Heat transfer system and method for operating a heat transfer system

Abstract

The invention relates to a heat transfer system (10) with a heat source (14) and a heat sink (50), wherein the heat source (14) has a heat discharge arrangement (34) for heat discharge from the heat source (14) by means of a working fluid (12), wherein within the heat discharge arrangement (34) the working fluid (12) can be thermally coupled or coupled to the heat source (14), and wherein by means of the working fluid (12) the heat source (14) can be thermally coupled or coupled to the heat sink (50).A high and defined heat transfer over a large operating temperature range can be achieved by the heat transfer arrangement (34) comprising at least two stages arranged parallel in terms of flow, a first stage (36) and a second stage (42), for heat transfer from the heat source (14) to the working fluid (12), wherein the stages (36, 42) are designed such that they have a different thermal resistance between the heat source (14) and the working fluid (12).

Description

[0001] The invention relates to a heat transfer system with a heat source and a heat sink, wherein the heat source has a heat discharge arrangement for heat discharge from the heat source by means of a working fluid, wherein within the heat discharge arrangement the working fluid can be thermally coupled or coupled to the heat source, and wherein by means of the working fluid the heat source can be thermally coupled or coupled to the heat sink, as well as a method for operating a heat transfer system.

[0002] Such a heat transfer system is described in DE 10 2019 113 292 A1. In this known heat transfer system, a working fluid is evaporated at a heat source and condensed in a heat sink. A riser pipe is provided through which the liquid working fluid is transported upwards, against the direction of gravity, and from there conveyed into an evaporator section. Evaporation takes place vertically downwards, for example, in a porous metal foam in contact with the heat source.

[0003] The evaporation of a working fluid is of particular interest for the thermal discharge of heat storage systems due to the potentially very high heat transfer coefficients during evaporation and subsequent condensation. Discharging a sensible / latent heat storage system over a very wide temperature range, spanning several hundred Kelvin, poses a significant challenge for an evaporation system, as various boiling ranges are traversed. Above a certain critical heat flux density or wall superheat, a drop in the transferred heat flux occurs, the so-called "boiling crisis" (see, e.g., "VDI Society for Process Engineering and Chemical Engineering, VDI Heat Atlas, 11th ed. Berlin: Springer, 2013"). During this process, a continuous vapor layer increasingly forms between the hot wall surface and the fluid, resulting in transition and / or film boiling.Besides performance losses due to certain wall overheating, this leads to problems regarding the controllability of heat dissipation and high thermomechanical stresses caused by the fluctuating behavior of the working fluid during transition boiling. For this reason, technical evaporators are generally operated significantly below the critical heat flux density, which reduces their efficiency.

[0004] Another approach to discharging thermal energy storage systems is presented in the publication "F. Nees, J. Feine, A. Katourtzidis, V. Stahl, and W. Kraft, Heat extraction characteristics of a small scale metallic latent heat thermal energy storage system, "Proceedings of the 17th International Heat Transfer Conference, IHTC-17, Cape Town, South Africa, 2023, doi: 10.1615 / IHTC17.430-40", which describes a high-temperature thermal energy storage system comprising a metallic phase-change material. The high-temperature thermal energy storage system has a heat extraction area designed for operation with air as the heat transfer fluid. However, at low heat source temperatures, the concept exhibits low performance due to the low heat transfer coefficients of air compared to an evaporating working fluid.

[0005] DE 10 2020 107 464 A1 discloses a heat storage device with a metallic phase-change material as the storage material, a heat input device, and a heat output device. To prevent adverse changes in the thermal contact between the storage material and the heat input device or heat output device, a coupling area is provided for thermal coupling, which is arranged at least partially at a distance from the storage material.

[0006] Further heat exchange devices are known from US 2019 / 0 339 013 A1, EP 3 379 191 B1, EP 3 708 923 B1, US 8 109 325 B2 and DE 10 2015 107 427 A1.

[0007] US 6 990 816 B1 shows a cooling arrangement with an evaporator and a condenser.

[0008] The invention is based on the objective of providing a heat transfer system of the type mentioned above and a method in which a comparatively high and defined heat output can be achieved over a large operating temperature range.

[0009] The problem is solved for the heat transfer system with the features of claim 1 and for the method with the features of claim 21.

[0010] The heat transfer system is designed to include at least two fluidically parallel stages, a first stage and a second stage, for heat transfer from the heat source to the working fluid. The stages are designed to exhibit different thermal resistances between the heat source and the working fluid. The design of the stages is such that, under identical operating conditions (operating parameters such as mass flow rate, temperature difference, etc.), different heat flux densities would result between the heat source and the working fluid. In particular, the thermal resistance within the first stage is higher than that within the second stage.

[0011] In the heat transfer system according to the invention, a boiling crisis can be advantageously avoided at least partially or its effects reduced even at high temperatures of the heat source (for example, more than 500 °C), and at the same time a comparatively high heat transfer rate can be achieved even at low and moderate temperatures, whereby a high and defined heat output is possible.

[0012] The heat transfer arrangement is particularly preferably designed as an evaporator arrangement, wherein the working fluid is at least partially evaporable or evaporates during operation in at least one of the at least two stages. The working fluid is particularly evaporable and / or can, for example, be composed of or comprise water.

[0013] Preferably, the heat dissipation arrangement comprises at least one flow channel, and in particular a group of flow channels, for the flow of the working fluid per stage. The flow channels are formed, in particular, within a pipe section with a defined, for example circular, flow cross-section.

[0014] Preferably, in the first stage, between the first flow channel and the heat source, an arrangement is provided to increase the thermal resistance compared to the second stage. Such an arrangement is specifically not present in the second stage. With more than two stages, such arrangements can be present in several stages, except for one, and are designed such that the thermal resistances differ between the stages.

[0015] In particular, the arrangement for increasing thermal resistance has a gap surrounding the first flow channel, in which a medium with low thermal conductivity, for example less than 5 W / (mK), preferably less than 1 W / (mK), is arranged, wherein the medium preferably comprises or is formed from a gas, e.g., air, a liquid, and / or a solid. Preferably, the first flow channel within the heat dissipation arrangement can run in an inner tube completely surrounded by the gap. In a particularly advantageous embodiment, for example, the inner tube can run in a bore within a solid storage material, with the gap, filled with air, being formed between the solid storage material and the outer wall of the inner tube.It is also possible to have a pipe-in-pipe arrangement with an outer pipe and the inner pipe coaxial to it, whereby the gap is arranged between the outer pipe and the inner pipe.

[0016] In a particularly preferred embodiment, the gap dimension (the radial thickness of the gap with respect to its longitudinal axis) is such that, taking the medium into account, the resulting heat flow from the heat source to the inner tube is limited to such an extent that, at the highest operating temperatures of the heat source, a critical heat flux density with respect to the working fluid via the inner tube is not exceeded, and preferably not exceeded, during discharge operation. At the same time, the design is preferably such that the heat flux density is as high as possible at the highest operating temperatures, with evaporation occurring, for example, in the range of nucleate boiling.

[0017] To reduce thermomechanical stresses, it can be advantageous to support the inner pipe outside the heat distribution system. This support can be provided, for example, by a manifold assembly and / or a support structure (thermally decoupled from the storage material) located outside the heat distribution system. In this way, the inner pipe is thermally decoupled from at least those parts of the heat source that exhibit the highest temperatures. High temperature gradients and associated material stresses are thus avoided, and thermomechanical stresses are reduced.

[0018] To achieve the highest possible heat transfer rates even at low operating temperatures, in the second stage the working fluid can be brought into direct contact with the heat source, with the flow channel being formed by the heat source. For example, the flow channel can be formed in a bore through a solid storage material of the heat source, with the solid storage material forming the wall of the flow channel. In this way, the thermal resistance between the heat source and the working fluid is advantageously minimized.

[0019] Flexible design options with different storage materials arise when, at least in one stage between the heat source and the flow channel, an outer tube is arranged around the respective flow channel. The outer tube can also separate the flow channel from phase-change materials and / or granular storage materials. This allows the heat transfer arrangement to be integrated even into a storage area containing such a storage material that is not a solid-state storage material. In the first stage, with the increased thermal resistance, the arrangement for increasing the thermal resistance, particularly the gap, is advantageously positioned between the outer and inner tubes.In the second stage, with the lower thermal resistance, it is advantageous to form the flow channel inside the outer tube, with the outer tube defining the flow channel.

[0020] Advantageously, a (working fluid) circuit, particularly a closed circuit, with conduits for conveying the working fluid, especially comprising flow channels, can be provided in which, in addition to the heat source and the heat sink, a reservoir for the working fluid and at least one conveying device are arranged. The circuit particularly forms a discharge circuit, which, during discharge operation, is used to discharge heat from the heat source, acting as a heat storage device. The conveying device is particularly a pump. The reservoir preferably has a size sufficient to accommodate all the working fluid in the circuit.

[0021] It is also possible to use it in an open circuit, where pressure equalization to the environment takes place.

[0022] Preferably, the flow elements within the heat transfer arrangement comprise, preferably per stage, a group of flow channels connected in parallel to one another, wherein a distribution device for dividing the working fluid among the flow channels is arranged upstream of the group, which is particularly in the form of a distribution strip located outside the heat transfer arrangement, and / or a collecting device for combining the working fluid (to form the total flow of working fluid) is arranged downstream of the group. By arranging the flow channels in groups, an improved heat transfer rate within the heat source can be achieved.

[0023] For optimized control and / or regulation of heat transfer from the heat source, it is preferably provided that the piping between the reservoir and the heat transfer arrangement can be divided into at least one partial line per stage, in order to distribute a total working fluid flow (the total mass flow of the working fluid circulating in the loop) into a partial (mass) flow of working fluid per stage. By dividing the total working fluid flow into the partial flows, particularly upstream of the distribution devices, a simplified adjustment of the respective proportion of the partial flows or the ratio of the partial flows to each other is possible.

[0024] In this context, it can be provided that exactly one pumping device and one control valve are located between the reservoir and the heat transfer arrangement, wherein the total flow of working fluid from the reservoir can be divided or split into the partial flows by means of the control valve. Alternatively or additionally, it can be provided that a pumping device is located in each partial line, wherein the partial lines preferably run separately from the reservoir to the respective stage of the heat transfer arrangement.

[0025] In a particularly preferred embodiment, the heat source is designed as a heat storage device, in particular as a high-temperature heat storage device, which includes a heat charging arrangement designed, in particular, for generating heat by means of electrical energy, for example, as an electric resistance heater, in particular comprising at least one heating element. The maximum operating temperatures (at full heat charging) of the heat storage device in the high-temperature heat storage device configuration can be 500 °C or more, in particular up to 1000 °C, preferably up to 800 °C, e.g., up to 650 °C.

[0026] In a preferred embodiment, the heat storage device is designed (or has) a phase-change heat storage device, which comprises a storage material arranged in an enclosure of the heat storage device, which is formed by or comprises a phase-change material, in particular a metallic one.

[0027] Alternatively or additionally, the heat storage device is designed as a sensible heat storage device, which comprises a storage material for sensible heat storage, in particular a solid-state storage material. The solid-state storage material can, for example, be made of or comprise steel. A storage material in granular form is also possible, which is arranged in a housing.

[0028] Advantageous design possibilities for the heat storage device arise when the sensible heat storage, in particular the solid storage material, is designed at least essentially cuboid and / or cylindrical.

[0029] A large possible operating temperature range is particularly achievable when the heat storage device comprises a first storage area, containing the phase-change heat storage medium, and a second storage area, containing the sensible heat storage medium, which are thermally coupled to one another, in particular mechanically fastened to each other. The second storage area can, in particular, encompass the solid storage material, which, for example, is formed in a plate-like form with a comparatively low height, wherein the phase-change heat storage medium (with the housing and the phase-change material arranged therein) is in surface contact with the plate, in particular, is attached to the plate. An embodiment of a heat storage device of this type is described, for example, in "F. Nees, J. Feine, A. Katourtzidis, V. Stahl, and W.Kraft, Heat extraction characteristics of a small scale metallic latent heat thermal energy storage system “Proceedings of the 17th International Heat Transfer Conference, IHTC-17, Cape Town, South Africa, 2023, doi: 10.1615 / IHTC17.430-40”, wherein the heat extraction arrangement has a different design.

[0030] Preferably, the heat dissipation arrangement and / or the heat charging arrangement are thermally coupled directly to the second storage area, in particular arranged on and / or within it, wherein the sensible heat storage unit forms a heat storage base body, and / or the heat dissipation arrangement and / or the heat charging arrangement are thermally coupled indirectly to the first storage area via the second storage area. In particular, the flow channels run within the heat storage base body. In addition to sensible heat storage, the sensible heat storage unit serves for heat conduction between the phase-change heat storage unit as the first storage area and the heat dissipation arrangement.

[0031] In a suitable embodiment, the heat sink is formed by a heat exchanger, particularly for the condensation of the working fluid. This heat exchanger is permeable to, or already permeated by, the working fluid on one side and another heat transfer medium, such as air or a water-glycol mixture, on the other. This allows heat absorbed from the heat source to be transferred to the second heat transfer medium. Alternatively or additionally, the heat exchanger serves to cool superheated vapor of the working fluid to saturation temperature and / or to subcool any condensate that forms. This embodiment advantageously allows the heat transferred to be transported in a targeted manner to another area, for example, a vehicle component or a vehicle interior, for its conditioning.

[0032] According to the invention, the method for operating a heat transfer system provides that at least two stages, a first stage and a second stage, within the heat dissipation arrangement can be traversed by the working fluid individually or in parallel flow, wherein the individual stages have different thermal resistances. These different thermal resistances are not achieved through operating parameters, but rather through the specific design of the stages, with at least one stage in particular featuring an arrangement with increased thermal resistance, especially low thermal conductivity.

[0033] In a preferred embodiment of the method, the discharge operation is controlled and / or regulated with respect to a defined heat discharge, whereby a total mass flow rate of working fluid flowing through the heat discharge arrangement and / or a ratio of partial mass flow rates of working fluid flowing through the individual stages is / are set. The heat discharge can relate to the heat source and / or to the entire heat transfer system. The heat discharge can, for example, be constant or adapted to a requested heat demand of a system to be tempered, into which the heat is transferred via the heat sink.

[0034] In a particularly preferred operating mode, at the beginning of a discharge cycle (a cycle between two charging cycles of the heat storage device) and / or at high temperature differences between the heat source and a saturation temperature of the working fluid, a proportion of the working fluid flowing through the first stage, which has the highest thermal resistance, is greatest, with the partial mass flow through the second stage, and optionally the other stages, being zero, i.e., no working fluid flows through the second stage. "High temperature differences" are defined as those at which, under the given operating conditions, the critical heat flux density would be exceeded within the second stage and the temperature of the heat source is greater than 75% of the maximum operating temperature in °C.

[0035] In this way, particularly with appropriate design of the first stage, ensuring that the critical heat flux density is not exceeded even at the highest operating temperatures, a boiling crisis can be advantageously prevented even at high operating temperatures of the heat source. This allows for a comparatively high heat flux density, defined controllability, and a low thermomechanical stress within the heat transfer system.

[0036] In a further particularly preferred operating mode, it is provided that, at moderate and / or small temperature differences between the heat source and a saturation temperature of the working fluid, both (or several, e.g., all) stages are operated in parallel, or (especially at small temperature differences) only the second stage is / are supplied with the working fluid. "Moderate temperature differences" are defined as those at which, under the given operating conditions, the critical heat flux density within the second stage would be exceeded and which are below the high temperature differences. "Small temperature differences" are defined as those at which, under the given operating conditions, the critical heat flux density within the second stage is not exceeded, i.e., which are below the moderate temperature differences.

[0037] The high, moderate, and low temperature differences are defined here in such a way that they cover the entire operating temperature range of the heat source. The corresponding temperature differences can be estimated for the relevant operating conditions using methods described in the literature (e.g., the VDI Heat Atlas). For example, the partial flow rate through the second stage can be continuously increased from an initially low mass flow rate, starting, for instance, from the presence of moderate temperature differences, while the partial flow rate through the first stage is reduced accordingly.

[0038] In this way, a high heat output from the heat source can be ensured even with small and moderate temperature differences.

[0039] Preferably, during a shutdown of the discharge operation, the working fluid is drained from the heat transfer assembly, preferably from all components and piping arranged in a circuit, and collected in a reservoir. This can be done by gravity and / or by means of a conveying device. The reservoir is, in particular, arranged in a (working fluid) circuit in which the heat source and the heat sink are also located.

[0040] The invention will now be explained in more detail using exemplary embodiments and with reference to the drawings. The drawings show: Fig. 1 a flow diagram of a heat transfer system according to the invention, with a heat source and heat sink arranged in a circuit, wherein the heat source has a heat discharge arrangement with a first stage and a second stage for heat transfer, which are arranged parallel in terms of flow technology, Fig. 2 a diagram with boiling characteristics for container and flow boiling, Fig. 3A,B two possible design variants of the heat source in perspective view, Fig. 4 a design variant of the heat discharge arrangement according to Fig. 1 in detailed representations and in schematic view, Fig. 5 a flow diagram of the heat transfer system according to Fig. 1 at the beginning of a discharge cycle of a discharge operation, Fig. 6 a flow diagram of the heat transfer system according to Fig. 1 during a shutdown process of the discharge operation, Fig. 7A, B two diagrams each with an example of expected performance characteristics for the first stage ( Fig. 7A) and for the second stage ( Fig. 7B), Fig. 8 a diagram with an exemplary expected performance characteristic for a discharge operation of the heat transfer system controlled for a constant heat output, Fig. 9 a flowchart with a opposite Fig. 1. Modified design variant of the heat transfer system with regard to the cycle, Fig. 10 A schematic cross-sectional representation of a sensible heat storage device for the heat source, Fig. 11A, B, C each have a flowchart with a opposite Fig. 1. a modified version of the heat transfer system with respect to the heat source, and Fig. 12A,B each represent a part of another variant of the heat source in a schematic cross-sectional representation.

[0041] Fig. Figure 1 shows a flow diagram of a heat transfer system 10 with a heat source 14 and a heat sink 50, between which heat is transferred during discharge operation by means of a working fluid 12. The working fluid 12 (heat transfer fluid) is preferably selected such that it evaporates in the heat source 14 under the given operating conditions. The working fluid 12 can, for example, be formed by or contain water.

[0042] The heat source 14 and the heat sink 50 are arranged in an exemplary closed circuit 60 of the heat transfer system 10. The circuit 60 includes conduits 62 for circulating a working fluid 12. Further components of the circuit 60 include a reservoir 54 for receiving the working fluid 12 and, if necessary, for use as an expansion tank, as well as at least one conveying device 56, in particular a pump, for conveying the working fluid 12. The reservoir 54 is, by way of example, arranged below the heat source 14 with respect to a weight force g. Additionally, the circuit 60 includes a reservoir 54 for receiving the working fluid 12 and, if necessary, for use as an expansion tank, as well as at least one conveying device 56, in particular a pump, for conveying the working fluid 12. Fig. In the embodiment shown in 1, a control valve 58 is provided for controlling and / or regulating the operation of the heat transfer system 10.

[0043] The heat sink 50 is designed as a heat exchanger 52, in particular as a condenser, within which the vaporized working fluid 12 is condensed, releasing heat to a further heat transfer medium. Preferably, the heat exchanger 52, in its condenser configuration, also serves to cool superheated vapor of the working fluid 12 to saturation temperature and / or to subcool any condensate that has formed. During operation, the heat exchanger 52 is permeated by the working fluid 12 on one side and by the further heat transfer medium on the other. The further heat transfer medium can be a gas, for example air, or a liquid, for example a water-glycol mixture, e.g., from another vehicle circuit, and can serve, for example, to regulate the temperature of a section and / or a component within a vehicle.

[0044] The heat source 14 has a heat discharge arrangement 34 for heat discharge from the heat source 14 by means of the working fluid 12. Within the heat discharge arrangement 34, the working fluid 12 is thermally coupled to the heat discharge arrangement 34 during discharge operation, whereby heat is transferred from the heat source 14 to the working fluid 12. For the purpose of conveying the working fluid 12 through the heat discharge arrangement 34, the heat discharge arrangement 34 has at least one flow channel 78, 80, which is associated with the conveying means 62.

[0045] The heat source 14 is in particular designed as a heat storage device 16 in the form of a high-temperature heat storage device, with maximum storage temperatures of preferably more than 400 °C, particularly preferably between 500 °C and 1000 °C. The heat storage device 16 has a heat charging arrangement 32 (see figure). Fig. 4), which is preferably designed to generate heat using electrical energy and for this purpose includes, for example, at least one electric resistance heater (in particular a heating cartridge).

[0046] For particularly efficient operation over a wide temperature range, the heat storage device 16 has a first storage area 20 with a phase-change heat storage element 18 and a second storage area 28 with a sensible heat storage element 26. The first storage area 20 and the second storage area 28 are thermally coupled to each other, in particular attached to each other such that heat conduction takes place between the first storage area 20 and the second storage area 28 over the largest possible contact area. An example of such a heat storage device is described in the publication "F. Nees, J. Feine, A. Katourtzidis, V. Stahl, and W. Kraft, Heat extraction characteristics of a small scale metallic latent heat thermal energy storage system, "Proceedings of the 17th International Heat Transfer Conference, IHTC-17, Cape Town, South Africa, 2023, doi: 10.1615 / IHTC17."430-40“ specified, wherein in this known heat storage device the heat discharge is solved differently than in the heat storage system 10 according to the invention.

[0047] The phase-change heat storage unit 18 comprises a preferably metallic phase-change material 22, which is arranged in a housing 24 of the phase-change heat storage unit 18. The phase-change material is, for example, made of AlSi. 12 formed or exhibits AlSi 12 on.

[0048] The sensible heat storage device 26 comprises a storage material for sensible heat storage, which is preferably formed by means of a solid-state storage material or comprises a solid-state storage material. The solid-state storage material can, for example, be steel or comprise steel.

[0049] The second storage area 28 with the sensible heat storage 26 preferably forms a heat storage base body 30. In Fig. 1 The heat storage base body 30 is exemplified as a kind of base plate on which the phase-change heat storage unit 18 is attached (see also Fig. 3A). The heat dissipation arrangement 34 and / or the heat charging arrangement 32 are arranged, in particular, on and / or in the second storage area 28 and are thus directly thermally coupled to it. The heat dissipation arrangement 34 and the heat charging arrangement 32 are indirectly thermally coupled to the first storage area 20, which comprises the phase-change heat storage unit 18, by means of the second storage area 28. During charging operation, heat is transferred from the heat charging arrangement 32 to the sensible heat storage unit 26 and from there to the phase-change heat storage unit 18. During discharging operation, heat is transferred from the phase-change heat storage unit 18 to the sensible heat storage unit 26 and from there to the working fluid 12.

[0050] It is also possible to train using only a sensitive heat storage device 26 (see e.g. Fig. 3B, Fig. 11B) or a phase-change heat storage system 18 (see Fig. 11C).

[0051] The heat transfer arrangement 34 is designed for efficient heat transfer over a large temperature range, in particular as an evaporator arrangement, wherein the working fluid 12 undergoes a phase change from liquid to gaseous.

[0052] The thermal discharge of a sensible and / or latent heat storage device over a large temperature range of several hundred Kelvin places high demands on an evaporation system, during which different boiling ranges are traversed.

[0053] Fig. Figure 2 shows, in a diagram 90 with a heat flux density 91 versus a temperature delta of a wall temperature with respect to a saturation temperature 92, three boiling characteristic curves 93 for different flow conditions (stream boiling and tank boiling), also known as the Nukiyama curve, here according to "R. Maurus, Determination of bubble behavior in supercooled stream boiling with digital image sequence analysis," Dissertation, Technical University of Munich, 2003. Depending on the temperature delta, different boiling ranges are traversed, from free / forced convection 94, through partial nucleate boiling 95, fully developed nucleate boiling 96, transition boiling 97, and film boiling 98. Above a critical heat flux density (CHF) or wall superheat, a drop in the transferable heat flux occurs, also referred to as the "boiling crisis."In this process, a continuous vapor layer increasingly forms between the hot wall surface and the fluid, resulting in transition and film boiling. Besides performance losses due to such high wall superheating, this also leads to problems with heat dissipation control and high thermomechanical stresses due to the fluctuating behavior in the transition boiling range. A more detailed description of the various boiling ranges and calculation principles is available in the literature, for example, in the VDI Heat Atlas (VDI Society for Process Engineering and Chemical Engineering, VDI Heat Atlas, 11th ed. Berlin: Springer, 2013).

[0054] To avoid the disadvantages associated with the boiling crisis, known technical systems for thermal discharge by evaporation are generally operated well below a critical heat flux density, in the range of nucleate boiling or free / forced convection.

[0055] How Fig. As shown in Figure 1, the heat transfer system 10 according to the invention is designed as a multi-stage system, preferably an evaporation system (with the evaporator arrangement), to achieve the highest possible heat transfer performance over a wide temperature range. The heat transfer system 10 has at least two stages, in this example exactly two, a first stage 36 and a second stage 42, which are designed in particular as a first evaporator stage 38 and a second evaporator stage 44. The stages 36 and 42 are arranged in parallel in terms of flow direction (flow-technically connected in parallel) and can be operated either simultaneously in parallel or individually, with flow through only one of the stages 36 or 42.The first stage 36 has at least one first flow channel 78, preferably a group of first flow channels 78, and the second stage 42 has at least one second flow channel 80, preferably a group of second flow channels 80.

[0056] To distribute the working fluid 12 to the individual stages 36, 42, the conduit 60 between the reservoir 54 and the heat source 14 is divided into a first partial conduit 64 for conveying a first partial flow 66 of working fluid 12 and a second partial conduit 68 for conveying a second partial flow 70 of working fluid 12. In the Fig. In the embodiment shown in 1, the division takes place at the control valve 58 downstream of the conveying device 56 to convey the total flow of working fluid 12.

[0057] The first partial line 64 terminates at a first distribution device 40, which is assigned to the first stage 36. The second partial line 68 terminates at a second distribution device 46, which is assigned to the second stage 42. The distribution devices 40 and 46 are, in this case, designed specifically as tubular distribution strips.

[0058] As especially Fig. 3A and Fig. As shown in Figure 3B, the partial lines 64, 68 are divided by means of the distribution devices 40, 46 onto the flow channels 78, 80 of the respective stages 36, 42.

[0059] Downstream of the heat source 14, a collecting device 48, designed in particular as a collecting strip, is arranged, into which the flow channels 78, 80 open and in which the partial flows 66, 70 are combined again to form the total flow.

[0060] As well as Fig. 3A and Fig. As shown in Figure 3B, the distributor devices 40, 46 and / or the collecting device 48 are preferably arranged outside the heat dissipation arrangement 34 and, for example, without direct mechanical contact with it, in order to reduce the thermal load.

[0061] Stages 36 and 42 are designed such that the thermal resistance between the heat source 14 and the working fluid 12 differs between the individual stages 36 and 42 during operation. This means that (with comparable operating parameters such as mass flow rate, temperature difference, etc.) a different heat flux density would be established between the heat source 14 and the working fluid 12. In particular, the thermal resistance within the first stage 36 is increased compared to the second stage 42.

[0062] For this purpose, the heat dissipation arrangement 34 includes an arrangement for increasing the thermal resistance by increasing the thermal resistance in the first stage 36. The arrangement is placed between the heat source 14 and, preferably, each first flow channel 78 of the first stage 36 and increases the thermal resistance compared to the heat transfer between the heat source 14 and, preferably, each second flow channel 80 of the second stage 42.

[0063] Fig. Figure 4 shows a more detailed design of the heat dissipation arrangement 34 according to Fig. 1 in detailed illustrations and in schematic representation of the individual stages 36, 42, whereby the arrangement for increasing the thermal resistance is evident. How Fig. As shown in Figure 4, the arrangement has a gap 72 surrounding the first flow channel 78 (or each), in which a medium with low thermal conductivity, for example, less than 5 W / (mK), preferably less than 1 W / (mK), is arranged. The medium can be a gas, a liquid, and / or a solid. In a particularly advantageous and effective embodiment, the medium is air. The first flow channel 78 is completely surrounded by the gap 72 within the heat dissipation arrangement 34. The first flow channel 78 runs within an inner tube 76, which is surrounded by the gap 72. To form the gap 72, the inner tube 76 is positioned, in particular, in a bore through the second storage area 28 formed from the solid storage material. The bore has a slightly larger diameter than the outer diameter of the inner tube 76.Preferably, the inner tube 76 is mounted outside the heat dissipation arrangement 34 or the heat source 14.

[0064] The gap dimension (radial thickness) and the gap medium are selected such that the resulting heat flow from the heat source 14 to the inner tube 76 is as large as possible, but limited to such an extent that, particularly at the highest operating temperatures of the heat source 14, the critical heat flux density (at which the boiling point occurs) across the inner tube 76 during discharge operation is not exceeded, and preferably remains below the limit. When air is used as the medium, the technical order of magnitude of the gap width can be, for example, between 0.1 mm and 1 mm, but depending on the dimensions of the heat source 14, it may also be above or below this range. Heat transfer across the gap 72 occurs by conduction through the medium and, in the case of a gas, by thermal radiation.

[0065] In this way, the occurrence of a boiling crisis is advantageously avoided even at high temperatures, and improved performance and controllability of the thermal discharge are maintained over a wide operating temperature range of the heat storage system 10. Furthermore, the presence of the gap 72 around the inner tube 76 mechanically decouples it from the heat source 14. This significantly reduces the thermomechanical stress within the heat storage system 10.

[0066] How Fig. As further shown in Figure 4, the second flow channel 80 is formed in the second stage 42, preferably by means of the heat source 14. Each second flow channel 80 runs in a bore through the second storage area 28 formed by the solid storage material. The solid storage material forms the wall around the second flow channel 80, defining its boundaries. In this way, the working fluid 12 is in direct contact with the heat source 14 when flowing through the second stage 42 during operation; that is, the second stage 42 forms a stage with direct contact between the working fluid 12 and the heat source 14. This design allows for a comparatively high heat flux density, even with smaller temperature gradients between the working fluid 12 and the heat source 14, thus enabling efficient deep discharge of the heat storage device 16.

[0067] During the discharge operation of the heat transfer system 10, with heat transfer from the heat source 14 to the heat sink 50, the heat storage device 16 is discharged over a temperature difference of several hundred Kelvin, e.g., up to 400 K, 500 K, or 800 K. For example, the working fluid 12 has a maximum temperature (immediately downstream of the heat source 14) between 100 °C and 200 °C (at operating pressures between 1 and 2 bar) and / or the heat source 14 has a maximum operating temperature (at full heat charging) of up to 1000 °C, preferably up to 800 °C, e.g., up to 650 °C. The two stages 36, 42 of the heat source 14 can be controlled independently, with each stage operating individually without operating the other stage 36, 42, and / or in parallel (simultaneously), i.e., being supplied with working fluid 12. The discharge operation is, for example,with regard to a defined, for example constant, heat output from the heat source 14 and / or from the heat transfer system 10 by means of the further heat transfer medium, defined, controlled and / or regulated.

[0068] For control and / or regulation, the following is used in the Fig. In the embodiment shown in Figure 1, in particular, the total mass flow of working fluid 12, which flows through the heat dissipation arrangement 34 and is guided in the circuit 60, is controlled by the conveying device 56 and / or the ratio of the partial flows 66, 70 flowing through the individual stages 36, 42 is set by means of the control valve 58. This setting is made in particular depending on the temperature level within the heat source 14 and / or the required heat dissipation from the heat source 14.

[0069] At the in Fig. In the discharge operation shown in Figure 1, during which heat stored in the heat storage device 16 is released, the working fluid 12 is circulated in the closed circuit 60. The liquid working fluid 12 flows from the reservoir 54 via the conveying device 56 through the heat source 14, whereby heat is transferred from the heat source 14 by evaporation and / or sensible heating of the working fluid 12, depending on the temperature range (discharge temperature of the heat storage device 16). The heat-laden working fluid 12 is then directed into the heat sink 50, where it releases the absorbed heat energy to the subsequent heat transfer medium and preferably condenses. The working fluid 12 is then conveyed to the reservoir 54 by gravity and / or via the conveying device 56.Reservoir 54 is specifically designed to accommodate the entire liquid system volume of the working fluid 12.

[0070] Fig. Figure 1 shows the preferred operating mode during discharge operation at moderate and / or small temperature differences between a saturation temperature of the working fluid 12 and the heat source 14. A discharge cycle refers to the discharge of the heat storage device 16 between two charging cycles, wherein the temperature within the heat source 14 is maintained by means of the heat charging arrangement 32 (see Figure 1). Fig. 4) is increased. "Moderate temperature differences" are defined as those temperature differences at which, under the given operating conditions within the second stage 42, the critical heat flux density would be exceeded and which are below the high temperature differences. "Low temperature differences" are defined as those temperature differences at which, under the given operating conditions within the second stage 42, the critical heat flux density is not exceeded, i.e., which are below the moderate temperature differences.

[0071] At moderate and / or small temperature differences, both stages, the first stage 36 and the second stage 42, are traversed in parallel by the working fluid 12. Within the second stage 42, the direct contact of the working fluid 12 with the heat source 14 within the second flow channel 80 allows for a high heat transfer (compared to the first stage 36 and / or with respect to the maximum possible heat flux density), even with low wall superheating. Even at wall temperatures below the saturation temperature of the working fluid 12, heat can still be transferred by forced convection within the liquid working fluid 12 without evaporation. Preferably, when stage 2 is switched on to stage 1, according to the operating mode at the beginning of a discharge cycle (see Figure 1), the following applies: Fig. 5), initially only a small amount of fluid is passed through the second stage 42. The amount of fluid is preferably increased continuously with a smaller temperature difference (increasing discharge of the heat source 14), particularly depending on the required amount of heat (the required heat transfer). Accordingly, the amount of working fluid 12 passed through the first stage 36 can decrease, or, e.g., if separate conveying devices 56, 56' are present for each stage 36, 42 (see Figure 5). Fig. 9), remain constant.

[0072] Fig. Figure 5 shows the preferred operating mode during discharge operation at the beginning of a discharge cycle and / or at high temperature differences between the working fluid 12 and the heat source 14. A discharge cycle refers to the discharge of the heat storage device 16 between two charging cycles, wherein the temperature within the heat source 14 is controlled by the heat charging arrangement 32 (see Figure 5). Fig. 4) is increased. "High temperature differences" are defined as those temperature differences at which, under the given operating conditions within the second stage 42, the critical heat flux density would be exceeded and the temperature of the heat source 14 is greater than 75% of the maximum operating temperature in °C.

[0073] As in Fig. As symbolized by 5, in this operating mode only the first stage 36 is traversed by the working fluid 12, so that the first partial flow 66 corresponds to the total flow of working fluid 12 within the circuit 60. The second stage 42 is not traversed. Heat is transferred from the heat source 14 to the working fluid 12 via the first stage 36, whereby, due to the suitably designed increased thermal resistance in the first stage 36, the heat flux density does not exceed the critical heat flux density, but rather remains below it. In this way, a boiling crisis is avoided, and both the highest possible heat flux density and defined controllability are achieved during discharge operation.

[0074] Fig. Figure 6 shows a shutdown process of the discharge operation, as it can occur particularly at the end of a discharge cycle, before recharging by means of the heat charging arrangement 32. During the shutdown process, all the liquid working fluid 12 is collected in the reservoir 54, whereby the components of the circuit 60, comprising the heat source 14 including stages 36, 42, the distribution devices 40, 46, the collecting device 48, the other piping elements 62 and the heat sink 50, are emptied of the working fluid 12. The emptying can be gravity-driven and / or forced by means of the conveying device 56.

[0075] Fig. 7A and Fig. 7B each show in a diagram 100, 100' an example of an expected performance characteristic 102, 102' of the first stage 36 ( Fig. 7A) and the second stage 42 ( Fig. 7B) for a constant mass flow rate as a function of the temperature T of the heat source. How Fig. Figure 7A for the first stage 36 shows that the heat output Q' increases continuously with increasing temperature T of the heat source. The first stage 36 is designed such that the critical heat flux density, at which the boiling crisis occurs, is not reached even at the highest temperature T of the heat source, the maximum operating temperature. However, Figure 7A shows that the heat output Q' increases continuously with increasing temperature T of the heat source, the temperature T of the heat source, the temperature T of the heat source, the temperature T of the heat source, and the temperature T of the heat source. Fig. 7B After a sharp increase in the heat output Q', the boiling crisis occurs at the critical heat flux density, with the associated characteristic sharp drop in the heat output Q' and a subsequent smaller increase depending on the temperature T of the heat source. According to the invention, the second stage 42 is controlled and / or regulated such that it is operated, in particular, at temperatures T of the heat source at or below the critical heat flux density, i.e., through which the working fluid 12 flows. However, the second stage 42 can already be slowly switched on at temperatures T in the heat source 14 above the critical heat flux density, wherein preferably the proportion of the second partial flow 70 is smaller than the proportion of the first partial flow 66.

[0076] Fig. Figure 8 shows a diagram 100" with an exemplary expected performance characteristic 102" for a discharge operation controlled for constant heat output. The operation is controlled by the flow through the two stages 36, 42 to achieve a constant heat output from the heat source 14 and the heat transfer system 10, respectively. How Fig. Figure 8 shows that at a high temperature T of the heat source, the heat is dissipated exclusively via the first stage 36. The second stage 42 is not operated. At lower and / or moderate temperatures of the heat source 14, the second stage 42 is switched on in parallel with the first stage 36. By continuously increasing the proportion of the second partial flow 70 (see Figure 8), the heat is dissipated exclusively via the first stage 36. Fig. 1) The heat output Q' of the second stage 42 increases continuously, while the heat output Q' of the first stage 36 decreases due to a reduction in the temperature difference and / or the proportion of the first partial flow 66 (see Fig. 1) decreases.

[0077] Fig. Figure 9 shows a flowchart of a opposite Fig. Figure 1 describes a modified embodiment of the heat transfer system 10 with respect to the control elements, wherein instead of exactly one pumping device 56 for pumping the total flow of working fluid 12 in each sub-line 64, 68, a separate pumping device 56, 56' is arranged. The control valve 58 is not present. Preferably, the sub-lines 64, 68 run separately from each other from the reservoir 54 to the respective stage 36, 42. By means of the separate pumping devices 56, 56', both the proportions of the sub-flows 66, 70 to each other and the total mass flow of working fluid 12 are controlled and / or regulated during operation.

[0078] Fig. Figure 10 shows a variant of the sensible heat storage element 26, particularly in its function as a heat storage base body 30, which has a cylindrical cross-section. Stages 36 and 42 each have groups of flow channels 78 and 80 (two each shown here as examples), which are distributed within the heat storage base body 30. The heat charging arrangement 32, for example with heating cartridges, can also be arranged within the heat storage base body 30 and / or outside of it (in Fig. 10 not shown).

[0079] Fig. 11A to Fig. 11C each show a flowchart with a opposite Fig. 1 modified embodiment of the heat transfer system 10 with respect to the heat source 14. The in Fig. Figure 11A shows a modification regarding the arrangement of the second storage area 28 in the form of a heat storage base body 30, which in this example is arranged vertically for flow from top to bottom. An inclined arrangement is also possible, e.g., depending on the orientation of the heat storage device 16.

[0080] Fig. Figure 11B shows a flow diagram of the heat transfer system 10 with a further variant of the heat source 14. In this variant, the heat storage device 16 is designed exclusively as a sensible heat storage device 26, without a phase-change heat storage device 18. The storage material comprises, in particular, a solid-state storage material and / or is formed from it.

[0081] Fig. Figure 11C shows a flow diagram of the heat transfer system 10 with a further embodiment of the heat source 14. In this embodiment, the heat storage device 16 comprises exclusively, for example, the phase change material 22 and / or a granular storage material (not shown here) within the housing 24, without a heat storage base body 30 containing the solid storage material. The heat storage device 16 is specifically designed as a phase change heat storage device 18.

[0082] For use in the Fig. The design variant of the heat transfer system shown in Figure 11C includes 10 suitable designs for stages 36 and 42. Fig. 12A (first stage 36) and Fig.Figure 12B (second stage 42) shows the two stages 36 and 42, each having an outer tube 74 and 74' respectively, for connection to the surrounding storage material. In the first stage 36, the inner tube 76 for receiving the first flow channel 78 is arranged inside the outer tube 74. The gap 72 is located between the outer tube 74 and the inner tube 76. In the second stage 42, the second flow channel 80 is arranged inside and enclosed by the outer tube 74'.

[0083] In addition to the illustrated embodiments with the two stages 36, 42, other embodiments of the heat transfer system 10, not shown here, may contain more than two stages with different thermal resistances (under comparable operating conditions).

[0084] In summary, the heat transfer system 10 according to the invention provides an arrangement with efficient heat dissipation over a wide temperature range, which is also characterized by defined controllability and long service life due to minimized thermomechanical stress on components. With appropriate design of the heat source 14, the latent and / or sensible heat energy can be advantageously utilized optimally by means of a multi-stage design of the heat source 14.

[0085] The thermal storage system 10 according to the invention can be advantageously used in both stationary and mobile applications. The solution principle is particularly suitable for thermal storage applications that exhibit a high specific discharge power as well as a high volumetric and / or gravimetric power density. This is especially true for thermal storage devices 16 with metallic phase-change materials, but is not limited to these. The thermal storage system 10 can, for example, be advantageously used in battery-electric vehicle systems for heating the cabin and / or vehicle components. Battery-electric buses and / or trains offer particular application potential in this regard. Use in aerospace applications is also conceivable, such as wing de-icing in electric flight systems and / or the provision of thermal energy for a satellite / space station in orbit.Stationary applications can be found in energy and / or process engineering as buffer storage and / or in building technology for heat supply. Reference symbol list 10 Heat transfer system 12 Working fluid 14 Heat source 16 Heat storage device 18 phase-change heat storage systems 20 first memory area 22 Phase change material 24 Enclosure 26 sensible heat storage 28 second memory area 30 heat storage base units 32 Heat loading arrangement 34 Heat discharge arrangement 36 first stage 38 first evaporator stage 40 first distribution device 42 second stage 44 second evaporator stage 46 second distributor device 48 Collecting device 50 Heat sink 52 Heat exchanger device 54 Reservoir 56, 56' Conveyor 58 Control valve 60 Circulation 62 Conduit 64 first sub-management 66 first partial stream 68 second sub-leadership 70 second partial flow 72 gap 74, 74' outer tube 76 Inner tube 78 first flow channel 80 second flow channel 90 Diagram 91 Heat flux density 92 temperature difference 93 Boiling characteristic curve 94 Convection 95 partial cystitis 96 trained bladder boiling 97 Transitional boiling 98 film sets 100, 100', 100" diagram 102, 102', 102" Performance characteristics g weight force Q' transferred amount of heat T Temperature of the heat source QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 113 292 A1

[0002] DE 10 2020 107 464 A1

[0005] US 2019 / 0 339 013 A1

[0006] EP 3 379 191 B1

[0006] EP 3 708 923 B1

[0006] US 8 109 325 B2

[0006] DE 10 2015 107 427 A1

[0006] US 6 990 816 B1

[0007] Cited non-patent literature

[0000] VDI Society for Process Engineering and Chemical Engineering, VDI Heat Atlas, 11th ed. Berlin: Springer, 2013 [0003, 0053] F. Nees, J. Feine, A. Katourtzidis, V. Stahl, and W. Kraft, Heat extraction characteristics of a small scale metallic latent heat thermal energy storage system, “Proceedings of the 17th International Heat Transfer Conference, IHTC-17, Cape Town, South Africa, 2023, doi: 10.1615 / IHTC17.430-40 [0004, 0046] F. Nees, J. Feine, A. Katourtzidis, V. Stahl, and W. Kraft, Heat extraction characteristics of a small scale metallic latent heat thermal energy storage system “Proceedings of the 17th International Heat Transfer Conference, IHTC-17, Cape Town, South Africa, 2023, doi: 10.1615 / IHTC17.430-40

[0029] R. Maurus, Determination of bubble behavior during supercooled flow boiling using digital image sequence analysis, Dissertation, Technical University of Munich, 2003

[0053]

Claims

[1] Heat transfer system (10) with a heat source (14) and a heat sink (50), wherein the heat source (14) has a heat discharge arrangement (34) for heat discharge from the heat source (14) by means of a working fluid (12), wherein within the heat discharge arrangement (34) the working fluid (12) is thermally coupled or connected to the heat source (14), and wherein by means of the working fluid (12) the heat source (14) is thermally coupled or connected to the heat sink (50), characterized by , that the heat transfer arrangement (34) comprises at least two stages arranged parallel in terms of flow, a first stage (36) and a second stage (42), for heat transfer from the heat source (14) to the working fluid (12), wherein the stages (36, 42) are designed such that they have a different thermal resistance between the heat source (14) and the working fluid (12). [2] Heat transfer system (10) according to claim 1, characterized by , that the heat transfer arrangement (34) is designed as an evaporator arrangement, wherein the working fluid (12) is at least partially evaporable or evaporated in at least one of the at least two stages (36, 42) during operation. [3] Heat transfer system (10) according to claim 1 or 2, characterized by , that the heat dissipation arrangement (34) per stage (36, 42) comprises at least one flow channel, at least one first flow channel (78) of the first stage (36) and at least one second flow channel (80) of the second stage (42), for flow through with the working fluid (12). [4] Heat transfer system (10) according to claim 3, characterized by , that in the first stage (36) between the first flow channel (78) and the heat source (14) an arrangement is provided to increase the thermal resistance compared to the second stage (80). [5] Heat transfer system (10) according to claim 4, characterized by , that the arrangement for increasing thermal resistance has a gap (72) circumferential around the first flow channel (78), in which a medium with a low thermal conductivity, for example less than 5 W / (mK), preferably less than 1 W / (mK), is arranged, wherein the medium in particular comprises or is formed from a gas, e.g. air, a liquid and / or a solid, and wherein preferably the first flow channel (78) within the heat dissipation arrangement (34) runs in an inner tube (76) completely surrounded by the gap (72). [6] Heat transfer system (10) according to claim 5, characterized by, that the gap dimension is such that, taking into account the medium, the resulting heat flux from the heat source (14) to the inner tube (76) is limited to such an extent that, at the highest operating temperatures of the heat source (14), a critical heat flux density with respect to the working fluid (12) via the inner tube (76) is not exceeded, preferably not undercut, during the discharge operation. [7] Heat transfer system (10) according to claim 5 or 6, characterized by , that the inner tube (76) is located outside the heat dissipation arrangement (34). [8] Heat transfer system (10) according to any one of the preceding claims, characterized by , that in the second stage (42) the working fluid (12) can be brought into direct contact with the heat source (14), wherein in particular the second flow channel (80) is formed by means of the heat source (14). [9] Heat transfer system (10) according to any one of claims 3 to 8, characterized by, that at least in one stage (36, 42) between the heat source (14) and the flow channel (78, 80) an outer tube (74, 74') is arranged around the respective flow channel (78, 80). [10] Heat transfer system (10) according to any of the preceding claims, characterized by , that a working fluid circuit (60), in particular a closed circuit, with conveying means (62) for conveying the working fluid (12), in particular comprising the flow channels (78, 80), is present, in which, in addition to the heat source (14) and the heat sink (50), a reservoir (54) for the working fluid (12) and at least one conveying device (56, 56') are arranged. [11] Heat transfer system (10) according to claim 3 and 10, characterized by, that the conducting means (62) within the heat dissipation arrangement (34), preferably per stage (36, 42), comprise a group of flow channels (78, 80) connected in parallel to each other in terms of flow technology, wherein a distributor device (40, 46) for dividing the working fluid (12) onto the flow channels (78, 80) is arranged upstream of the group in terms of flow technology, which is arranged in particular in the form of a distributor strip outside the heat dissipation arrangement (34), and / or that a collecting device (48) for combining the working fluid (12) is arranged downstream of the group. [12] Heat transfer system (10) according to claim 10 or 11, characterized by, that between the reservoir (54) and the heat extraction arrangement (34) the conduit means (62) can be divided into at least one partial conduit (64, 68) per stage (36, 42) for dividing a total flow of working fluid (12) into one partial flow (66, 70) of working fluid (12) per stage (36, 42). [13] Heat transfer system (10) according to claim 12, characterized by , that exactly one conveying device (56, 56') and one control valve (58) are provided between the reservoir (54) and the heat dissipation arrangement (34), wherein the total flow of working fluid (12) flowing from the reservoir (54) can be divided or split into the partial flows (66, 70) by means of the control valve (58), and / or that in each sub-pipe (64, 68) a conveying device (56, 56') is provided, wherein preferably the sub-pipes (64, 68) run separately from the reservoir (54) to the respective stage (36, 42) of the heat extraction arrangement (34). [14] Heat transfer system (10) according to any of the preceding claims, characterized by , that the heat source (14) is designed as a heat storage device (16), in particular as a high-temperature heat storage device, which has a heat charging arrangement (32) which is designed in particular for generating heat by means of electrical energy. [15] Heat transfer system (10) according to claim 14, characterized by , that the heat storage device (16) is designed as a phase-change heat storage device (18) comprising a storage material arranged in a housing (24) of the heat storage device (16), which is formed by or comprises a phase-change material (22), in particular a metallic one. [16] Heat transfer system (10) according to claim 14 or 15, characterized by , that the heat storage device (16) is designed as a sensible heat storage device (26) which comprises a storage material for sensible heat storage, in particular a solid storage material. [17] Heat transfer system (10) according to claim 16, characterized by , that the sensible heat storage (26), in particular the solid storage material, is at least substantially cuboid and / or cylindrical in shape. [18] Heat transfer system (10) according to claim 15 and claim 16 or 17, characterized by , that the heat storage device (16) comprises a first storage area (20), with the phase-change heat storage (18) and a second storage area (28), with the sensible heat storage (26), which are thermally coupled to each other, in particular attached to each other. [19] Heat transfer system (10) according to claim 18, characterized by, that the heat dissipation arrangement (34) and / or the heat charging arrangement (32) are thermally directly coupled to the second storage area (28), in particular arranged on and / or in it, wherein the sensible heat storage (26) forms a heat storage base body (30), and / or that the heat discharge arrangement (34) and / or the heat charging arrangement (32) is / are indirectly thermally coupled to the first storage area (20) by means of the second storage area (28). [20] Heat transfer system (10) according to any of the preceding claims, characterized by, that the heat sink (50) is formed by a heat exchange device (52), in particular for the condensation of the working fluid, which is permeable or permeated on the one hand by the working fluid (12) and on the other hand by a further heat transfer medium, e.g. air or a water-glycol mixture, for the transfer of heat absorbed from the heat source (14) to the further heat transfer medium. [21] Method for operating a heat transfer system (10), which is designed in particular according to one of the preceding claims, in which, during a discharge operation, heat is transferred from a heat source (14) to a heat sink (50) by means of a working fluid (12), wherein, for the purpose of heat removal from the heat source (14), a heat removal arrangement (34) is flowed through by the working fluid (12), characterized by, that within the heat dissipation arrangement (34) at least two stages (36, 42), a first stage (36) and a second stage (42), can be flowed through individually or in parallel by the working fluid (12), wherein the individual stages (36, 42) have a different thermal resistance to each other. [22] Method according to claim 21, characterized by , that the discharge operation is controlled and / or regulated with regard to a defined heat discharge, whereby a total mass flow rate of working fluid (12) which flows through the heat discharge arrangement (34) and / or a ratio of partial mass flow rates of working fluid (12) which flow through the individual stages (36, 42) is / are set. [23] Method according to claim 21 or 22, characterized by, that at the beginning of a discharge cycle of the discharge operation and / or at high temperature differences between the heat source (14) and a saturation temperature of the working fluid (12) a proportion of the working fluid (12) through the first stage (36), with the highest thermal resistance, is greatest, wherein in particular the partial mass flow through the second stage (42), and possibly the other stages, is zero. [24] Method according to claim one of claims 21 to 23, characterized by , that with moderate and / or small temperature differences between the heat source (14) and a saturation temperature of the working fluid (12) both stages (36, 42) are flowed through in parallel or only the second stage (42) is flowed through with the working fluid (12). [25] Method according to any one of claims 21 to 24, characterized by, that during a shutdown process of the discharge operation the working fluid (12) is emptied from the heat dissipation arrangement (34), preferably from all components and conduit media (62) arranged in a circuit (60) and is collected in a reservoir (54).

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