment, the phase-change material comprises at least one organic and/or inorganic salt. 
         [0014]    In one embodiment, a can bottom and/or a can lid are joined to the can body by seam rolling. 
         [0015]    In one embodiment, a cylindrical can body has an aspect ratio of greater than one. 
         [0016]    Another embodiment provides a latent heat storage device, comprising a can body with a phase-change material arranged within the can body, wherein the can body is closed in a fluid-tight manner by seam rolling. 
         [0017]    In one embodiment, a cylindrical can body, wherein a can bottom and/or a can lid are secured to the cylindrical can body by seam rolling. 
         [0018]    In one embodiment, the cylindrical can body has rolled grooves. 
         [0019]    In one embodiment, the can body has a chemically inert coating on an inner side facing the phase-change material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    Example aspects and embodiment of the invention are described below with reference to the drawings, in which: 
           [0021]      FIG. 1  shows an example can-type latent heat storage device, according to one embodiment; and 
           [0022]      FIG. 2  shows an example seam-rolled closure of the latent heat storage device, according to one embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Embodiments of the present invention are provided to improve the production of a latent heat storage device. 
         [0024]    In the method according to the invention for producing a latent heat storage device, a can body is filled with a phase-change material in the liquid or solid state. In addition, in the method according to the invention, the can body filled with the solid or liquid phase-change material is closed in a fluid-tight manner by seam rolling. 
         [0025]    According to the invention, the method permits a technically efficient and cost-effective encapsulation of a phase-change material and consequently a technically efficient and cost-effective production of a latent heat storage device. 
         [0026]    In other words, the phase-change material is canned in the liquid or solid state, as is common for drinks or food cans. The closed can body therefore forms a can. Encapsulation of the phase-change material is effected according to the invention by seam rolling. Advantageously, encapsulation of the phase-change material by seam rolling, according to the invention, uses a cost-effective and technically proven method for the production of a latent heat storage device. According to the invention, the latent heat storage device is closed in a fluid-tight manner, that is to say liquid-tight and gas-tight. By canning the phase-change material, according to the invention, it is possible to use the latent heat storage device according to the invention even at temperatures above 100° C. (373.15 K). 
         [0027]    Tempered steel and/or aluminum sheets can for example be provided as materials for the can body. Preference is given to a metallic can body since it has good and adequate thermal and mechanical stability and strength, and good heat conductivity. 
         [0028]    The latent heat storage device according to the invention comprises at least one can body with a phase-change material arranged within the can body, the can body being closed in a fluid-tight manner by seam rolling. 
         [0029]    In other words, the phase-change material is encapsulated in a can or tin can. The advantages are similar and equivalent to those of the above-mentioned method according to the invention. 
         [0030]    According to one embodiment of the invention, the solid phase-change material and the can body are heated prior to filling and the heated can body is filled with the phase-change material that has been liquefied by heating. 
         [0031]    In other words, the phase-change material may advantageously be liquefied or melted prior to filling of the can body, and is used in the liquid state to fill the previously heated can body. Heating the can body advantageously ensures that the phase-change material does not immediately solidify or freeze when introduced into the can body. 
         [0032]    Filling of the can body with the liquefied phase-change material is intended to be performed using a funnel, wherein the phase-change material can be heated in the funnel. Once the phase-change material is almost completely liquefied, the phase-change material is introduced into the previously heated can body via an opening of the tunnel. In this context, the temperature of the can body and of the liquefied phase-change material should be approximately equal. Overall, this may permit particularly cost-effective and technically efficient filling of the can body. 
         [0033]    In one embodiment of the invention, the seam rolling is performed after solidification of the introduced liquefied phase-change material. 
         [0034]    This may ensure that the can body is close to entirely filled with the phase-change material. The specified process can be repeated until the solidified introduced phase-change material takes up close to all of the internal volume of the can body. This advantageously permits a particularly efficient latent heat storage device. 
         [0035]    According to one embodiment of the invention, the can body is filled with a powdery phase-change material. 
         [0036]    In other words, the can body is filled with a phase-change material in powder form. This may permit particularly simple filling of the can body. In this context, it is provided to re-heat the powdery phase-change material prior to closure of the can body by seam rolling. This avoid—as much as possible—inclusions of air within the closed can body. 
         [0037]    It may be advantageous to fill the can body with a pelletized and/or molded phase-change material having a form fit. 
         [0038]    In other words, the geometric shape of the phase-change material matches the geometric shape of the internal volume of the can body such that the pelletized and/or molded phase-change material fits in a form-fitting manner inside the can body. In this context, the phase-change material is for example in the form of a tablet, that is to say a compressed tablet. Filling of the can body is then carried out by arranging the tablet-like phase-change material in the can body. The tablet-like phase-change material therefore seals the interior of the can body in a form-fitting manner, so as to avoid interspaces and therefore air inclusions inside the closed can body (can). In other words, the tablet-like phase-change material matches an internal geometry of the interior of the can body in terms of its geometric shape. 
         [0039]    When filling the can body using a powdery phase-change material or using a pelletized and/or molded phase-change material, it may be advantageous to heat the introduced phase-change material and/or the filled can body prior to seam rolling, wherein said heating liquefies the introduced phase-change material. 
         [0040]    In other words, the powdery or pelletized and/or molded phase-change material is first inserted into the can body and is then liquefied by direct heating of the phase-change material and/or by indirect heating via the can body. It may be advantageously ensured that the available internal volume of the can body is close to entirely filled with the introduced phase-change material. Also, air inclusions are avoided as far as possible. 
         [0041]    In particular, when the liquefied powdery or granular phase-change material solidifies or freezes inside the can body, the volume of the phase-change material usually reduces, since interspaces or air inclusions, that form due to the powdery structure of the phase-change material, are reduced or almost entirely eliminated by liquefaction of the phase-change material. This frees up additional internal volume in the can body, which can for example be filled with additional phase-change material. 
         [0042]    According to one embodiment of the invention, the liquefied, introduced phase-change material and/or the filled can body are cooled prior to seam rolling, the liquefied, introduced phase-change material being re-solidified or frozen by said cooling. 
         [0043]    Expediently, this brings the latent heat storage device into a state that is appropriate for further treatment of the latent heat storage device. This can involve repeated heating and cooling. 
         [0044]    Of particular preference are phase-change materials that comprise at least one organic and/or inorganic salt. Advantageous inorganic salts are for example metal nitrates, metal nitrites, metal chlorides and/or metal hydroxides. Intended organic salts are in particular metal acetates, for example sodium or potassium acetates. These salts may be particularly advantageous as phase-change materials for temperatures above 100° C. 
         [0045]    Furthermore, it is provided to compress the phase-change material arranged in the can body prior to seam rolling. This may improve the heat capacity of the latent heat storage device. 
         [0046]    According to one embodiment of the invention, the can body is joined to a can bottom and/or to a can lid by seam rolling. 
         [0047]    In other words, the can body forms, in conjunction with the can bottom and/or the can lid, a can. This may achieve a particularly technically efficient and cost-effective method for producing a latent heat storage device. In this context, the can bottom and/or the can lid are joined to the can body in a fluid-tight manner by seam rolling, for example as in the case of a drinks can or food can. It is expedient to join the can bottom to the can body in a fluid-tight manner prior to filling of the can body. It is possible to provide other joining methods for the can lid or the can bottom. It is in particular possible to provide a can body that already comprises a can bottom. In that context, only the can lid is joined to the can body by seam rolling. 
         [0048]    In some embodiments the can body has an aspect ratio of greater than one. 
         [0049]    Here, the aspect ratio is defined as the ratio of the maximum extent of the can body to the minimum extent of the can body. 
         [0050]    Preference is given to a cylindrical can body whose maximum extent is its diameter (can body diameter) and whose minimum extent is its height (can body height). In this context, particular provision is made of an aspect ratio significantly greater than one, in particular greater than five. In other words, the can body or the can (closed can body) forms a flattened cylinder. The aspect ratio of greater than one improves the transfer of heat to the phase-change material arranged in the can body. This facilitates take-up and shedding of heat by the latent heat storage device. 
         [0051]    According to one embodiment of the invention, the cylindrical can body has rolled grooves. 
         [0052]    The rolled grooves may improve the mechanical stability of the cylindrical can body. In particular, the rolled grooves run in parallel and encircle the cylindrical can body. 
         [0053]    In one embodiment of the invention, the can body has a chemically inert coating on an inner side facing the phase-change material. 
         [0054]    In other words, the inside of the can body has an anti-corrosion coating such that salt-containing phase-change materials, in particular in the liquid state, do not lead to corrosion of the can body, in particular of a metal can body. An anti-corrosion (i.e. chemically inert) coating is also provided for the can lid and/or the can bottom. 
         [0055]      FIG. 1  shows a latent heat storage device  1  that comprises a can body  2 . In this context, the closed can body  2  forms a can  2 . The can body  2  is joined in a fluid-tight manner to a can lid  4  by means of a closure  42  formed by seam rolling. A can bottom (not shown) is also joined to the can body  2  by seam rolling. 
         [0056]    A phase-change material (not shown) is arranged inside the can body  2 . The can body  2  is for example made of sheet steel or sheet aluminium and has an aspect ratio of greater than one. Other sheets or materials for the can body  2  are provided, in particular materials that are chemically resistant to salt-containing phase-change materials, in particular in the liquid state of the phase-change material. 
         [0057]    Furthermore, rolled grooves  12  are arranged on the outside of the can body  2  in order to increase the mechanical stability of the cylindrical can body  2 . In this context, the rolled grooves  12  encircle the cylindrical can body  2 . The can lid  4  also has rolled grooves  12  which are circular and are arranged concentric with one another. 
         [0058]    The can body  2  has an aspect ratio of greater than one. This may improves the transfer of heat from the can body  2  to the phase-change material arranged inside the can body  2 . The aspect ratio is understood here as the ratio of the can body diameter  100  to the can body height  102 . Of particular advantage is an aspect ratio of greater than five, in particular of greater than ten. It is also possible to provide rod-shaped (i.e. long and thin) cylinder shapes for the can body. 
         [0059]      FIG. 2  shows a section view of a closure  42  between a can body  2  and a can lid  4 . Here, the closure  42  is formed by seam rolling. The can body  2  and the can lid  4  are folded or shaped and intertwined with one another so as to produce a fluid-tight connection  42  between the can body  2  and the can lid  4 . In other words, the closure  42  forms a double seam as may be found in drinks cans or food cans. To that end, the can body  2  and the can lid  4  each have, after folding or after seam rolling, a hook-shaped end, said two hook-shaped ends engaging in one another. It is in particular possible, in this context, for a form-fitting connection to be provided for the closure  42 . 
         [0060]    A phase-change material  10  is arranged on the inside  6  of the can body  2 . In other words, the can formed by the can body  2 , the can lid  4  and a can bottom is filled with the phase-change material  10 . On an outside  8 , the can body  2  can have rolled grooves for improving mechanical stability. The latent heat storage device according to the invention is in particular intended for temperatures above 100° C. 
         [0061]    Thus, what is achieved is a latent heat storage device that is cost-effective to produce and has both high mechanical stability and high thermal stability. 
         [0062]    Although the invention has been described and illustrated in detail by way of the preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived here from by a person skilled in the art without departing from the scope of protection of the invention.