LATENT HEAT STORAGE MATERIAL FOR ULTRA-COLD APPLICATIONS AND CONTAINER FOR TEMPERATURE-CONTROLLED TRANSPORT AT ULTRA-COLD TEMPERATURES

Abstract

A latent heat storage material for ultra-cold applications, comprising at least one lithium salt, at least one solvent, and at least one nucleating agent, wherein the at least one nucleating agent is selected from one or a combination of sodium carbonate, lithium carbonate, potassium carbonate, barium fluoride, sodium nitrate, and/or lithium hydroxide.

Claims

1. Latent heat storage material for ultra-cold applications, comprising at least one lithium salt, at least one solvent, and at least one nucleating agent, wherein the at least one nucleating agent is selected from one or a combination of sodium carbonate, lithium carbonate, potassium carbonate, barium fluoride, sodium nitrate, and/or lithium hydroxide.

2. Latent heat storage material according to claim 1, wherein said at least one lithium salt comprises lithium bromide and/or lithium chloride.

3. Latent heat storage material according to claim 1, wherein the at least one solvent comprises water.

4. Latent heat storage material according to claim 1, comprising the at least one lithium salt in a range between 20 wt.-% to 45 wt.-%.

5. Latent heat storage material according to claim 1, wherein the proportion and/or composition of the at least one lithium salt and the proportion and/or composition of the at least one solvent is selected such that the melting temperature Ts of the latent heat storage material is in a range between -60° C. ≥ Ts ≥ -85° C., in particular in a range between -60° C. ≥ Ts ≥ -75°.

6. Latent heat storage material according to claim 5, wherein the proportion and/or the composition of the at least one nucleating agent is selected such that the following applies to the crystallization temperature T.sub.K of the latent heat storage material and the melting temperature Ts of the latent heat storage material: 0 K ≥ T.sub.K - Ts ≥ -15 K, in particular 0 K ≥ T.sub.K - T.sub.s ≥ -10 K.

7. Latent heat storage material according to claim 6, comprising the at least one nucleating agent in a range between 0.01 wt.-% to 30 wt.-%, in particular in a range between 0.5 wt.-% to 5 wt.-%.

8. Container for temperature-controlled transport at ultra-cold temperatures, comprising a container wall which completely encloses an interior space, and at least one latent heat storage element comprising a latent heat storage material according to claim 1, wherein the at least one latent heat storage element is disposed within the interior space and/or in the container wall.

9. Container according to claim 8, comprising at least one vacuum insulation element disposed in the container wall.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In the following, the invention is explained in greater detail by means of exemplary embodiments:

[0016] FIG. 1 shows the temporal progression of cooling and heating of an exemplary embodiment of a latent heat storage material not according to the invention;

[0017] FIG. 2 shows the temporal progression of cooling and heating of a first exemplary embodiment of a latent heat storage material according to the invention;

[0018] FIG. 3 shows the temporal progression of cooling and heating of a second exemplary embodiment of a latent heat storage material according to the invention; and

[0019] FIG. 4 shows a cross-section through a container for temperature-controlled transport at ultra-cold temperatures.

DETAILED DESCRIPTION

[0020] According to a preferred aspect, the at least one lithium salt comprises lithium bromide and/or lithium chloride.

[0021] According to a preferred aspect, the at least one solvent comprises water.

[0022] The use of lithium bromide and water enables to provide a latent heat storage material having a melting temperature T.sub.s in a range between -75° C. and -60° C.

[0023] According to an advantageous aspect, the latent heat storage material comprises the at least one lithium salt in a range between 20 wt.-% to 45 wt.-%.

[0024] These compositions have proven to be particularly advantageous for ultra-low temperature applications in a temperature range between -50° C. ≥ T ≥ -85° C.

[0025] According to a particularly advantageous aspect, the proportion and/or composition of the at least one lithium salt and the proportion and/or composition of the at least one solvent are selected such that the melting temperature T.sub.s of the latent heat storage material is in a range between -60° C. ≥ Ts ≥ -85° C., in particular in a range between -60° C. ≥ Ts ≥ -75° C.

[0026] Exemplary embodiments are described in connection with FIG. 2 and FIG. 3.

[0027] According to a preferred aspect, the proportion and/or composition of the nucleating agent is selected such that the following applies for the crystallization temperature T.sub.K of the latent heat storage material and the melting temperature T.sub.s of the latent heat storage material: 0 K ≥ T.sub.K - T.sub.S ≥ -15 K, in particular 0 K ≥ T.sub.K - T.sub.S ≥ -10 K.

[0028] Thus, no severe overcooling of the latent heat storage material occurs, so that the latent heat storage material can be used in an economically and ecologically advantageous manner.

[0029] According to a further advantageous aspect, the latent heat storage material comprises the at least one nucleating agent in a range between 0.01 wt.-% to 30 wt.-% and in particular in a range between 0.5 wt.-% to 5 wt.-%.

[0030] This concentration of nucleating agent ensures that when the latent heat storage material is cooled down, it does not overcool too much without a crystallization process starting. In this regard, sodium carbonate and/or lithium carbonate with a proportion in a range between 0.5 wt.-% and 1.0 wt.-% has proven to be particularly advantageous.

[0031] The invention further encompasses a container for temperature-controlled transport at ultra-cold temperatures, comprising a container wall completely enclosing an interior space, and at least one latent heat storage element, comprising a latent heat storage material as described above, wherein the at least one latent heat storage element is disposed within the interior space and/or in the container wall.

[0032] By the container comprising at least one latent heat storage element, comprising a latent heat storage material as described above, the container is suitable for ultra-low temperature applications, for example temperature controlled transport, in a temperature range between -50° C. ≥ T ≥ -85° C., in particular in a temperature range between -60° C. ≥ T ≥ -85° C. In particular, this allows the air in the interior space to be maintained in a temperature range between -50° C. ≥ T ≥ -85° C., especially in a temperature range between -60° C. ≥ T ≥ -85° C., throughout the period of transport.

[0033] Such a container is technically, economically and environmentally advantageous, especially compared to other containers using dry ice for ultra-low temperature applications.

[0034] According to an advantageous aspect, the container comprises at least one vacuum insulation element arranged in the container wall.

[0035] By arranging at least one vacuum insulation element in the container wall, the insulation capability of the container is greatly enhanced and the time period for transport at ultra-low temperatures can be extended.

[0036] First, the process of cooling and heating of an exemplary embodiment of a latent heat storage material not according to the invention is explained in more detail with reference to FIG. 1. Here, the exemplary embodiment of the latent heat storage material not according to the invention comprises lithium bromide at 45 wt.-% and water at 60 wt.-%. In addition, the latent heat storage material does not comprise a nucleating agent.

[0037] The temporal progression demonstrates that no crystallization plateau and no melting plateau are formed during the cooling and heating of this latent heat storage material. No crystallization is observed in this latent heat storage material until it cools down to a temperature of -85° C. for several hours. This is an indication of overcooling of the latent heat storage material to below -85° C. This demonstrates the unsuitability of this latent heat storage material not according to the invention, especially for latent heat storage application in an ultra-low temperature range between -50° C. ≥ T ≥ -85° C.

[0038] The same applies to a latent heat storage material, comprising an unsuitable nucleating agent and/or a nucleating agent in an unsuitable concentration.

[0039] FIG. 2 shows a temporal progression of cooling and heating of a first exemplary embodiment of a latent heat storage material according to the invention.

[0040] Here, the latent heat storage material comprises lithium bromide at 45 wt.-% and water at 60 wt.-%. In addition, the latent heat storage material comprises lithium carbonate as a nucleating agent at 0.5 wt.-%.

[0041] The temporal progression reveals that crystallization is formed at approx. -80° C. during cooling, and that a melting plateau is created at approx. -68° C. during heating. This latent heat storage material thus has crystallization (Tc) and melting (Ts) temperatures that are close to each other.

[0042] Accordingly, the specified latent heat storage material is suitable for latent storage of refrigeration/heat energy for applications in an ultra-low temperature range between -50° C. ≥ T ≥ -85° C., in particular between -60° C. ≥ T ≥ -85° C.

[0043] FIG. 3 shows a temporal progression of cooling and heating of a second exemplary embodiment of a latent heat storage material according to the invention.

[0044] Here, the latent heat storage material comprises lithium bromide at 40 wt.-% and water at 60 wt.-%. In addition, the latent heat storage material comprises sodium carbonate as a nucleating agent at 1.0 wt.-%.

[0045] The temporal progression shows that crystallization forms at approx. -76° C. during cooling, and that a melting plateau forms at approx. -68° C. during heating. This latent heat storage material thus has crystallization and melting temperatures that are close to each other.

[0046] Accordingly, the specified latent heat storage material is suitable for latent storage of refrigeration/heat energy in an ultra-low temperature range between -50° C. ≥ T ≥ -85° C., in particular between -60° C. ≥ T ≥ -85° C.

[0047] FIG. 4 shows a cross-section through a container 0 for temperature-controlled transport at ultra-low temperatures.

[0048] This container comprises a container wall 1 with side walls and a lid. The container wall 1 completely encloses the interior space 2. A vacuum insulation element 4 is arranged inside each of the container walls 1 (side walls and lid). This provides optimum insulation of the container, extending the time period for transport at ultra-low temperatures compared to containers without vacuum insulation elements 4.

[0049] A latent heat storage element 3 is each arranged inside the interior space 2 and in the lid part of the container wall 1. The latent heat storage elements 3 thereby comprise a latent heat storage material as described above, being suitable for latent storage of refrigeration/heat energy in an ultra-low temperature range between -50° C. ≥ T ≥ -85° C.

[0050] Thus, the container 0 is also suitable for ultra-low temperature applications, for example temperature-controlled transport, in a temperature range between -50° C. ≥ T ≥ -85° C., since the air in the interior space 2 is maintained in a temperature range between -50° C. ≥ T ≥ -85° C. throughout the period of transport.

[0051] Such a container 0 is technically, economically and ecologically advantageous, especially compared to other containers using dry ice for ultra-low temperature applications, since the latent heat storage materials in the form of latent heat storage elements 3 are easily transportable and reusable.