Transport container for transporting temperature-sensitive goods

Abstract

The invention relates to a transport container (1) for transporting temperature-sensitive goods to be transported, said container comprising container walls (2, 3, 4, 5, 6, 11) which surround and close off all sides an inner space provided for receiving the goods to be transported, wherein each container wall (2, 3, 4, 5, 6, 11) has at least one latent-heat storage layer (9) which comprises a phase change material, and preferably the latent-heat storage layers (9) of adjacent container walls are connected to one another in a thermally conductive manner. According to the invention, a material which increases the thermal conductivity of the latent-heat storage layers (9) in at least one direction is introduced into the phase change material.

Description

[0001] The invention relates to a transport container according to claim 1 for transporting temperature-sensitive goods, comprising container walls which surround and enclose an interior space provided for receiving the goods, wherein each container wall has at least one latent heat storage layer comprising a phase change material, and preferably the latent heat storage layers of adjacent container walls are thermally connected to each other.

[0002] The publications WO 2021 / 024061 A1, F. Frusteri et al., "Thermal conductivity measurement of a PCM based storage system containing carbon fibers", Applied Thermal Engineering, Pergamon, Oxford, GB, Vol. 25, No. 11-12, 1 August 2005, pages 1623-1633 as well as WO 2008 / 006669 A1 and JPWO2016194745A1 form the technical background to the subject matter of the present invention.

[0003] When transporting temperature-sensitive goods, such as pharmaceuticals, over periods of several hours or days, specific temperature ranges must be maintained during storage and transport to ensure the usability and safety of the medication. For various pharmaceuticals, temperature ranges of 2 to 25°C, and in particular 2 to 8°C, are prescribed as storage and transport conditions.

[0004] The desired temperature range can be above or below the ambient temperature, requiring either cooling or heating of the transport container's interior. If ambient conditions change during transport, the necessary temperature control may involve both cooling and heating. To ensure that the desired temperature range is maintained consistently and verifiably during transport, transport containers with superior insulation are used. These containers are equipped with passive or active temperature control elements. Passive temperature control elements do not require an external energy supply during operation; instead, they utilize their thermal storage capacity, transferring or absorbing heat to or from the interior of the transport container depending on the temperature level.However, such passive temperature control elements are exhausted as soon as temperature equalization with the interior of the transport container is complete.

[0005] A special type of passive temperature control element is the latent heat storage system, which can store thermal energy in phase-change materials whose latent heat of fusion, solution, or absorption is significantly greater than the heat they can store based on their normal specific heat capacity. A disadvantage of latent heat storage systems is that they lose their effectiveness once the entire material has completed a phase change. However, the latent heat storage system can be recharged by performing the reverse phase change.

[0006] One problem with transport containers of the type mentioned above is that the energy input into the container during transport is heterogeneous. If the container is exposed to thermal radiation, the energy input is significantly greater in the area of ​​radiation exposure than in the areas where no radiation is acting on the container. Nevertheless, the temperature inside the container must be kept constant and homogeneous within a permissible range. With inhomogeneous energy input, the problem arises that the latent heat storage capacity is not used up homogeneously. Thus, after a certain time, local temperature changes occur inside the transport container. If these local temperature changes exceed or fall below a certain threshold, the transported goods are no longer protected.

[0007] Transport containers are therefore typically designed so that each side functions independently. This means that each side must be designed to withstand the maximum possible load. However, the energy potential of one area cannot be used for another. For example, if thermal radiation acts on the transport container from above, this energy is absorbed by the latent heat storage element in the upper area, where it undergoes a phase transition. Once the phase transition has occurred, the energy enters the interior of the container and leads to heating in the upper area. The remaining energy absorption potential of the latent heat storage element in the lower area cannot be used.This means that with conventional transport containers, where the temperature is controlled by latent heat storage elements, each side is designed independently for the maximum expected thermal energy input. However, this results in a significant increase in weight and / or volume. Both lead to a considerable loss of efficiency during transport. Pharmaceutical products are usually transported by air, where even a small increase in weight or volume leads to significant additional costs.

[0008] To solve the aforementioned problem, EP 3128266 A1 proposed the placement of an energy distribution layer made of a highly thermally conductive material on the side of the latent heat storage unit facing away from and / or towards the interior. This makes it possible to distribute the thermal energy acting on the transport container from the outside, for example, only on one side, particularly as thermal radiation, to the other sides of the container. If the energy distribution layer completely surrounds the interior of the transport container, the acting thermal energy is distributed over the entire circumference of the container shell. The energy thus distributed is transferred to the inner layers of the container wall and leads to a uniform consumption of the latent heat storage capacity across the entire area of ​​the latent heat storage layer.The volume of the planned latent heat storage system therefore does not need to be designed for the maximum energy input expected from each side, but rather for the sum of the energy input expected from all sides. Since it can be assumed that not every side of the transport container is individually exposed to the maximum expected energy input, the total volume of the latent heat storage system can be reduced.

[0009] However, the arrangement of energy distribution layers increases the weight of the transport container and also reduces the volume available inside for accommodating the transported goods.

[0010] The present invention therefore aims to overcome the aforementioned disadvantages and, in particular, to maximize the usable volume of the transport container for the transported goods without impairing its temperature retention capacity. This should reduce transport costs per unit weight of the transported goods.

[0011] To solve this problem, the invention of a transport container according to claim 1 essentially provides that a material increasing the thermal conductivity of the latent heat storage layers in at least one direction is incorporated into the phase change material. By increasing the thermal conductivity of the latent heat storage layers, the locally introduced heat is distributed more evenly throughout the entire latent heat storage system. This allows a larger proportion of the stored enthalpy to be utilized and increases the efficiency of the transport container. Since the heat distribution occurs within the latent heat storage layers themselves due to the material incorporated into the phase change material, rather than being achieved with the aid of separate energy distribution layers adjacent to the latent heat storage layer, the weight increase and space requirements caused by the energy distribution layers are avoided.According to the invention, the material increasing thermal conductivity exhibits a direction-dependent thermal conductivity and is incorporated into the phase-change material in such a way that the latent heat storage layer has a higher thermal conductivity in the plane of the respective latent heat storage layer than perpendicular to the plane of the layer. This leads to improved heat distribution in the circumferential direction and simultaneously to a thermal insulation effect in the radial direction, i.e., from the environment to the interior of the transport container and vice versa. The direction-dependent thermal conductivity can be achieved, for example, by using particles of the incorporated material, such as, in particular, particles of expanded graphite.The layers of expanded graphite are arranged essentially parallel to each other and parallel to the plane of the latent heat storage layer, as is possible, for example, with the expanded graphite plate described above. The thermal conductivity of the expanded graphite is high along its outer surface, but low as it passes through the material. This dual functionality leads, on the one hand, to the desired heat distribution within the layer plane and, on the other hand, to a reduction in heat input into the transported material perpendicular to the layer plane.

[0012] In this description, the terms "container wall" and "container walls" are synonymous with the terms "wall" and "walls," as also used herein. Furthermore, any door described herein is also considered a container wall, unless explicitly stated otherwise.

[0013] In a preferred embodiment, if the latent heat storage layers of adjacent container walls are thermally connected to one another, temperature equalization occurs not only within the respective latent heat storage layer, but also between adjacent latent heat storage layers. Since the latent heat storage layers are arranged in each container wall, temperature equalization occurs, in particular, over the entire circumference of the container.

[0014] The transport container is preferably designed as a cuboid container with six container walls arranged at right angles to each other, each containing a latent heat storage layer according to the invention. One of the container walls can be designed as a door, e.g., as a revolving door, in particular as a double-leaf revolving door. The container walls comprise a bottom wall, two side walls, a rear wall, a top wall, and a front wall for the door.

[0015] The latent heat storage layers preferably extend over the entire length of the respective wall, so that the latent heat storage layers of adjacent walls are abutting each other. This can be achieved by arranging a single plate-like latent heat storage element in each wall, which borders the latent heat storage element of the respective adjacent wall. Alternatively, multiple plate-like latent heat storage elements can be provided in each wall, which are thermally connected to each other to distribute the heat across the entire wall. In both cases, this results in heat distribution over the entire height of the interior of the container, which leads to the following advantage in larger containers: If the closed container is placed in a room that is below the phase transition temperature of the phase change material, the phase change material is recharged by inducing the phase transition.In contrast, this is not the case with a container that does not possess the heat distribution capability according to the invention, because the warm air inside the container rises. If such a closed container is placed in a room that is below the phase transition temperature of the phase change material, the phase change material in the lower part of the container initially charges up because the rising air inside prevents homogeneous charging. The phase change material in the upper part of the container only charges up after the phase change material in the lower part is fully charged, i.e., below the phase transition temperature. Therefore, short intermediate stops of the container during transport in warehouses with temperatures below the phase transition temperature cannot be used for recharging, i.e., for extending the operating time.

[0016] Preferably, the latent heat storage layers of adjacent container walls are thermally connected to one another, such that, for example, one of the container walls is connected to a container wall opposite it in terms of the interior. This results in a circumferential distribution of heat around the circumference of the container. The thermally conductive connection between adjacent container walls is preferably designed such that the thermal conductivity from one wall to the adjacent wall is at least 5 W / mK, preferably at least 50 W / mK, and preferably at least 100 W / mK.

[0017] In principle, the thermal conductivity of the latent heat storage layers can be increased by any foreign material introduced into the phase change material that has a higher thermal conductivity than the phase change material itself. However, an effective increase in thermal conductivity is achieved when the introduced material has a significantly higher thermal conductivity in at least one direction than the phase change material. Preferably, the introduced material has a thermal conductivity in at least one direction of > 190 W / mK, and in particular > 300–380 W / mK.

[0018] The most preferred material for this process is graphite or expanded graphite, which increases thermal conductivity. Expanded graphite is characterized by its low density and can theoretically exhibit a thermal conductivity of up to 600 W / mK. Expanded graphite (also called swellable graphite) is produced by intercalating foreign materials (intercalates) between the graphite lattice layers. Such expandable graphite intercalation compounds are typically prepared by dispersing graphite particles in a solution containing an oxidizing agent and the intercalated compound. Commonly used oxidizing agents include nitric acid, potassium chlorate, chromic acid, potassium permanganate, and the like. Concentrated sulfuric acid, for example, is used as the intercalated compound.When heated to a temperature above the so-called onset temperature, the expandable graphite intercalation compounds undergo a significant increase in volume with expansion factors of more than 200. This is caused by the fact that the intercalation compounds embedded in the layered structure of the graphite decompose rapidly upon heating to this temperature, forming gaseous substances. This causes the graphite layers to be pulled apart in an accordion-like manner, i.e., the graphite particles expand or swell perpendicular to the layer plane.

[0019] According to a preferred embodiment, the material increasing thermal conductivity is in the form of particles distributed within the phase change material.

[0020] Alternatively, the material increasing thermal conductivity can be in the form of at least one plate embedded in the phase-change material. A plate of expanded graphite can, for example, be produced by compacting the fully expanded graphite under directed pressure, whereby the graphite layer planes preferably align perpendicular to the direction of the pressure, with the individual aggregates interlocking with one another.

[0021] Due to the high thermal conductivity of the incorporated material, a relatively small amount is sufficient to significantly increase the thermal conductivity of the latent heat storage layer. Preferably, the material increasing the thermal conductivity comprises 3-10 vol% of the total volume of the phase change material.

[0022] According to a preferred embodiment, the thermal conductivity of the latent heat storage layer in the plane of the layer corresponds to at least 2 times, preferably at least 5 times, preferably at least 10 times, in particular at least 50 times, the thermal conductivity perpendicular to the plane of the layer.

[0023] In particular, the thermal conductivity of the latent heat storage layer in the plane of the layer can be at least 5 W / mK, preferably at least 50 W / mK, preferably at least 100 W / mK, in particular at least 500 W / mK, and the thermal conductivity of the latent heat storage layer perpendicular to the plane of the layer can be between 0.2 W / mK and 10 W / mK.

[0024] Alternatively, the expanded graphite particles can also be arranged in an unoriented manner within the phase change material, thus increasing the thermal conductivity of the latent heat storage layer uniformly in all directions. The same effect is achieved if conventional graphite powder is incorporated into the phase change material instead of expanded graphite.

[0025] To further improve heat distribution, each container wall can be provided with an energy distribution layer made of a material with a thermal conductivity λ > 80 W / mK, preferably λ > 150 W / mK, on ​​the side facing away from and / or towards the interior of the at least one latent heat storage layer. The energy distribution layers of adjacent container walls are thermally connected to each other, in particular in contact with each other. This allows the stored enthalpy in the latent heat storage layers to be utilized at the respective adjacent walls, further improving the overall efficiency of the transport container.

[0026] The energy distribution layers can consist at least partially, preferably entirely, of aluminum, copper, carbon nanotubes, or expanded graphite. In particular, the energy distribution layers are each formed by a plate made of one of the aforementioned materials.

[0027] The energy distribution layers or plates preferably surround the interior of the transport container completely and without gaps. The energy distribution layers or plates thus form, for example, a shell in which the transported goods are located. Depending on whether the energy distribution layers or plates are arranged on the side of the latent heat storage layer facing away from and / or towards the interior, an outer and / or an inner shell is formed. In the case of a cuboid transport container, each of the six container walls is preferably assigned an energy distribution layer or plate, so that the aforementioned shell is composed of six energy distribution layers or plates. The energy distribution layers or plates, especially their edge regions, preferably contact each other directly, so that heat equalization occurs around the entire interior, with heat being transferred via the shell of energy distribution layers or plates.-plates, for example, can be directed from one side of the interior to the opposite side.

[0028] According to a preferred embodiment, the circumferential energy distribution is improved by providing each container wall with an insulating layer of a thermally insulating material on the side of the at least one latent heat storage layer facing away from the interior. This insulating layer has a thermal conductivity perpendicular to the layer plane of < 0.04 W / mK, preferably < 0.01 W / mK. The insulating layer reduces the energy flow in the radial direction towards the interior of the transport container. The insulating layer preferably surrounds the interior of the transport container on all sides.

[0029] The insulation layer may preferably consist of vacuum panels, polyisocyanurate (PIR), expanded polystyrene (EPS), extruded polystyrene foam (XPS), or ISOPET. Furthermore, the insulation layer may have a honeycomb structure. An advantageous configuration is achieved when the insulation layer has a plurality of, in particular, honeycomb-shaped cavities, with a honeycomb structure element according to WO 2011 / 032299 A1 being particularly advantageous.

[0030] The latent heat storage layer is preferably designed as a planar chemical latent heat storage system, and conventional materials can be used for the phase change material. Preferred media for the phase change material are paraffins and salt mixtures. The phase transition of the phase change material preferably lies in the temperature range of 2–10°C, 2–25°C, -82–72°C, or -15–30°C.

[0031] The transport container according to the invention is preferably designed as an air freight container and therefore preferably has external dimensions of at least 0.4x0.4x0.4 m 3< , preferably 0.4x0.4x0.4 m 3< to 1.6x1.6x1.6 m 3< , preferably 1.0x1.0x1.0 m 3< to 1.6x1.6x1.6 m 3< .

[0032] The invention is explained in more detail below with reference to exemplary embodiments schematically illustrated in the drawing. In this drawing, Fig. 1 a schematic representation of the transport container according to the invention, Fig. 2 a detailed view of the corner joint between ceiling and floor with side walls and rear wall of the transport container, Fig. 3 a detailed view of the corner joint between ceiling and floor with the door of the transport container and Fig. 4 A detailed view of the corner joint between the side walls and the door of the transport container.

[0033] In Fig. 1 A cuboid transport container 1 according to claim 1 is shown, the walls of which are designated 2, 3, 4, 5 and 6. The sixth side of the transport container 1 is shown open to reveal the layered structure of the walls. The open side can be closed, for example, by means of a door that has the same layered structure as the walls 2, 3, 4, 5 and 6. The six walls of the transport container 1 all have the same layered structure. The layered structure comprises an insulating layer 7, an outer energy distribution layer 8, a latent heat storage layer 9 into which a highly thermally conductive material, such as expanded graphite, is introduced, and an inner energy distribution layer 10. Fig. 2 The corner connection between the ceiling 2 and the floor 4 with the side walls 3, 5 and the rear wall 6 of the transport container 1 according to claim 1 is represented. The outer heat distribution layers 8 and inner heat distribution layers 10 are connected to each other at the corner in such a way that optimal heat conduction takes place without heat entering the interior of the transport container. The latent heat storage elements 9 with highly thermally conductive material are located between the inner and the outer heat distribution layers.

[0034] Fig. 3 The door 11 forms the corner connection between the ceiling 2, the floor 4, and the door 11 of the transport container 1 according to claim 1. The door 11 consists of an insulating layer 7, an outer heat distribution layer 8, and a latent heat storage element 9 made of highly thermally conductive material. The outer heat distribution layer 8 of the door 11 is connected to the heat distribution layer 8 in the floor 4 and ceiling 2 in such a way that optimal heat conduction takes place without heat entering the interior of the transport container. For this purpose, the heat distribution layer 8 in the door 11 is extended outwards to such an extent that contact is established with the heat distribution layers 8 in the ceiling 2 and floor 4. The latent heat storage elements 9, made of highly thermally conductive material, are located within the outer heat distribution layer 8.

[0035] Fig. 4The corner connection between the side walls 3, 5 and the door 11 of the transport container 1 according to claim 1 is defined. The door 11 consists of an insulating layer 7, an outer heat distribution layer 8, and a latent heat storage element 9 made of highly thermally conductive material. The outer heat distribution layer 8 of the door 11 is connected to the heat distribution layer 8 in the base 4 and ceiling 2 in such a way that optimal heat conduction takes place without heat entering the interior of the transport container. Thermal contact is achieved at the sides by an aluminum door hinge. The latent heat storage element 9, made of highly thermally conductive material, is located within the outer heat distribution layer 8.

[0036] The insulating layer 7 is designed as a high-performance insulation and preferably has a thermal conductivity of 0.02 W / mK to 0.3 W / mK. It consists either of vacuum insulation panels (VIP), PIR, EPS, XPS, ISOPET or is designed as ultra-insulation.

Claims

1. Transport container (1) for transporting temperature-sensitive goods, comprising container walls (2, 3, 4, 5, 6, 11) which surround and close off on all sides an inner space provided for receiving the goods, wherein each container wall (2, 3, 4, 5, 6, 11) has at least one latent heat storage layer (9) which comprises a phase change material, and wherein preferably the latent heat storage layers (9) of adjacent container walls (2, 3, 4, 5, 6, 11) are connected to one another in a thermally conductive manner, characterized in that a material increasing the thermal conductivity of the latent heat storage layers (9) in at least one direction is introduced into the phase change material, wherein the material increasing the thermal conductivity has a direction-dependent thermal conductivity and is introduced into the phase change material in such a way that the latent heat storage layer (9) has a higher thermal conductivity in the layer plane of the respective latent heat storage layer (9) than perpendicular to the layer plane..

2. Transport container according to claim 1, characterized in that the material increasing the thermal conductivity is formed by graphite or expanded graphite.

3. Transport container according to claim 1 or 2, characterized in that the material increasing the thermal conductivity is present in the form of particles which are distributed within the phase change material.

4. Transport container according to claim 1 or 2, characterized in that the material increasing the thermal conductivity is present in the form of at least one plate which is embedded in the phase change material.

5. Transport container according to any one of claims 1 to 4, characterized in that the material increasing the thermal conductivity takes up 3-10% by volume of the total volume of the phase change material.

6. Transport container according to any one of claims 1 to 5, characterized in that the thermal conductivity of the latent heat storage layer (9) in the layer plane is at least 2 times, preferably at least 5 times, preferably at least 10 times, in particular at least 50 times the thermal conductivity perpendicular to the layer plane.

7. Transport container according to any one of claims 1 to 6, characterized in that the thermal conductivity of the latent heat storage layer (9) in the layer plane is at least 5 W / mK, preferably at least 50 W / mK, preferably at least 100 W / mK, in particular at least 500 W / mK, and the thermal conductivity of the latent heat storage layer (9) perpendicular to the layer plane is between 0.2 W / mK and 10 W / mK.

8. Transport container according to any one of claims 1 to 7, characterized in that each container wall (2, 3, 4, 5, 6, 11) comprises, on the side of the at least one latent heat storage layer (9) facing away from the inner space and / or on the side of the at least one latent heat storage layer (9) facing the inner space, an energy distribution layer (8,10) made of a material with a thermal conductivity λ > 80 W / mK, preferably λ > 150 W / mK, wherein the energy distribution layers (8, 10) of adjacent container walls are connected to one another in a thermally conductive manner, in particular are arranged in contact with one another.

9. Transport container according to claim 8, characterized in that the energy distribution layer (8, 10) consists at least partially, preferably completely, of aluminium, copper, carbon nanotubes or expanded graphite.

10. Transport container according to any one of claims 1 to 9, characterized in that each container wall (2, 3, 4, 5, 6, 11) has, on the side of the at least one latent heat storage layer (9) facing away from the inner space, an insulating layer (7) of a heat-insulating material with a thermal conductivity perpendicular to the layer plane of < 0.04 W / mK, preferably < 0.01 W / mK.

11. Transport container according to claim 10, characterized in that the insulating layer (7) consists of vacuum panels, polyisocyanurate (PIR), expanded polystyrene (EPS), extruded polystyrene foam (XPS) or ISOPET.

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