Method and device for electrically heating flow of heat transfer fluid

Abstract

The method according to the invention is provided for heating the fluid by infrared radiation of the infrared radiation surface in the electric heating device (80). For this purpose, the heating device (80) has a resistive heating element arrangement (12) having resistive heating elements (13), the surfaces of which form infrared radiation surfaces, and outputs infrared radiation into an absorber space (16) through which a fluid to be heated flows. The fluid has an infrared absorbing gas and is heated by absorbing infrared radiation (15). At high temperatures, a non-inert gas, i.e. A non-inert fluid, will corrode the resistive heating element (13). The protective gas assembly (82) prevents corrosive fluid from contacting the resistive heating element (13).

Description

Technical Field

[0001] The present invention relates to a method and apparatus for electrically heating a heat transfer fluid having an IR-absorbing gas to at least 800°C. Background Technology

[0002] Process heat with temperatures of 800°C or higher, up to 1300°C, is used in many fields. This process heat is typically transported via a heat transfer fluid. It is relatively rare to find this type of process heat generated in solar power plants; it is usually generated by electric heating systems.

[0003] In the field of solar power plants, receivers are used that reach temperatures of 1300°C. Solar radiation enters the structure of the absorber, heating it within its depth and thereby heating the fluid passing through the structure via convection. This results in a highly unpredictable and irregular heat distribution within the absorber structure, accompanied by mechanical problems and uneven heating of the fluid. These drawbacks are exacerbated by weather-dependent and alternating solar radiation. Therefore, in the field of receivers, it has been proposed to increasingly utilize absorption to heat the fluid, offering the advantages of simpler receiver construction and mitigating the irregular heat distribution along with uneven heating of the fluid.

[0004] Aside from relatively rare, location-limited, or weather-dependent solar power plants, electric heating systems are widely used to heat gases used as heat transfer fluids. These systems, by standard practice, avoid potential heat absorption and deliberately employ forced convection, as disclosed, for example, in US 8,119,954. The construction of such complex heating systems offers numerous advantages; the technology is mature, and mechanical issues and heat distribution within the fluid are largely controlled through structural design by those skilled in the art. Even at temperatures such as 1300°C, the operation of such electric heating systems should not be problematic. However, at such temperatures, an increasing risk arises from fluid corrosion of the heating system, as corrosion depends not only on the pairing of the materials used for the electric heating elements with the heat transfer fluid but also on the temperature.

[0005] Therefore, the disadvantage of existing electric heating systems is that at higher temperatures, starting from 800°C and generally exceeding 1000°C, the inherently conductive material of the resistance heating element is prone to oxidation, thus it can only heat inert gases or gases that are not corrosive to the corresponding materials at said temperatures as heat transfer fluids. Summary of the Invention

[0006] Accordingly, the objective of the present invention is to provide a method and a corresponding electric heating device for electrically heating both non-corrosive gases and corrosive gases (e.g., water vapor) to at least 800°C.

[0007] This task is accomplished by a method having the features of claim 1 or by an electric heating device having the features of claim 17.

[0008] By equipping the heat transfer fluid with an infrared-absorbing gas and exposing it to the infrared radiation of the electric heating device in the absorber space, heat transfer is primarily achieved through absorption. As a result, an electric heating device with an advantageously simplified structure is provided, which in turn allows the device to be modularly configured with a protective gas assembly for the resistance heating element with only minor further structural costs, enabling the device to be used even on an industrial scale for corrosive heat transfer fluids.

[0009] In addition to the tasks proposed, according to the invention it is also possible to reach temperatures as high as 1400°C, 1600°C or higher, for which electric heating devices for practical (and industrial) use have not yet been available, as well as for non-corrosive gases.

[0010] It is concluded that, according to the present invention, not only non-corrosive gases (such as CO2) but also corrosive gases (such as water vapor) can be heated to temperatures above 800°C or even the aforementioned temperatures, wherein, for corrosive gases, the method or heating device configuration according to claims 5 and 27 is advantageous.

[0011] Other preferred embodiments have the features of the remaining dependent claims. Attached Figure Description

[0012] The invention will now be described in more detail with the aid of the accompanying drawings.

[0013] The attached diagram shows: Figure 1 A known circuit is schematically shown in which the heat transfer fluid circulates and is heated by an electric heating device; Figure 2 An embodiment of the electric heating device according to the present invention is illustrated schematically; Figures 3a to 3e Different embodiments of the electric heating device according to the present invention are illustrated schematically; Figure 4 An embodiment of an electric heating device modified for corrosive gases is schematically shown; Figure 5 Another embodiment of the electric heating device for corrosive gases according to the present invention is shown schematically; Figure 6 Another embodiment of the electric heating device is schematically shown; and Figure 7A method for separating a protective gas present in the circuit of a heat transfer fluid in an electric heating device for corrosive gases according to the invention is schematically shown. Detailed Implementation

[0014] Figure 1 A circuit for a heat transfer fluid, known per se, is schematically shown. This circuit has a fluid delivery line 1 in which the heat transfer fluid is transported in the direction of the arrow, heated to at least 800°C in an assembly for heating the fluid (here, an electric heating device 2 according to the invention), and directed to a consumer 3. There, the heat transfer fluid outputs its heat and is then directed back to the heating device 2 for reheating. The consumer 3 itself uses the acquired heat as process heat, which allows for the input and output of the consumer, as is known to those skilled in the art, and is indicated by the arrow drawn at the consumer 3. The electric heating device 2 has a circuit for cold fluid (with a temperature of T). u The fluid supply connection 4 and the fluid supply connection for hot fluid (with a temperature of T) o The fluid output connection 5 of the device further includes electrical lines 6 and 6' for supplying the current required for heating the fluid from a suitable current source 7, which is symbolically shown. It is therefore preferable to guide the heat transfer fluid in a loop in which the component 2 for heating the fluid and the consumer 3 for consuming the heat from the heated fluid are located.

[0015] It should be noted that the method or electric heating device according to the invention is not limited to applications in fluid circuits, although this relates to the primary application scenarios.

[0016] Figure 2 A cross-sectional view is shown of an assembly for heating a heat transfer fluid, configured as an electric heating device 10 according to the invention, including its fluid supply connection 4 and a collection pipe (constructed here as an annular pipe 11) with a fluid collection opening 11', which serves as a collector for the heated fluid and leads to a fluid output connection 5, which is omitted to reduce the visual burden. Figure 1 a).

[0017] The infrared radiation device is constructed as follows: a resistance heating element assembly 12 (hereinafter referred to as "IR"): preferably concentrically arranged resistance heating elements 13 are heated to a temperature above 800°C during operation (i.e. when the current source 7 is activated), for example up to 1200°C, 1400°C, 1600°C, 1800°C or higher, and thus output IR radiation 15 symbolically indicated by arrows through its surface 14 according to the physical blackbody model.

[0018] The IR radiating surface 14 formed by the various surfaces of the heating element 13 points towards the absorber space 16, which extends along its length from one end (here, the supply connection 4) to the other end (here, the resistance heating element assembly 12), and has transverse sidewalls 17 connecting them, which here have a cylindrical section and a conical section. The absorber space 16 is traversed by fluid in the direction of arrow 18. Therefore, the resistance heating element assembly 12, through the resistance heating element 13, constitutes an IR radiating device having an IR radiating surface 14 facing the absorber space 16. In other words, the IR radiating surface 14 is configured to output the heat generated by the resistance heating element assembly 12 as much as possible as IR radiation 15 into the absorber space 16 during operation.

[0019] Temperature T is input from supply connection 4. u (The input temperature may be, for example, 600°C or within other temperature ranges.) The fluid flowing through the absorber space 16 in the direction of arrow 18 now contains an IR-absorbing gas, which is exposed to IR radiation 15, absorbs the IR radiation, and thus continues until the collection opening 11' is heated to a higher output temperature T. o Here, the IR-absorbing gas region near the resistance heating element 13 or the IR radiating surface 14 absorbs a large portion of the IR radiation 15, thereby being heated. It then emits IR radiation according to the blackbody model, and thus heats its adjacent gas region, for example, upstream in the direction opposite to arrow 18. Therefore, the fluid present in the absorber space 16 can be heated against the flow direction towards the supply connection 4.

[0020] Meanwhile, the sidewall 17 is also partially heated by the IR radiation 15 of the resistance heating element 13 and partially by the IR radiation of the heated IR-absorbing gas, and then emits IR radiation into the absorber space 16 according to the blackbody model, thus also contributing to the heating of the gas.

[0021] As an example, consider a point 17′ on the sidewall 17, which is reached by IR rays 15′ from the IR radiating surface 14, and thus heated, thereby emitting IR radiation 15* according to the blackbody model itself, which enters the absorber space 16. The IR radiation 15*, for example, reaches a volume element 18′ of an IR-absorbing gas in the fluid, is absorbed by that volume element, and thus heats that volume element 18′. If the fluid contains another non-IR-absorbing gas (e.g., a protective gas, as described below) in addition to the IR-absorbing gas, the volume element 18′ will sooner or later collide with a volume element 19′ of that non-IR-absorbing gas, and heat the non-IR-absorbing gas at the molecular level through the collision of corresponding molecules. Therefore, if the heat transfer fluid contains other non-IR-absorbing gases in addition to the IR-absorbing gas, these other non-IR-absorbing gases will eventually also be heated through the collision of corresponding molecules, so that the entire fluid is ultimately heated directly and indirectly by the absorption of IR radiation 15 through the mixing of IR radiation 15 and the gases.

[0022] In addition, the fluid inevitably comes into contact with the hot sidewall 17 and also with the surface 14 that radiates IR due to its high temperature, thus also causing secondary convection heating (minor because convection heating is not structurally supported—the electric heating device 10 is designed for absorption).

[0023] The aforementioned relationships are complex, resulting in a temperature distribution within the absorber space 16 during operation. While this distribution may be uniform, it is essentially composed of a mixture of locally superheated or supercooled gas regions, which are caused more or less by absorption of IR radiation 15, 15* or by convective heat transfer at the wall 17 or the IR radiation surface 14. It has been shown that heat transfer from the resistance heating element 13 to the fluid is more efficient when the share of heat transfer is increased through absorption, and a significantly more uniform temperature distribution in the fluid can also be achieved, at least in the region of the collection opening 11'. Furthermore, the dimensions of the absorber space 16 and the IR radiation surface 14 are its defining parameters.

[0024] According to the present invention, the heat transfer in the electric heating device 10 is reversed from the forced convection according to the prior art (achieved by a high ratio of the heating wall area to the volume of the fluid to be heated), and high IR absorption is sought, which is achieved by the large volume fraction of the fluid to be heated relative to the hot wall area surrounding the fluid.

[0025] Considering the dimensions of the absorber space 16 and the IR radiation surface 14, those skilled in the art can now coordinate the fluid flow rate as another determining parameter to these dimensions such that the ratio χ of the heating achieved by the IR absorbing gas through absorption of IR radiation to the total heating achieved by it through absorption and convection is ≥0.5, or ≥0.6, preferably ≥0.7, particularly preferably ≥0.8, and very preferably ≥0.9. Here, the heat distribution in the fluid is uniform and efficient, and almost perfectly uniform at the collection opening 11′.

[0026] Advantageously, the electric heating device 10 (including the resistance heating element assembly 12 configured as an IR radiation device) has a simpler structure and is correspondingly less expensive than conventional electric heating devices, and also has relatively low flow resistance, which contributes to efficiency, i.e., higher effectiveness.

[0027] It should be noted here that the heating power of the resistance heating element 13 itself (i.e., the flux of IR radiation 15) has only a minor effect on the ratio χ under the first-order approximation. This ratio is mainly determined by the coordination between the dimensions of the absorber space 16, the IR radiation surface 14, and the flow rate. However, if more stringent specifications are required (e.g., involving the desired output temperature T), the ratio will be affected. o (In accordance with the specifications), those skilled in the art may preferably include the IR radiation flux entering the absorber space 16, given by the heating power, as another parameter in the parameters to be coordinated.

[0028] Those skilled in the art can, in specific circumstances, coordinate the aforementioned dimensions, flow rates, and, if possible, the IR flux entering the absorber space 16 through simulation or experimentation. Preferably, those skilled in the art first determine the fluid, i.e., the IR-absorbing gas, and then, based on the absorption capacity of the IR-absorbing gas and the temperature T... u and T o The dimensions of the absorber space 16 are determined, and thus the dimensions of the IR radiation surface 14 are also determined, and finally the flow rate of the fluid through the absorber space 16 is determined.

[0029] Using the aforementioned electric heating device 10, an output temperature of at least 800°C can be achieved not only for small mass flow rates but also for industrial applications, as described above. oHowever, higher temperatures can also be achieved, such as at least 1000°C, 1200°C, 1400°C, 1600°C, or higher. To avoid corrosion of the resistance heating element 13 or its IR radiating surface 14, the material of the resistance heating element can be compatible with the type of gas in the fluid. Therefore, preferably, the IR radiating surface is made of, for example, nickel-iron (NiFe), nickel-chromium (NiCr), and iron-chromium-aluminum (APN) high-temperature alloys, silicon carbide, or molybdenum disilicide (MoSi2); the fluid consists of water vapor or carbon dioxide or a mixture thereof; or alternatively, the infrared radiating surface (14) is made of silicon carbide, and the fluid has carbon dioxide (CO2) as an infrared-absorbing gas. Not only the IR radiating surface but also the fluid can be made of the above materials.

[0030] The aforementioned iron-chromium-aluminum alloy is available under the trademark Kanthal® APM from Kanthal GmbH in Germany, and is referred to in the category of "Resistance Heating Wires and Resistance Wires" as "Powder Metallurgy, Dispersion Strengthened Ferritic Iron-Chromium-Aluminum Alloy (FeCrAl Alloy) for Use at Temperatures Up to 1425°C". Therefore, the first group of high-temperature resistance metal alloys (such as APM, silicon carbide, or molybdenum disilicide) is particularly suitable for fluid temperatures up to approximately 1200°C, while the second group of materials containing silicon carbide and molybdenum disilicide is suitable for temperatures exceeding this.

[0031] Specifically, for example, an output temperature T of 1000℃, 1500℃, or even 2000℃. o Interestingly, the selectivity of materials for resistance heating elements decreases as temperature rises because, on the one hand, temperature resistance itself reaches its limit, and on the other hand, corrosion susceptibility increases sharply. Therefore, in terms of material selection, the output temperature T... o Yes, it is relevant. It should be added that, for example, highly absorbent water vapor (H2O) is advantageous as a heat transfer fluid because it allows for high-quality flow in the electric heating device according to the invention due to its high absorption—however, water vapor undergoes strong oxidation, i.e., strong corrosion, as the temperature rises.

[0032] For output temperatures covering a lower temperature range, such as 1000°C, a wide variety of material combinations (resistance heating elements / fluids) are available, which are known to those skilled in the art of convection electric heating elements, where no protective gas is required. These include, for example, the known and inexpensive iron-chromium-aluminum alloy, which can operate with steam as a fluid.

[0033] For output temperatures spanning a moderate range, such as 1500°C, the advantageous combination of iron-chromium-aluminum alloys with water vapor is no longer feasible. While a combination of silicon carbide (SiC) and carbon dioxide (CO2) as the fluid is suitable in the absence of a protective gas, it is relatively expensive. Similarly, a combination of molybdenum disilicide (MoSi2) with water vapor or carbon dioxide (CO2) as the fluid is possible, with or without a protective gas.

[0034] However, for output temperatures such as 1500°C, when using carbon dioxide (CO2) as the protective gas and silicon carbide (SiC) for the resistance heating element, water vapor can still be used as the fluid, even with the protective gas. This is because silicon carbide (SiC) forms a protective layer that is resistant to carbon dioxide (CO2) but not to water vapor. Furthermore, the combination of silicon carbide, water vapor, and carbon dioxide as the protective gas has the advantage that carbon dioxide is also absorbent, which additionally supports rapid heating within the absorber space and thus supports large-volume flow. If a non-absorbent protective gas is desired in a specific situation, argon (Ar) can be chosen as the protective gas, for example, in the case of water vapor as the fluid, and graphite can be chosen as the material for the resistance heating element. It is also possible that the resistance heating element assembly (12,22,32,42,52,62,92) has a resistance heating element made of silicon carbide and the infrared absorbing gas is carbon dioxide (CO2); or water vapor (H2O) with a protective gas, i.e., air (which is in principle very inexpensive even after treatment involving dirt or moisture, which may be expected).

[0035] Alternatively, for high-temperature applications, commercially available molybdenum (Mo) alloys can also be used as materials for heating elements, and hydrogen (H2) can be used as a protective gas.

[0036] For output temperatures encompassing, for example, an upper temperature range of 2000°C, the material selection for resistance heating elements becomes less restrictive. Graphite or commercially available tungsten alloys for high-temperature applications are feasible in principle, but they are incompatible with both water vapor (H2O) and CO2, thus requiring a protective gas. Inert gases, such as argon (Ar), are suitable as protective gases for both graphite and tungsten alloys, with hydrogen (H2) also applicable to the latter. However, these materials suitable for resistance heating elements at 2000°C corrode even at 1000°C with water vapor (H2O) or carbon dioxide (CO2), making a protective gas assembly meaningful even within this temperature range—the corresponding electric heating device would then operate advantageously over a wide temperature range from 800°C to 2000°C.

[0037] In general, it is concluded that those skilled in the art must combine the various materials according to specific circumstances (e.g., lower temperature range, middle temperature range, or upper temperature range). However, the electric heating device according to the present invention, due to its simple structure, is applicable to any combination of materials and any temperature range, thus, compared with the prior art, ultimately achieving the desired temperature T of the fluid to be heated or the output temperature. o There are no limitations in this regard. In the aforementioned prior art, for example, it is virtually impossible to modify the structure in a simple way (if possible) for the protective gas.

[0038] Finally, it should be noted that the flow direction is not mandatory to be toward the IR radiating surface 14, but can be reversed. In this case, the direction of arrow 18 will be reversed, and... Figure 2 The opening marked as collection opening 11' is used for fluid supply, and the fluid passes through... Figure 2 The discharge is indicated by the connector 4. Those skilled in the art can then coordinate the dimensions, flow rate, and, if possible, the IR flux entering the absorber space 16, as per [the provided text]. Figure 2 In the case of the flow direction in the implementation method.

[0039] Regarding the construction of the electric heating device 10, according to Figure 1 In the embodiment shown, preferably, the absorber space 16 has a length between its ends along the fluid flow direction, and a sidewall 17 with connecting ends is provided transversely to this length. An IR radiating surface 14 is constructed at one end, and a supply or output connection is constructed at the same end, but through the sidewall 17, while the other connection is located at the opposite end and is preferably constructed as a narrowing connection. For example, Figure 1 The upper region of the middle sidewall 17 tapers in a conical shape, thus forming a narrowed connection. Furthermore, it is preferable that the resistance heating element assembly 12 has concentrically arranged annular heating elements 13, and the absorber space 17 preferably has a cylindrical section connected thereto, which is connected to the absorber space along a portion of its length.

[0040] This provides a method for electrically heating a heat transfer fluid containing an IR-absorbing gas to at least 800°C, characterized in that: the fluid is guided through an absorber space 16 of an assembly for heating the fluid, the assembly being provided with an IR radiating device acting on the absorber space 16 via an IR radiating surface 14, and wherein the dimensions of the absorber space 16, the dimensions of the IR radiating surface 14 of the IR radiating device, and the fluid flow rate are coordinated such that the amount of heating achieved by the IR-absorbing gas in the absorber space 16 by absorbing infrared radiation 15, 15* is proportional to the total amount of heating achieved by it through absorption and convection, χ ≥ 0.5, and wherein an IR radiating device having a resistance heating element assembly 12 is used, the surface of which is configured as an IR radiating surface 14, and the resulting IR radiation 15, 15* is directed toward the absorber space 16.

[0041] Therefore, the electric heating device 10 according to the invention for heating a heat transfer fluid having an IR-absorbing gas to at least 800°C has a supply connection 4 for cold fluid to be supplied to the electric heating device and an output connection 5 for heated fluid to be drawn away from the electric heating device, as well as an assembly for heating the fluid guided through the heating device 10, wherein the assembly has an absorber space 16 and an IR radiation device configured as a resistance heating element assembly 12, the surface of which is configured as an IR radiation surface 14 facing the absorber space so that, during operation, the heat generated by the resistance heating element assembly 12 is output as IR radiation 15, 15* into the absorber space 16, wherein, furthermore, the size of the absorber space 16 and the size of the IR radiation surface 14 are coordinated with each other such that, during operation, when the fluid passes through the absorber space 16 at a predetermined flow rate, the heating amount achieved by the IR-absorbing gas due to the absorption of infrared radiation 15, 15* is χ ≥ 0.5 relative to the total heating amount achieved by it in the absorber space through absorption and convection.

[0042] exist Figure 2 In the other accompanying drawings, the electric heating device 10 is oriented vertically, but this is not mandatory. Those skilled in the art can arrange the electric heating device in any orientation under specific circumstances, such as horizontally, tilted, or inverted, so that… Figure 2 The output connection of the heating device 10 shown points downwards.

[0043] Figure 3aA schematic cross-sectional view of one embodiment of the electric heating device 20 is shown, featuring a modified resistance heating element assembly 22 having rod-shaped resistance heating elements 23 and cylindrical IR radiating surfaces 24. An absorber space 26 adapted to the resistance heating elements 23 is provided with rectangular sidewalls 27. Side channels 21, 21' (opposite to each other and including the rod-shaped resistance heating elements 23 in the spacing between them) extend along opposing wall sections 27, 27' forming the sidewalls 27 of the absorber space 26. The side channels 21, 21' connect to a supply connection for heat transfer fluid (omitted for brevity in the drawings), the heat transfer fluid entering the absorber space 26 corresponding to arrow 28 and exiting the absorber space again via an output connection 25. For completeness, ... Figure 3a The diagram also shows a point 17′ on the wall of the absorber space 26, which is heated by the IR radiation 15 of the rod-shaped heating element 23 and generates its own IR radiation 15* that enters the absorber space 26.

[0044] This arrangement has advantages. Preferably, the resistance heating element assembly 20 has parallel arranged rod-shaped resistance heating elements 23, wherein the absorber space 26 preferably has a rectangular section connected thereto, which is rectangular along a portion of its length.

[0045] Figure 3b A schematic cross-sectional view of one embodiment of the electric heating device 30 is shown, featuring a modified resistance heating element assembly 32. This assembly also has parallelly arranged rod-shaped resistance heating elements 33 with IR radiating surfaces 34. However, instead of being positioned at one end of the absorber space 36, which has columnar sidewalls 37, the resistance heating elements are arranged dimensionally through the absorber space. A supply connection 4 is located on one side of the absorber space 36, and an output connection 5 is located on the other side, allowing fluid to flow through the resistance heating elements 33 in the direction of arrow 38 and absorb IR radiation from the IR radiating surfaces 34. As can be seen in the figure, the flow component of the fluid is transverse to the length of the resistance heating elements. In a single resistance heating element 33', power supply via electrical lines 6, 6' and a current source 7 is symbolically indicated, wherein the power supply, of course, supplies current to all resistance heating elements 33 in an operable manner (or functionally operational, i.e., betriebsfähig).

[0046] Preferably, the absorber space 36 is traversed by parallel rod-shaped resistance heating elements 33, the surfaces of which form an IR radiation surface 34, and the supply connection 4 and the output connection 5 are arranged such that the flow component of the fluid flowing through it is transverse to the length of the resistance heating elements 33.

[0047] Figure 3c A schematic cross-sectional view of one embodiment of the electric heating device 40 is shown, which includes a resistance heating element assembly 42, similar to... Figure 3b The resistance heating element assembly is constructed and has a rod-shaped resistance heating element 43 extending through the absorber space 46 in its dimensions. Here, the absorber space 46 has parallel walls, through which the fluid flowing according to arrow 48 flows in a nearly laminar manner in the region of the resistance heating element 43, which supports uniform absorption heating of the fluid.

[0048] Figure 3d A schematic cross-sectional view of one embodiment of the electric heating device 50 is shown, featuring a modified resistance heating element assembly 52. ​​Preferably, the absorber space 56 has a length along the fluid flow direction 58 between its ends formed by the supply connection 4 and the output connection 5, and a sidewall 57 transverse to this length with connecting ends. This sidewall narrows towards the ends in sections 59 and 59', preferably in a funnel shape, and the resistance heating element 53 is arranged in a funnel-shaped narrowing region 59 or 59'. This arrangement has the advantage of being extremely simple in structure.

[0049] Figure 3e A schematic cross-sectional view of one embodiment of the electric heating device 60 is shown, wherein the absorber space 66 is divided into a plurality (here, three) of chambers 66′, 66′′, and 66′′′ arranged sequentially along the flow direction. In each chamber 66′, 66′′, and 66′′′, the supply connection 4 has an annular conduit 61′, 61′′, 61′′′ associated with the chamber, constructed by a partial supply connection. Fluid is distributed through the annular conduit to an opening 11′ and through the opening to the interior of the corresponding chamber 66′, 66′′, and 66′′′. Each chamber 66′, 66′′, and 66′′′ has a resistance heating element assembly 62′, 62′′, 62′′′ with a resistance heating element 63. Each chamber 66′, 66′′, and 66′′′ is connected to the heating device 20 (… Figure 2 The fluid flowing in the direction of arrows 68′, 68′′ and 68′′′ is heated in the same manner, wherein chambers 66′′ and 66′′′ additionally receive at least partially heated fluid through intermediate output connections 65′ and 65′′.

[0050] Advantages of this arrangement include a large IR radiation surface area relative to the total volume of the absorber space 66, provided by a large number of resistance heating elements 63, while the absorber space is still designed to achieve maximum absorption with minimal convection. Thus, even with high fluid temperatures T at the output section 5, absorption remains efficient. oAlternatively, a resistance heating element 63 made of a material whose maximum operating temperature is relatively close to the output temperature T can be used. o Above, a correspondingly relatively small flux of IR radiation enters the respective chambers 66′, 66′′, and 66′′′ (blackbody radiation intensity increases with the fourth power of temperature (K)). For example, at a low output temperature T o Below, the operating temperature and output temperature T of the resistance heating element 63 are... o The slight differences offer the advantage of using simple or inexpensive materials. Furthermore, this arrangement has the advantage of small lateral dimensions and remains suitable for operation with a protective gas assembly, as described below. This results in an electric heating device in which multiple local supply connections 61′, 61′′, 61′′′ are arranged at the absorber space 66, and the resistance heating element assembly has multiple IR radiation devices arranged sequentially along the fluid flow direction 68, such that each IR radiation device is associated with a local supply connection and heats the fluid flowing into the IR radiation device from that supply connection.

[0051] Figure 4 A schematic cross-sectional view of one embodiment of the electric heating device 70 is shown, corresponding to... Figure 2 It has an electric heating device, but with two differences.

[0052] The first difference is that the direction of fluid flow is reversed, as mentioned above. Figure 2 The description mentions it as a possible alternative. Therefore, the fluid flows into the absorber space 16 through the annular pipe 11 as indicated by arrow 71, and exits the absorber space through the output connection 5 located at the end of the absorber space 16 opposite to the resistance heating element assembly 12.

[0053] The second difference is that a protective gas assembly 72 for the resistance heating element assembly 12 is preferably present, which includes a protective gas supply conduit assembly 73 that extends into the region of the IR radiating surface 14. This allows the protective gas exiting the protective gas supply conduit assembly during operation to circulate and scour the IR radiating surface 14, forming a protective gas region 74, thereby operably sealing the IR radiating surface relative to the fluid to be heated in the absorber space 16. The protective gas assembly 72 allows the fluid to contain at least one gas fraction that, upon contact, corrodes the corresponding resistance heating element 13 at its operating temperature. Specifically, the various conduit sections 73' of the protective gas supply conduit assembly 73 extend into the heating element 13 and thus flow along its IR radiating surface toward the absorber space 16. The protective gas forms a cushion above the IR radiating surface 14 and below the inlet 11', thus forming the protective gas region 74 and preventing fluid entering through the inlet 11' from reaching the IR radiating surface 14.

[0054] Although in the illustrated embodiment both the protective gas and the fluid flow toward the output connection 5, some mixing of the protective gas and fluid (albeit in small amounts) cannot be completely eliminated within the protective gas region 74, and this mixing is determined by the specific design of the heating device 70 or the protective gas assembly 72. Therefore, if necessary, those skilled in the art can establish maintenance intervals for the maintenance or replacement of the resistance heating element 13, thereby ensuring that the IR radiating surface 14 is operationally sealed through the protective gas region 74 during the maintenance interval. "Operational" thus includes minor corrosion that occurs over time, which does not negatively impact the theoretical function of the IR radiating surface 14 during the maintenance interval.

[0055] This provides a method in which a protective gas is preferably supplied to the IR radiating device in a region of the IR radiating surface 14, such that the protective gas circulates and washes over the IR radiating surface in a region where it may come into contact with a fluid, thereby forming a protective gas region 74 that protects the IR radiating surface from contact with the heat transfer fluid in an operable manner.

[0056] The protective gas can be IR-transparent or IR-absorbing. For example, a material with ohmic resistance (preferably graphite, molybdenum, or tungsten) can be used as the material for the resistance heating element (and therefore for the IR radiating surface), an oxidizing and therefore corrosive water vapor H₂O or carbon dioxide (CO₂) or a mixture thereof can be used as the fluid, and an inert gas, preferably argon (Ar) or helium (He), can be used as the protective gas. e), that is, an IR-transparent inert gas. Silicon carbide (SiC) can also be used, for example, as a material for the resistance heating element (and therefore for the IR radiating surface 14), with H2O or CO2 that corrodes silicon carbide, wherein carbon dioxide (CO2) is used as a protective gas, which is IR-absorbent.

[0057] Figure 5 A schematic cross-sectional view of one embodiment of the electric heating device 80 is shown, which is consistent with... Figure 4 The electric heating device is constructed similarly, but has a modified protective gas assembly 82, which, although corresponding to the protective gas supply... Figure 4 The system includes a protective gas assembly, but additionally includes a protective gas recirculation assembly 84. This protective gas recirculation assembly has a protective gas recirculation opening 81' arranged in the protective gas region 74 and below the fluid opening 11', and a protective gas recirculation annular conduit 81 connected to the protective gas recirculation opening.

[0058] The protective gas supplied to the protective gas region 74 via the protective gas supply line assembly 73 can now be extracted through the opening 81', led out through the annular line 81, and guided, for example, to a protective gas return line (not shown to reduce the burden on the drawings), which itself leads back into the protective gas supply line assembly 73, thus forming a protective gas loop. This provides a method in which, preferably, at least a portion of the protective gas is again drawn out from the protective gas region 74. Furthermore, an electric heating device 80 is also provided, whose protective gas assembly 82 has a protective gas return assembly 84 drawn from the protective gas region.

[0059] Figure 6 Schematic illustration of heating device 20 ( Figure 2 A cross-sectional view of one embodiment of an electric heating device 90 constructed according to the principle of [missing information - likely a specific principle or design], which includes a modified fluid supply connection 91, a modified resistance heating element assembly 92, and a modified protective gas assembly 93. In addition, as mentioned, the heating device 90 is basically constructed according to [missing information - likely a specific principle or design]. Figure 2 Or other corresponding implementation methods.

[0060] The fluid supply connection 91 has a number of end pipes 94 extending into the absorber space 16, each with an inlet 94' branching off from a distributor 95 for fluid, allowing fluid to be advantageously distributed across the entire cross-section of the absorber space 16 into the absorber space. Fluid flows into the distributor 95 corresponding to arrow 95'.

[0061] The resistance heating element assembly 92 is constructed as a plate 97 arranged with openings 96 for protective gas. This plate forms one end of the absorber space 16, and its IR radiating surface 98 points towards the absorber space 16. To reduce the visual burden, the current connection for the resistance heating element assembly 92 is omitted. The corresponding plate-shaped IR radiating surface 98 can advantageously act uniformly within the absorber space 16.

[0062] The protective gas supply assembly 93 has a protective gas inlet line 99 into which protective gas flows from the protective gas source as indicated by arrow 100, enters the distributor space 101, and from there circulates through opening 92 to flush the IR radiating surface 98, thereby forming a protective gas region 102 drawn by dashed lines, which extends from the IR radiating surface 98 to near the inlet 94' of the end pipe 98 of the output fluid.

[0063] Those skilled in the art can easily provide Figure 6 The embodiment shown includes a protective gas recirculation assembly 84 (not shown in the figure). Figure 5 The method is as follows: a protective gas reflux opening 81' is arranged at the upper end of the protective gas region 102 in the absorber space 16. Figure 5 ), and connect it to the protective gas return loop 81 ( Figure 5 Connect the protective gas circuit. Then, a protective gas circuit can be formed by connecting the protective gas return assembly to the protective gas input line 99.

[0064] Another embodiment of the protective gas recirculation assembly, not shown in the accompanying drawings, involves a fluid supply connection 91 ( Figure 6 The end tube 94 is constructed with double walls, thus having an inner tube with an annular outer tube. The inner tube is connected to the distributor 95, and the outer tube is connected to the distributor space 101. Accordingly, fluid is supplied to the absorber space through the inner tube, while the outer tube draws in protective gas near the inlet and exits it from the electric heating device through the outer tube.

[0065] As mentioned above, regarding Figure 2 As mentioned in the description, the electric heating device does not need to be in a vertical position, so the resistance heating element assembly does not need to be in an upright position and radiate upwards, for example, heating device 70 ( Figure 4 The opposite posture is also possible, for example, with heating device 50 ( Figure 3d It has a downward-radiating resistance heating element 53, which is oriented inverted relative to the heating device 70. Of course, given its simple construction principle, the electric heating device 50 may also be equipped with a protective gas assembly, similar to the protective gas assembly 72. Figure 4The protective gas supply piping assembly directs the protective gas to each resistance heating element 53. (For completeness, it should be noted that those skilled in the art can also easily configure a protective gas return assembly—for example, similar to...) Figure 5 (Protective gas reflux assembly 84).

[0066] For example, when water vapor is used as the fluid, it is advantageous for the protective gas in the arrangement of upward-radiating heating devices (see example...). Figure 3a , 4 5, 6), argon (Ar) is used as the protective gas. On the other hand, for example, according to Figure 3d The inverted arrangement shown is reasonable for using hydrogen (H2) as a protective gas. This is because the molecular weight of the protective gas is related to the molecular weight of the fluid: within a temperature range of 500°C to 2500°C, for the same temperature interval, the molecular weight of water is higher than that of hydrogen (or helium), but lower than that of argon (or CO2 or air).

[0067] That is, during operation, the temperature of the protective gas and the surrounding area (see example) Figure 4 Protective gas zone 74 or Figure 6 The temperatures of the fluids in the protective gas region 102 are quite close to each other, and in the sense of the previous paragraph, they are within the same temperature range: when the electric heating device operates at different theoretical temperatures T o The molecular weight ratio does not change during operation.

[0068] Currently, among these combinations of protective gas and fluid, it is advantageous that when the heating device is in an upright position, the fluid is lighter and the protective gas is heavier, resulting in them mixing less well, meaning the protective gas can perform its function better; conversely, in an inverted position, the lighter protective gas remains more in the upper region of the absorber space, and thus better protects the resistance heating element arranged above.

[0069] This leads to a method in which the protective gas and the fluid preferably have different densities. Vertically, when the protective gas density is higher, the protective gas region is positioned at the lower part of the absorber space; while when the protective gas density is lower, it is positioned at the upper part. For the electric heating device, the protective gas supply line is positioned vertically at a distance from the output connection. Furthermore, when the molecular weight of the heat transfer fluid is less than that of the protective gas, the protective gas supply line is positioned below the supply connection for the heat transfer fluid; while when the molecular weight of the heat transfer fluid is greater than that of the protective gas, it is positioned above the supply connection for the heat transfer fluid.

[0070] Figure 7A schematic diagram 110 shows a circuit 111 for heat transfer fluid, which in the illustrated embodiment is coupled to a circuit 112 for a protective gas, symbolically indicated by an arrow 112' around which the flow direction of the protective gas is indicated by the direction of the arrow 112'. Fluid delivery line 1 (see also...) Figure 1 The flow direction symbolically indicated by arrow 1′ will, for example, be based on... Figure 4 Heating device 70 or according to Figure 6 The electric heating device 113 and the consumable device 3 (see also heating device 90) are constructed with heating device 90. Figure 1 The connection includes a branch 114 after the consumer, in which a branch 115 of the fluid line 1 is led to the separation station 116, and thereafter reintroduced into the loop line 1 downstream at the confluence 117.

[0071] A protective gas pipeline 118 is also led out from the separation station 116 to send the protective gas separated in the separation station back to the heating device 113 in the loop 112, and thereby supply it with protective gas.

[0072] This provides a method in which fluid flowing through an absorber space is preferably enriched with protective gas from a protective gas region. The enriched fluid is guided through and removed from the absorber space, and downstream, the protective gas from the protective gas region is separated from the fluid again. The fluid returns to the absorber space in a fluid loop, and preferably, the protective gas is guided back to the IR radiation surface in the protective gas loop. PA29 Furthermore, a heating device is provided in which a fluid output connection and its supply connection are closed into a loop via a fluid delivery line. This loop has a consumer for the heat of the heated fluid, and a branch line is also provided, preferably branching off from the loop at a branch point after the consumer, leading to a separation station constructed for separating the protective gas from the fluid, and then reintroduced into the loop downstream after the branch point and before the supply connection.

[0073] In schematic diagram 110, the position of the mass arrow indicates the molar mass flow: I indicates that I moles of protective gas flow into the heating device 113, for example, through the protective gas supply pipeline assembly 73. Figure 4 ) or through the protective gas supply piping assembly 93 ( Figure 6 Therefore, the fluid is enriched with 1 mole of protective gas as it passes through the heating device 113.

[0074] M represents the flow rate of M moles of protective gas and fluid through the absorber space 16 or the consumer 3 of the heating device 113, wherein the fluid in M ​​moles is enriched with I moles of protective gas. The total share of protective gas is N moles because the fluid already has a share of L moles of protective gas before entering the heating device 113. This share of L is desirable and important for the efficiency of the fluid loop 111, as described below.

[0075] C represents the flow rate of C moles through branch 115 of fluid line 1 to separation station 116. When the separation station separates the protective gas from the fluid, it outputs the protective gas to the protective gas circuit 112 through protective gas line 118, and only outputs the fluid through branch 115 to the confluence 117, and thus outputs it back to fluid line 1.

[0076] To prevent the protective gas content in the fluid from continuously increasing during the operation of the heating device 113, the continuous enrichment of 1 mole of protective gas must correspond to the continuously separated protective gas content, that is, the flow rate of the separated protective gas through the pipeline 118 must be 1 mole.

[0077] If the fluid flowing into heating device 113 does not contain any protective gas, the entire fluid flow must be diverted through separation station 116 to separate the supplied protective gas again. Now, since the fluid flowing into heating device 113 already contains K moles of protective gas, the protective gas concentration after heating device 113 is... k = (I+ L) / M This results in a C-molar sub-stream of protective gas, which already contains I moles of protective gas. Therefore, to separate the protective gas in separation station 116, the energy consumption is only for the C-molar sub-stream, not for the entire M-molar fluid stream. Simple calculations show that at this point... C=(I·M) / N Taking water vapor as the fluid and argon as the protective gas as an example, the energy savings are particularly illustrative: in separation station 116, argon is separated by condensing water vapor, and then the water needs to be brought back to the input temperature T at branch 117. u Even with the recovery of condensation waste heat, energy loss still occurs, leading to a decrease in the efficiency of fluid loop 112. These energy losses are smaller when the flow rate of fluid or steam guided through separation station 116 is smaller, and the efficiency of fluid loop 112 is correspondingly higher. Those skilled in the art can now determine, in specific cases, the predetermined proportion of protective gas (L moles) in the fluid flow. Therefore, it is preferable that, during operation, the fluid has a predetermined proportion of protective gas before reaching the supply connection. Furthermore, it is preferable that the protective gas is separated from the fluid by condensing other components of the fluid.

[0078] It should be emphasized that one advantage of this absorption-type electric heating device lies in its possible structural diversity, which is absent in existing electric heating devices. The absorber space can be constructed differently, as can the resistance heating element assembly, the resistance heating element itself, and its arrangement within the absorber space. What remains consistent is that the corresponding electric heating device is manufactured with a simple structure and low cost. This also applies to the protective gas assembly and, where possible, the protective gas recirculation assembly: it is also structurally simple and can be appropriately arranged within the electric heating device without problems, i.e., without additional costs. The various individual features of the embodiments shown in the figures can be combined almost arbitrarily according to the specific requirements.

Claims

1. A method for electrically heating a heat transfer fluid containing an infrared-absorbing gas to at least 800°C, characterized in that, The fluid is guided through absorber spaces (16, 26, 36, 46, 56, 66) of an assembly for heating the fluid. This assembly is provided with an infrared radiation device that acts on the absorber spaces (16, 26, 36, 46, 56, 66) via an infrared radiation surface (14). The dimensions of the absorber spaces (16, 26, 36, 46, 56, 66), the dimensions of the infrared radiation surface (14) of the infrared radiation device, and the flow rate of the fluid are coordinated such that the infrared-absorbing gas... The heating amount achieved by absorbing infrared radiation in the absorber space (16,26,36,46,56,66) is χ≥0.5 relative to the total heating amount achieved by absorption and convection, and wherein an infrared radiation device with a resistance heating element assembly (12,22,32,42,52,62,92) is used, the infrared radiation device having a surface configured as an infrared radiation surface (14), and wherein the infrared radiation generated therefrom is directed towards the absorber space (16,26,36,46,56,66).

2. The method according to claim 1, wherein, The infrared-absorbing gas is an anisopolar gas, and is preferably one or a mixture of gases CO2, water vapor, CH4, NH3, CO, SO2, SO3, HCl, NO and NO2, with a particularly preferred mixture containing water vapor and CO2.

3. The method according to claim 1, wherein, The fluid is guided in the loop, and components for heating the fluid and a heat consuming device (3) for the heated fluid are located in the loop.

4. The method according to claim 2, wherein, The infrared radiating surface (14) has a high-temperature alloy of iron, chromium and aluminum, silicon carbide or molybdenum disilicide, and the fluid has water vapor or carbon dioxide or a mixture thereof.

5. The method according to claim 1, wherein, A protective gas is supplied to the infrared radiation device in the region of the infrared radiation surface (14) such that the protective gas circulates and washes the infrared radiation surface in the region where it may come into contact with the fluid, thereby forming a protective gas region (74, 102) that protects the infrared radiation surface (14) in an operable manner from contact with the heat transfer fluid.

6. The method according to claim 1 or 5, wherein, High-temperature resistant materials with ohmic resistance, preferably silicon carbide (SiC) or graphite (C), or molybdenum (Mo) or tungsten (W), are used as the material for the infrared radiation surface 14; in addition, the heat transfer fluid has water vapor (H2O) or carbon dioxide (CO2) or a mixture thereof; and an inert gas is preferably used as the protective gas, preferably argon (Ar) or hydrogen (H2) or carbon dioxide (CO2) as the protective gas.

7. The method according to claim 5, wherein, At least a portion of the protective gas is drawn away again from the protective gas region (74, 102).

8. The method according to claim 5, wherein, The fluid flowing through the absorber space (16,26,36,46,56,66) is enriched with a protective gas supplied in the region of the infrared radiating surface (14). The enriched fluid is guided through the absorber space (16,26,36,46,56,66) and taken away from the absorber space. Downstream, the supplied protective gas is separated from the fluid again, wherein the fluid is guided back to the absorber space (16,26,36,46,56,66) in a fluid loop (111), and preferably the protective gas is guided back to the infrared radiating surface (14) in a protective gas loop (112).

9. The method according to claim 5 or 8, wherein, The heat transfer fluid has a predetermined proportion (L) of protective gas before entering the component used for heating the fluid.

10. The method according to claim 8, wherein, The protective gas is separated from the fluid by condensing other components of the fluid.

11. The method according to claim 8, wherein, The protective gas is separated from the fluid after the consumer (3).

12. The method according to claim 5, wherein, Silicon carbide is used as the material for the infrared radiation surface (14), the heat transfer fluid has water vapor or a mixture of water vapor and carbon dioxide, and the protective gas has carbon dioxide.

13. The method according to claim 1, wherein, The flux of infrared radiation entering the absorber space (16, 26, 36, 46, 56, 66) is also included in the parameters that need to be coordinated.

14. The method according to claim 1, wherein, The ratio χ ≥ 0.6, preferably ≥ 0.7, particularly preferably ≥ 0.8, and completely preferably ≥ 0.

9.

15. The method according to claim 5, wherein, The protective gas and the fluid have different densities, and in the vertical direction, when the density of the protective gas is greater, the protective gas region (74, 102) is arranged in the lower part of the absorber space (16, 26, 36, 46, 56, 66); when the density of the protective gas is less, the protective gas region is arranged in the upper part of the absorber space.

16. The method according to claim 1, wherein, The fluid is heated to at least 1000°C, preferably 1200°C, more preferably 1400°C, or even more preferably 1600°C or higher.

17. An electric heating device (2,10,20,30,40,50,60,70,80,90,113) for heating a heat transfer fluid containing an infrared-absorbing gas to at least 800°C, said electric heating device having a supply connection 4 for cold fluid to be supplied to the electric heating device and an output connection (5,25) for heated fluid to be withdrawn from the electric heating device, and said electric heating device having an assembly for heating the fluid guided through said heating device (2,10,20,30,40,50,60,70,80,90,113), characterized in that, The component has an absorber space (16, 26, 36, 46, 56, 66) and an infrared radiating device configured as a resistance heating element assembly (12, 22, 32, 42, 52, 62, 92). The surface of the infrared radiating device is configured as an infrared radiating surface (14) facing the absorber space (16, 26, 36, 46, 56, 66) so that, during operation, the heat generated by the resistance heating element assembly (12, 22, 32, 42, 52, 62, 92) is output as infrared radiation to the absorber space (16, 26, 36, 46, 56, 66). In the absorber space (16,26,36,46,56,66), and furthermore, the size of the absorber space (16,26,36,46,56,66) is so coordinated with the size of the infrared radiating surface (14) that, during operation, when the fluid passes through the absorber space (16,26,36,46,56,66) at a certain flow rate, the amount of heating achieved by the infrared absorbing gas due to the absorption of infrared radiation is χ ≥ 0.5 relative to the total amount of heating achieved by it in the absorber space (16,26,36,46,56,66) through absorption and convection.

18. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 17, wherein, The ratio χ is ≥0.6, preferably ≥0.7, particularly preferably ≥0.8, and most preferably ≥0.

9.

19. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 17, wherein, The infrared absorbing gas is an anisopolar gas or a mixture, and is preferably one or a mixture of more than one of the following: CO2, water vapor, CH4, NH3, CO, SO2, SO3, HCl, NO, and NO2, and is particularly preferably a mixture containing water vapor and CO2.

20. The electric heating device (2,10,20,30,40,50,60,70,80,90,113) according to claim 17, wherein, The resistance heating element assembly (12,22,32,42,52,62,92) has a resistance heating element made of silicon carbide, and the infrared absorbing gas is carbon dioxide (CO2), or water vapor (H2O) with a protective gas, namely carbon dioxide (CO2) or argon (Ar).

21. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 17, wherein, The absorber space (16,26,36,46,56,66) has a length between its ends in the direction of fluid flow and has sidewalls (17,37,57) transverse to this length connecting ends. The infrared radiating surface (14) is constructed at one end, and a supply connection (4) or an output connection (5) is constructed at the same end, but configured to pass into the sidewall (17,37,57). Another connection (5,4) is provided at the opposite end and is preferably constructed as a narrowing connection (5,4).

22. The electric heating device (2,10,20,30,40,50,60,70,80,90,113) according to claim 21, wherein, The resistance heating element assembly (12,22,32,42,52,62,92) includes concentrically arranged annular resistance heating elements (13), and the absorber space (16,26,36,46,56,66) preferably has a cylindrical section connected to the resistance heating element and extending along a portion of its length.

23. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 21, wherein, The resistance heating element assembly (12,22,32,42,52,62,92) has parallel arranged rod-shaped resistance heating elements (23), and the absorber space (16,26,36,46,56,66) preferably has a rectangular section connected to the resistance heating element and extending along a portion of its length.

24. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 17, wherein, The absorber space (16,26,36,46,56,66) is penetrated by parallel rod-shaped resistance heating elements (23), the surface of which forms an infrared radiation surface (14), and the supply connection (4) or the output connection (5) is arranged such that the flow component of the fluid flowing through it is transverse to the length of the resistance heating elements (23).

25. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 17, wherein, The absorber space (56) has a length between its ends in the direction of fluid flow and has a sidewall (57) connecting the ends transversely to the length, the sidewall preferably being funnel-shaped and narrowing toward the ends in sections 59, 59', and wherein the resistance heating element (53) is arranged in one or both sections 59, 59'.

26. The electric heating device (60) according to claim 17, wherein, Multiple local supply connections are arranged in the absorber space (66), and the resistance heating element assembly (62, 62′, 62′′) has multiple infrared radiation devices arranged sequentially along the fluid flow direction (68), such that each infrared radiation device is associated with a local supply connection and heats the fluid flowing from the local supply connection to the infrared radiation device.

27. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 17, wherein, A protective gas assembly (72, 82, 93) is provided for the infrared radiating surface (14), the protective gas assembly having a protective gas supply line assembly (73, 93) that extends into the region of the infrared radiating surface, such that during operation, the protective gas exiting therefrom circulates and washes the infrared radiating surface (14) in a protective gas region (74, 102), and thereby operably seals the infrared radiating surface relative to the fluid to be heated in the absorber space (16, 26, 36, 46, 56, 66).

28. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 27, wherein, The protective gas assembly (72, 82, 93) has a protective gas return assembly (84) that draws the protective gas away from the protective gas region (74, 102).

29. The electric heating device (2,10,20,30,40,50,60,70,80,90,113) according to claim 27, wherein, The output connection (5) for the fluid and its supply connection (4) are closed into a loop via a fluid transport line (1), the loop having a consuming device (3) for the heat of the heated fluid, wherein a branch line (115) is further provided, the branch line preferably branching off from the loop line (1) at a branch (114) after the consuming device (3) to a separation station (116) constructed for separating protective gas from the fluid, and reintroduced into the loop line (1) downstream after the separation station, after the branch (114) and before the supply connection (4).

30. The electric heating device (2,10,20,30,40,50,60,70,80,90,113) according to claim 27, wherein, During operation, the fluid has a predetermined proportion of protective gas (L) before the supply connection (4).

31. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 27, wherein, The separation station (116) is connected to the protective gas supply pipeline assembly (4) and is configured to deliver the separated protective gas to the protective gas supply pipeline assembly (4) during operation.

32. The electric heating device (2,10,20,30,40,50,60,70,80,90,113) according to claim 27, wherein, The protective gas supply line (4,118) is at a distance from the output connection (5) in the vertical direction, and wherein when the molecular weight of the heat transfer fluid is less than the molecular weight of the protective gas, the protective gas supply line is arranged below the supply connection (4) for the heat transfer fluid; and when the molecular weight of the heat transfer fluid is greater than the molecular weight of the protective gas, the protective gas supply line is arranged above the supply connection for the heat transfer fluid.

33. The electric heating device (2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 113) according to claim 17, wherein, The resistance heating element assembly (12,22,32,42,52,62,92) has a resistance heating element made of silicon carbide, and the infrared absorbing gas is carbon dioxide (CO2) or water vapor (H2O) with a protective gas, i.e., air.

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