Heat transport device and method for transporting energy

Abstract

A heat transport device (100) for transporting energy (5) from a heat source to a heat sink comprises a transport container (110) with a first heat exchange area (111) and a second heat exchange area (112), and a transport fluid (120) contained in the transport container (110). The transport fluid (120) contains a surfactant (121). The first heat exchange area (111) and the second heat exchange area (112) are each configured to exchange energy (5) between an environment and the transport fluid (120). The transport fluid (120) is configured to form a foam (127) based on the surfactant (121). The heat transport device (100) is thus designed to transport the energy (5) between the first heat exchange area (111) and the second heat exchange area (112) based on the foam (127) and to cause a return of the transport fluid (120).

Description

[0001] The present invention relates to a heat transport device and a method for transporting energy from a heat source to a heat sink, in particular using a foam. BACKGROUND

[0002] In current technology, heat pipes and thermosiphons are used for the spatial transport of thermal energy.

[0003] Fig. 6 Part (a) of the figure shows a conventional heat pipe 1. For the transport of thermal energy 5, it comprises a closed tube 10 that encloses a working fluid 20 or a transport fluid. The working fluid 20 can be, for example, water or ammonia. At a first heat exchange area 11, the heat pipe 1 is located close to a heat source. Near the first heat exchange area 11, the working fluid 20 evaporates, forming vapor, which travels through the tube 10 to a second heat exchange area 12 of the tube 10, which is cooler than the first heat exchange area 11. Near the second heat exchange area 12, the vapor condenses, releasing latent heat. The condensed working fluid 20 returns to the first heat exchange area 11 through a wick structure 18 (or drain structure) of the tube 10. The wick structure 18 is located inside the tube 10. It comprises thin channels and causes the return of the working fluid 20 by capillary forces.The overall cycle of the working fluid 20 is a passive process that does not require external pumps and is based on the phase transition in the working fluid 20 and on the capillary forces of the wick structure 18.

[0004] Part (b) of the figure shows a conventional thermosiphon 2. The thermosiphon 2 is designed for passive heat transfer based on the principle of natural convection. The thermosiphon 2 comprises a sealed transport container 10, which contains water or another liquid as the transport fluid 20. To hold a sufficient quantity of the transport fluid 20, the transport container 10 in this example includes a reservoir 17. When energy 5 is supplied to the liquid transport fluid 20 via a first heat exchange area 11 at a lower end of the thermosiphon 1, the liquid evaporates. This reduces the density of the transport fluid 20, causing it to rise as vapor or gas to an upper end of the thermosiphon 1. There, a cooler second heat exchange area 12 is located, near which the transport fluid 20 releases energy 5 and condenses back into a liquid.The heat transfer can be accelerated by external cooling or a heat sink near the second heat exchange area 12. Due to gravity, the now cooler fluid 20 flows downwards again. In this way, a heat transfer cycle is also formed, which does not require external pumps.

[0005] Conventional heat pipes are susceptible to damage, particularly to the wick structure. Over time, blockages and corrosion can occur there due to impurities in the transport fluid. These reduce the efficiency and lifespan of the wick structure. Furthermore, Marangoni forces can arise in the wick structure near the heated first heat exchange zone due to temperature gradients. Such forces, caused by changes in surface tension, can counteract the return of the condensed transport fluid and thus limit the transport capacity of the heat pipe.

[0006] Since the wick structure necessarily extends continuously between the first and second heat exchange zones, even more complex geometries are subject to clear limitations. Heat pipes cannot simply be "plugged together" to form branches. On the one hand, there are topological obstacles to the wick structure's path; on the other hand, the necessary fine channels can easily become clogged during assembly, for example, by solder or welding material.

[0007] Therefore, there is a need for heat pipes or thermosiphons that avoid efficiency losses due to impurities, have complex geometries and can be used in different directions. BRIEF DESCRIPTION OF THE INVENTION

[0008] This is achieved by a heat transport device according to claim 1 and a method for transporting energy from a heat source to a heat sink according to claim 10. The dependent claims relate to advantageous embodiments of the subject matter of the independent claims.

[0009] The present invention relates to a heat transfer device for transporting energy from a heat source to a heat sink. The energy can be, in particular, thermal energy. The heat transfer device comprises a transport container with a first heat exchange area and a second heat exchange area, as well as a transport fluid contained in the transport container. The transport fluid comprises a surfactant. The first heat exchange area and the second heat exchange area are each configured to exchange energy (or the energy) between the environment of the transport container around the respective heat exchange area and the transport fluid. The transport fluid is configured to form a foam based on the surfactant. The heat transfer device is thus configured to transfer energy based on this, i.e., in particular based on the foam.to transport energy between the first and second heat exchange areas, and to recirculate the transport fluid. Recirculation can be understood as moving the transport fluid in a direction opposite to the direction of energy transport.

[0010] The heat exchanger can externally resemble a conventional heat pipe or a thermosiphon. The transport container is a hollow body that completely encloses the transport fluid. The transport container can be watertight, airtight, or hermetically sealed.

[0011] In exemplary embodiments, the surfactant is present in a surfactant solution. The transport fluid can therefore comprise a carrier substance, for example water, in which the surfactant is dissolved. The transport fluid can, for example, comprise an aqueous solution of the surfactant. The transport fluid can comprise air or another gas; however, in exemplary embodiments, the transport fluid consists entirely of the surfactant solution. The surfactant is a substance whose particles each have both a part soluble in the carrier substance (in the case of water, hydrophilic) and a part insoluble in the carrier substance (in the case of water, hydrophobic).

[0012] In exemplary embodiments, the transport fluid has a liquid phase and a gaseous phase in all areas of its intended use, with a predominant mass fraction of the carrier being present in the liquid phase. The term "foam" can be understood as a liquid foam comprising gas-filled bubbles, particularly small gas bubbles, separated by liquid walls formed, in particular, by the surfactant and the carrier. The gas may comprise air and / or evaporated surfactant solution. Some surfactants are not suitable for foam formation on their own. In such cases, the surfactant solution or the transport fluid may contain an additive and / or another surfactant that enables and / or promotes foam formation.

[0013] Energy exchange means the transfer of energy, specifically thermal energy, from or into the transport fluid. During operation of the heat transfer device, this occurs as intended in or through the first heat exchange zone and in or through the second heat exchange zone. The design of these heat exchange zones for heat exchange means that other areas of the transport vessel are not intended for such exchange or suppress the exchange of thermal energy compared to the heat exchange zones. Exchange can be a supply, where thermal energy is added to the transport fluid. Exchange can be a removal, where thermal energy flows out of the transport fluid.

[0014] The function of the heat transfer device, to transport energy between the first heat exchange area and the second heat exchange area and to cause the return of the transport fluid, is based on the process described below.

[0015] The surfactant solution forms a stable foam within the transport container. At the interface between the liquid and gaseous phases of the transport fluid, the surfactant particles align themselves with their hydrophilic (i.e., soluble in the carrier) portion in the liquid and their hydrophobic (i.e., insoluble in the carrier) portion in the gas. They can then form a stable boundary layer. Based on the arrangement of the surfactant particles at the interface, a repulsive effect occurs between two adjacent, dissimilar interfaces, and thus between bubbles in the foam. In this way, the surfactant solution prevents the merging or aggregation of bubbles within the foam.

[0016] If bubbles or gas bubbles form in the transport container, or if the volume of the bubbles increases, the bubbles repel each other. This allows the bubbles to spread out over a spatial volume.

[0017] When thermal energy is supplied to the transport fluid near the first or second heat exchange zone, bubbles can form through evaporation or expansion. Conversely, when thermal energy is removed from the transport fluid near the second or first heat exchange zone, bubbles can shrink or disintegrate through condensation. This creates a transport or pumping effect that moves the gas and liquid, along with the energy stored within them, away from the first or second heat exchange zone and, in particular, towards the corresponding second or first heat exchange zone, thus transporting the energy.

[0018] Furthermore, small liquid channels form between the bubbles due to the repulsive effect between them. A capillary effect then occurs, causing condensing fluid, particularly near the second and first heat exchange zones, to move through these channels. The repulsive effect also creates a suction effect that draws fluid into the channels. This results in a passive pumping effect, moving fluid away from the second and first heat exchange zones and, in particular, towards them, thus returning a portion of the transport fluid.

[0019] Overall, a cycle of the transport fluid is established within the transport container, with the cycle being based on the foam and, in particular, able to function without a wick structure permanently formed within the transport container. The heat transfer device is therefore not, or not necessarily, a "heat tube with surfactants," since the transport container does not require any wick structure.

[0020] The circulation of the transport fluid can exist independently of gravity or any other force acting in a preferred direction (e.g., centrifugal force). The first and second heat exchange zones can therefore each be used as a heat sink or, conversely, as a heat source.

[0021] In other words, the transport fluid is designed to form a foam based on the surfactant, in order to transport energy between the first heat exchange area and the second heat exchange area, and to cause the transport fluid to be returned through liquid channels between bubbles of the foam.

[0022] In further embodiments, the transport container does not include a separate path for returning the transport fluid. Instead, the transport of energy between the first heat exchange area and the second heat exchange area can take place in the same channel as the return of the condensed transport fluid. The (condensed) transport fluid is thus returned to the first heat exchange area or to the heat source via the foam.

[0023] Optionally, the transport container may have (special) thermal insulation or a thermal insulation device in a transport area located away from the first and second heat exchange areas. The term "transport area" can be understood as a region of the transport container where a directed transport of energy occurs during a cycle. The thermal insulation can, for example, comprise a thicker boundary or wall of a vessel or pipe of the transport container compared to the first and second heat exchange areas. Thermal insulation can also be achieved by using a different material in the transport area than in the first and second heat exchange areas. Alternatively, thermal insulation can be achieved through a special design of a vessel or wall of the transport container in the transport area.In particular, one wall of the transport container can be double-layered, enclosing a vacuum or insulating material.

[0024] Optionally, the transport container may have a branch. Due to its dynamic design, the transport fluid circuit adapts to a wide variety of geometric shapes. The transport container may, particularly in the transport area, have a pipe along which energy can be transported by the fluid. A branch can then be understood as a point on the transport container where two or more pipes connect or merge. The pipe may, for example, have a bifurcation.

[0025] Optionally, the transport container has at least one additional heat exchange zone, which is designed to exchange energy between the environment surrounding the transport container and the transport fluid. Due to the adaptability of the circuit to different geometries of the transport container, multiple heat sinks and / or multiple heat sources can be used at the various heat exchange zones. The number of heat sinks does not necessarily have to equal the number of heat sources. Each heat exchange zone can be configured to be used for both supplying and removing energy to or from the transport fluid, as required.

[0026] Optionally, the transport container has a reservoir for holding a supply of the transport fluid. For example, a reservoir or container with a larger cross-section than the pipes in the transport area of ​​the container can be provided near the first, second, or a subsequent heat exchange area. A reservoir may be provided, in particular, if the heat transport device is intended or designed for use with a fixed orientation relative to a direction of gravity or another preferred direction defined by a force (e.g., centrifugal force).

[0027] Optionally, the transport container includes an area that is at least partially surrounded by a structured fiber sheathing.

[0028] The area can be, for example, a vessel or a pipe. In particular, the area can be the transport area. Advantageously, the area has a wall or lining made of a non-structured material, such as steel or plastic, which is surrounded by the structured fiber sheathing. The area can be located in the first or second heat exchange area, in a further heat exchange area within a transport area, or in a storage area of ​​the transport container. In exemplary embodiments, the entire heat exchange device or the entire transport area of ​​the heat exchange device can also have a structured fiber sheathing.

[0029] A structured fiber cladding material can be a fiber-reinforced composite. The term fiber-reinforced composite can refer to a multiphase or mixed material comprising a matrix of filler or adhesive, as well as fibers embedded within the matrix. Through the interactions between the matrix and the fibers, the fiber-reinforced composite can exhibit superior properties compared to either the matrix or the fibers alone. The matrix can be, in particular, a resin, and the fibers can be high-tensile fiber tapes.

[0030] The transport container can therefore be designed entirely or partially as a composite overwrapped pressure vessel (COPV) in exemplary embodiments.

[0031] The structured fiber sheathing improves the durability of the transport container under high pressure differentials between the internal pressure of the container and the external pressure in its surroundings. The inner wall or lining can be made thinner than it would be without the structured fiber sheathing. Therefore, the fiber sheathing design can also be used to reduce the weight of the transport container.

[0032] In exemplary embodiments, the transport container (with or without fiber sheathing) is designed to withstand pressure differences between an external vacuum (e.g., an external pressure below 0.03 Pa) and an internal pressure of up to 100 bar during intended use. This can depend not only on the circumstances of use but also, in particular, on the type or composition of the transport fluid. For example, in exemplary embodiments where the transport fluid comprises CO₂ (especially as a carrier fluid), the transport container can be designed to withstand pressure differences of up to 100 bar.

[0033] Optionally, the surfactant comprises at least one of the following substances: sodium 1,5-bis[(1H,1H,2H,2H-perfluorohexyl)oxy]-1,5-dioxopentane-2-sulfonate ("FG4"), C 18 H 37 SO 4 Na ("LSES"), sodium dodecyl sulfate ("SDS", CAS number 151-21-3), an octylphenol ethoxylate, in particular polyethylene glycol [4-(1,1,3,3-tetramethylbutyl)phenyl] ether or polyoxyethylated toctylphenol ("Triton-X-100") with CAS number 9002-93-1, and / or a polysorbate, in particular polyethylene sorbitan monooleate or polysorbate 80 ("Tween 80") with CAS number 9005-65-6.

[0034] Surfactants can generally be ionic or non-ionic. Particles of ionic surfactants carry an electrical charge on their carrier liquid-soluble or hydrophilic head, whereby the charge can be positive (cationic) or negative (anionic). This charge enhances a surface-active property of the surfactant, making it very suitable for foam formation. Non-ionic surfactants can produce a synergistic effect in combination with an ionic surfactant, which amplifies their effect, and in particular the previously described process of thermal energy transport and recirculation of condensed liquid.

[0035] In general, it has been shown that anionic surfactants can form more stable foams and bubbles compared to cationic surfactants. FG4, LSES, and SDS are advantageous anionic surfactants where the electrostatic repulsion between bubbles can be particularly strong, and which exhibit significantly less foam coarsening and reduced bubble aggregation compared to cationic surfactants such as (C16H33NMe3)Br ("CTAB"). FG4, in particular, has proven to be a particularly stable foam formator.

[0036] Optionally, the transport fluid includes at least one of the following substances as a carrier: water, acetone or ethanol.

[0037] Optionally, a cyclical path for the transport fluid is formed within the transport container. The transport container can, for example, comprise pipes or other vessels that form a circle or a simple closed path.

[0038] The term "cyclic path" does not refer to a wick structure; rather, in the intended use of the heat exchanger, condensed fluid can continue to move through the same space as the heat-transferring bubbles. However, the cyclic path can be advantageous in embodiments where the same heat exchange areas are to be used alternately as a heat source (i.e., for supplying heat to the transport fluid) and as a heat sink (i.e., for removing energy from the transport fluid).

[0039] Exemplary embodiments also relate to methods for transporting energy from a heat source to a heat sink. The energy can, in particular, be thermal energy. The method comprises transferring energy to a transport fluid containing a surfactant, wherein the transport fluid is configured to form a foam based on the surfactant. The method further comprises transporting the energy based on the foam. The method further comprises transferring energy from the transport fluid. The method further comprises recirculating the transport fluid based on the foam. The energy transport and the recirculation of the transport fluid are based on the process described above. The recirculation particularly concerns a liquid portion of the transport fluid. Preferably, the method can be carried out in a heat exchanger of the type described above.

[0040] Important aspects of the heat transfer device and the presented method can also be represented as follows.

[0041] In many conventional applications, heat pipes are used for efficient heat transfer because they operate passively and are highly efficient. They can be used independently of gravity and therefore also in microgravity applications. However, the required internal capillary structure limits their current use to simple geometries with usually only one heat source and one heat sink. Extending and, in particular, branching the heat pipe is generally not possible, as this would disrupt the internal capillary structure and thus render it ineffective. To connect multiple heat sources and heat sinks, several heat pipes or active systems (e.g., pumped systems) can be used, depending on the application. However, active systems are more complex to manufacture and less flexible. Pumped systems, in particular, are more complex and have a higher probability of failure.In addition, especially in zero-gravity applications, the usually higher mass is a factor.

[0042] The presented heat transport device creates an internal capillary structure through foam formation. This is achieved by adding a surfactant to the transport fluid or working fluid. As a result, a foam structure forms spontaneously within the transport container, independent of its geometry, thus enabling the filling of even complex geometries. Traditionally, certain surfactants have been used to reduce surface tension in the working fluid, but foam formation is a disadvantage. In the presented heat transport device, however, the surfactant is specifically designed to form the foam; it does not, or not necessarily, reduce surface tension in the transport fluid.

[0043] Some advantages of the presented heat transfer device and method can be described as follows.

[0044] Unlike conventional heat pipes, the presented heat transport device, in its exemplary embodiments, requires no separately manufactured capillary or wick structure, yet still enables energy transport independent of the direction of gravity or any other preferred direction of external force. These embodiments are particularly suitable for use in space travel or in zero gravity. The presented heat transport device can therefore be manufactured without the complex fabrication of an internal structure. Furthermore, these embodiments can be used in complex geometries with multiple heat sources and heat sinks.

[0045] A further advantage lies in the possibility of reducing the mass of the heat transfer device compared to conventional heat pipes or thermosiphons. The absence of rigid wick structures can contribute to this reduction. The structured fiber sheathing can also contribute to a reduction in mass. Overall, embodiments of the heat transfer device can therefore be advantageous in applications where mass plays a significant role. These embodiments are particularly suitable for use in aerospace applications, for example, on aircraft, in space stations, or on satellites.

[0046] A further advantage lies in the possibility of operating the heat transfer device passively. The heat transfer device can function without external pumps or other mechanical means for moving the transport fluid. Exemplary embodiments utilize only the properties of the transport fluid (or surfactant solution) containing the surfactant and its phase transitions.

[0047] A further advantage lies in the possibility of using the heat transfer device or the transport circuit in different orientations. Unlike thermosiphons, the generation and maintenance of the transport fluid circuit in the presented heat transfer device does not depend on gravity or any other external force defining a preferred direction. Exemplary embodiments of the heat transfer device can be effectively used in any orientation during operation, i.e., for heat transfer or energy transfer in any direction between the heat exchange areas.

[0048] A further advantage lies in the ability to easily adapt the heat transfer device to different conditions, particularly the design of transport vessels for a wide variety of situations. Specifically, multiple heat sources and sinks can be connected via a single transport vessel. This allows for flexible adaptation of the heat transfer device to numerous scenarios. Therefore, highly complex and highly efficient heat transfer systems can be achieved using this device.

[0049] Another advantage lies in the possibility of using the heat transfer device in microgravity environments. Certain foams have proven to be very stable in reduced-gravity or zero-gravity environments, and the heat transfer device can be used particularly in the aerospace industry. Examples of its use include cooling electronic components in satellites or other spacecraft or stations.

[0050] Another advantage lies in the possibility of designing the heat transfer device with a complex geometry. The transport container can easily be manufactured in various external shapes, and the disadvantages of conventional heat pipes, which during assembly lead to difficulties with the arrangement of the wick structure and to clogging by adhesive or soldering material, are overcome. BRIEF DESCRIPTION OF THE FIGURES

[0051] The embodiments of the present invention are better understood with reference to the following detailed description and the accompanying drawings of the different embodiments, which, however, should not be understood as limiting the disclosure to the specific embodiments, but merely serve for explanation and understanding. Fig. 1 shows a heat exchange device according to the present invention. Fig. 2 illustrates aspects of the surfactant and the foam on which the intended use of the heat exchange device is based. Fig. 3 shows an embodiment with insulation. Fig. 4 shows an embodiment with branching and illustrates problems of such branching in a conventional heat pipe. Fig. 5 shows steps of a method according to the present invention. Fig. 6 shows a conventional heat pipe and a conventional thermosiphon. DETAILED DESCRIPTION

[0052] Fig. 1 Figure 1 shows a heat transport device 100 for transporting energy 5 from a heat source to a heat sink. The energy 5 can be, in particular, thermal energy. The heat transport device 100 comprises a transport container 110 with a first heat exchange area 111 and a second heat exchange area 112, as well as a transport fluid 120 contained in the transport container 110, which includes a surfactant 121. The first heat exchange area 111 and the second heat exchange area 112 are each configured to exchange energy 5 between an environment around the first heat exchange area 111 and the second heat exchange area 112, respectively, and the transport fluid 120. The transport fluid 120 is configured to form a foam 127 based on the surfactant 121.Based on the foam 127, the heat transport device 100 is designed to transport energy 5 between the first heat exchange area 111 and the second heat exchange area 112 and to recirculate the transport fluid 120. Optionally, the transport fluid may include an additive in addition to the surfactant to enable or enhance foam formation.

[0053] Near the first heat exchange area 111, some of the transport fluid 120 evaporates due to heat input from the heat source. Vapor (or a saturated gas) and possibly further gas bubbles 128 of the foam 127 are formed; in particular, bubbles 128 of the foam 127 increase in volume and thus push transport fluid 120 through a transport area 114 of the transport container 110 to the second heat exchange area 112 of the transport container 110, which is cooler than the first heat exchange area 111. The second heat exchange area 112 represents a heat sink. Near the second heat exchange area 112, some of the vapor condenses, and the volume of the bubbles 128 in the foam 127 decreases, with some bubbles 128 of the foam 127 potentially collapsing. The latent heat 5 released during condensation escapes from the heat transport device 100.

[0054] During condensation, a portion of the transport fluid 120 liquefies. Consequently, a liquid forms near the second heat exchange area 112. Simultaneously, foam 127 persists near the second heat exchange area 112. Liquid channels 129 located between bubbles 128 of the foam 127 exert capillary forces on the liquid, causing it to flow back into the liquid channels 129 near the first heat exchange area 111. At the same time, electrostatic repulsion between the bubbles 128 creates an additional suction force, drawing the liquid into the liquid channels 129 and further contributing to its return to the vicinity of the first heat exchange area 111.

[0055] In this way, without a fixed wick structure, a cycle of the transport fluid 120 is established, which transports energy 5, in particular in bubbles 128 of evaporated transport fluid 120, from the first heat exchange area 111 to the second heat exchange area 112 and conversely returns liquid transport fluid 120 from the second heat exchange area 112 to the first heat exchange area 111.

[0056] In this process, the cycle can also be set up with the roles of the first heat exchange area 111 and the second heat exchange area 112 reversed, depending on the external circumstances.

[0057] In further embodiments, the transport container comprises 110 additional heat exchange areas. Such an embodiment can, for example, be designed to transport energy 5 from a source to several heat sinks or from a first heat exchange area to several further heat exchange areas.

[0058] Fig. 2 shows aspects of the process for transporting energy 5 and recirculating liquid transport fluid 120.

[0059] The figure shows a schematic representation of a particle 122 of the surfactant 121 in the upper left. The particle 122 comprises a head 123 that is soluble (e.g., hydrophilic) in a carrier liquid 125 of the surfactant 121 and a tail 124 that is not soluble (e.g., hydrophobic) in the carrier liquid 125.

[0060] The figure at the top right further shows a drop of the carrier liquid 125; for example, a water droplet, surrounded by a gas. The particles 122 of the surfactant 121 arrange themselves on a surface of the droplet with their hydrophilic head 123 in the water 125 or in the droplet itself, with their hydrophobic tail 124 pointing outwards and lying in the gas. The droplet is therefore surrounded by particles of the surfactant 121.

[0061] Furthermore, the figure below left shows the stable foam 127 with several bubbles 128 of different sizes and the carrier fluid 125 or liquid components of the transport fluid 120 in between.

[0062] A section of this view is shown in the figure below right. It shows the interfaces of the bubbles 128 with an intervening thin liquid film of carrier fluid 125, for example water. At the interfaces, particles 122 of the surfactant 120 arrange themselves in the manner described above.

[0063] The operating principle of the heat transfer device 100 can be described as follows.

[0064] First, the working principle includes the formation of the foam 127.

[0065] In an evaporation zone near a heat exchange area 111, the carrier fluid 125 containing the surfactant 121 absorbs energy 5 of the transport fluid 120. This causes liquid components of the transport fluid 120 to evaporate, forming gas or vapor bubbles 128. These bubbles, as well as any existing bubbles 128, are stabilized by particles 122 of the surfactant 121 based on electrostatic repulsion. The particles 122 of the surfactant 121 prevent the bubbles 128 from growing together or merging. The gas bubbles 128 form the foam 127 within the transport container 110. This foam 127 acts as a dynamic wick system in which thin liquid films 129 between the bubbles play an important role in the transport of energy 5 and liquid transport fluid 120.The evaporation of the carrier liquid 125 in the evaporation zone and the condensation in a condensation zone causes a pressure gradient that drives the foam 127 (especially also the vapor) from the evaporation zone to the condensation zone.

[0066] Furthermore, the working principle includes a pumping effect.

[0067] During evaporation, the resulting gas bubbles 128 do not merge due to the properties of the surfactant 121. Instead, the gas bubbles 120 push against each other, thus causing the passive pumping effect. This effect efficiently transports vapor from the evaporation zone to the condensation zone.

[0068] Furthermore, the working principle includes the recycling of liquid components of the transport fluid 120.

[0069] The heat transfer device 100 can ensure the return of the condensed transport fluid 120 based on two mechanisms. A first mechanism relies on a dynamic wicking effect, which is caused by thin liquid films 129 located between the bubbles 128 of the foam 127 generating a capillary-like effect that helps to move the condensed transport fluid 120 or the carrier fluid 125 with dissolved surfactant 121 back into the evaporation zone. A second mechanism is based on a repulsion-induced pumping effect. Here, the repulsion between the bubbles 128 creates an additional suction effect that supports the return of the condensed transport fluid 120 or the carrier fluid 125 with dissolved surfactant 121.

[0070] Fig. 3 Figure 1 shows an embodiment with a transport area 114 that has a heat-insulating sheath 115. This suppresses or prevents the release of energy 5 from the transport container 110 into the transport area 114. The transport of energy 5 in this area of ​​the transport container 110 is completely or substantially adiabatic. The sheath 115 can comprise not only an insulating material but also a structured fiber sheath. The structured fiber sheath can contribute to the resistance of the transport container 110 to a large difference between internal and external pressure. At the same time, the lining or vessel can be made thinner. The fiber sheath can comprise a resin matrix with embedded, aligned fibers.

[0071] Fig. 4 Figure 1 on the left illustrates problems that can arise at the branching points 30 of conventional heat pipes 1. The heat pipe 1 includes a bifurcation where two pipes 10 and 10' meet. In operation, energy 5 can enter pipe 10 through, for example, a first heat exchanger 11 and evaporate a working fluid 20 there. Based on this, energy 5 is transported to a second heat exchanger 12 and a further heat exchanger 13, where the working fluid 20 condenses and energy 5 is released from the heat pipe 1. A wick structure 18 is arranged on an inner wall of the heat pipe 1. It should be designed to return the condensed working fluid 20 to the first heat exchanger 11 via capillary action. However, in a region of the branching point 30, the wick structure 20 can hardly be meaningfully connected or made continuous.Ideally, the heat pipe 1 should also be operable in such a way that, for example, either the second heat exchange area 12 or the further heat exchange area 13 serves as the heat source. With a continuous connection, however, the wick structure would connect two heat sinks or condensation zones (in the example with the heat source in the first heat exchange area 11, i.e., the second heat exchange area 12 and the further heat exchange area 13) in at least one of these operating modes. Furthermore, the fine channels of the wick structure 18 can easily become clogged when the pipes 10, 10' are joined in the area of ​​the branch 30, for example, by penetrating solder or other material used to join the pipes 10, 10'.

[0072] In contrast, the figure on the right illustrates an embodiment of the heat transfer device 100 of the type presented here. The transport container 110 has an external shape that is identical to the external shape of the heat pipe 1 in the left part of the figure. However, the transport container 110 does not include a fixed wick structure 18. Rather, a wick structure forms dynamically through the foam 127 when the heat transfer device 100 is used as intended. This allows, for example, each of the individual heat exchange areas 111, 112, 113 to be used as a heat source. Assembling the transport container 110 from individual pipes, for example, does not pose a problem here. In exemplary embodiments, the foam 127 is distributed evenly and stably throughout the entire transport container 110.

[0073] Fig. 5Figure 1 shows the steps of an embodiment of the method presented here for transporting energy 5 from a heat source to a heat sink. The energy 5 can, in particular, be thermal energy. The method comprises supplying energy 5 (S110) to a transport fluid 120 containing a surfactant 121. The transport fluid 120 is designed to form a foam 127 based on the surfactant 121. The method further comprises transporting the energy 5 (S120) based on the foam 127. Here, a temperature gradient causes a pressure gradient in the foam 127, which leads to the transport of the transport fluid 120 and the energy 5 stored in it. The method further comprises extracting energy 5 (S130) from the transport fluid 120. During this extraction, bubbles 128 in the foam 127 shrink, and some of them collapse. Overall, a portion of the energy-carrying transport fluid 120 condenses, releasing the energy 5 in the process.The process further includes a recycling S140 of the transport fluid 120 based on the foam 127. This is based on thin films of liquid.

[0074] Transport fluid 120 between bubbles 128 of the foam 127. The bubbles 128 of the foam 127 repel each other due to the action of the surfactant 121. This creates thin fluid channels 129, which, through a combination of capillary forces and suction, cause the return of condensed transport fluid 120. Overall, a dynamic cycle of the transport fluid 120 is established, which facilitates the transport of energy 5.

[0075] The features of the invention disclosed in the description, claims and figures may be essential for the realization of the invention, either individually or in any combination. REFERENCE MARK LIST

[0076] 1 Heat pipe 2 Thermosiphon 5 Energy 10 Transport vessel, pipe 11, 12, 13 Heat exchange areas 15 Insulation 18 Wick structure 17 Storage vessel 20 Working fluid 30 Branch 100 Heat transport device 110 Transport vessel 111, 112, 113 Heat exchange areas 114 Transport area 115 Sheathing 120 Transport fluid 121 Surfactant 122 Particles 123 Head 124 Tail 125 Carrier fluid 127 Foam 128 Bubble 129 Liquid channel S110, S120, S130, S140 Process steps

Claims

1. A heat transport device (100) for transporting energy (5) from a heat source to a heat sink, comprising: a transport container (110) with a first heat exchange area (111) and a second heat exchange area (112); and a transport fluid (120) contained in the transport container (110) and comprising a surfactant (121), wherein the first heat exchange area (111) and the second heat exchange area (112) are each configured to exchange energy (5) between an environment and the transport fluid (120), and wherein the transport fluid (120) is configured to form a foam (127) based on the surfactant (121) in order to transport the energy (5) between the first heat exchange area (111) and the second heat exchange area (112) and to recirculate the transport fluid (120).

2. The heat transport device (100) according to claim 1, wherein the transport container (110) has a heat insulation (115) in a transport area (114).

3. The heat transport device (100) according to one of the preceding claims, wherein the transport container (110) has a branch (30).

4. The heat transport device (100) according to one of the preceding claims, wherein the transport container (110) has at least one further heat exchange area (113) configured to exchange energy (5) between an environment and the transport fluid (120).

5. The heat transport device (100) according to one of the preceding claims, wherein the transport container (110) has at least one of the following: - a storage area for holding a supply of the transport fluid (120).

6. The heat transport device (100) according to one of the preceding claims, wherein the transport container (110) comprises a vessel which is at least partially surrounded by a structured fiber sheathing (115).

7. The heat transfer device (100) according to one of the preceding claims, wherein the surfactant (121) comprises at least one of the following substances: - sodium 1,5-bis[(1H,1H,2H,2H-perfluorohexyl)oxy]-1,5-dioxopentane-2-sulfonate, - C 18 H 37 SO4Na, - sodium dodecyl sulfate, - an octylphenol ethoxylate, - a polysorbate.

8. The heat transport device (100) according to one of the preceding claims, wherein the transport fluid (110) comprises at least one of the following substances: - water, - acetone, - ethanol.

9. The heat transport device (100) according to one of the preceding claims, wherein a cyclic path for the transport fluid (120) is formed in the transport container (110).

10. A method for transporting energy (5) from a heat source to a heat sink, comprising: supplying (S110) the energy (5) to a transport fluid (120) comprising a surfactant (121), wherein the transport fluid (120) is configured to form a foam (127) based on the surfactant (121); transporting (S120) the energy (5) based on the foam (127); extracting (S130) energy (5) from the transport fluid (120); and returning (S140) the transport fluid (120) based on the foam (127).

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