Fluid guiding module fluid heater and fluid heating apparatus

Abstract

A fluid guiding module (2), a fluid heater (30), and an apparatus (50) are disclosed. The module (2) comprising a number of tubes (4) and a header (6) forming an inlet chamber (16). The tubes (4) are arranged to form a boundary around a central longitudinal space (10). The header (6) is ring-shaped and arranged around an open central portion (22). The inlet chamber (16) is arranged in fluid communication with an inside of each tube (4). The open central portion (22) is arranged in juxtaposition and open communication with the central longitudinal space (10) formed by the tubes (4). Outlet openings (20) of the tubes (4) collectively form a fluid outlet from the fluid guiding module (2). At the second end portion (14), insides (37) of the tubes (4) are arranged in fluid communication with outsides (39) of the tubes (4) via the outlet openings (20).

Description

[0001] FLUID GUIDING MODULE FLUID HEATER AND FLUID HEATING APPARATUS

[0002] TECHNICAL FIELD

[0003] The invention relates to a fluid guiding module for a fluid heater, to a fluid heater comprising a fluid guiding module, and to a fluid heating apparatus.

[0004] BACKGROUND

[0005] When heating gases to high temperatures, such as up to 1200 °C or even higher, it is required to use both convection heat transfer and thermal radiation. In order to achieve good convection heat transfer, a large heat transfer surface being in contact with the gas flow is advantageous.

[0006] A common solution to provide a large heat transfer surface is to use two concentrical tubes, the inner tube being heated and feeding the gas in the gap in between the two tubes. Since long tubes with a small gap between them are required for heating gas to high temperatures, it becomes difficult to provide tubes straight enough to be arranged concentrically with each other. Moreover, if a concentrical arrangement is possible it might still be difficult or impossible to withdraw the inner tube from the outer tube once they have been exposed to high temperature. This so, as a consequence of distortion of the tubes due to the high temperature exposure.

[0007] DE 19610593 discloses a heat exchanger comprising a container and a tubular heat exchanger element configured for a fluid to be heated to flow past its outer surface. The tubular heat exchanger element is at least partially surrounded by a concentric tube, the fluid flowing in the annular gap between the tube and the element. A heating wire is provided in the tubular heat exchange element.

[0008] US 4453496 discloses a multi-tubular once-through boiler. The multi-tubular once-through boiler comprises a combustion device, a ring-shaped upper header which functions as a vapor chamber, a ring-shaped lower header which functions as a water chamber, a plurality of vertical water-tubes connecting the upper and lower headers to form a single-row ringshaped water-tube wall, a combustion chamber which is a cylindrical inner space surrounded by the water-tube wall, and a ring-shaped combustion gas passage formed between the water tube wall and an outer wall of the boiler. WO 2023 / 183190 discloses a fluid heater configured to increase the temperature of a process fluid flowing through the fluid heater. The fluid heater includes multiple tubes that route the process fluid through the fluid heater. The fluid heater includes one manifold assembly at each end of the multiple tubes. The multiple tubes of the fluid heater are formed from a polymer. As such the fluid heater is devised for heating fluids up to a temperature of 120 degrees Celsius in hazardous locations or up to a temperature of 180 degrees Celsius in non-hazardous locations.

[0009] SUMMARY

[0010] It would be advantageous to provide a reliable and efficient fluid heater. It would further be desirable to provide a fluid guiding arrangement for, and in, a fluid heater, the arrangement being configured to be essentially deformation resistance even when subjected to high temperatures. To better address one or more of these concerns, one or more of a fluid guiding module, a fluid heater, and a fluid heating apparatus having the features defined in one or more of the independent claims is provided.

[0011] According to an aspect, there is provided a fluid guiding module for a fluid heater, the module comprising a number of tubes and a header forming an inlet chamber. Each tube of the number of tubes extends in parallel with a longitudinal axis. The tubes of the number of tubes are arranged side by side such that each tube has two adjacent tubes. The header is ringshaped and arranged around an open central portion. The fluid guiding module has a first end portion and a second end portion opposite to the first end portion seen along the longitudinal axis. The header is arranged at the first end portion with the inlet chamber arranged in fluid communication with an inside of each tube of the number of tubes. Outlet openings of the tubes are arranged at the second end portion.

[0012] The number of tubes are arranged side by side such that collectively, the tubes of the number of tubes form a boundary around a central longitudinal space. The open central portion of the ring-shaped header is arranged in juxtaposition and open communication with the central longitudinal space formed by the tubes of the number of tubes. The outlet openings of the tubes collectively form a fluid outlet from the fluid guiding module. At the second end portion, insides of the tubes of the number of tubes are arranged in fluid communication with outsides of the tubes via the outlet openings of the tubes. Since the outlet openings collectively form a fluid outlet from the fluid guiding module and the outlet openings of the tubes collectively form a fluid outlet from the fluid guiding module, and since at the second end portion, insides of the tubes of the number of tubes are arranged in fluid communication with outsides of the tubes via the outlet openings of the tubes, the end portions of the tubes at the second end portion of the fluid guiding module are unrestrictedly arranged in the fluid guiding module. Accordingly, the natural thermal expansion of the tubes when heated does not lead to deformation of the tubes in a radial direction, at least not to any degree which would impede the functionality and / or the operation of the fluid guiding module in a fluid heater or a fluid heating apparatus, and / or which would not impede servicing of the fluid guiding module in a fluid heater or a fluid heating apparatus.

[0013] More specifically, because the tubes of the number of tubes are not being physically connected to an outlet arrangement, such as an outlet header or manifold, when the tubes are heated during operation, axial expansion of the individual tubes is unimpeded at the second end portion of the fluid guiding module.

[0014] According to a further aspect, there is provided a fluid heater comprising a fluid guiding module according to any one of examples and / or aspects discussed herein and an electric heating element or a fuel burner positioned through the open central portion of the ringshaped header and into the central longitudinal space formed by the tubes of the number of tubes. According to embodiments, a fluid heater may comprise more than one fluid guiding module according to any one of examples and / or aspects discussed herein and one or more electric heating elements.

[0015] Again, since the outlet openings of the tubes of the number of tubes collectively form a fluid outlet from the fluid guiding module and the outlet openings of the tubes collectively form a fluid outlet from the fluid guiding module, and since at the second end portion, insides of the tubes of the number of tubes are arranged in fluid communication with outsides of the tubes via the outlet openings of the tubes, the end portions of the tubes at the second end portion of the fluid guiding module are unrestrictedly arranged in the fluid guiding module and the fluid heater. Accordingly, when the tubes are heated by an electric heating element or a fuel burner, the thermal expansion of the tubes, does not lead to any substantial deformation of the tubes in a radial direction, at least not to any degree that would impede the functionality, the operation, and / or the serviceability of the fluid heater. According to a further aspect, there is provided a fluid heating apparatus comprising a housing extending along a housing axis, the fluid heating apparatus comprising at least one fluid heater according to any one of examples and / or aspects discussed herein arranged at last partially within the housing, wherein the longitudinal axis of the fluid guiding module of each of the at least one fluid heater extends in parallel with the housing axis.

[0016] Again, since the outlet openings of the tubes of the number of tubes collectively form a fluid outlet and the outlet openings of the tubes collectively form a fluid outlet from the fluid guiding module, and since at the second end portion, insides of the tubes of the number of tubes are arranged in fluid communication with outsides of the tubes via the outlet openings of the tubes, the end portions of the tubes at the second end portion of the fluid guiding module are unrestrictedly arranged in the fluid guiding module, the fluid heater, and the fluid heating apparatus. Accordingly, when the tubes are heated by the electric heating element or the fuel burner, the thermal expansion of the tubes does not lead to any substantial deformation of the tubes in a radial direction, at least not to any degree that would impede the functionality, the operation, and / or the serviceability of the fluid heating apparatus.

[0017] Moreover, since the fluid guiding module of the at least one fluid heater is arranged within the housing of the fluid heating apparatus, during operation of the fluid heating apparatus, the outlet openings of the tubes lead heated fluid into the housing. Accordingly, the housing may be provided with an outlet for heated fluid and thus, may function as a collector for the heated fluid.

[0018] The inventor has realised that by letting the outlet openings collectively form the fluid outlet from the fluid guiding module, i.e. by providing open tube ends in the fluid guiding module, the unavoidable natural thermal expansion of the tubes is not restrained by any outlet arrangement of the fluid guiding module. The fluid guiding module, accordingly, is devised for free for axial expansion. Furthermore, the inventor has realised that by arranging the fluid guiding module in a housing of a fluid heating apparatus, the heated fluid can be admitted from the tubes of the fluid guiding module into the housing and in turn, the housing may be provided with an outlet arrangement for the heated fluid. Thus, the tubes can freely expand within the housing without risking deformation in a radial direction, while the heated fluid is taken out from the housing, instead of directly from the fluid guiding module. The fluid guiding module, herein also referred to as the module, is configured for use as part of a fluid heater. As such, during use of the fluid heater, the fluid to be heated flows through the fluid guiding module while it is subjected to heat from e.g., an electric heating element or a fuel burner of the fluid heater arranged in the central longitudinal space of the fluid guiding module.

[0019] More specifically, since the number of tubes form, and accordingly extend along, the central longitudinal space, the number of tubes is subjected to the heat and the fluid is heated while flowing through number of tubes from the first end portion of the fluid guiding module to its second end portion.

[0020] In the fluid guiding module, each individual tube will form a gastight passage and therefore the tubes of the number of tubes do not have to be fixed or sealed in relation to each other along their lengths. Thus, thermal elongation and / or any stress induced by varying temperature gradients in the individual tubes will not lead to any angular deformation of the fluid guiding module relative the longitudinal axis. Natural thermal expansion is unavoidable but due to the freedom for axial expansion, the fluid guiding module is only elongated and not subjected to angular deformation.

[0021] The fluid to be heated may be a liquid or a gas. In particular, the fluid guiding module is devised for gas which is to be heated to high temperatures, such as such as up to 1200 °C or even higher. It is at high temperatures where the resistance against deformation of the herein discussed fluid guiding module becomes most advantageous.

[0022] Purely mentioned as examples, the fluid to be heated may be a gas such as air, nitrogen, hydrocarbons (e.g. methane), hydrogen, vapour, carbon oxide, carbon dioxide and helium.

[0023] The tubes of the number of tubes forming the boundary around the central longitudinal space means that the number of tubes delimit the central longitudinal space. Two adjacent tubes of the number of tubes may abut against each other. However, the tubes of the number of tubes need not abut against each other, and specifically not along their entire lengths.

[0024] Irrespective of whether the tubes abut against each other or not, the tubes of the number of tubes are considered to form a boundary around the central longitudinal space. Since each tube of the number of tubes extends in parallel with the longitudinal axis and the number of tubes forms a significant part of the fluid guiding module, the longitudinal axis also forms a longitudinal axis of the fluid guiding module. Accordingly, herein, unless otherwise specified, axial, radial, and circumferential references relate to the longitudinal axis.

[0025] In order to ensure that the tubes remain arranged side by side and that the tubes of the number of tubes remain positioned to form the boundary around the central longitudinal space, the tubes may be kept in position by one or more girdles arranged around the number of tubes. Such girdles may take the form of outer ringlike members extending around the number of tubes. Also, radially supporting inner ringlike members may be arranged inside the number of tubes circumferentially along the longitudinal space. Such inner and outer ringlike members may be arranged in concentrical pairs.

[0026] As in the fluid guiding module, the open central portion of the ring-shaped header is arranged in juxtaposition and in open communication with the central longitudinal space formed by the tubes of the number of tubes, an electric heating element or a fuel burner which is insertable through the open central portion into the central longitudinal space to from a fluid heater of the herein discussed kind.

[0027] In the fluid heating apparatus, at least the number of tubes of the at least one fluid heater may be arranged within the housing of the fluid heating apparatus.

[0028] The herein discussed fluid heater may be utilised in any kind of fluid heating apparatus which provides for a collecting of the heated fluid from the outlet openings of the tubes of the number of tubes. One or more fluid heaters may be used depending on the need.

[0029] Accordingly, as mentioned above, the housing of the herein discussed fluid heating apparatus may be provided with an outlet for heated fluid and thus the housing may function as a collector for the heated fluid.

[0030] As mentioned above, in the fluid guiding module, at the second end portion, insides of the tubes of the number of tubes are arranged in fluid communication with outsides of the tubes via the outlet openings of the tubes. In this manner, the outlet openings of the tubes collectively form a fluid outlet from the fluid guiding module. Thus, during use of the fluid guiding module, heated fluid may flow from the fluid guiding module directly out of the outlet openings of the tubes. Accordingly, the fluid guiding module does not include any outlet header.

[0031] Just for explanatory purpose: An outlet header, such as e.g. discussed in US 4453496, of the fluid guiding module would collect the heated fluid within the fluid guiding module for conducting it from the fluid guiding module to a recipient for the heated fluid. Such an outlet header would prevent the insides of the tubes from being arranged in fluid communication with the outsides of the tubes.

[0032] According to some examples, perpendicularly to the longitudinal axis, each tube of the number of tubes may have a circular or an oval cross section. In this manner, the heat from an electric heating element or a fuel burner within the fluid guiding module may be efficiently transferred to the fluid flowing through the tubes during use of the fluid guiding module, the fluid heater, and the fluid heating apparatus.

[0033] With an oval cross section of the tubes, the short axis of the oval cross section may extend in a radial direction of the central longitudinal space.

[0034] Further features of, and advantages with, the invention will become apparent when studying the appended claims and the following detailed description.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Various aspects and / or examples of the invention, including its particular features and advantages, will be readily understood from the examples discussed in the following detailed description and the accompanying drawings, in which:

[0037] Figs. 1a - 1c illustrate a fluid guiding module for a fluid heater,

[0038] Figs. 2a and 2b schematically illustrate a longitudinal section through fluid heaters according to some examples,

[0039] Fig. 3 illustrates a perspective view of a section of Fig. 2a,

[0040] Fig. 4 schematically illustrates a partial section of a fluid heating apparatus according to an example, and

[0041] Fig. 5 schematically illustrates a section of a fluid heating apparatus according to an example. DETAILED DESCRIPTION

[0042] Aspects and / or examples of the invention will now be described more fully. Like numbers refer to like elements throughout. Well-known functions or constructions will not necessarily be described in detail for brevity and / or clarity.

[0043] Figs. 1a - 1c illustrate a fluid guiding module 2 for a fluid heater. The fluid heater may be a fluid heater as discussed below with reference to Figs. 2a - 4. Fig. 1a shows a side view of the fluid guiding module 2, Fig. 1b shows a cross section along line B-B in Fig. 1a, and Fig. 1c shows an isometric view of the module 2.

[0044] The module 2 comprises a number of tubes 4 and a header 6. Each tube 4 of the number of tubes 4 extends in parallel with a longitudinal axis 8. The longitudinal axis 8 may be seen as a longitudinal axis of the module 2, which longitudinal axis 8 extends along a general extension of the module 2.

[0045] The tubes 4 of the number of tubes 4 are arranged side by side. Accordingly, each tube 4 has two adjacent tubes 4. Moreover, the number of tubes 4 form a boundary around a central longitudinal space 10. Put differently, collectively, all the tubes 4 form a radial boundary of the central longitudinal space 10. The longitudinal space 10 extends along the longitudinal axis 8.

[0046] According to some examples, perpendicularly to the longitudinal axis 8, the central longitudinal space 10 formed by the tubes 4 of the number of tubes 4 may have a square, a round, or an oval cross-sectional shape. Each of the square, round, or oval cross-sectional shape is a general approximation, which excludes the effect the tubes 4 have on the cross- sectional shape.

[0047] For instance, the cross-sectional shape may be one that permits a relevant heating element or burner to be positioned and operated within the central longitudinal space 10.

[0048] In the illustrated examples, the cross-sectional shape of the central longitudinal space 10 is round.

[0049] According to some examples, such as the illustrated examples, each tube 4 of the number of tubes 4 is arranged in abutment with two adjacent tubes 4. In this manner, during use of the module 2, an efficient heat transfer from a heating element or burner within the central longitudinal space 10 to the tubes 4 and the fluid flowing through the tubes 4 may be provided.

[0050] According to some examples, the tubes 4 of the number of tubes 4 alternatively, may be arranged such that a gap is formed between adjacent tubes 4. According to some examples, the gap may be narrow, the advantage of having a narrow gap is that the heat radiated from the heating element or burner have the possibility to reach a larger surface portion of the tubes 4 than if the tubes 4 abut against each other.

[0051] Mentioned purely as an example, such a gain in heat radiation reaching the tubes 4 may be anticipated with a largest circumferential gap within a range of 0.1 - 15 mm between outer surfaces of adjacent tubes 4, measured at a position where adjacent tubes 4 are at their closest to each other.

[0052] Accordingly, if in examples having abutting tubes 4, circumferential gaps would occur between adjacent tubes 4, the heating performance of the module 2 would not have to be negatively affected, it might even be positively affected by such circumferential gaps.

[0053] It follows from the above discussion that the boundary formed by the tubes 4 of the number of tubes 4 may be a closed boundary when the tubes 4 abut against each other or a scattered boundary when there is a distance (narrow gap) between the tubes 4.

[0054] According to some examples, at least some of the tubes 4 of the number of tubes 4 may be provided with one or more external fins to increase their outer surface areas, which are exposed to heat radiated from the heating element or burner. For instance, such fins could project from the tubes 4 into the central longitudinal space 10.

[0055] The tubes 4 are not directly fixedly connected to each other. The connection between the header 6 and the tubes 4 ensures their relative position in relation to each other within the module 2. Girdles, such as ringlike members, may be arranged at intervals along the number of tubes 4 in order to maintain the relative radial positions of the tube 4 along the longitudinal axis 8. See further below with reference to Fig. 3. According to some examples, a further layer of tubes may be provided in the fluid guiding module. More specifically, radially outside the number of tubes 4, a further number of tubes may be arranged. The tubes of the further number of tubes extending in parallel with the longitudinal axis 8 and being arranged side by side. Accordingly, each tube of the further number of tubes has two adjacent tubes.

[0056] For instance, in examples wherein the tubes 4 of the number of tubes 4 are arranged with a gap between adjacent tubes 4, the further number of tubes arranged radially outside the number of tubes 4 may receive heat radiated from the heating element or burner through the gaps.

[0057] The fluid guiding module 2 has a first end portion 12 and a second end portion 14 opposite to the first end portion 12 seen along the longitudinal axis 8.

[0058] The header 6 is arranged at the first end portion 12. The header 6 forms an inlet chamber 16. During use of the fluid guiding module 2, fluid to be heated is conducted to the inlet chamber 16, from which the fluid flows into the tubes 4 via inlet openings 18 thereof. Accordingly, the inlet chamber 16 is arranged in fluid communication with insides of the tubes 4 via the inlet openings 18 of the tubes 4.

[0059] Outlet openings 20 of the tubes 4 are arranged at the second end portion 14 of the module 2. During use of the module 2, the fluid that has been heated as it flows within the tubes 4, leaves the fluid guiding module 2 via the outlet openings 20 of the tubes 4.

[0060] The header 6 is ring-shaped and arranged around an open central portion 22. Accordingly, the header 6 may be considered to be a hollow flange.

[0061] The ring-shaped header 6 is considered to be ring-shaped since it extends around the open central portion 22. As with the central longitudinal space 10 formed by the tubes 4 of the number of tubes 4, the ring-shaped header 6 and / or the open central portion 22 may have a square, a round, or an oval cross-sectional shape perpendicularly to the longitudinal axis 8. Similarly, the inlet chamber 16 may have a square, a round, or an oval cross-sectional shape corresponding to the cross-sectional shape of the header 6. The open central portion 22 of the ring-shaped header 6 is arranged in juxtaposition and open communication with the central longitudinal space 10 formed by the tubes 4. This is clearly visible in the view of Fig. 1b.

[0062] The open central portion 22 of the ring-shaped header 6 may be aligned along the longitudinal axis 8 with the central longitudinal space 10 formed by the tubes 4 of the number of tubes 4.

[0063] As mentioned above, the outlet openings 20 of the tubes 4 of the number of tubes 4 are arranged at the second end portion 14 of the module 2. The outlet openings 20 collectively form the fluid outlet from the module 2.

[0064] Since the module 2 excludes an outlet header connected to the tubes 4 at the second end portion 14 of the module 2, during use of the module 2, axial expansion of the individual tubes 4 is unobstructed at the second end portion 14. Thus, the natural thermal expansion of the tubes 4 does not lead to any deformation of the tubes in the radial direction to any degree that would render one or more of the functionality, operation, or servicing of the fluid guiding module 2 difficult or impossible.

[0065] As mentioned above, the tubes 4 are not fixedly connected to each other along their lengths. Accordingly, the tubes 4 are arranged in the module 2 such that they can unrestrictedly expand along the longitudinal axis 8 in relation to each other.

[0066] The tubes 4 are attached to the header 6, such as welded to the header 6, at the first end portion 12 of the module 2. Thus, in a direction towards the second end portion 14 and beyond, the tubes 4 can expand.

[0067] At the second end portion 14 of the fluid guiding module 2, the insides of the tubes 4 of the number of tubes 4 are arranged in fluid communication with outsides of the tubes 4 via the outlet openings 20 of the tubes 4. This arrangement provides for the outlet openings 20 of the tubes 4 collectively forming the fluid outlet of the fluid guiding module 2. See also below with reference to Fig. 3. According to some examples, perpendicularly to the longitudinal axis 8, an inner cross- sectional area of each tube 4 of the number of tubes 4 may be within a range of 50 - 200 mm2.

[0068] For a tube 4 having a circular cross-section this means that an inner diameter of the tube 4 is within a range of approximately 8 - 16 mm.

[0069] According to some examples, each tube 4 of the number of tubes 4 may have a wall thickness within a range of 1.5 - 4 mm.

[0070] Within this range, the thinner the wall thickness, the better heat transfer through the tube walls. On the other hand, the thicker the wall thickness, the longer before corrosion has errored the tubes 4. Thus, the choice of wall thickness may depend inter alia on how corrosive the fluid to be heated is.

[0071] According to some examples, the tubes 4 of the number of tubes 4 may be made from one or more of the alloys in the group including a FeCrAI-alloy, a NiCr-alloy, and a NiCrFe-alloy. In this manner, a high temperature resistance fluid guiding module 2 may be provided. The fluid guiding module 2 may be utilised for heating fluid, such as gas, up to 1200 °C or even higher.

[0072] According to some examples, each tube 4 of the number of tubes 4 may have a length within a range of 2 - 10 m. In this manner, the fluid to be heated may be guided within the tubes 4 over a sufficiently long distance, such that the fluid is heated up to 1200 °C or higher.

[0073] Within this range, a common foreseeable range of the lengths of the tubes 4 may be 1 to 10 m, such as 2 to 10 m, such as 3 to 9 m, such as 3 to 4 m.

[0074] In use of the module 2, the longitudinal axis 8 may be arranged horizontally or vertically or at an angle therebetween.

[0075] A fluid guiding module 2 comprising tubes 4 having a length at an upper end of the range may be arranged with the longitudinal axis 8 extending vertically in order to eliminate any bending effect that gravity may have on heated, and thus, comparatively easily deformable tubes 4. Each tube 4 of the number of tubes 4 may have a circular cross-section as shown in e.g. in Fig. 1b. Other cross-sectional shapes of the tubes 4 are feasible, such as oval, square, or rectangular.

[0076] Figs. 2a and 2b schematically illustrate longitudinal sections through fluid heaters 30 according to some examples.

[0077] Each fluid heater 30 comprises a fluid guiding module 2. The fluid guiding module 2 may be a module 2 as discussed above with reference to Figs. 1a - 1c. Accordingly, in the following reference is also made to the above description.

[0078] The fluid heater 30 of Fig. 2a comprises an electric heating element 32. The fluid heater 30 of Fig. 2b comprises a fuel burner 34.

[0079] Each of the electric heating element 32 and the fuel burner 34 is positioned in the module 2 through the open central portion 22 of the ring-shaped header 6 and into the central longitudinal space 10 formed by the tubes 4 of the number of tubes 4.

[0080] Accordingly, each of the electric heating element 32 and the fuel burner 34 is positioned centrally within the respective fluid guiding module 2 such that the tubes 4 and accordingly, a fluid flowing through the tubes 4, can be heated by the electric heating element 32 and the fuel burner 34, respectively.

[0081] As is clearly visible in Figs. 2a and 2b, the outlet openings 20 of the tubes 4 collectively form the fluid outlet from the fluid guiding module 2. When the tubes 4 are heated by the electric heating element 32 or the fuel burner 34, unrestricted longitudinal thermal expansion of the tubes 4 is enabled in the module 2 and the fluid heater 30.

[0082] According to some examples, such as the illustrated examples in Fig. 2a, the electric heating element 32 comprises one or more resistive members 36 extending in parallel with the longitudinal axis 8.

[0083] During use of the fluid heater 30, the resistive members 36 of the heating element 32 are heated by an electric current. The heat from the resistive members 36 radiates and heats the tubes 4 and the fluid flowing through the tubes 4, from the header 6 to their outlet openings 20.

[0084] The resistive members 36 may be of various known types or forms, such as wire members, strip members, or tubular members. The resistive members 36 extend along the longitudinal axis 8 and are electrically isolated from each other by isolator members 38. The isolator members 38 may also position the resistive members 36 in relation to each other within the heating element 32.

[0085] Alternating current, AC, electric power or direct current, DC, electric power may be connected to at least two connectors 40 for electric power in order to supply electric power to the resistive members 36.

[0086] The resistive members 16 may be made from any suitable known material, such as one or more of iron-chromium-aluminium (FeCrAI)alloy, nickel chromium (NiCr) alloy, and nickel- chromium-iron (NiCrFe) alloy.

[0087] Fig. 3 illustrates a perspective view of a section of the fluid heater 30 along line III - III in Fig. 2a. In the following, reference is also made to Fig. 2a.

[0088] Accordingly, in Fig. 3 the central longitudinal space 10 formed by the tubes 4 is clearly shown. In Fig. 3 also two of the isolator members 38 are arranged to isolate the resistive members 36 of the electric heating element 32 from each other.

[0089] Also, clearly visible in Fig. 3 are insides 37 of two of the tubes 4 and outsides 39 of the tubes 4. The insides 37 of the tubes 4 are arranged in fluid communication with the outsides 39 of the tubes 4 via the outlet openings 20 of the tubes, as discussed above.

[0090] The tubes 4 of the number of tubes 4 in the example of Fig. 3 have an oval cross-section perpendicularly to the longitudinal axis 8.

[0091] According to some examples, such as the examples of Figs. 2a - 3, the tubes 4 of the number of tubes 4 are held together around the central longitudinal space 10 by at least one ring member 42 extending around the number of tubes 4. In this manner, the tubes 4 may be held in position in a radial direction around the central longitudinal space 10. More specifically, the ring member 42 may form a girdle around the number of tubes 4 and hold them in position, such that the central longitudinal space 10 is precisely defined by the tubes 4 of the number of tubes 4. The tubes 4 may abut against the ring member 42 and against each other. Thus, the positions of the tubes 4 may be defined. As shown in Fig. 3, a further ring member 44 may be arranged concentrically with the ring member 42 within the central longitudinal space 10 and abut against the tubes 4 from inside the central longitudinal space 10. Thus, the tubes 4 may be reliably positioned to form the central longitudinal space 10.

[0092] As mentioned above, the tubes 4 are not fixedly connected to each other. Neiter need the tubes 4 be fixedly connected to the ring member 42 and the further ring member 44. Accordingly, the tubes 4 are only prevented from any substantial movement in a radial direction by the ring member 42 and the further ring member 44. Axially, the tubes 4 may move in relation to the ring member 42, the further ring member 44, and each other. Thus, the individual thermal elongation of the tubes 4 during use of the fluid heater 6 may be ensured.

[0093] However, if an even distribution of heat from the heating element or the fuel burner within the central longitudinal space 10 is ensured, a fixed connection of the ring member 42 and / or the further ring member 44 to the tubes 4 may be viable since in such case the thermal elongation of the tubes 4 at each axial position within the central longitudinal space 10 may be the same and thus, a fixed attachment to the ring member 42 and / or the further ring member 44 will not cause angular deformation of the fluid guiding module 2.

[0094] Fig. 4 schematically illustrates a partial section of a fluid heating apparatus 50 according to an example.

[0095] The fluid heating apparatus 50 comprises a housing 52 extending along a housing axis 54.

[0096] The fluid heating apparatus 50 comprises at least one fluid heater 30 arranged within the housing 52. The at least one fluid heater 30 may be at least one fluid heater 30 as discussed above with reference to Figs. 1a - 3. Accordingly, in the following reference is also made to Figs. 1a - 3. The longitudinal axis 8 of the fluid heating module 2 of the at least one fluid heater 30 extends in parallel with the housing axis 54.

[0097] Again, it is clearly visible that the outlet openings 20 of the tubes 4 of the number of tubes 4 collectively form a fluid outlet from the fluid guiding module 2 of each of the at least one fluid heater 30.

[0098] Thus, the tubes 4 can thermally expand along the longitudinal axis 8 within the fluid heating apparatus 52.

[0099] In the example of Fig. 4, each fluid heater 30 comprises an electric heating element 32 as shown in Fig. 2a. The electric heating elements 32 are connected to an electric power supply / regulation unit 55 for controlling the heat generated by the heating elements 32.

[0100] Alternatively, each fluid heater 30 may comprise a burner 34 in accordance with the example fluid heater 30 of Fig. 2b.

[0101] According to some examples, the fluid heating apparatus 50 comprises a fluid inlet arrangement 56 arranged in fluid communication with the inlet chamber 16 of the fluid guiding module 2 of each of the at least one fluid heater 30. In this manner, the fluid to be heated may be admitted into the fluid heating apparatus 50 and each of the fluid heaters 30 thereof.

[0102] For instance, the fluid inlet arrangement 56 may comprise one or more conduits extending to the headers 6 and the inlet chambers 16 of the fluid heating modules 2 of each of the fluid heaters 30.

[0103] The headers 6 and the inlet chambers 16 of the fluid heating modules 2 of each of the fluid heaters 30 may be arranged outside the housing 52 of the fluid heating apparatus 50. The number of tubes 4 of the fluid heating modules 2 of each of the fluid heaters 30 may be arranged inside the housing 52 of the fluid heating apparatus 50.

[0104] According to some examples, the fluid heating apparatus 50 comprises a fluid outlet arrangement 58. The fluid outlet arrangement 58 is arranged in fluid communication with an internal space 60 of the housing 52. The outlet openings 20 of the number of tubes 4 of each of the at least one fluid heater 30 are arranged in fluid communication with the fluid outlet arrangement 58 via the internal space 60 of the housing 52. In this manner, the heated fluid may be led from the fluid heating apparatus 50.

[0105] Put differently, during use of the fluid heating apparatus 50, the outlet openings 20 of the tubes 4 lead heated fluid from the fluid heaters 30 into the internal space 60 of the housing 52 of the apparatus 50. The housing 52 functions as a collector for the heated fluid. The outlet arrangement 58 comprises an outlet conduit 62, through which the heated fluid is lead from the internal space 60 and the apparatus 50.

[0106] The housing 52 may be an insulated housing i.e. , may comprise an outer load bearing structure, such as a casing, which on its inside may be provided with an insulation layer. The insulation layer may be made from a fibrous ceramic material, such as aluminium oxide.

[0107] According to a further example, within the fluid heating apparatus 50, each fluid heater 30 may be arranged within a cylindrical insulation member. Thus, heat radiating from the respective fluid heater 30 may be insulated to a large extend from the housing 52. The housing 52 thus, may not have to withstand such high temperatures as if each fluid heater 30 were not arranged with a cylindrical insulation member. The load bearing material of the housing 52, such as an outer steel casing, may be made from a less heat-resistant steel material.

[0108] A further alternative may be for two or more fluid heaters 30 to be arranged within a common insulation member, which would achieve the same purpose of insulating the heat radiating from these modules from the housing 52.

[0109] An outer steel casing of the housing 52 may form a pressure vessel. For instance, the steel casing may form a pressure vessel devised for pressure up to 16 bar.

[0110] Fig. 5 schematically illustrates a section of a fluid heating apparatus 50 according to an example. In much this example resembles the example of Fig. 4.

[0111] In the Fig. 5 example, the fluid heating apparatus 50 is configured for heating a pressurised fluid. Accordingly, the outer steel casing of the housing 52 forms a pressure vessel. Additionally, the headers 6 enclosing the inlet chambers 16 are devised as pressure vessels. Thus, an entire fluid path through the fluid heating apparatus 50 is devised for a pressurised fluid. Further, a pressure sealing arrangement 64 may be provided at the at least two connectors 40 for electric power of the heating modules 2. Thus, the fluid heating apparatus 50 may be configured for use with pressurised fluid, such as for a pressure of up to 10 bar or up to 16 bar.

[0112] The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises," "comprising," "includes," and / or "including" when used herein specify the presence of stated features, integers, actions, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, components, and / or groups thereof.

[0113] It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure.

[0114] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0115] It is to be understood that the foregoing is illustrative of various examples and that the invention is defined only by the appended claims. A person skilled in the art will realize that the examples may be modified, and that different features of the examples may be combined to create examples other than those described herein, without departing from the scope of the invention, as defined by the appended claims.

Claims

CLAIMS1. A fluid guiding module (2) for a fluid heater (30), the module (2) comprising a number of tubes (4) and a header (6) forming an inlet chamber (16), wherein each tube (4) of the number of tubes (4) extends in parallel with a longitudinal axis (8), wherein the tubes (4) of the number of tubes (4) are arranged side by side such that each tube (4) has two adjacent tubes (4), wherein the header (6) is ring-shaped and arranged around an open central portion (22), wherein the fluid guiding module (2) has a first end portion (12) and a second end portion (14) opposite to the first end portion (12) seen along the longitudinal axis (8), wherein the header (6) is arranged at the first end portion (12) with the inlet chamber (16) arranged in fluid communication with an inside of each tube (4) of the number of tubes (4), and wherein outlet openings (20) of the tubes (4) are arranged at the second end portion (14), characterised in that the number of tubes (4) are arranged side by side such that collectively, the tubes (4) of the number of tubes (4) form a boundary around a central longitudinal space (10), wherein the open central portion (22) of the ring-shaped header (6) is arranged in juxtaposition and open communication with the central longitudinal space (10) formed by the tubes (4) of the number of tubes (4), wherein the outlet openings (20) of the tubes collectively form a fluid outlet from the fluid guiding module (2), and wherein at the second end portion (14), insides (37) of the tubes (4) of the number of tubes (4) are arranged in fluid communication with outsides (39) of the tubes (4) via the outlet openings (20) of the tubes (4).

2. The fluid guiding module (2) according to claim 1, wherein each tube (4) of the number of tubes (4) is arranged in abutment with two adjacent tubes (4).

3. The fluid guiding module (2) according to any one of the preceding claims, wherein perpendicularly to the longitudinal axis (8) an inner cross-sectional area of each tube (4) of the number of tubes (4) is within a range of 50 - 200 mm2.

4. The fluid guiding module (2) according to any one of the preceding claims, wherein each tube (4) of the number of tubes (4) has a wall thickness within a range of 1.5 - 4 mm.

5. The fluid guiding module (2) according to any one of the preceding claims, wherein the tubes (4) of the number of tubes (4) are made from one or more of the alloys in the group including a FeCrAI-alloy, a NiCr-alloy, and a NiCrFe-alloy.

6. The fluid guiding module (2) according to any one of the preceding claims, wherein each tube (4) of the number of tubes (4) has a length within a range of 2 - 10 m.

7. The fluid guiding module (2) according to any one of the preceding claims, wherein perpendicularly to the longitudinal axis (8), each tube (4) of the number of tubes (4) has a circular or an oval cross section.

8. The fluid guiding module (2) according to any one of the preceding claims, wherein perpendicularly to the longitudinal axis (8) the central longitudinal space (10) formed by the tubes (4) of the number of tubes (4) has a square, a round, or an oval cross-sectional shape.

9. The fluid guiding module (2) according to any one of the preceding claims, wherein the tubes (4) of the number of tubes (4) are held together around the central longitudinal space (10) by at least one ring member (42) extending around the number of tubes (4).

10. A fluid heater (30) comprising a fluid guiding module (2) according to any one of the preceding claims and an electric heating element (32) or a fuel burner (34) positioned through the open central portion (22) of the ring-shaped header (6) and into the central longitudinal space (10) formed by the tubes (4) of the number of tubes (4).

11. The fluid heater (30) according to claim 10, wherein the electric heating element (32) comprises one or more resistive members (36) extending in parallel with the longitudinal axis (8).

12. A fluid heating apparatus (50) comprising a housing (52) extending along a housing axis (54), the fluid heating apparatus (50) comprising at least one fluid heater (30) according to claim 10 or 11 arranged at last partially within the housing (52), wherein the longitudinal axis(8) of the fluid guiding module (2) of each of the at least one fluid heater (30) extends in parallel with the housing axis (54).

13. The fluid heating apparatus (50) according to claim 12, comprising a fluid inlet arrangement (56) arranged in fluid communication with the inlet chamber (16) of the fluid guiding module (2) of each of the at least one fluid heater (30).

14. The fluid heating apparatus (50) according to claim 12 or 13, comprising a fluid outlet arrangement (58), wherein the fluid outlet arrangement (58) is arranged in fluid communication with an internal space (60) of the housing (52), and wherein the outlet openings (20) of the number of tubes (4) of each of the at least one fluid heater (30) are arranged in fluid communication with the fluid outlet arrangement (58) via the internal space (60) of the housing (52).

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