Device for receiving a volume flow and method for realizing a volume flow

Abstract

Device (1) for receiving a volume flow of a medium which, in the solidified state, forms an ionic crystal structure, comprising at least one wall surface (10) which limits the volume flow (3) at least on one side, wherein the wall surface (10) has convex shape elements (20), wherein the device (1) for receiving a volume flow is a tube on the inner wall of which the convex shape elements (20) are arranged, characterized in that each convex shape element (20) has a cross-sectional area in its plane of section perpendicular to the plane of the surface (11) of the wall surface (10) and through its vertex (21) and along the longitudinal direction of the tube, which is bounded by an arc-shaped edge (22) and an edge connected to the arc-shaped edge (22) which is designed as a tangent (23), wherein the edge designed as a tangent (23) transitions into the surface (11).

Description

[0001] The present invention relates to a device for receiving a volume flow of a medium, a heat exchanger, a solar thermal power plant, a method for realizing a volume flow of a medium, and a method for generating electrical energy.

[0002] Crystal-forming heat transfer fluids, such as molten salts, exhibit significantly higher temperature resistance than organic heat transfer fluids. However, when transporting such crystal-forming heat transfer fluids in pipelines, their high freezing point, especially during cooling, can lead to the formation of solid crystals within the pipes, potentially causing a complete blockage. This occurs because, as the temperature decreases, crystal nuclei form, which increasingly adhere to the inner pipe walls and ultimately create a continuous layer that drastically reduces heat transfer.

[0003] Ordinary smooth tubes in heat exchangers do not inhibit this phenomenon. Essentially independent of roughness, solid crystals can deposit along the tube walls.

[0004] When heat is absorbed and the crystal-forming medium liquefies, flows initially form only on the inner walls of the pipe, while a crystalline structure remains in the pipe's central axis. Consequently, only a small volume of the medium is available for generating the flow rate and absorbing heat.

[0005] In Fig. 1 is a conventional device for receiving a volume flow 1, in the illustrated variant a pipe. Particles 5 are guided in a volume flow 3 in its longitudinal direction 2. Particularly with crystal-forming media, crystal deposition occurs upon cooling of the melt, as can be seen on the right side in Fig. As indicated in Figure 1, this reduces the cross-sectional area of ​​the device for receiving a volume flow 1. Furthermore, it is evident that if heat is introduced in the area of ​​the particle deposits 5, the heat must be introduced into the volume flow 3 via or through the deposit, making efficient heating of the medium impossible.

[0006] To prevent the molten salt from solidifying during the respective process runs, the salt tanks are positioned to ensure self-emptying (gravity return). The molten salt is liquefied in the salt tank using an immersion heater.

[0007] To prevent the molten salt from solidifying in the pipes, all pipes carrying molten salt in such processes are equipped with heating elements designed to prevent the liquid from solidifying. In addition to the technical effort involved, operating these heating elements requires a relatively high amount of energy.

[0008] Furthermore, devices for receiving a volume flow are known, for example, from US 2 080 626 A and from DE 10 2010 028 681 A1.

[0009] US Patent 2,080,626 A teaches a tube consisting of an elongated tube body constructed from opposing, grooved elements forming an elliptical tube in cross-section, longitudinal flanges supported by the longitudinal edges of the elements, means for fastening the opposing flanges to one another, and 0 to 5 spaced-apart convex projections supported by each element, the projections of one element being alternately spaced with respect to the projections of the other element.

[0010] DE 10 2010 028 681 A1 discloses a solar thermal steam generator comprising a container with an inlet and an outlet for conveying a heat transfer medium, further comprising heat exchanger tubes arranged in the container through which a working medium can be conveyed and which are designed in such a way that heat can be transferred from the heat transfer medium to the working medium, wherein the heat exchanger tubes have ribs at least partially on their inside.

[0011] The invention is based on the objective of providing a device for receiving a volume flow of a medium which forms an ionic crystal structure in the solidified state, as well as a method for realizing a volume flow of this medium, with which the medium can be transported and / or heat exchange between the medium and an ambient medium can be realized in a simple, low-maintenance and cost-effective manner.

[0012] This problem is solved by the device according to the invention for receiving a volume flow of a medium according to claim 1, by the heat exchanger according to claim 2, and by the method for realizing a volume flow of a medium according to claim 7. Advantageous embodiments of the method according to the invention for realizing a volume flow of a medium are specified in dependent claims 8 and 9. In addition, a solar thermal power plant is provided according to claim 3, which also uses the device according to the invention for receiving a volume flow, and a method for generating electrical energy is provided according to claim 10.

[0013] The device according to the invention for receiving a volume flow of a medium which forms an ionic crystal structure in the solidified state comprises at least one wall surface which limits the volume flow at least on one side, wherein convex shape elements are arranged on or in this wall surface.

[0014] The device for receiving a volume flow is a pipe on whose inner wall the convex shaping elements are arranged.

[0015] Each convex shape element has a cross-sectional area in its cutting plane perpendicular to the plane of the surface of the wall surface and through its vertex and along the longitudinal extension direction of the tube, which is bounded by a substantially arc-shaped edge and an edge connected to the arc-shaped edge, which is essentially tangent, with the tangent edge transitioning back into the surface.

[0016] The convex shaping elements extend into the medium. This medium, which forms an ionic crystal structure in the solidified state, is, for example, a molten salt, an organometallic compound, a melt of organic compounds, or a metal oxide melt. The volumetric flow rate of the melt is directly limited by the wall surface of the device according to the invention and thus also by the convex shaping elements arranged therein.

[0017] Alternatively, it can be provided that the device according to the invention forms a flow path for receiving a volume flow, wherein one or more intermediate layers are present between the medium and the wall surface, but are thin, and also have the shape of the wall surface and its convex shape elements.

[0018] The convex elements are preferably arranged in a structure. They have several positive effects on the crystal-forming medium. Firstly, they lead to greater heat absorption due to convection resulting from the increased surface area of ​​the wall. Secondly, they inhibit the settling of solid crystals due to turbulence generated in the medium flow. This ensures that the cross-section of the device remains unobstructed for longer, even during crystallization. Another positive property is improved heat transfer, caused by the turbulence in the medium. This turbulence causes the individual layers, which have different temperatures, to mix, resulting in excellent mixing within the medium. Consequently, heat is optimally conducted and distributed between the particles of the medium. This also prevents partial cooling and particle deposition.

[0019] Furthermore, the convex shape elements cause heat to be introduced relatively close to the central area of ​​the device for receiving a volume flow, thus distributing the heat input over a large area of ​​the device's cross-section. This ensures that not only the outer layers of the medium are heated, but also areas in the central region of the medium being transported. This also counteracts cooling-induced solidification and crystallization of the medium in the area near the center of the volume flow.

[0020] The present invention is not limited to a pipe as a device for receiving a volumetric flow; it can also be implemented as a channel in whose inner wall the convex shaped elements are arranged. The pipe or channel can be designed such that it has corresponding concave shaped elements on its outer surface, which develop into the aforementioned convex shaped elements on the inner surface. Such structured tubes, particularly when used with molten salts as the medium, offer the advantage that heat dissipation in the boundary layers between the medium and the pipe material leads to turbulence and eddies, which significantly hinders the deposition of crystal nuclei on the inner wall of the tube and thus slows down the formation of crystalline layers.

[0021] Furthermore, due to the convex shape elements, heat transfer occurs closer to the central axis of the pipe when the medium absorbs heat, so that a medium that may be in a solidified state can be liquefied more evenly and quickly than is possible in smooth pipes.

[0022] The convex shape elements are designed such that, in a section plane extending perpendicular to the surface and through their vertex or the point furthest from the surface, as well as along their longitudinal extent, they have a cross-sectional area bounded by a substantially arc-shaped edge and by an edge connected to the arc-shaped edge, which is essentially tangent to it, with this tangent edge in turn transitioning into the surface. Preferably, the edge connected to the arc-shaped edge is tangent to the arc of the arc-shaped edge. The transitions from the surface of the wall to the arc-shaped edge and to the tangent edge may be rounded.

[0023] Such a convex element thus has the shape of half a so-called NACA profile or half a teardrop profile. This means that the entire convex element is a convexly curved structure, with the tangent edge continuing the arc-shaped edge. The convex element is positioned in the flow-containing device such that the tangent edge in the cross-sectional area is the first area over which the medium flows, and only then is the arc-shaped edge over which the medium flows. This means that the flatter area of ​​the convex element is the first to be overflowed, creating strong turbulence on and behind the element, which prevents the formation of deposits or the settling of crystals.

[0024] In an alternative embodiment, the convex shape element is designed to be essentially symmetrically curved, possibly having a circular or elliptical shape in cross-section.

[0025] Adjacent convex elements can be arranged in a linear row along the longitudinal direction of the device to accommodate a volume flow, or they can be arranged laterally offset in several linear rows. This means that the convex elements closest to each other can be arranged in a row or in a zigzag pattern.

[0026] Preferably, the device for receiving a volume flow has a clear opening W of 10 mm to 200 mm. In the case of a pipe, the clear opening is the inner diameter. In the case of a channel, the clear opening is the maximum distance between the channel legs. The inner diameter of the pipe or the distance between the channel legs can, in particular, be 10 mm to 80 mm.

[0027] The height H of each convex element, relative to the surface on which the convex element is located, should be in the ratio H ≤ 0.167 W to the clear width W. The height is to be measured perpendicularly from the surface on which the convex element is located to the apex of the convex element.

[0028] The maximum width of each convex shape element should be in the following ratio to the clear width W: B ≤ 0.33 W.

[0029] Regarding the preferred spacing A between individual, adjacent convex shape elements, it is preferably provided that this spacing A to the clear width is in the ratio of A = 0.125 W to 1.5 W. In a favorable embodiment, it is provided that the spacing A is exactly the same as the clear width W.

[0030] The invention further provides a device for ammonia heating and urea decomposition, which includes a device according to the invention for receiving a volumetric flow. Such a device can be used in particular in melamine production. The device according to the invention serves to receive a volumetric flow for transporting a crystallizing urea melt.

[0031] Furthermore, a device for aluminum production is provided which also has the device according to the invention for receiving a volume flow, wherein this serves to receive a volume flow of an aluminum melt.

[0032] Another aspect of the invention is a heat exchanger comprising several devices according to the invention for receiving a volume flow for transporting a medium, which are arranged in a space through which a fluid which forms an ionic crystal structure in the solidified state flows or can flow through.

[0033] The devices for receiving a volume flow are advantageously provided here as bulged pipes.

[0034] The space is formed by the heat exchanger or by its housing or jacket.

[0035] The fluid, which forms an ionic crystal structure in the solidified state, is also preferably a molten salt heated by solar energy.

[0036] The medium transported by the devices for receiving a volume flow can be described as a heating or cooling medium and can be, for example, water.

[0037] This means that, unlike the realization of a volume flow using the device according to the invention for receiving a volume flow in the heat exchanger, the molten salt flows around the devices for receiving a volume flow and does not flow through them.

[0038] Due to the course of the devices for receiving a volume flow through the flow space of the heat exchanger, heat is transferred from the medium in the devices for receiving a volume flow to the fluid in the space through which the devices for receiving a volume flow run, or vice versa, wherein the fluid in the space flows around the devices for receiving a volume flow, which are preferably designed as tubes.

[0039] Furthermore, the present invention relates to a solar thermal power plant which has a device according to the invention for receiving a volume flow for transporting a medium heated by solar energy which forms an ionic crystal structure in the solidified state, in particular for transporting a molten salt.

[0040] The device for receiving a volume flow can be arranged in such a way that it is exposed to solar radiation or can be exposed.

[0041] The device according to the invention for receiving a volume flow can, for example, be a parabolic trough in which a molten salt, heated by solar energy, is guided. Alternatively, the device for receiving a volume flow can be a pipeline running inside the parabolic trough, which is designed as a solar collector. In both configurations, sunlight is directed onto the medium in the trough, so that it is heated or kept at a specific temperature, allowing the resulting molten salt to be transferred to a heat exchanger.

[0042] The device for receiving a volume flow is therefore directly exposed to, or can be exposed to, solar radiation, particularly due to the arrangement in a focus area of ​​focused solar rays.

[0043] Preferably, molten salts with an operating temperature between 200 °C and 500 °C are used. Such molten salts typically consist of a mixture of alkali nitrites, which, depending on the mixture, can have a melting point above 140 °C. They are liquid at room temperature between 180 °C and 550 °C. Special salts or molten salts can be used up to 650 °C. This allows heat transfer at higher temperatures than, for example, with thermal oils, whereby the heated molten salt also exhibits a relatively low viscosity, good heat transfer capacity, and high heat capacity. The material of the device that contacts the medium and receives the volumetric flow must be correspondingly corrosion-resistant and also possess sufficient ductility for the integration of the convex shaped elements.

[0044] To further increase the efficiency of heat transfer and / or to enable catalytic reactions, the device for receiving a volume flow can have a microstructure at least in certain areas on its surface.

[0045] The microstructure can be located on the side where the convex features are formed, or on the side where the flow-containing device has concave features. For example, the concave features on the outside of a flow-containing device designed as a tube can form convex features on the inside of the tube.

[0046] The microstructure can be applied to the shape elements and / or next to them.

[0047] The microstructure can consist of several protrusions, the maximum distance of which from the surface is less than 100 µm.

[0048] Preferably, the projections have the shape of a pin, which extends with its longitudinal axis either perpendicularly or at an angle between 30° and 90° to the surface.

[0049] The number of protrusions per unit area is designed depending on the thickness of the pin-shaped protrusions, with a number of 10 2 / cm 2 up to 10 8 / cm 2 the thickness is between 100 µm and 0.2 µm.

[0050] The length of the pin-shaped protrusions should be between 10 µm and 195 µm.

[0051] The clear width between the pin-shaped projections should be between 0.6 µm and 1000 µm.

[0052] The pin shape can vary towards a mushroom, cone or needle shape.

[0053] In an alternative embodiment, the microstructure consists of a porous layer with pores less than 200 µm deep. Here too, the pores are essentially hollow cylindrical, with their longitudinal axis extending either perpendicular to the surface or at an angle between 30° and 90°.

[0054] The number of pores per unit area is designed depending on the clear width of the pores, with a number of 10 2 / cm 2 up to 10 8 / cm 2 The clear width is between 100 µm and 0.2 µm.

[0055] The length of the pores should be between 10 µm and 195 µm.

[0056] The distance between the pores should be between 0.6 µm and 1000 µm.

[0057] The porous layer is preferably made of a material from the zeolite group.

[0058] In this configuration, the microstructure serves as a so-called "black trap", i.e., as a device with which energy from solar radiation can be efficiently absorbed and transferred as heat into the device for receiving a volume flow, from which the heat can be transferred to the medium or the molten salt, so that the viscosity of the medium or the molten salt and / or the tendency to crystallize is kept low.

[0059] A further embodiment of the power plant according to the invention is that the power plant has a heat exchanger according to the invention. Individual devices for receiving a volume flow, which are exposed to solar radiation, can lead into the heat exchanger and form a component of the heat exchanger there.

[0060] Another aspect of the invention is a method for generating a volume flow of a medium which, in its solidified state, forms an ionic crystal structure, in which a melt of the medium, in particular a molten salt, is passed through a device according to the invention for receiving a volume flow. This means that the medium is transported by a device which has at least one wall surface that limits the volume flow at least on one side, wherein convex shaped elements are arranged on or in this wall surface and extend into the medium.

[0061] Preferably, the melt of the medium has a temperature of 150 °C to 650 °C, in particular a temperature of 180 °C to 550 °C.

[0062] In the embodiment of the device for receiving a volumetric flow, in which each convex element has a cross-sectional area in its plane perpendicular to the plane of the wall surface and through its apex and along the longitudinal direction of the tube, bounded by a substantially arcuate edge and an edge connected to the arcuate edge that is essentially tangent to the surface, the melt flows towards the respective convex element at the area formed as a tangent in cross-section. That is, when a convex element is arranged in a half-droplet shape, the melt flows towards this convex element from the narrow side. This results in strong turbulence and correspondingly good mixing of the melt, and consequently, effective prevention of crystal deposits.Furthermore, this results in efficient heat conduction within the medium.

[0063] The inventive method for realizing a volume flow of a medium can be used in particular in a method for generating electrical energy, in which a medium heated by solar energy, which forms an ionic crystal structure in the solidified state, is transported in an inventive device for receiving a volume flow, the heated medium is made available and the thermal energy of the medium is converted at least partially into electrical energy.

[0064] This allows the heated medium to be fed, for example, to a heat exchanger, in which the heat of the melt is at least partially transferred to another medium, whereby the thermal energy of this medium is converted into mechanical energy and this in turn into electrical energy.

[0065] In the configuration where solar energy is converted into electrical energy, it is provided that the device for receiving a volume flow is exposed to solar radiation during the transport of the medium.

[0066] In the embodiment in which a heat exchanger is used for the transfer of thermal energy, it is provided that in a heat exchanger according to the invention, at least partial heat is transferred from a fluid flowing through the space of the heat exchanger to the medium in the devices for receiving a volume flow, the heated medium is made available, and the thermal energy of the medium is at least partially converted into electrical energy.

[0067] The present invention will be explained below with reference to the exemplary embodiments shown in the accompanying drawings. These show: Fig. 1 a conventional device for recording a volume flow in cross-sectional view from the side, Fig. 2 a device according to the invention for recording a volume flow in a sectional view from the side, Fig. 3 a device according to the invention for receiving a volume flow in a cross-section, Fig. 4 a section of a device according to the invention for receiving a volume flow in a sectional view from the side, Fig. 5 the arrangement of a device according to the invention for receiving a volume flow over a reflector in sectional view, and Fig. 6 a heat exchanger with a plurality of devices according to the invention for receiving a volume flow in sectional view from the side.

[0068] On the in Fig. The conventional device for receiving a volume flow shown in Figure 1 has already been discussed in the explanation of the prior art.

[0069] Fig. Figure 2 shows a device according to the invention for receiving a volume flow 1 in a sectional view from the side, wherein, for better clarity of the features of the invention, the representation of the inner and outer wall of the pipe forming the device for receiving a volume flow has been omitted.

[0070] In this device for receiving a volume flow 1, a volume flow 3 is realized, which flows along the convex shape elements 20 in

[0071] Longitudinal direction 2 leads through the pipe. On the inside or on the wall surface 10, convex shaped elements 20 are arranged, which extend into the medium forming the volume flow 3. This creates turbulence 4 in the volume flow, which causes the deposits of particles, such as those found in Fig. As indicated in Figure 1, this prevents the formation of particles or crystal nuclei. Furthermore, in the area of ​​the convex shape elements 20, the outer surface of the device for receiving a volume flow 1 extends closer to the center of the volume flow 3, thus partially enabling heat input or heat transfer to more central layers of the medium. The turbulence 4 not only prevents the settling of particles or crystal nuclei, but also ensures optimal mixing of individual layers in the volume flow, so that optimal heat distribution in the volume flow is achieved via heat conduction.

[0072] The convex shape elements 20 have a distance A from each other, which corresponds to the minimum distance between two convex shape elements arranged linearly one behind the other in the longitudinal direction.

[0073] The convex shape elements 20 have a width B that corresponds to their maximum extent along the longitudinal direction 2.

[0074] In Fig. Figure 3 shows that the convex shape elements 20 extend towards the center of the device for receiving a volume flow. This device for receiving a volume flow 1, insofar as it is as shown in Fig. 3 is shown as a tube, a clear width W which is the maximum distance between opposing surfaces 11.

[0075] From a synthesis of Fig. 2 and Fig. Figure 3 shows that the convex shape elements 20, which have a minimal distance between them, are arranged offset around the circumference in several rows. That is, when the shape is developed in Fig. In Figure 2 of the illustrated tube, the closest adjacent convex shape elements 20 are arranged in a zigzag pattern. The present invention is not limited to such an arrangement; it can also be provided that the convex shape elements 20, which are closest to each other, are arranged linearly in a row.

[0076] In Fig. Figure 4 shows only a section of the device according to the invention for receiving a volume flow, in which a convex shaping element 20 is arranged. The following is shown in Fig. Figure 4 shows a particular embodiment of the convex form elements, in which the convex form element 20 has an arcuate edge 22 and a tangent 23 connected to this arcuate edge 22, wherein the arcuate edge 22 and the tangent 23 transition back into the surface 11 of the wall surface via rounded edges 24. This means that such a convex form element is asymmetrically designed. It has a vertex 21, which is the point on the arcuate edge 22 furthest from the surface 11 of the wall surface 10. The convex form element 20 thus has a height that is to be measured between the vertex 21 and the surface 11 of the wall surface 10. The convex form element 20 is preferably arranged such that the volume flow 3 first flows towards or around the tangent 23 and then around the arcuate edge 22.In particular, this causes strong turbulence 4, which prevents particles 5 from settling, even if they are in crystalline form.

[0077] In Fig. Figure 5 shows another possible application of a device according to the invention for receiving a volume flow 1. Here, the device 1 according to the invention is positioned in relation to a reflector 31 such that incident solar radiation 30 is reflected into Fig. Figure 5, shown with dashed lines, depicts the direct impact of the volume flow 1 on the device for receiving it, or the reflection from the reflector 31, which is then directed as reflected radiation 31 towards the device for receiving the volume flow 1. For the sake of clarity, the graphic representation of the convex shape elements on the inside of the device for receiving the volume flow 1 has been omitted.

[0078] Particularly in the application shown, it is advantageous to arrange a microstructure on the outside of the device according to the invention for receiving a volume flow 1, which is shown here as a tube. This microstructure can consist of a porous mass or of a plurality of individual structural elements, wherein the structural elements preferably have a needle, rod, or mushroom shape. The microstructure serves here as a so-called "black trap," i.e., as a design measure to improve the absorption behavior of the device for receiving the volume flow 1 with respect to the incident solar radiation 30. With a tube or tube designed in this way,With such a device designed to receive the volume flow 1, not only can a volume flow be realized efficiently and with little maintenance, but also optimal use of incident solar radiation 30 to heat the medium in the device to receive a volume flow 1 and / or to maintain a certain temperature.

[0079] Fig. Figure 6 shows a further possible application of the device according to the invention for receiving a volume flow 1, wherein several of these devices 1 are preferably arranged parallel to each other in a heat exchanger 40 as shown, and the devices for receiving a volume flow 1 extend through a space 43 formed by the heat exchanger 40, which is or can be flowed through by a fluid 42. That is, here an optimal heat transfer from the fluid 42 in the space 43 to the medium 41 in the devices for receiving a volume flow 1 can be achieved.In particular, this embodiment provides that the convex shaping elements directed towards the inside of the device for receiving a volume flow 1 form corresponding concave shaping elements on the outside of the device for receiving a volume flow 1, so that turbulences are also formed on the outside of the devices for receiving a volume flow 1 by these concave shaping elements, which hinder the deposition of contaminants contained in the fluid 42.

[0080] That is, the device according to the invention for receiving a volume flow 1, for example for transporting a molten salt as medium 41, as in Fig. 5 shown, can be used, or also for flow around with a molten salt as fluid 42, as in Fig. 6 shown.

[0081] Overall, this provides a device which, due to the arrangement of certain convex shape elements 20, can largely prevent the deposition of crystals and also optimally enables heat exchange between a medium within the device and an ambient medium. Thus, in addition to the advantage of being virtually maintenance-free, the efficiency of heat transfer is also increased. Reference symbol list 1 Device for receiving a volume flow 2 Longitudinal direction 3 Volume flow 4. Vortexing 5 particles 10 wall surface 11 Surface 20 convex shape element 21 Vertex 22 arc-shaped edge 23 Tangent 24 rounding W clear width H height B Width A distance 30 solar radiation 31 Reflector 32 Reflected radiation 40 heat exchangers 41 Medium 42 Fluid Room 43

Claims

[1] Device (1) for receiving a volume flow of a medium which, in the solidified state, forms an ionic crystal structure, comprising at least one wall surface (10) which limits the volume flow (3) at least on one side, wherein the wall surface (10) has convex shape elements (20), wherein the device (1) for receiving a volume flow is a tube on the inner wall of which the convex shape elements (20) are arranged, characterized by , that each convex shape element (20) has a cross-sectional area in its section plane perpendicular to the plane of the surface (11) of the wall surface (10) and through its vertex (21) and along the longitudinal extension direction of the tube, which is bounded by an arc-shaped edge (22) and an edge connected to the arc-shaped edge (22) which is designed as a tangent (23), wherein the edge designed as a tangent (23) transitions into the surface (11). [2] Heat exchanger (40) comprising several devices (1) for receiving a volume flow according to claim 1 for transporting a medium (41), which are arranged in a space (43) through which a fluid (42) which forms an ionic crystal structure in the solidified state flows or can flow through. [3] Solar thermal power plant comprising a device (1) for receiving a volume flow according to claim 1 for transporting a medium (41) heated by solar energy which forms an ionic crystal structure in the solidified state, in particular for transporting a molten salt. [4] Solar thermal power plant according to claim 3, characterized by , that the device (1) for receiving a volume flow is arranged in such a way that it is exposed or can be exposed to solar radiation (30). [5] Solar thermal power plant according to one of claims 3 or 4, characterized by, that the surface of the device (1) for receiving a volume flow has a microstructure at least in certain areas. [6] Solar thermal power plant according to one of claims 3 to 5, characterized by , that it has a heat exchanger (40) according to claim 2. [7] Method for realizing a volume flow of a medium (41) which in the solidified state forms an ionic crystal structure, in which a melt of the medium (41), in particular a salt melt, is passed through a device (1) for receiving a volume flow according to claim 1. [8] Method for realizing a volume flow of a medium (41) according to claim 7, characterized by , that the melt of the medium (41) has a temperature of 150 °C to 650 °C. [9] Method for realizing a volume flow of a medium according to one of claims 7 or 8, characterized by, that each convex shape element (20) has a cross-sectional area in its section plane perpendicular to the plane of the surface (11) of the wall surface (10) and through its vertex (21) and along the longitudinal extension direction of the tube, which is bounded by an arc-shaped edge (22) and an edge connected to the arc-shaped edge, which is designed as a tangent (23), wherein the edge designed as a tangent (23) transitions into the surface (11), wherein the melt flows towards the respective convex shape element (20) at the area designed as a tangent (23) in the cross-section. [10] Method for generating electrical energy in which a medium (41) heated by solar energy, which forms an ionic crystal structure in the solidified state, is transported in a device (1) for receiving a volume flow according to claim 1, the heated medium (41) is made available and the thermal energy of the medium (41) is converted at least partially into electrical energy. [11] Method for generating electrical energy according to claim 10, characterized by , that the device (1) for receiving a volume flow during the transport of the medium (41) is exposed to solar radiation. [12] Method for generating electrical energy according to claim 10, characterized by, that in a heat exchanger (40) according to claim 2, heat is transferred at least partially from a fluid (42) which flows through the space (43) of the heat exchanger (40) to the medium (41) in the devices (1) for receiving a volume flow, the heated medium (41) is made available and the thermal energy of the medium (41) is converted at least partially into electrical energy.

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