Transport container

Abstract

The invention relates to a transport container (1) for transporting temperature-sensitive goods to be transported, comprising an interior for receiving the goods to be transported, a multi-layer casing enclosing the interior and comprising thermal insulation (8), and a cooling device for cooling the interior with a distribution system for a cooling medium, wherein the cooling device has two cooling systems, namely a first cooling system and a second cooling system, wherein each cooling system has a vapour-compression refrigeration system such that the interior can optionally be cooled either by the first or the second cooling system, and wherein a controller is provided for controlling the cooling systems and is designed to operate both cooling systems simultaneously in response to a maximum cooling demand.

Description

[0001] Transport container

[0002] The invention relates to a transport container having an interior space for receiving the transported goods, a multi-layered shell enclosing the interior space, which includes thermal insulation and preferably at least one latent heat storage layer, and a cooling system for cooling the interior space with a distribution system for a cooling medium, which is preferably thermally coupled to the latent heat storage layer.

[0003] Such transport containers are used for transporting temperature-sensitive goods, such as pharmaceuticals, blood products, temperature-sensitive chemicals or biological samples, where a specified temperature must be precisely maintained over a longer period of time.

[0004] When transporting temperature-sensitive goods, especially pharmaceuticals, specific temperature ranges, for example from 2°C to 8°C, must be strictly maintained over periods of several hours or days to ensure the usability and safety of the goods. This poses a particular challenge when the ambient temperature fluctuates significantly during transport or when the transport lasts for several days.

[0005] Various transport containers are known from the prior art to solve this problem. These containers typically have thermal insulation and are equipped with active and / or passive cooling elements. Latent heat storage materials containing a phase change material (PCM) are frequently used as passive cooling elements. These materials can absorb or release large amounts of heat through their phase change, thus contributing to the temperature control of the interior.

[0006] Active cooling elements for transport containers include compression refrigeration machines, in which a refrigerant circulates in a closed loop and extracts heat from the area to be cooled through evaporation. Another option is thermoelectric cooling elements, so-called Peltier elements, which, when an electrical voltage is applied, cause heat transfer from a cold to a warm side. These systems have the advantage of having no moving parts, but their cooling capacity is limited and they have a comparatively low efficiency. Absorption refrigeration machines are also known, which use thermal energy to drive the refrigeration cycle.

[0007] From EP 3128268 Al, a transport container is known which has a multi-layered shell with thermal insulation and a latent heat storage layer. The latent heat storage layer contains a phase change material (PCM) that serves to regulate the temperature of the interior. Cooling or heating coils are integrated into the latent heat storage layer, through which a cooling or heating medium flows. The medium is cooled or heated by means of an active unit. The thermal insulation is designed as vacuum insulation to achieve the best possible insulation.

[0008] One problem with the described state of the art lies in the limited reliability and adaptability of the cooling system. The system uses a single active cooling unit, so a failure of this component would jeopardize the entire temperature control, which can have serious consequences for temperature-sensitive goods. Furthermore, the cooling unit is typically sized to handle even the highest possible cooling demands, such as those encountered at extreme ambient temperatures. However, in typical operating scenarios where only moderate cooling is required, this leads to inefficient operation, as the unit frequently switches between on and off phases to prevent overcooling. This intermittent operation increases energy consumption.

[0009] Against this background, the present invention aims to provide an improved transport container that ensures increased operational reliability and flexibility in temperature control.

[0010] In particular, the invention is intended to minimize the risk of system failure and enable efficient adaptation to different cooling requirements.

[0011] To solve this problem, the invention essentially provides, in a transport container of the type mentioned at the outset, that the cooling device has two cooling systems, namely a first cooling system and a second cooling system, wherein each cooling system has a compression refrigeration machine and is preferably thermally coupled to the latent heat storage layer, so that the interior can be cooled selectively by either the first or the second cooling system, and that a control system for controlling the cooling systems is provided and is configured to operate both cooling systems simultaneously when maximum cooling demand is met.

[0012] The inventive design with two separate cooling systems, each comprising its own compression refrigeration unit and preferably thermally coupled to the latent heat storage layer, offers several advantages. First, the redundancy of the cooling systems ensures increased operational reliability. Should one of the cooling systems fail or be impaired in its performance, the other cooling system can take over the cooling function, thereby maintaining the temperature of the transported goods within the specified range even under adverse conditions. This is particularly crucial when transporting temperature-sensitive pharmaceuticals, biological samples, or other critical goods, as even short-term temperature deviations can render the transported goods unusable.

[0013] A further advantage of the design according to the invention lies in the possibility of operating the two cooling systems in different modes. At moderate ambient temperatures, which prevail during most transport operations (typically around 20°C), only one cooling system is usually required for cooling in the range of 2-8°C. This can then be operated continuously without having to switch to intermittent operation with frequent on / off cycles. In contrast, a single, appropriately sized cooling system would inevitably have to cycle on and off under such conditions to prevent the interior from becoming too cold. The design according to the invention with two cooling systems thus enables more energy-efficient operation, since the frequent on / off cycles, which lead to energy losses with each switching operation and reduce the overall efficiency of the system, are avoided.

[0014] If the transport container is exposed to extreme environmental conditions, such as very high ambient temperatures, the control system can activate both cooling systems simultaneously to achieve maximum cooling capacity. This operating mode makes it possible to maintain the required internal temperature even under demanding environmental conditions. The individual cooling systems are dimensioned so that a single system is sufficient for the most statistically frequent environmental conditions, while extreme conditions can be handled by operating both systems simultaneously. This design represents an optimal compromise between energy efficiency during normal operation and performance under extreme conditions.

[0015] The advantages of the inventive design with two cooling systems will be explained using a specific example. A typical transport scenario is considered, where the ambient temperature is 20°C and a temperature of 5°C is to be maintained inside the vehicle. In this scenario, the required cooling capacity is, for example, 20 W. In the inventive design with two cooling systems, this cooling capacity can be met by a single cooling system operating continuously. Due to the moderate cooling capacity, the system can operate with optimal parameters: The evaporation temperature can be kept close to the interior temperature at 4°C, since a temperature difference of only 1 K is sufficient for heat transfer. The waste heat of approximately 24 W generated during cooling can be dissipated with a temperature difference of only 5 K, resulting in a condensation temperature of 25°C.Under these favorable conditions, the cooling system achieves a coefficient of performance (COP) of 5.4, which means that only 4 W of electrical power is required to generate the 20 W of cooling power.

[0016] In comparison, a single cooling system tasked with the same cooling load would need to be designed for a significantly higher cooling capacity, for example, three times the capacity of 60 W, which would then only be required for a third of the time. However, this higher capacity necessitates less favorable operating conditions: the evaporation temperature must be lowered to 2 °C, corresponding to a 2 K greater temperature difference. Simultaneously, the condensation temperature must be 15 K above the ambient temperature due to the increased amount of heat to be dissipated. These larger temperature differences result in a considerably lower coefficient of performance (COP) of only about 2.7, meaning that 22 W of electrical power is required for the 60 W cooling capacity. Considering the shorter operating time, this equates to an average energy consumption of 7.3 W.The inventive design with two cooling systems, one of which operates in energy-efficient continuous operation, therefore requires only about half the electrical power (4 W compared to 7.3 W) under these typical operating conditions compared to a single, larger cooling system.

[0017] An advantageous embodiment of the invention provides that each of the two cooling systems comprises a primary circuit with a refrigerant, configured as the circuit of the respective compression chiller, and a secondary circuit comprising the distribution system and filled with a liquid or gaseous cooling medium. The primary circuit is thermally coupled to the secondary circuit via a heat exchanger to cool the cooling medium. This dual-circuit configuration of each cooling system combines the advantages of an energy-efficient compression chiller with a liquid- or gas-based distribution system for optimal heat transfer.The primary circuit's compression chiller can operate at its optimal operating point, as it only needs to cool the secondary circuit's refrigerant via a heat exchanger. This allows the evaporation and condensation temperatures to be selected to achieve maximum coefficient of performance (COP). Simultaneously, using a liquid or gaseous refrigerant in the secondary circuit enables particularly efficient heat transfer between the refrigerant and the environment, such as the latent heat storage layer. This is because such media have a significantly better heat transfer coefficient than air, resulting in more uniform and efficient cooling of the environment, such as the latent heat storage layer.A further advantage of this separation into primary and secondary circuits is the possibility of minimizing the amount of refrigerant in the primary circuit, which is particularly relevant when using sustainable, yet flammable refrigerants such as propane (R290) or isobutane (R600a) with a low GWP (Global Warming Potential), since strict quantity restrictions apply to these refrigerants in air transport. Another preferred embodiment of the invention provides that the primary circuit of the first cooling system is thermally coupled to the secondary circuit of the first cooling system via a first heat exchanger, and the primary circuit of the second cooling system is thermally coupled to the secondary circuit of the second cooling system via a second heat exchanger.This separate design of the two cooling systems offers the significant advantage of complete redundancy, as each cooling system can operate independently and fully take over the cooling function in the event of a failure of the other system. The separate heat exchangers for each cooling system also prevent malfunctions in one system, such as leaks or contamination in the heat exchanger, from affecting the other system. Furthermore, this decoupling of the systems enables a differentiated control strategy, allowing the controller to individually adjust the optimal operating parameters for each cooling system, such as evaporation temperature, condensation temperature, and the flow rate of the cooling medium, to meet the current cooling demand in an energy-efficient manner.The complete thermal and functional separation of the two cooling systems not only significantly increases reliability, but also ensures that in the event of a defect in one of the systems, maintenance or replacement of components of that system can be carried out without affecting the operation of the other system, thus even enabling maintenance during ongoing transport under certain conditions.

[0018] Another advantageous embodiment of the invention provides that the primary circuit of the first cooling system is additionally thermally coupled to the secondary circuit of the second cooling system via the first heat exchanger, and the primary circuit of the second cooling system is additionally thermally coupled to the secondary circuit of the first cooling system via the second heat exchanger. This cross-thermal coupling of the primary and secondary circuits offers comprehensive redundancy that goes beyond mere system redundancy. A significant advantage of this design is that even in the event of a defect in one of the secondary circuits, for example, due to a leak or blockage in the distribution system, both compression chillers can continue to contribute to cooling via their respective intact secondary circuits.

[0019] Conversely, if one of the compression chillers fails, the remaining functioning chiller can cool both secondary circuits, thus providing full cooling capacity across the entire distribution system. This arrangement maximizes the availability of the cooling system under virtually all fault conditions and ensures that full area coverage of the distribution system is maintained even in the event of partial failures. Furthermore, the cross-coupling allows for high flexibility in the control strategy, as the controller can selectively determine which combination of primary and secondary circuits represents the most energy-efficient solution for the current cooling demand and ambient conditions, thereby minimizing both operating costs and environmental impact.

[0020] Another advantageous embodiment of the invention provides that the control system comprises a first control device for controlling the first cooling system and a second control device for controlling the second cooling system, each control device being connected to its own temperature sensor and optionally its own pressure sensor for detecting the pressure in the associated primary circuit, so that the respective compression refrigeration machine can be controlled depending on the measurement data from the temperature and, optionally, pressure sensor. This separate design of the control devices with their own sensors provides complete redundancy at the control level and prevents a failure of one control device or sensor from affecting both cooling systems.The autonomous operation of the control units, which, after the initial setting of the operating point, act independently of each other based on their respective sensor data, ensures a particularly high level of operational reliability, as the systems operate without external influence and are thus protected against manipulation or external interference. For example, if the first cooling system can no longer maintain the temperature within the defined range, the second control unit independently recognizes the need for support based on its sensor data and activates the second cooling system. The use of separate sensors for each control unit also guarantees precise monitoring of the operating parameters of each compression refrigeration unit, thereby enabling optimal and energy-efficient operation of each cooling system.Furthermore, the redundant design of the sensors ensures that reliable measurement data remains available for the control system even in the event of a sensor failure, thereby minimizing the risk of a complete system failure due to faulty sensor data. A particularly advantageous embodiment of the invention provides that the control device for the first cooling system and for the second cooling system each comprises at least one, and preferably several redundant, temperature sensors for detecting the supply and return temperatures of the respective secondary circuit. Preferably, each control device has three temperature sensors for detecting the supply temperature and three temperature sensors for detecting the return temperature.This triple configuration of temperature sensors enables reliable plausibility checks of the measurement data, as a faulty sensor can be clearly identified. With only two sensors, it would be impossible to determine which sensor was providing correct readings if discrepancies were observed. The triple configuration allows for the identification and elimination of faulty measurements through majority decision or statistical analysis, thus achieving exceptionally high operational reliability.

[0021] According to a further advantageous embodiment, each control device additionally has at least one, and in particular two, temperature sensors for measuring the suction gas temperature upstream of the compressor of the respective compression chiller and a temperature sensor for measuring the hot gas temperature downstream of the compressor. Furthermore, each control device can have at least one, and in particular two, pressure sensors for measuring the evaporation pressure. Such a sensor configuration enables precise monitoring of the thermodynamic state of the compression chiller and allows for the early detection of malfunctions or deviations from the optimal operating state. The dual design of the suction gas temperature sensors and the pressure sensors also ensures increased reliability, while a triple design can be omitted, as these parameters have been classified as less critical for reliable operation.

[0022] Preferably, the control device further comprises at least one, and in particular two, temperature sensors for measuring the internal temperature of the transport container, as well as at least one temperature sensor for measuring the ambient temperature. The preferably dual internal sensors provide redundant monitoring of the temperature inside the container holding the goods, ensuring reliable determination of the actual temperature of the goods. The ambient temperature sensor provides important information for optimizing the operation of the cooling systems and for adjusting the cooling capacity to the current ambient conditions. The combination of these diverse sensor data enables precise control of the cooling capacity, taking into account all relevant operating parameters, and thus ensures energy-efficient operation of the cooling systems.

[0023] A particularly advantageous embodiment of the invention provides that the control device of the first cooling system is equipped with at least one sensor for detecting the

[0024] The control device of the second cooling system is connected to at least one sensor for detecting the return temperature of the first cooling system, particularly the secondary circuit of the second cooling system. Conversely, the control device of the second cooling system is connected to at least one sensor for detecting the return temperature of the first cooling system, particularly the secondary circuit of the first cooling system. This comprehensive data acquisition enables the control devices to monitor the operating status of each other's cooling systems and to intervene as needed. For example, if the control device of the second cooling system determines, based on the return temperature of the first cooling system, that it is unable to provide the required cooling capacity, the second cooling system can be automatically activated to provide support.This ensures that optimal cooling performance is always available when needed, regardless of whether a system fails or whether there is a temporary increase in cooling demand.

[0025] Another advantageous embodiment of the invention provides that the control device of the first cooling system is connected to at least one sensor for detecting the compressor speed of the compression refrigeration unit of the second cooling system, and conversely, the control device of the second cooling system is connected to at least one sensor for detecting the compressor speed of the compression refrigeration unit of the first cooling system. This can be used as an alternative or additional measure to the aforementioned detection of the

[0026] The return temperature is measured. This comprehensive data acquisition allows the control devices to monitor the operating status of each cooling system and intervene as needed. For example, if the control device of the second cooling system determines, based on the compressor speed of the first cooling system, that it is unable to provide the required cooling capacity, the second cooling system can be automatically activated to provide support. The second cooling system can be activated particularly when the first cooling system exceeds a predefined compressor speed, such as 4000 rpm. It has been found that above a certain speed, which corresponds to a certain heat input, it is more efficient for both systems to operate in parallel.This also makes it possible to detect a malfunction of a cooling system, for example, if the compressor speed of this cooling system remains at 0 rpm, even though the return temperature of this cooling system increases at the same time.

[0027] In a preferred configuration, a higher-level secondary control system is provided, which designates one of the two cooling systems as the lead system and the other as the backup system before the start of a transport mission. The secondary control system activates and assigns these roles, but does not actively intervene in the control processes during further operation or transport; instead, it merely monitors the operation and records data. This architecture, with autonomous primary control systems and passive monitoring by the secondary control system, ensures a high level of operational reliability, as active control is completely transferred to the autonomous control devices of the two cooling systems. Based on the collected sensor and operational data, these devices can independently decide whether activation or adjustment of the cooling capacity is necessary.

[0028] Another advantageous implementation provides that the autonomous control devices of the two cooling systems additionally acquire and analyze operating data such as the compressor speed and / or the opening degree of the electronic expansion valve (EEV) of the primary circuit. This data acquisition enables a precise assessment of the operating status of the cooling systems and allows for optimal adaptation of the operating parameters to the current requirements.

[0029] Thermal coupling of the distribution system with the latent heat storage layer is understood to mean a connection between the distribution system and the latent heat storage layer that enables heat transfer with a thermal conductivity of at least 30 W / K, preferably at least 100 W / K, and particularly preferably at least 200 W / K. The thermal conductivity describes the heat transfer between the cooling medium in the distribution system and the phase change material of the latent heat storage layer, taking all intermediate layers into account. A high thermal conductivity is required to transfer the necessary cooling capacity with the smallest possible temperature difference between the cooling medium and the phase change material.

[0030] The thermal coupling of the distribution system with the latent heat storage layer ensures efficient use of the cooling capacity even if the phase change material is not completely distributed within the container. The good heat transfer between the cooling medium and the phase change material allows the stored cold to be optimally distributed within the container, something that was not possible with air-based systems.

[0031] A particularly efficient embodiment of the invention provides that the secondary circuits of the first cooling system and the secondary circuits of the second cooling system are embedded in the latent heat storage layer. This embedding of both secondary circuits directly into the latent heat storage layer ensures optimal heat transfer between the cooling media and the phase change material, since the distribution systems of the secondary circuits are completely surrounded by the phase change material, thus providing a maximum contact area for heat exchange. The parallel arrangement of the two secondary circuits within the latent heat storage layer ensures that each PCM element can be reached and cooled by both cooling systems, resulting in a particularly uniform temperature distribution within the phase change material.This is particularly advantageous when freezing the phase change material, as it avoids local temperature differences and allows for homogeneous crystallization. Furthermore, this embedding enables a compact design, since no additional heat transfer surfaces or elements are required between the secondary circuits and the latent heat storage layer. The redundant design of the secondary circuits embedded in the latent heat storage layer also ensures that even if one circuit fails, the remaining circuit maintains complete thermal coupling to the entire latent heat storage layer, thus ensuring that the cooling capacity continues to be distributed evenly across the entire volume of the phase change material.

[0032] An alternative design involves the secondary circuits of the first cooling system and the secondary circuits of the second cooling system being located on a single surface of the latent heat storage layer. In this variant, the elements of each secondary circuit are attached to the latent heat storage layer across its entire surface, for example, by gluing or mechanical fastening. This design has the advantage that the latent heat storage layer can be manufactured as a separate unit and the distribution system can be added subsequently. To ensure good heat transfer, this design preferably incorporates a thermally conductive contact layer between the distribution system and the latent heat storage layer.

[0033] Another advantageous embodiment provides that the secondary circuit of the first cooling system and the secondary circuit of the second cooling system are thermally coupled to the latent heat storage layer via heat-conducting plates. The heat-conducting plates are preferably made of a material with high thermal conductivity, such as aluminum or copper. The heat-conducting plates can be in thermal contact with the respective secondary circuit on one side and with the latent heat storage layer on the other. This design enables a particularly uniform heat distribution, as the heat-conducting plates introduce the cooling provided by the secondary circuit into the latent heat storage layer over a large area. Furthermore, the heat-conducting plates can be designed to provide additional mechanical stabilization of the structure.

[0034] In all the aforementioned designs, it is advantageous if the thermal coupling between the secondary circuit and the latent heat storage layer is designed to cover as large an area as possible in order to ensure efficient heat transfer.

[0035] According to a preferred embodiment, the secondary circuit of the first cooling system and the secondary circuit of the second cooling system each comprise cooling coils. These can be designed as continuous, curved tubes that guide the liquid cooling medium through the latent heat storage layer or along its surface. Cooling coils offer the advantage of a simple and robust design and, due to their flexibility, can be readily adapted to different geometric requirements. The cooling coils can be made of materials such as copper, aluminum, or stainless steel and preferably have an inner diameter of 4 to 12 mm to ensure optimal heat transfer with an acceptable pressure drop.

[0036] A particularly advantageous embodiment of the invention provides that the cooling coils of the secondary circuit of the first cooling system and the secondary circuit of the second cooling system run parallel to each other. This parallel arrangement of the cooling coils enables optimal coverage of the latent heat storage layer with a uniform distribution of cooling capacity, since both secondary circuits can reach every area of ​​the phase change material equally. The parallel design of the cooling coils ensures that if one secondary circuit fails, the other circuit can continue to supply the entire surface of the latent heat storage layer with its cooling capacity, thereby preventing local temperature differences or insufficiently cooled areas.Another advantage of this arrangement is that the flow resistances in both secondary circuits are almost identical, resulting in a uniform flow of the respective cooling medium and thus ensuring optimal heat transfer. Furthermore, the parallel routing of the cooling coils allows for a compact and manufacturing-efficient design, as the cooling coils can be arranged at defined intervals from each other, eliminating the need for complex intersections or overlapping of the pipework.

[0037] A particularly advantageous embodiment of the invention provides that the flow direction of the cooling medium in the parallel cooling coils is opposite. This counter-rotating flow results in a more uniform temperature distribution in the latent heat storage layer, since the areas with the lowest cooling medium temperature of one secondary circuit are opposite the areas with the highest cooling medium temperature of the other secondary circuit. This minimizes local temperature differences in the latent heat storage layer and ensures homogeneous cooling of the transported goods.

[0038] According to another design, the secondary circuit of the first cooling system and the secondary circuit of the second cooling system are each designed in a meandering shape. This design combines the advantages of a simple construction with good area coverage. The meandering shape makes it possible to cool a large area with a single continuous pipe or duct.

[0039] According to a particularly preferred embodiment, the liquid cooling medium of the second circuit is a water-glycol mixture. Water-glycol mixtures are characterized by a high specific heat capacity, which ensures effective heat transfer even at relatively low flow rates. The glycol component, preferably ethylene glycol or propylene glycol, lowers the freezing point of the mixture and thus prevents unwanted freezing of the cooling medium, even at low temperatures. A mixing ratio of 60:40 to 40:60 (water:glycol) is particularly preferred, resulting in freezing points of -25°C to -45°C. Water-glycol mixtures also exhibit a moderate viscosity, which allows for reasonable energy expenditure for circulation, even at low temperatures.

[0040] Another advantageous embodiment provides that the secondary circuit of the first cooling system and the secondary circuit of the second cooling system each have a pump for circulating the liquid cooling medium. The pump is preferably a gear pump and enables controlled and continuous circulation of the cooling medium. By using a separate pump, the flow rate of the cooling medium, and thus the cooling capacity, can be precisely adjusted. The pump is preferably speed-controlled, allowing the flow rate to be adapted to the current cooling demand. This enables energy-efficient operation of the system. To ensure high operational reliability, the pump is preferably designed for continuous operation and equipped with dry-running protection.

[0041] The multi-layered shell of the transport container serves to thermally insulate the interior from the environment while simultaneously enabling active temperature control. The shell's layered structure is designed to minimize heat gain from the outside while ensuring efficient and uniform temperature regulation of the interior. The individual layers of the shell fulfill different functions and are optimized in their arrangement for maximum interaction. A preferred design features a multi-layered shell with an insulating layer and a latent heat storage layer from the outside in. This arrangement has the advantage that the outer insulating layer effectively protects both the latent heat storage layer and the interior from external heat gain.The insulating layer is preferably designed as vacuum insulation and has a heat transfer coefficient of less than 0.1 W / (m²K). 2 -K), particularly preferably less than 0.05 W / (m²). 2 -K) on . The internal latent heat storage layer is in direct or indirect thermal contact with the interior and buffers temperature fluctuations.

[0042] A particularly preferred embodiment provides that the insulating layer comprises at least one vacuum insulation panel (VIP). A vacuum insulation panel consists of a porous core material enclosed by a gas- and vapor-tight shell, with the space between the two being evacuated. The core material preferably used is fumed silica, also known as highly dispersed silica or fumed silicon dioxide, which has an open-pore structure with pore sizes in the nanometer range. Alternatively, other microporous materials such as aerogels, glass fibers, or open-cell polyurethane foams can also be used. The gas-tight shell preferably consists of a multilayer high-barrier film, typically having a multilayer structure of plastic and metal films, for example, a combination of polyethylene terephthalate (PET) and aluminum foil.The internal pressure in the evacuated panel is preferably below 1 mbar, particularly preferably below 0.1 mbar. This design almost completely prevents heat conduction through the gas in the core material, resulting in vacuum insulation panels having a very low thermal transmittance coefficient of typically less than 0.005 W / (m²K).

[0043] The buffering effect of the latent heat storage layer is achieved through the use of a phase change material (PCM) that can absorb or release a large amount of thermal energy during the transition between the liquid and solid phases. The energy stored or released during the phase transition is called latent heat and is typically many times greater than the sensible heat that can be stored simply by changing the material's temperature.

[0044] Various classes of materials can be used as phase change materials. Organic PCMs such as paraffins and fatty acids are characterized by good chemical stability and low supercooling effects. Inorganic PCMs, especially salt hydrates and eutectic salt mixtures, exhibit a higher volumetric storage capacity but are more prone to supercooling and phase separation. PCM compounds, in which the phase change material is embedded in a polymer matrix, can also be used. The selection of the appropriate PCM depends on the desired phase transition temperature, the required storage capacity, and the specific requirements for mechanical and chemical stability.

[0045] A particularly preferred embodiment provides that the latent heat storage layer comprises a phase change material with a phase transition in the temperature range of 2 °C to 8 °C. This temperature range is particularly suitable for the transport of pharmaceuticals and other refrigerated products that typically need to be stored at 2 °C to 8 °C.

[0046] For transport containers used to carry temperature-sensitive goods, the uneven distribution of external heat energy presents a particular challenge. If, for example, the container is exposed to direct sunlight, the heat input occurs primarily on one side, while the other sides are heated less. This uneven thermal load can lead to local temperature differences within the container and impair the function of the latent heat storage layer. This is especially critical if the phase change material in the more heated areas is already completely melted, while it remains solid in other areas. To avoid such local temperature differences and ensure the most uniform temperature distribution possible within the container, special measures are required to distribute the thermal energy circumferentially around the container.

[0047] In this context, an advantageous embodiment provides that the casing has a first energy distribution layer made of a thermally conductive material, which serves to uniformly distribute thermal energy acting on the container from the outside. This first energy distribution layer is preferably arranged outside the latent heat storage layer and ensures that local heat inputs, such as those that can occur from solar radiation, are distributed circumferentially around the container. This prevents the formation of local hotspots, which would lead to an uneven load on the latent heat storage layer.

[0048] Another advantageous design provides that the casing has a second energy distribution layer made of a thermally conductive material, facing the interior. This second energy distribution layer serves to homogenize the temperature on the inside of the casing and thus ensure a uniform temperature distribution inside. This is particularly important if the latent heat storage layer does not operate completely homogeneously or if the transported goods are unevenly distributed inside.

[0049] A particularly advantageous design is one in which the latent heat storage layer is positioned between the first and second energy distribution layers. This sandwich construction ensures both a uniform distribution of external heat input and a homogeneous temperature distribution within the interior. The two energy distribution layers act as thermal equalization layers, compensating for local temperature differences and optimizing the function of the latent heat storage layer.

[0050] The energy distribution layer(s) preferably has a thermal conductivity of X > 100 W / (m⁻¹K), particularly preferably X > 200 W / (m⁻¹K). This high thermal conductivity in the layer or plate plane is necessary to ensure effective temperature equalization in the circumferential direction. Suitable materials for the energy distribution layer(s) include, for example, aluminum (X ≥ 230 W / (m⁻¹K)) or copper (X ≥ 380 W / (m⁻¹K)). The energy distribution layers can be designed as continuous sheets or as structured elements, for example, as heat-conducting plates with integrated reinforcing ribs. The thickness of the energy distribution layer(s) is selected to ensure sufficient thermal conductivity in the circumferential direction while avoiding unnecessary increase in the weight of the transport container. Preferred thicknesses are in the range of 0.5 to 5 mm.

[0051] Alternatively, the energy distribution layer(s) can consist of graphite or a graphite composite material, in particular graphite sheets or expanded graphite, which is applied, for example, to the aluminum plates, e.g., glued on. Such materials also lead to mechanical reinforcement of the container wall at a low weight.

[0052] A particularly advantageous design involves thermally connecting the energy distribution layers of adjacent container walls. For this purpose, the energy distribution layers at the container edges can be joined, for example, by welding, soldering, gluing, or using thermally conductive connecting elements. This continuous thermal connection enables heat transfer not only within a single wall but across the entire circumference of the container. The connection points are designed such that their thermal resistance is less than 0.01 (K⁻¹ m).2 ) / W, preferably less than 0.005 (K -m 2 ) / W is . This can be achieved, for example, by large-area overlaps of the energy distribution layers to be joined or by additional heat-conducting plates in the corner area. The thermal resistance of the connection point should not exceed 1.5 times the thermal resistance of an equally long section in the energy distribution layer itself.

[0053] Preferably, the insulation, the latent heat storage layer (if present), and the first and / or second energy distribution layer enclose the interior space on all sides, except for an access opening, such as a door. The first and / or second energy distribution layer preferably surrounds the interior space completely and without interruption, except for the opening; that is, each wall of the envelope includes an energy distribution layer, with the energy distribution layers of all walls being thermally connected to each other at the adjacent edges and corners, i.e., by a connection having a thermal conductivity of > 100 W / (mK).

[0054] Preferably, the door assembly also consists of the same layered structure used for the construction of the walls. In particular, the door assembly consists of a layered structure comprising, from the outside to the inside, insulation and an energy distribution layer made of a material with a thermal conductivity of > 100 W / (mK).

[0055] A preferred design involves arranging the latent heat storage layer in the ceiling and / or floor of the enclosure. This arrangement utilizes natural temperature equalization through convection within the container. Warm air rises and is cooled by the latent heat storage layer in the ceiling, while cold air sinks and is potentially tempered by the latent heat storage layer in the floor. This positioning allows for a reduction in the amount of phase-change material required, as the interior temperature is regulated more efficiently than with a latent heat storage layer located in the side walls.

[0056] In a particularly advantageous embodiment, the latent heat storage layers in the ceiling and floor are thermally connected to each other by vertical energy distribution layers in the side walls. These energy distribution layers, with a thermal conductivity preferably greater than 200 W / (m-K), enable heat transfer between the horizontal latent heat storage layers, thus ensuring thermal equilibrium.

[0057] The transport container can have various geometric shapes, with the shell comprising several walls that meet at an angle. Preferably, it is a cuboid container with six walls, of which the wall structure forms five walls and the door device forms the sixth wall.

[0058] The transport container according to the invention is preferably designed as an air freight container and therefore preferably has external dimensions of at least 0.4 x 0.4 x 0.4 m, preferably 0.4 x 0.4 x 0.4 m 3 up to 3.0 x 2.5 x 1.8 m 3 preferably 1.0 x 1.0 x 1.0 m 3 up to 3.0 x 2.5 x 1.8 m 3 on .

[0059] The invention is described in more detail below with reference to the embodiments schematically depicted in the drawing. These show

[0060] Fig. 1 a schematic representation of a transport container with redundant cooling systems in a partial view; Fig. 2 a schematic representation of a modified version of the transport container with redundant cooling systems;

[0061] Fig. 3 shows a schematic representation of the redundant cooling systems, wherein the primary cooling circuits are each connected to only one secondary cooling circuit;

[0062] Fig. 4 shows a schematic representation of the redundant cooling systems, with the primary cooling circuits being interconnected with both secondary cooling circuits;

[0063] Fig. 5 shows a schematic representation of a control system; and

[0064] Fig. 6 shows a section through a transport container according to the invention.

[0065] Figures 1 and 2 schematically show a transport container 1 for transporting temperature-sensitive goods. The transport container 1 has an interior space for holding the goods, which is enclosed by a multi-layered shell. The multi-layered shell comprises thermal insulation (not shown) and a latent heat storage layer 2, which is formed by several latent heat storage elements in the form of PCM elements. A cooling device is thermally coupled to the latent heat storage layer 2 and includes a distribution system for a cooling medium. The cooling device has two cooling systems, each thermally coupled to the latent heat storage layer 2, so that the latent heat storage layer can be selectively cooled by either the first or the second cooling system.

[0066] Each cooling system comprises a primary circuit and a secondary circuit. The primary circuit of the first cooling system is designated 5, and the primary circuit of the second cooling system is designated 6. The primary circuits 5 and 6 are each designed as a circuit of a compression refrigeration machine in which a refrigerant circulates. The primary circuit 5 of the first cooling system is thermally coupled to an associated secondary circuit 4, and the primary circuit 6 of the second cooling system is thermally coupled to an associated secondary circuit 3. The respective secondary circuits 3 and 4 form the distribution system for distributing the cooling and introducing the cooling into the latent heat storage layer and are filled with a liquid cooling medium, preferably a water-glycol mixture. The first secondary circuit 3 and the second secondary circuit 4 are designed as pipes that are thermally coupled to the latent heat storage units.

[0067] Figures 1 and 2 show two different

[0068] From different implementations of the thermal coupling between the primary and secondary circuits, wherein the thermal coupling in the embodiment according to Fig. 1 is shown in Fig. 3 and the thermal coupling of the embodiment according to Fig. 2 is shown in Fig. 4. In Figs. 1 and 3, an embodiment is shown in which the primary circuit 5 of the first cooling system is thermally coupled exclusively to the secondary circuit 4 of the first cooling system via a first heat exchanger 5.5, and the primary circuit 6 of the second cooling system is thermally coupled exclusively to the secondary circuit 3 of the second cooling system via a second heat exchanger 6.5.

[0069] In contrast, Figures 2 and 4 show an embodiment in which the primary circuit 5 of the first cooling system is thermally coupled to the secondary circuit 4 of the first cooling system via the first heat exchanger 5.5 and additionally to the secondary circuit 3 of the second cooling system via a third heat exchanger 5.6. The primary circuit 6 of the second cooling system is thermally coupled to the secondary circuit 3 of the second cooling system via the second heat exchanger 6.5 and additionally to the secondary circuit 4 of the first cooling system via a fourth heat exchanger 6.6. This cross-thermal coupling of the primary and secondary circuits provides overarching redundancy that goes beyond mere system redundancy.

[0070] The first primary circuit 5 comprises a refrigerant circuit 5.1, an electronic expansion valve 5.2, a condenser 5.3, a compressor 5.4, and a first and, if applicable, a third plate evaporator 5.5 or 5.6, which serves as a heat exchanger for thermal coupling with the secondary circuit 4 or 3. Similarly, the second primary circuit 6 comprises a refrigerant circuit 6.1, an electronic expansion valve 6.2, a condenser 6.3, a compressor 6.4, and a second and, if applicable, a fourth plate evaporator 6.5 or 6.6, which serves as a heat exchanger for thermal coupling with the secondary circuit 3 or 4.

[0071] Figure 5 shows the control device 16 of the first cooling system. The control device 16 is connected to a plurality of sensors to monitor the operating status of the cooling system and to regulate it as needed. The secondary circuit 4 has three temperature sensors for measuring the return temperature Tr and three temperature sensors for measuring the supply temperature Tv. This triple configuration of temperature sensors allows for plausibility checks of the measured values, so that if a sensor malfunctions, it can be identified and the measurement discarded. Furthermore, the primary circuit 5 has two redundant temperature sensors for measuring the suction gas temperature TI upstream of the compressor 5.4, one temperature sensor for measuring the hot gas temperature T2 downstream of the compressor 5.4, and two redundant pressure sensors for measuring the evaporation pressure pe.Furthermore, a sensor for measuring the ambient temperature Tamb and two redundant sensors for measuring the internal temperature Tint of the transport container are provided. The control device 16 also monitors the return temperature TrS2 of the second secondary circuit 3 in order to intervene if necessary. Similarly, an additional sensor is provided for recording the return temperature Tr of the secondary circuit 4, the measurement data of which are supplied to the control unit of the second primary circuit 6.

[0072] The corresponding control device of the second cooling system is designed analogously.

[0073] The control devices of the two cooling systems operate autonomously and can independently decide, based on the acquired measurement data, whether activation of the respective cooling system is necessary. For each transport mission, one of the two primary circuits is designated as the lead system and the other as the backup system. If the backup system is deemed insufficient based on the overall measurement of the

[0074] If the system detects that the lead system cannot maintain the desired temperature range (Tr) or the internal temperature (Tint), it automatically activates to provide support. The backup system operates regardless of whether its support is needed for load sharing and efficiency improvement or as a complete replacement in the event of a lead system failure.

[0075] Fig. 6 shows a section through a cuboid-shaped transport container 1, which has an upper wall, a lower wall (forming the base), a rear wall, and two side walls. A door element 7 is provided on the sixth side, with which an access opening to the interior can be closed. The transport container 1 has a multi-layered shell that completely encloses the interior. The shell comprises a two-layer thermal insulation 8 as the outer insulating layer, wherein at least one layer of the multi-layered thermal insulation 8 can have or be formed from vacuum insulation panels. The shell further comprises at least one latent heat storage layer 2, which has a phase-change material. In the present embodiment, the latent heat storage layer 2 is provided only in the upper wall, specifically on the side of the thermal insulation 8 facing the interior.

[0076] On the inside of the thermal insulation 8, a heat distribution layer 9 is arranged on the rear wall and on each of the two side walls. An inner heat distribution layer 10 is provided on the upper wall within the latent heat storage layer 2, and an outer heat distribution layer 11 is located outside the latent heat storage layer 2. The heat distribution layers 9, 10, and 11 serve to ensure a uniform temperature distribution within the transport container 1. Access to the interior is via a door opening, which can be closed with a door element 7. The latent heat storage layer 2 is equipped with flow-through cooling channels 15 of the secondary circuits 3 and 4 of the first and second cooling systems. A base plate 12 is arranged on the underside of the transport container 1, to which several container feet 13 are attached. Energy storage units 14 are integrated into the container feet 13, which supply the cooling systems, in particular their pumps and compressors 5.4 and 6.4, with electrical energy.

Claims

34 Patent claims:

1. Transport containers for transporting temperature-sensitive goods an interior space to accommodate the transported goods, a multi-layered shell enclosing the interior, comprising thermal insulation ( 8 ) and preferably at least one latent heat storage layer (2 ), and a cooling device for cooling the interior with a distribution system for a cooling medium, which is preferably thermally coupled to the latent heat storage layer (2), characterized in that that the cooling device has two cooling systems, namely a first cooling system and a second cooling system, wherein each cooling system has a compression refrigeration machine and is preferably thermally coupled to the latent heat storage layer (2) so that the interior can be cooled selectively by either the first or the second cooling system, and that a control system for controlling the cooling systems is provided and designed to operate both cooling systems simultaneously when maximum cooling demand is met.

2. Transport container according to claim 1, characterized in that each cooling system comprises a primary circuit (5, 6) with a refrigerant, which is designed as a circuit of the respective compression refrigeration machine, and a secondary circuit (3, 4) which has the distribution system and is filled with a liquid or gaseous cooling medium, wherein the primary circuit (5, 6) is thermally coupled to the secondary circuit (3, 4) via a heat exchanger (5.5, 6.5) to cool the cooling medium.35 3. Transport container according to claim 1 or 2, characterized in that the primary circuit (5) of the first cooling system is thermally coupled to the secondary circuit (4) of the first cooling system via a first heat exchanger (5.5) and the primary circuit (6) of the second cooling system is thermally coupled to the secondary circuit (3) of the second cooling system via a second heat exchanger (6.5).

4. Transport container according to claim 2 or 3, characterized in that the primary circuit (5) of the first cooling system is additionally thermally coupled to the secondary circuit (3) of the second cooling system via the first heat exchanger (5.5) or a third heat exchanger (5.6) and the primary circuit (6) of the second cooling system is additionally thermally coupled to the secondary circuit (4) of the first cooling system via the second heat exchanger (6.5) or a fourth heat exchanger (6.6).

5. Transport container according to one of claims 1 to 4, characterized in that the control system comprises a first control device (16) for controlling the first cooling system and a second control device for controlling the second cooling system, wherein each control device (16) is connected to its own temperature sensor and optionally its own pressure sensor for detecting the pressure in the associated primary circuit, so that the respective compression refrigeration machine can be controlled depending on measurement data from the temperature and optionally pressure sensor.

6. Transport container according to one of claims 2 to 5, characterized in that the secondary circuit (4) of the first cooling system and the secondary circuit (3) of the second cooling system are at least partially embedded in the latent heat storage layer (2).

7. Transport container according to one of claims 2 to 5, characterized in that the secondary circuit (4 ) of the first cooling system and the secondary circuit (3) of the second cooling system are located on a surface of the latent heat storage layer (2 ).

8. Transport container according to one of claims 2 to 7, characterized in that the secondary circuit (4 ) of the first cooling system and the secondary circuit (3) of the second cooling system each comprise cooling coils ( 15 ).

9. Transport container according to claim 8, characterized in that the cooling coils ( 15 ) of the secondary circuit (4 ) of the first cooling system and of the secondary circuit (3 ) of the second cooling system run parallel to each other.

10. Transport container according to one of claims 2 to 9, characterized in that the secondary circuit (4 ) of the first cooling system and the secondary circuit (3) of the second cooling system are each designed in a meandering shape.

11. Transport container according to any one of claims 2 to 10, characterized in that the liquid cooling medium is a water-glycol mixture.

12. Transport container according to any one of claims 2 to 11, characterized in that the secondary circuit (4) of the first cooling system and the secondary circuit (3) of the second cooling system each have a pump for circulating the liquid cooling medium.

13. Transport container according to one of claims 1 to 12, characterized in that the latent heat storage layer (2 ) is arranged in a ceiling area and / or a bottom area of ​​the shell .

14. Transport container according to one of claims 1 to 13, characterized in that the thermal insulation ( 8 ) comprises vacuum insulation .

15. Transport container according to one of claims 1 to 14, characterized in that the latent heat storage layer (2 ) comprises a phase change material with a phase transition in the temperature range of 2 °C to 8 °C .

16. Transport container according to one of claims 1 to 15, characterized in that the shell has a first energy distribution layer ( 9, 11 ) made of a thermally conductive material for the uniform distribution of thermal energy acting on the container ( 1 ) from the outside .

17. Transport container according to one of claims 1 to 16, characterized in that the shell has a second energy distribution layer ( 10) facing the interior made of a heat-conducting material .

18. Transport container according to claim 17, characterized in that the latent heat storage layer (2)38 is arranged between the first and the second energy distribution layer ( 10 , 11 ).

19. Transport container according to one of claims 16 to 18, characterized in that the energy distribution layer ( 9 , 10 , 11 ) has a thermal conductivity of X > 100 W / (m -K) .

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