Heat transfer system having a heat source and a heat sink and method for operating a heat transfer system
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- DEUTSCHES ZENTRUM FÜR LUFT UND RAUMFAHRT E V
- Filing Date
- 2026-01-22
- Publication Date
- 2026-07-30
Smart Images
Figure EP2026051576_30072026_PF_FP_ABST
Abstract
Description
[0001] JECK, FLECK & PARTNER mbB P.O. Box 1469 • D-71657 Vaihingen / Enz PATENTA NWÄ LTE Telephone (07042) 9728 - 0
[0002] Fax (07042) 9728 - 11
[0003] A25834-PCT - JF / construction January 22, 2026
[0004] German Aerospace Center (DLR)
[0005] Königswinterer Str. 522 - 524
[0006] 53227 Bonn
[0007] - 1 -
[0008] Heat transfer system with a heat source and a heat sink and method for operating a heat transfer system
[0009] 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 removal from the heat source during a discharge operation by means of a working fluid, wherein within the heat discharge arrangement the working fluid is thermally coupled or coupled to the heat source, wherein the heat discharge arrangement is designed as an evaporator arrangement with a first channel arrangement, within which the first working fluid is at least partially evaporable or evaporated during operation, and wherein the heat source is thermally coupled or coupled to the heat sink by means of the working fluid, as well as a method for operating a heat transfer system.
[0010] 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 liquid working fluid flows upwards. [A 25834-PCT - JF / bau - 2 - 22 January 2026]
[0011] The fluid is transported against the direction of gravity and from there conveyed into an evaporator section. Evaporation takes place vertically downwards in a porous metal foam in contact with the heat source.
[0012] 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, presents 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 "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.
[0013] 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 zone, which A 25834-PCT - JF / bau - 3 - 22 January 2026
[0014] It is 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.
[0015] DE 102020 107464 A1 discloses a heat storage device with a metallic phase-change material as the storage material, comprising 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.
[0016] Further heat exchange devices are known from US 2019 / 0339013 A1, EP 3 379 191 B1, EP 3 708 923 B1, US 8 109 325 B2 and DE 10 2015 107 427 A1.
[0017] US 6 990 816 B1 shows a cooling arrangement with an evaporator and a condenser.
[0018] DE 10 2014 212 188 A1 discloses a heat transfer device with a storage unit and a first channel for transporting a first medium, as well as a second channel for transporting a different second medium. Heat transfer takes place between at least one of the two media and the storage unit, which may contain a phase-change material. After a cold start of a vehicle, the two cooling media are heated by the phase-change material via heat transfer surfaces. In this way, the warm-up of a motor vehicle engine can be accelerated. During operation, the phase-change material can be recharged for another cold start by releasing heat from the respective cooling medium. A 25834-PCT - JF / bau - 4 - January 22, 2026
[0019] German patent DE 10 2023 001 326 A1 discloses a system for high-temperature storage and energy conversion with a high-temperature storage unit 13. The high-temperature storage unit can comprise a latent heat storage unit and a sensible heat storage unit, consisting of a storage material bed. To extract the high-temperature heat, gas is conveyed through the storage material bed. In the event of deep discharge, the heat can be transferred to a heater, which comprises a heat transfer medium in gaseous or liquid form.
[0020] 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 heat output can be achieved over a large operating temperature range.
[0021] The problem is solved for the heat transfer system with the features of claim 1 and for the method with the features of claim 17.
[0022] The heat transfer system is designed in such a way that it is possible to switch between heat discharge from the heat discharge arrangement by means of (at least) two different working fluids, a first working fluid, in particular one that is evaporable (within the operating temperature range), and / or a second working fluid, in particular one that is gaseous (within the operating temperature range), within a discharge cycle of the discharge operation.
[0023] The heat transfer arrangement is designed for thermal coupling with the first working fluid and / or with the second working fluid, in particular for heat transfer to the first and / or the second working fluid by means of flow through them. For its design as an evaporator arrangement, the flowable (total) volume and / or the total flow cross-section of the ers-A 25834-PCT - JF / bau - 5 - January 22, 2026
[0024] The channel arrangement (i.e., the sum of the flow cross-sections of all flow channels of the same) is designed accordingly.
[0025] The volatile working fluid can be composed of or contain water. The gaseous working fluid can be composed of or contain CO2.
[0026] The discharge mode represents the operation during the thermal discharge of the heat source, during which heat is transferred from the heat source to the working fluid. The discharge cycle constitutes a discharge operation between two charging cycles. During the charging cycles, thermal energy is supplied to the heat source in a charging operation.
[0027] In particular, the heat transfer system for controlling and / or regulating the discharge operation includes a suitably designed control device and / or a suitably designed control device is assigned to the heat transfer system.
[0028] In this way, a kind of hybrid heat transfer system is provided, which advantageously avoids or reduces the effects of a boiling crisis even at high temperatures of the heat source (for example, more than 500 °C) during operation, while also achieving a comparatively high heat transfer rate at low and / or moderate temperatures, with a high and defined heat output.
[0029] 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, in particular for generating heat by means of electrical energy, and in particular comprising at least one heating element. The maximum operating temperatures (at full heat charging) of the heat storage device-A 25834-PCT - JF / bau -6 - January 22, 2026
[0030] The temperature of the device, when designed as a high-temperature heat storage device, can be 500 °C or more, in particular up to 1000 °C, preferably up to 800 °C, e.g. up to 650 °C.
[0031] In a suitable 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.
[0032] Alternatively or additionally, the heat storage device is preferably 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, in particular, be in the form of a solid material and be, for example, made of or comprise steel. A storage material in granular form is also possible, which is arranged, in particular, in an enclosure.
[0033] Advantageous design options arise when the sensible heat storage, in particular the solid storage material, is at least essentially cuboid and / or cylindrical in shape.
[0034] A wide operating temperature range is achievable if the heat storage device comprises a first storage area, containing the phase-change heat storage, and a second storage area, containing the sensible heat storage, which are thermally coupled, in particular mechanically connected. The second storage area can, in particular, comprise the solid storage material, which, for example, is plate-like and has a comparatively low profile (e.g., at least three times lower than the first storage area). The phase-change heat storage (with the housing and the phase-change A 25834-PCT - JF / bau - 7 - January 22, 2026)
[0035] The material (e.g., [material]) is in contact with the plate over a flat surface and is, in particular, attached to the plate. An embodiment of a heat storage device of this type is given, for example, 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", wherein the heat transfer arrangement has a different design.
[0036] 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, any existing 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.
[0037] In a suitable embodiment, the heat sink is formed by a heat exchanger, particularly for the condensation of the first working fluid. This heat exchanger is permeable (or already permeated) on one side (hot side) by the first working fluid and / or the second working fluid, and on the other side (cold side) by another heat transfer medium, such as air or a water-glycol mixture, for the transfer of heat absorbed from the heat source to the other heat transfer medium. Alternatively or additionally, the heat exchanger serves to cool superheated vapor of the working fluid to saturation temperature and / or to cool any condensate that forms. This embodiment allows heat that is discharged to be directed to another area. (A 25834-PCT - JF / bau - 8 - January 22, 2026)
[0038] for example, a vehicle component or a vehicle interior that needs to be transported for conditioning.
[0039] Preferably, the heat transfer arrangement comprises a second channel arrangement in the form of a gas channel arrangement, which is optimized for heat transfer to a gas (which forms the second working fluid). As optimization measures, the gas channel arrangement has a larger total flow cross-section (i.e., the sum of the flow cross-sections of all flow channels of the gas channel arrangement) than the first channel arrangement and / or a larger surface area for heat transfer. The gas channel arrangement and the first channel arrangement (in particular, an evaporator arrangement) can, for example, be arranged in different planes with respect to the direction of gravity within the heat storage base. For example, the gas channel arrangement is arranged below the first channel arrangement.To optimize heat transfer, the gas channel arrangement can have a heat conduction structure, for example a rib structure, which can be arranged between the individual flow channels of the gas channel arrangement.
[0040] Advantageously, the heat transfer system is provided to comprise a first circuit, preferably a closed circuit, for conveying the first working fluid with first conveying means, and (at least) a second circuit, preferably a closed circuit, for conveying the second working fluid with second conveying means, within which the heat source and the heat sink are arranged so that the first and second working fluids can flow through them, and which preferably each include a conveying device. The first circuit is preferably designed as an evaporation-condensation circuit, wherein the conveying device is preferably arranged in the form of a liquid pump in a section of the first circuit through which liquid flows. The second circuit is preferably designed as a pure gas circuit, wherein the conveying device preferably includes a blower. The conveying devices die-A 25834-PCT - JF / bau - 9 - 22.January 2026.
[0041] especially for controlling and / or regulating the mass flow of the first working fluid and / or the second working fluid.
[0042] To accommodate the entire volume of the first working fluid, e.g., when the system is switched off and / or as a buffer against pressure changes within the first circuit, a reservoir may be provided, at least in the first circuit. The reservoir is appropriately sized. Alternatively, with appropriate sizing, the piping system (the first piping elements) or another device may perform one or both of these functions.
[0043] In one design variant, the first and second circuits can be completely decoupled from each other (and not connectable), with the reservoir being located exclusively in the first circuit. The piping of the two circuits is completely separate. The heat exchanger can be, for example, a three-stream heat exchanger or two heat exchangers arranged in series or parallel. This decoupled design advantageously allows for an increase in the gas pressure in the second circuit, for example, to a level between 5 bar and 10 bar, which significantly improves heat transfer relative to ambient pressure.
[0044] In a particularly alternative design variant, it is provided that the first circuit and the second circuit are fluidically coupled or can be coupled, whereby, in particular, the first and second piping elements between the heat source and the reservoir are identical. The same pressure level prevails in both circuits. The first and second piping elements are at least partially identical, i.e., the first piping elements also form the second piping elements at least partially, and are supplied simultaneously or sequentially by both the first and second circuits. (Ar-A 25834-PCT - JF / bau - 10 - 22 January 2026)
[0045] The system is permeated by both the working fluid and the second working fluid. This advantageously allows for a more compact and simpler design of the heat transfer system, particularly with regard to the piping and / or the heat exchanger.
[0046] Particularly in this context, it can be advantageously provided that the reservoir is arranged in the first circuit and in the second circuit, wherein a first extraction point of the first circuit for extracting the liquid first working fluid and a second extraction point of the second circuit for extracting the gaseous second working fluid are arranged on the reservoir. Alternatively or additionally, the first and second piping elements between the reservoir and the heat source are preferably designed to be at least partially separate from one another, with the conveying devices in particular being arranged in these separate piping sections.
[0047] Furthermore, it can be advantageously provided, particularly in this context, that the heat source (concerning the channel arrangements for discharging, in addition to the loading arrangement) comprises exclusively the first channel arrangement, not the second channel arrangement, which is arranged within the first and second conduit means, through which the first working fluid and / or the second working fluid flows. That is to say, the first and second conduit means are identical in this section.
[0048] For efficient heat transfer, the first conduit means preferably comprise, within the heat transfer arrangement, a first group of first flow channels connected in parallel to each other in terms of flow characteristics, and (if present) the second conduit means comprise a second group of second flow channels connected in parallel to each other in terms of flow characteristics. A distribution device for dividing (a total flow) of the first working fluid and / or (a total flow) of the A 25834-PCT - JF / bau - 11 - 22 January 2026
[0049] The second working fluid is introduced upstream of the first flow channels and, if applicable, the second flow channels, in a flow-optimized manner, particularly in the form of a distribution strip located outside the heat dissipation arrangement. Alternatively or additionally, a collecting device for combining the first working fluid and / or the second working fluid into the overall flow is expediently connected downstream of the first group and, if applicable, the second group.
[0050] According to the invention, the method for operating a heat transfer system provides that the heat dissipation arrangement can be simultaneously and / or sequentially flushed with a first working fluid and a second working fluid during a discharge cycle of the discharge operation. For this purpose, it is possible to switch between discharge operation exclusively with the first working fluid, exclusively with the second working fluid, or with both working fluids simultaneously (in parallel) in a single flow.
[0051] Preferably, the discharge operation is controlled and / or regulated with respect to a defined heat transfer, whereby a mass flow rate of the first and / or second working fluid, which flows through the heat transfer arrangement, is set, particularly as a function of a temperature difference between the heat source and a saturation temperature of the first working fluid. The heat transfer can relate to the heat source and / or to the entire heat transfer system. The heat transfer can, for example, be constant or adapted to a requested heat demand of a system to be tempered, into which the heat is transported via the heat sink.
[0052] In one process variant for improving heat dissipation, it is provided that the first working fluid is circulated in a first circuit and the second working fluid in a second circuit, which are completely decoupled in terms of flow technology, whereby a higher flow rate is maintained at least temporarily in the second circuit. A 25834-PCT - JF / bau - 12 - 22 January 2026
[0053] The pressure is set as ambient pressure and / or as in the first circuit, for example between 2 bar and 15 bar, preferably between 5 bar and 10 bar. Alternatively, the circuits can be coupled, with the same pressure prevailing in both circuits.
[0054] In a particularly preferred operating mode, at the beginning of a discharge cycle and / or when there are high temperature differences between the heat source and the saturation temperature of the first working fluid, the heat dissipation arrangement is exclusively permeated by the second working fluid. "High temperature differences" are defined in particular as those at which, under the prevailing operating conditions, the critical heat flux density of the first working fluid would be exceeded and the temperature of the heat source is greater than 75% of the maximum operating temperature (maximum temperature of the heat source during operation of the heat transfer system) in °C.
[0055] In this way, a boiling crisis can be advantageously avoided even at high operating temperatures of the heat source. This ensures not only a comparatively high heat flow density but also defined controllability.
[0056] 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, the heat dissipation arrangement is flowed through by both working fluids simultaneously or exclusively by the first working fluid. "Moderate temperature differences" are defined as those at which, under the given operating conditions, the critical heat flux density would be exceeded with respect to the first working fluid 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 of the first working fluid would not be exceeded. A 25834-PCT - JF / bau - 13 - January 22, 2026
[0057] The heat flow density is not exceeded, i.e., those that lie below the moderate temperature differences.
[0058] The high, moderate, and low temperature differences are defined in such a way as to cover the entire operating temperature range of the heat source. The corresponding temperature differences for the respective operating conditions can be estimated using the first working fluid and methods described in the literature (e.g., the VDI Heat Atlas).
[0059] Preferably, during a shutdown process of the discharge operation, the first working fluid is emptied from the heat dissipation arrangement, preferably from all components and conduits arranged in a first circuit, and collected in a reservoir.
[0060] The invention will now be explained in more detail using exemplary embodiments and with reference to the drawings. The drawings show:
[0061] Fig. 1 shows a flow diagram of a heat transfer system according to the invention with a heat source and a heat sink, wherein the heat source has a heat discharge arrangement for simultaneous or alternating flow with a first working fluid and a second working fluid, at the beginning of a discharge cycle of a discharge operation,
[0062] Fig. 2 shows a diagram with boiling characteristics for tank and flow boiling,
[0063] Fig. 3 shows a flow diagram of the heat transfer system according to Fig. 1 during discharge operation at moderate and / or small temperature differences, A 25834-PCT - JF / bau - 14 - 22 January 2026
[0064] Fig. 4 shows a flow diagram with a modified version of the heat transfer system compared to Fig. 1 with regard to the heat source and circuits, at the beginning of a discharge cycle of a discharge operation.
[0065] Fig. 5 shows a flow diagram of the heat transfer system according to Fig. 4 during discharge operation at moderate and / or small temperature differences.
[0066] Fig. 6 shows a flow diagram of the heat transfer system according to Fig. 4 during a shutdown process of the discharge operation.
[0067] Fig. 7 shows a schematic cross-sectional representation of a sensible heat storage device for the heat source.
[0068] Fig. 8A, B two diagrams each with an exemplary expected performance characteristic when operating with the first working fluid (Fig. 8A) and with the second working fluid (Fig. 8B),
[0069] Fig. 9 shows a diagram with an exemplary expected performance characteristic for a discharge operation of the heat transfer system controlled for a constant heat output,
[0070] Fig. 10 shows a flow diagram of the heat transfer system with one possible design variant of the heat source.
[0071] Fig. 11 shows a possible design variant of the heat source in cross-sectional view along a longitudinal axis, and A 25834-PCT - JF / bau - 15 - 22 January 2026
[0072] Fig. 12 shows a flow diagram of the heat transfer system with another possible design variant of the heat source.
[0073] Fig. 1 shows a flow diagram of a heat transfer system 10 with a heat source 14 and a heat sink 50, which are thermally coupled. The heat source 14 has a heat discharge arrangement 34, which is designed for heat transfer from the heat source 14 by means of a vaporizable working fluid as the heat transfer fluid. The vaporizable working fluid is subsequently referred to as the first working fluid 12 and is selected such that, under the given operating conditions, it vaporizes within the heat source 14 and condenses completely within the heat sink 50. For example, the first working fluid 12 is made of or contains water.
[0074] Within the heat dissipation arrangement 34, the first working fluid 12 is thermally coupled to the heat dissipation arrangement 34 in a discharge operation, whereby heat is transferred from the heat source 14 to the first working fluid 12. For the purpose of conveying the first working fluid 12 through the heat dissipation arrangement 34, the heat dissipation arrangement 34 has at least a first channel arrangement 36 with at least one first flow channel 78.
[0075] The heat sink 50 is designed as a heat exchanger 52, in particular as a condenser, within which the vaporized first 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 first working fluid 12 to saturation temperature and / or to subcool any condensate that has formed.
[0076] The heat source 14 is designed in particular 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 A 25834-PCT - JF / bau - 16 - 22 January 2026
[0077] 500 °C and 1000 °C. The heat storage device 16 has a heat loading arrangement 32 (see Fig. 7), which is preferably designed for generating heat by means of electrical energy and for this purpose comprises, for example, at least one electric resistance heater, in particular a heating cartridge.
[0078] 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 between the first storage area 20 and the second storage area 28 takes place 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" is specified, whereby in this known heat storage device the heat discharge is solved differently than in the heat storage system 10 according to the invention.
[0079] The phase-change heat storage device 18 comprises a preferably metallic phase-change material 22, which is arranged in an enclosure 24 of the phase-change heat storage device 18. The phase-change material is, for example, formed from or comprises AlSii 2.
[0080] The sensible heat storage device 26 comprises a storage material for sensible heat storage, preferably formed by means of a solid-state storage material or comprising a solid-state storage material. The solid-state storage material can, for example, be steel, e.g., be made of steel. A 25834-PCT - JF / bau - 17 - January 22, 2026
[0081] The second storage area 28, comprising the sensible heat storage element 26, preferably forms a heat storage base 30. In Fig. 1, the heat storage base 30 is shown by way of example in the form of a kind of base plate, on which the phase-change heat storage element 18 is mounted. The heat discharge 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 discharge arrangement 34 and the heat charging arrangement 32 are indirectly thermally coupled to the first storage area 20, comprising the phase-change heat storage element 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 element 26 and from there to the phase-change heat storage element 18.During discharge operation, the heat is transferred from the phase-change heat storage 18 to the sensible heat storage 26 and from there to the working fluid 12.
[0082] It is also possible to design the system with only a sensible heat storage unit 26 or only a phase-change heat storage unit 18, in particular without the heat storage base body 30 (see Fig. 12).
[0083] The heat transfer arrangement 34 is designed as an evaporator arrangement 38 for efficient heat transfer over a large temperature range, wherein the first working fluid 12 undergoes a phase change from liquid to gaseous within the first channel arrangement 36.
[0084] In general, the thermal discharge of a heat storage system over a large temperature range, from several hundred Kelvin, places high demands on an evaporation system, passing through different boiling ranges.
[0085] Fig. 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 at-A 25834-PCT - JF / bau - 18 - 22 January 2026
[0086] Three boiling characteristic curves 93 for different flow conditions (flow boiling and container boiling), also known as the Nukiyama curve, are shown here according to "R. Maurus, 'Determination of bubble behavior during supercooled flow boiling using digital image sequence analysis,' Dissertation, Technical University of Munich, 2003". Depending on the temperature delta, various 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 decrease in the transferable heat flux occurs, also referred to as the "boiling crisis". Here, a continuous vapor layer increasingly forms between the hot wall surface and the fluid, resulting in transition and film boiling.In addition to performance losses due to such high wall superheating, this also results in problems regarding the controllability of heat dissipation and high thermomechanical stresses due to the fluctuating behavior in the transition boiling range. 97 A more detailed description of the various boiling ranges and calculation principles is available in the literature, for example, in addition to the source mentioned above, also in the VDI Heat Atlas (VDI Society for Process Engineering and Chemical Engineering, VDI Heat Atlas, 11th ed. Berlin: Springer, 2013).
[0087] To avoid the disadvantages associated with 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.
[0088] The heat transfer system 10 according to the invention, shown in Fig. 1, is designed to achieve the highest possible heat transfer performance over a large temperature range such that a heat discharge from the heat discharge arrangement 34 is achieved by means of at least two different working fluids within a discharge cycle of the discharge operation (thermal discharge of the A 25834-PCT - JF / bau - 19 - 22 January 2026
[0089] The heat storage device 16 can be switched (with heating of the working fluid). The design according to the invention advantageously avoids or minimizes the occurrence of a boiling crisis even at high temperatures and provides improved performance and controllability of the thermal discharge over a large operating temperature range of the heat storage system 10.
[0090] One of the working fluids is the first working fluid 12, which is at least partially liquid during discharge operation. A second working fluid 13 is gaseous throughout the entire discharge cycle within the entire heat transfer system 10. The second working fluid 13 is, for example, formed by or contains CO2.
[0091] The heat transfer system 10 comprises a first circuit 60, in particular a closed circuit, for conveying the first working fluid 12, with first conveying means 62. Furthermore, the heat transfer system 10 comprises a second circuit 61, in particular a closed circuit, for conveying the second working fluid 13, with second conveying means 63.
[0092] In this way, the heat transfer system 10 is designed as a hybrid heat transfer system, with the liquid-based first circuit 60, wherein the liquid is evaporated in the heat source 14 and condensed in the heat sink 50 according to an evaporation-condensation cycle, and with at least one further fluid circuit, the second circuit 61, wherein the heat transfer occurs due to forced convection of the single-phase, gaseous, second working fluid 13. During discharge operation with high temperature differences between the heat source 14 and a saturation temperature of the first working fluid 12, particularly during the start-up process, only the second circuit 61 (gas circuit) is activated. At moderate and / or low temperature differences, the first circuit 60 is activated in addition to or alternatively to the second circuit 61. A 25834-PCT - JF / bau - 20 - January 22, 2026
[0093] For the control and / or regulation of the discharge operation, the heat transfer system 10 has in particular a control device and / or a control device (e.g. in a higher-level plant control system) is assigned to it.
[0094] To accommodate at least the first working fluid 12, a reservoir 54 is arranged in at least the first circuit 60, for example, with respect to a weight force g below the heat source 14. The reservoir 54 has a volume such that, in states where the circuit 60 is not in operation, at least all of the first working fluid 12 in the circuit 16 can be accommodated. Furthermore, the reservoir 54 can serve as a buffer against pressure changes within the heat transfer system 10. It is also possible to dispense with the reservoir and dimension the piping 62, 63 in such a way that they can take over the function of the reservoir 54. Alternatively, the reservoir can be replaced by another device that performs the function of the reservoir 54.
[0095] In the first circuit 60 and in the second circuit 61, a conveying device 56, 56' is arranged for conveying the first working fluid 12 and the second working fluid 13 respectively, which in the first circuit 60 is designed, for example, as a liquid pump and in the second circuit 61, for example, as a blower.
[0096] The heat source 14 and the heat sink 50 are arranged in both the first circuit 60 and the second circuit 61.
[0097] In the embodiment shown in Fig. 1, the first circuit 60 and the second circuit 61 are fluidically coupled. The first conduit 62 and the second conduit 63 are identical, particularly within the heat dissipation arrangement 34 and between the heat source 14 and the reservoir 54. A 25834-PCT - JF / bau - 21 - 22 January 2026
[0098] Between reservoir 54 and heat source 14, the first conduit 62 and the second conduit 63 are separated from each other in sections. In this section, the first conduit 62 has a first conduit section 64 for conveying a liquid flow 66 of first working fluid 12. The second conduit 63 has a second conduit section 68 for conveying the second working fluid 13. The conveying devices 56, 56' are arranged in the first conduit section 64 and the second conduit section 68, respectively.
[0099] To ensure the controlled supply of the first working fluid 12 and / or the second working fluid 13 to the heat source 14, a valve assembly 58, 58' is arranged within each of the line sections 64, 68. To prevent the first and / or the second working fluid 12, 13 from flowing into the line sections 64, 68 of the respective other circuit 60, 61, the valve assemblies 58, 58' are preferably designed as check valves.
[0100] Downstream of the valve devices 58, 58', the line sections 64, 68 open into a first distribution device 40 for distributing the first working fluid 12 and / or the second working fluid 13 to the first channel arrangement 36. In the embodiment shown in Fig. 1, the first distribution device 40 and the first channel arrangement 36 are thus arranged in both the first circuit 60 and the second circuit 61 and can be permeated by the first working fluid 12 and / or the second working fluid 13.
[0101] Reservoir 54 is integrated into both the first circuit 60 and the second circuit 61. A first extraction point 82 of the first circuit 60 for extracting the liquid first working fluid 12 and a second extraction point 84 of the second circuit 61 for extracting the gaseous second working fluid 13 are located on or in the reservoir 54. The first extraction point 82 is located, in particular, on a lower side with respect to the direction of gravity g within A 25834-PCT - JF / bau - 22 - January 22, 2026
[0102] of reservoir 54, where the liquid first working fluid 12 collects. The second sampling point 84 is located, in particular, on an upper side of reservoir 54 with respect to the direction of gravity g, where the gaseous second working fluid 13 collects.
[0103] Between the first channel arrangement 36 and the heat sink 50 a first collecting device 48 is arranged, in which, during discharge operation, the at least partially evaporated first working fluid 12 and / or the second working fluid 13 is collected from the first channel arrangement 36 and combined into a total flow for forwarding to the heat sink.
[0104] The distributor device 40 and / or the collector device 48 is / 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.
[0105] 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, up to 400 Kelvin, 500 Kelvin, or 800 Kelvin. For example, the first working fluid 12 and / or the second working fluid 13 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, up to 650 °C. The two circuits 60 and 61 can be controlled independently, with the working fluids 12 and 13 flowing through the heat source 14 sequentially and / or simultaneously (in a mixed flow). The unloading 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. A 25834-PCT - JF / bau - 23 - January 22, 2026.
[0106] For control and / or regulation, in the embodiment shown in Fig. 1, a mass flow of first working fluid 12 and / or second working fluid 13, which flows through the heat dissipation arrangement 34 and is guided in the first circuit 60 and / or second circuit 61, is adjusted by means of the conveying device 56 and / or the conveying device 56'. The adjustment 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.
[0107] Fig. 1 shows the preferred operating mode during discharge operation at high temperature differences between the saturation temperature of the first working fluid 12 and the heat source 14, particularly at the beginning (during the start-up process) of a discharge cycle, between two charging cycles. In this mode, the heat dissipation arrangement 34 is exclusively permeated by the gaseous second working fluid 13, whereby heat is transferred to the single-phase second working medium 13. The heat-laden second working fluid 13 is then directed into the heat sink 50, where the absorbed heat energy is transferred to the further heat transfer medium. Subsequently, the second working fluid 13 is directed into the reservoir 54.
[0108] Fig. 3 shows the heat transfer system according to Fig. 1 in a preferred operating mode during discharge operation at moderate and / or small temperature differences between the saturation temperature of the first working fluid 12 and the heat source 14.
[0109] For moderate and / or small temperature differences, circuits 60 and 61 are operated in parallel as an example, and thus the heat source 14 is supplied in parallel with the first working fluid 12 and the second working fluid 13, whereby the first working fluid 12 in particular evaporates at least partially. A high heat transfer can be achieved by means of the first working fluid 12 even with slight wall superheating. This is also the case at wall temperatures below the saturation temperature of the A 25834-PCT - JF / bau - 24 - January 22, 2026
[0110] Heat can be dissipated from the first working fluid 12 by convection within the liquid working fluid 12 without evaporation. Preferably, when the first circuit 60 is switched on, according to the operating mode at the beginning of a discharge cycle (at high temperature differences), only a small proportion or mass flow of the first working fluid 12 is initially switched on. The amount of fluid in the first working fluid 12 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 dissipation). Accordingly, the amount of second working fluid 13 conveyed by the second circuit 61 can decrease or remain constant.
[0111] Fig. 4 shows a further embodiment of the heat transfer system 10, wherein the first circuit 60 and the second circuit 61 are completely decoupled from each other in terms of pressure. The heat dissipation arrangement 34 comprises a second channel arrangement 42 located in the second circuit 61, with at least one flow channel 80, preferably a group of second flow channels 80 connected in parallel to each other in terms of flow. A second distributor arrangement 46 for distributing the second working fluid 13 to the individual flow channels 80 is connected upstream of the second channel arrangement 42, and a second collecting device 49 for combining the individual flows of the second working fluid 13 into a single overall flow is connected downstream.
[0112] The second channel arrangement 42 is specifically designed as a gas channel arrangement 44, which is optimized for heat transfer to a gas. The gas channel arrangement 44 has a larger overall flow cross-section than the first channel arrangement 36 and / or a larger surface area for heat transfer.
[0113] Reservoir 54 is located exclusively in the first circuit 60. A 25834-PCT - JF / bau - 25 - January 22, 2026
[0114] The heat sink 50 is designed, for example, as a three-stream heat exchanger (e.g., as a "brazed fin heat exchanger" or "plate fin heat exchanger"). Alternatively, two two-stream heat exchangers connected in parallel or in series can be used.
[0115] Fig. 4 shows the preferred operating mode at high temperature differences, wherein the heat dissipation arrangement 34 is exclusively through which the second working fluid 13 flows.
[0116] The fluid decoupling allows the pressure within the second circuit 61 to be increased, for example to 5 bar to 10 bar. In this way, the heat transfer from the heat source 14 by means of the second working fluid 13 can be significantly improved compared to operation at ambient pressure.
[0117] Fig. 5 shows the preferred operating mode of the heat transfer system 10 according to Fig. 4 at moderate and / or small temperature differences, wherein the heat discharge arrangement 34 is by way of example through which both the first working fluid 12 and the second working fluid 13 flow.
[0118] Fig. 6 shows the heat transfer system 10 according to Fig. 4 during a shutdown process of the discharge operation, when no heat is to be discharged from the heat source 14. During the shutdown process, all the liquid first working fluid 12 is collected in the reservoir 54, whereby the components of the first circuit 60, comprising the heat source 14, the first distribution device 40, the first collection device 48, the remaining first piping elements 62, and the heat sink 50, are emptied of the first working fluid 12. The emptying can be gravity-driven and / or forced by means of the pumping device 56.
[0119] Fig. 7 shows by way of example the part of the heat source 14 designed as a heat storage device 16, which serves as a sensible heat storage medium 26 and / or in the case of the ge-A 25834-PCT - JF / bau - 26 - 22 January 2026
[0120] The illustrated design variant serves as the heat storage base body 30. The sensible heat storage unit 26 has, in particular, two differently configured levels arranged one above the other. In the upper level, e.g., with respect to the direction of gravity, the first channel arrangement 36 is arranged, for example. Several first flow channels 78 are interconnected in a first group, flow-wise parallel to each other. Each first flow channel 78 is, for example, arranged in a straight cylindrical conduit, which is designed, for example, as a bore in the sensible heat storage unit 26. The several first flow channels 78 run, for example, at least partially parallel to each other.
[0121] The charging arrangement 32 can, for example, be arranged in the same plane as the first flow channels 78 and, in particular, have heating cartridges running parallel to the individual first flow channels 78. For example, the heating cartridges are arranged alternately with the first flow channels 78. In this way, the sensible heat storage unit 26 or the heat storage base body 30 forms a component with two functions, namely the thermal charging and the thermal discharging of the heat storage device 16.
[0122] The second flow channels 80 of the second channel arrangement 42 are preferably distributed over a flat area on the lower plane (underside), e.g., in the form of rectangular channels with a heat-conducting structure 72 (e.g., a ribbed structure). The individual flow channels 80 can be separated from one another by means of the heat-conducting structure 72 or be fluidically connected. The heat-conducting structure 72 can, for example, be made of the same material as the rest of the heat storage base body 30 or sensible heat storage element 26. Alternatively, the heat-conducting structure 72 can be attached to the heat storage base body 30 by various joining methods, such as soldering. A 25834-PCT - JF / bau - 27 - January 22, 2026
[0123] Figures 8A and 8B each show, in a diagram 100, 100', an exemplary expected performance characteristic 102, 102' of the first circuit 60 (Figure 8A) and the second circuit 61 (Figure 8B) for a constant mass flow rate as a function of the temperature T of the heat source 14. Figure 8A shows, for the first circuit 60 (evaporation-condensation circuit), after a sharp increase in heat output Q', the onset of the boiling crisis at the critical heat flux density with respect to the first working fluid 12, with the associated characteristic sharp drop in heat output Q' and subsequent smaller increase as a function of the temperature T of the heat source 14. In contrast, according to Figure 8B, the heat output Q' via the second circuit 61 (gas circuit) increases continuously with increasing temperature T of the heat source 14.Preferably, the first circuit 60 is controlled and / or regulated such that it is operated, particularly at temperatures T of the heat source 14 at or below the critical heat flux density, with the heat source 14 being supplied with the first working fluid 12. However, the first circuit 60 can also be switched on slowly, for example, at temperatures T in the heat source 14 above the critical heat flux density, preferably with the proportion of the first working fluid 12 initially being lower than the proportion of the second working fluid 13.
[0124] Fig. 9 shows a diagram 100" with an exemplary expected performance characteristic 102" for a discharge cycle in discharge operation controlled for constant heat output. In this operation, both circuits 60 and 61 are controlled for a constant heat output from the heat source 14 and the heat transfer system 10, respectively. As Fig. 9 shows, at a high temperature T of the heat source 14, the heat is discharged exclusively via the second circuit 61 using the gaseous working fluid 13. The first circuit 60 is not operated. At lower and / or moderate temperatures of the heat source 14, the first circuit 60 is connected in parallel to the second circuit 61. By continuously increasing the proportion of the first working fluid 12, the heat output Q' via the first circuit 60 increases continuously, while the heat-A 25834-PCT - JF / bau - 28 - 22 January 2026
[0125] meaustrag Q' decreases via the second circuit 61 due to the reduction of the temperature difference and / or the proportion of the second working fluid 13.
[0126] Fig. 10 shows a flow diagram with a modified embodiment of the heat transfer system 10 compared to Fig. 4 with respect to the heat source 14. The embodiment shown in Fig. 10 shows a modification with respect to 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 bottom to top, and centrally within the phase-change heat storage unit 18, surrounded by it. An inclined arrangement is also possible, depending on the orientation of the heat storage device 16.
[0127] Fig. 11 shows a variant embodiment of the sensible heat storage element 26, particularly in its function as a heat storage base body 30, which has a cylindrical cross-section. The first channel arrangement 36 and / or the second channel arrangement 42 each have groups of flow channels 78, 80 (two each shown here as an example), 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 (not shown in Fig. 11).
[0128] Fig. 12 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 the phase change material 22 and / or a granular storage material (not shown) within the housing 24, without the presence of the heat storage base body 30 containing the solid storage material. The first channel arrangement 36 and the second channel arrangement 42 are in direct contact with the first storage area 20. A 25834-PCT - JF / bau - 29 - January 22, 2026
[0129] 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. With appropriate design of the heat source 14, the latent and / or sensible heat energy can be advantageously utilized optimally by means of the at least two different circuits 60, 61, with different working fluids 12, 13.
[0130] The heat transfer system 10 according to the invention can be advantageously used in both stationary and mobile applications. The solution principle is particularly suitable for heat storage applications that exhibit high specific discharge power as well as high volumetric and / or gravimetric power density. This is especially true for heat storage devices 16 with metallic phase-change materials, but is not limited to these. The heat 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. A 25834-PCT - JF / bau 22 January 2026.
[0131] Reference symbol list
[0132] 10 Heat transfer system
[0133] 12 first working fluid
[0134] 13 second working fluid
[0135] 14 Heat source
[0136] 16 Heat storage device
[0137] 18 Phase-change heat storage 20 First storage area
[0138] 22 Phase change material
[0139] 24 Enclosure
[0140] 26 sensible heat storage
[0141] 28 second memory area
[0142] 30 Heat storage base body 32 Heat charging arrangement
[0143] 34 Heat dissipation arrangement 36 First channel arrangement
[0144] 38 Evaporator arrangement
[0145] 40 first distribution device
[0146] 42 second channel arrangement
[0147] 44 Gas channel arrangement
[0148] 46 second distributor device
[0149] 48 first collecting device
[0150] 49 second collecting device
[0151] 50 Heat sink
[0152] 52 Heat exchanger device
[0153] 54 Reservoir
[0154] 56, 56' Conveyor
[0155] 58, 58' Valve assembly
[0156] 60 first cycle A 25834-PCT - JF / bau January 22, 2026
[0157] 61 second circuit
[0158] 62 first conduit
[0159] 63 second conductor 64 first conductor section 66 liquid flow
[0160] 68 second line section 72 heat conduction structure
[0161] 78 first flow channel 80 second flow channel 82 first extraction point
[0162] 84 second sampling point
[0163] 90 Diagram
[0164] 91 Heat flux density
[0165] 92 Temperature difference 93 Boiling characteristic curve
[0166] 94 Convection
[0167] 95 partial cystitis 96 full cystitis 97 transitional cystitis
[0168] 98 film sets
[0169] 100, 100', 100" diagram
[0170] 102, 102', 102" Power characteristic g Gravity direction
[0171] Q' Heat output
[0172] Temperature
Claims
A 25834-PCT - JF / bau - 32 - January 22, 2026 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) during a discharge operation by means of a working fluid (12, 13), wherein within the heat discharge arrangement (34) the working fluid (12, 13) is thermally coupled or connected to the heat source (14), wherein the heat discharge arrangement (34) is designed as an evaporator arrangement (38), with a first channel arrangement (36), within which the first working fluid (12) is at least partially vaporizable or vaporized during operation, 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 system (10) is designed such that it is possible to switch between heat discharge from the heat discharge arrangement (34) by means of two different working fluids (12, 13), a first, in particular evaporable, working fluid (12) and / or a second, in particular gaseous, working fluid (13), within a discharge cycle of the discharge operation.
2. Heat transfer system (10) according to claim 1, 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.
3. Heat transfer system (10) according to claim 2,A 25834-PCT - JF / bau - 33 - January 22, 2026 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.
4. Heat transfer system (10) according to claim 2 or 3, 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.
5. Heat transfer system (10) according to claim 4, characterized by that the sensible heat storage (26), in particular the solid storage material, is at least substantially cuboid and / or cylindrical in shape.
6. Heat transfer system (10) according to claim 3 and claim 4 or 5, characterized in that, 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.
7. Heat transfer system (10) according to claim 6, characterized by that the heat discharge arrangement (34) and / or the heat charging arrangement (32) are thermally directly connected to the second storage area A 25834-PCT - JF / bau - 34 - 22 January 2026 (28) coupled, in particular arranged on and / or in this, 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).
8. Heat transfer system (10) according to one of the preceding claims, characterized in that that the heat sink (50) is formed by a heat exchange device (52), in particular for the condensation of the first working fluid (12), which is through which, on the one hand, the first working fluid (12) and / or the second working fluid (13) and, on the other hand, a further heat transfer medium, air or a water-glycol mixture, can flow for the transfer of heat absorbed from the heat source (14) to the further heat transfer medium.
9. Heat transfer system (10) according to one of the preceding claims, characterized in that that the heat dissipation arrangement (34) has a second channel arrangement (42) in the form of a gas channel arrangement (44) which is optimized for heat transfer to a gas, wherein the gas channel arrangement (44) has a larger overall flow cross-section than the first channel arrangement (36) and / or a larger surface area for heat transfer.
10. Heat transfer system (10) according to one of the preceding claims, characterized in that that the heat transfer system (10) has a, in particular closed, first circuit (60) for conveying the first working fluid (12) with first conveying means (62) and a, in particular closed, second circuit. A 25834-PCT - JF / bau - 35 - 22 January 2026 (61) for conveying the second working fluid (13) with second conveying means (63) in which the heat source (14) and the heat sink (50) are arranged to allow flow through the first working fluid (12) and the second working fluid (13) and which preferably each comprise a conveying device (56, 56').
11. Heat transfer system (10) according to claim 10, characterized by that at least in the first circuit (60) a reservoir (54) is arranged.
12. Heat transfer system (10) according to claim 10 or 11, characterized by that the first circuit (60) and the second circuit (61) are designed to be completely decoupled from each other in terms of fluid dynamics, with the reservoir (54) being arranged exclusively in the first circuit (60).
13. Heat transfer system (10) according to claim 10 or 11 , characterized by that the first circuit (60) and the second circuit (61) are fluidically coupled or can be coupled together, wherein in particular the first conduit means (62) and the second conduit means (63) between the heat source (14) and the reservoir (54) are identical.
14. Heat transfer system (10) according to claim 13, characterized by that the reservoir (54) is arranged in the first circuit (60) and in the second circuit (61), wherein a first extraction point (82) of the first circuit (60) is for extracting the liquid first working fluid (12) and a second extraction point (84) of the second circuit (61) is for extracting the A 25834-PCT - JF / bau - 36 - 22 January 2026 gaseous, second working fluids (13) are arranged at the reservoir (54), and / or that the first conduit means (62) and the second conduit means (63) between the reservoir (54) and the heat source (14) are at least sectionally separated from each other.
15. Heat transfer system (10) according to one of claims 13 or 14, characterized in that, that the heat source (14) exclusively comprises the first channel arrangement (38) which is arranged within the first conduit means (62) and the second conduit means (63) through which the first working fluid (12) and / or the second working fluid (13) can flow or is flowed through.
16. Heat transfer system (10) according to one of claims 10 to 15, characterized in that, that within the heat dissipation arrangement (34) the first conduit means (62) comprise a first group of first flow channels (78) connected in parallel to each other in terms of flow characteristics, and the second conduit means (63) comprise a second group of second flow channels (80) connected in parallel to each other in terms of flow characteristics, wherein a distributor device (40, 46) for distributing the first working fluid (12) and / or the second working fluid (13) to the first flow channels (78) and to the second flow channels (80) is arranged upstream of the first, and optionally the second, group in terms of flow characteristics, and 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, 49) for combining the first working fluid (12) and / or the second working fluid (13) is connected downstream of the first group, and possibly the second group. A 25834-PCT - JF / bau - 37 - 22 January 2026 17. Method for operating a heat transfer system (10), which is designed in particular according to one of the preceding claims, in which, during discharge operation, heat is transferred from a heat source (14) to a heat sink (50) by means of a working fluid (12, 13), wherein, for heat discharge from the heat source (14), a heat discharge arrangement (34) is flowed through by the working fluid (12, 13), wherein the first working fluid (12) in the heat discharge arrangement (34) is at least partially evaporated in a first channel arrangement (36) depending on the operating conditions, characterized by that the heat dissipation arrangement (34) can be simultaneously and / or successively flushed with a first working fluid (12) and with a second working fluid (13) during a discharge cycle of the discharge operation.
18. Method according to claim 17, characterized by that the discharge operation is controlled and / or regulated with respect to a defined heat discharge, whereby a mass flow rate of first and / or second working fluid (12,13) which flows through the heat discharge arrangement (34) is set, in particular depending on a temperature difference between the heat source (14) and a saturation temperature of the first working fluid (12).
19. Method according to claim 17 or 18, characterized by that the first working fluid (12) is circulated in a first circuit (60) and the second working fluid (13) is circulated in a second circuit (61), which are completely decoupled in terms of fluid flow, wherein a higher pressure than ambient pressure and / or than in the first circuit (60) is set at least temporarily in the second circuit, for example between 2 bar and 15 bar, preferably between 5 bar and 10 bar. A 25834-PCT - JF / bau - 38 - 22 January 2026 20. Method according to any one of claims 17 to 19, 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 first working fluid (12) the heat dissipation arrangement (34) is exclusively through which the second working fluid (13) flows.
21. Method according to claim one of claims 17 to 20, characterized by that, with moderate and / or small temperature differences between the heat source (14) and a saturation temperature of the working fluid (12), the heat dissipation arrangement (34) is flowed through by both working fluids (12, 13) simultaneously or exclusively by the first working fluid (12).
22. Method according to one of claims 17 to 21 , characterized by that during a shutdown process of the discharge operation, the first working fluid (12) is emptied from the heat dissipation arrangement (34), preferably from all components and conduit media (62) arranged in a first circuit (60) and is collected in a reservoir (54).