Heat exchanger component with varying twist angle

Abstract

A component for a heat exchanger can comprise a body including a ceramic and can have a central cavity extending along a length of the body; a plurality of spirals extending around the central cavity; a plurality of interspiral channels disposed between the plurality of spirals; a plurality of intraspiral channels contained within the plurality of spirals; wherein a twist angle of each spiral of the plurality of spirals in relation to a length direction of the body is varying. The heat exchanger component can be used for making a heat exchanger having three flow paths and can reach an exceptional efficiency while allowing an economic manufacturing.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a component for a heat exchanger comprising a ceramic body, and a heat exchanger containing the component for a heat exchanger.BACKGROUND ART

[0002] Standard industry high temperature heat exchangers which operate at temperatures above 800°C typically support efficiencies close to 70%. An increased efficiency of up to 88% can be obtained with regenerative heat exchangers. Regenerative heat exchangers require, however, a complex combination of two burners, regenerative beds, and computer controlled valves, which make regenerative systems cost prohibitive. US4589844 A describes a recuperator for increasing the efficiency of operation of furnaces equipped with and without radiant tube type burner systems. JP 2018 017470 describes a heat exchanger having a cylindrical main body, a hemispherical tip portion, and a disk-shaped flange located on the rear end side of the main body, which are integral with each other.

[0003] There exists a need to bridge the gap between standard industry and regenerative systems to develop heat exchangers with increased efficiencies and costs.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings. FIG. 1 includes an illustration of a section of a body of a component for a heat exchanger according to one embodiment. FIG. 2 includes an illustration of a side view of a cross-cut of a heat exchanger containing a component for a heat exchanger according to one embodiment. FIG. 3 includes an illustration of a side view of a cross-cut of a spiral attached to the surface of a tube wall according to one embodiment. FIG. 4 includes an illustration of a side view of a cross-cut of two spirals attached to the surface of a tube wall according to one embodiment. FIG. 5 shows an illustration of a perspective view of a body of a component for a heat exchanger according to one embodiment. FIG. 6 includes an illustration of a perspective view of a cross-cut in the length direction of a body of a component for a heat exchanger according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0005] The present disclosure is directed to a component for a heat exchanger comprising a body including a ceramic. The body can contain a plurality of spirals extending around a central cavity of the body, wherein a twist angle of each spiral in relation to the length direction of the body is varying. The component for a heat exchanger of the present disclosure can be adapted as an insert for use in a radiant U or W tube as typically used, for example, for steel annealing, coating, or heat treating furnaces. A particular use of the heat exchanger insert of the present disclosure can be for large diameter heat exchangers to recover waste energy. As used herein, the term "component for a heat exchanger" is interchangeable used with the term "heat exchanger insert."

[0006] A non-limiting embodiment of a body of a component for a heat exchanger is illustrated in FIG. 1. The body includes a plurality of spirals (11), which can extend around a tube (12) that surrounds a central cavity (not seen). It can be seen that a first twist angle α1at the proximal end (18) of the body is different than a second twist angle α2 at the distal end (19) of the body.

[0007] The plurality of spirals (11) contain a plurality of intraspiral channels (not shown in FIG. 1). In a particular aspect, each spiral of the plurality of spirals can include at least one intraspiral channel. The spirals can be positioned next to each other with spaces between the spirals, herein called interspiral channels (14). As used herein, the term intraspiral channel means a hollow channel within a spiral, while the term interspiral channel means a channel formed by the space between two spirals.

[0008] In another embodiment, as illustrated in FIG. 2, the component for a heat exchanger can be inserted into an exactly fitting pipe surrounding the spirals, thereby forming a heat exchanger. The heat exchanger can have three fluid flow paths for allowing different fluids to flow from the proximal end to the distal end of the heat exchanger and vice versa. The first flow path is the path of hot gas (16) coming from a location of heat generation, for example, hot gas developed by the burning flame of a burner, herein also called the gas of heat generation. The gas of heat generation (16) can enter the heat exchanger at the proximal end (18) and may flow through the interspiral channels (14) between the plurality of spirals (11) and leave the heat exchanger at the distal end (19). The second flow path can be the path of cold air (15A) entering at the distal end (19) of the heat exchanger and flowing through the intraspiral channels (17) of the plurality of spirals (11) in opposite direction to the flow of the gas of heat generation (16). During the flow through the intraspiral channels (17), the air (15A) is heated by the exchange of heat with the gas of the heat generation (16), wherein the heat is transferred through the walls of the plurality of spirals, such that the two types of gases cannot mix. A portion of the heated air reaching the proximal end (18) of the heat exchanger is used for mixing with fuel gas and be provided to a burner (not shown), while another portion of the heated air is returned and directed through the central cavity (13) surrounded by the center tube (12) as the third flow path. In a certain embodiment, all the heated air (15B) can be returned at the proximal end (18) of the heat exchanger and may flow through the central cavity (13) of the tube (12) back to the distal end (19) and leave the heat exchanger for further use.

[0009] The fluids that can flow through the heat exchanger of the present disclosure are not limited to gases, as described in the embodiment above, but can be also liquids, or both gases and liquids.

[0010] In a particular embodiment, as shown in FIG. 1, the first twist angle α1 at the proximal end (18) of the body can be larger than the second twist angle α2 at the distal end (19) of the body. In another particular embodiment (not shown), the first twist angle α1 at the proximal end of the body can be smaller than a second twist angle α2 at the distal end of the body.

[0011] In one aspect, the twist angle can vary by at least 1 degree per 0.1 meter length direction of the body, such as at least 3 degrees per 0.1 meter length, or at least 5 degrees per 0.1 meter length, or at least 7 degrees per 0.1 meter length, or at least 10 degrees per 0.1 meter length, or at least 15 degrees per 0.1 meter length, or at least 20 degrees per 0.1 meter length. As used herein, the term "length direction of the body" is intended to mean the direction from the proximal end (18) to the distal end (19) of the body or vice versa.

[0012] In one particular embodiment, the twist angle of the spirals can continuously increase or decrease along the length direction of the body. In another particular embodiment, the twist angle of the spirals may increase or decrease discontinuously along the length direction of the body.

[0013] In one embodiment, the twist angle of the spirals throughout the length of the body can be at least 15 degrees, or at least 20 degrees, or at least 25 degrees, or at least 30 degrees, or at least 35 degrees, or at least 40 degrees, or at least 45 degrees, or at least 50 degrees, or at least 60 degrees. In another aspect, the twist angle may be not greater than 90 degrees, such as not greater than 85 degrees, not greater than 80 degrees, not greater than 75 degrees, not greater than 70 degrees, not greater than 65 degrees, or not greater than 60 degrees. Moreover, the twist angle can be within a range including any of the minimum and maximum values noted above, such as at least 15 degrees and not greater than 90 degrees, or at least 20 degrees and not greater than 80 degrees, or at least 25 degrees and not greater than 75 degrees, or at least 30 degrees and not greater than 70 degrees.

[0014] In a further embodiment, each spiral of the plurality of spirals can comprise at least 2 turns per meter in a length direction of the body, such as at least 3 turns per meter or at least 4 turns per meter or at least 5 turns per meter or at least 6 turns per meter or at least 7 turns per meter. In another aspect, the amount of turns per meter of each spiral may be not greater than 10 turns per meter, such as not greater than 9 turns per meter or not greater than 8 turns per meter. Moreover, the amount of turns per meter of each spiral can within a range including any of the minimum and maximum numbers note above.

[0015] FIG. 3 illustrates a particular embodiment of the shape and position of the plurality of spirals in relation to the center tube, based on one exemplary spiral. The spiral (31) can contain two spiral walls (32) framing the intraspiral channel (33), wherein the two spiral walls (32) may be positioned parallel to each other and extend orthogonal (y-direction) to a length direction (x-direction) of the tube wall (34).

[0016] In a particular embodiment, the intraspiral channel (33) can have a thickness (T C1 ) of at least 3 mm, or at least 5 mm, or at least 10 mm, or at least 15 mm, or at least 20 mm, or at least 25 mm, or at least 30 mm. In another aspect the thickness of the intraspiral channel (T C1 ) may be not greater than 125 mm, such as not greater than 100 mm or not greater than 80 mm or mot greater than 50 mm or not greater than 45 mm or not greater than 40 mm or not greater than 35 mm. Moreover, the thickness of the intraspiral channel (T C1 ) may be within a range including any of the minimum and maximum values noted above.

[0017] In another aspect, the wall thickness (T WS ) of the spirals (31) can be at least 1 mm, or at least 1.5 mm, or at least 2 mm, or at least 3 mm, or at least 4 mm. In a further aspect, the thickness of the spiral wall (T WS ) can be not greater than 5 mm, or not greater than 4 mm, or not greater than 3.5 mm. Moreover, the wall thickness (T WS ) of the spirals can be within a range including any of the minimum and maximum values noted above.

[0018] In a further embodiment, the tube (34) surrounding the central cavity can have a wall thickness (T WT ) of at least 1 mm, or at least 1.5 mm, or at least 2 mm, or at least 3 mm. In another aspect the thickness of the tube wall (T WT ) may be not greater than 5 mm, or not greater than 4 mm, or not greater than 3.5 mm. Moreover, the wall thickness of the tube (T WT ) can be within a range including any of the minimum and maximum values noted above.

[0019] In yet a further embodiment, the height (H S ) of the spiral (31) can be at least 7.5 mm, or at least 15 mm, or at least 20 mm. In another aspect, the height of the spiral (Hs) may be not greater than 43 mm, or not greater than 40 mm, or not greater than 35 mm. The height (H S ) of the spirals can be within a range including any of the minimum and maximum values noted above.

[0020] In another embodiment, the cross-sectional surface area of the intraspiral channel (33) can be at least 245 mm 2< , or at least 500 mm 2< , or at least 800 mm 2< , or at least 1000 mm 2< , or at least 1200 mm 2< . In a further aspect, the cross-sectional surface area of the intraspiral channel may be not greater than 1500 mm 2< , or not greater than 1450 mm 2< , or not greater than 1300 mm 2< . Moreover, the cross-sectional surface area of an intraspiral channel can be within a range including any of the minimum and maximum values noted above.

[0021] In yet another aspect, the height H C of the intraspiral channels can be at least 6.4 mm, or at least 7.0 mm, or at least 10.0 mm, or at least 15 mm, or at least 20 mm, or at least 25 mm. In another aspect, the height of the intraspiral channels H C may be not greater than 38 mm, or not greater than 35 mm, or not greater than 30 mm. Moreover, the height H C of the intraspiral channels can be within a range including any of the minimum and maximum values noted above.

[0022] FIG. 4 illustrates a cross-cut of a side view section of the body, wherein two spirals (41) are positioned next to each other, and are attached to the tube wall (44). As described above, the spaces between the plurality of spirals are called herein plurality of interspiral channels (42) and may allow the flow of a fluid in a length direction of the body.

[0023] In one embodiment, the average thickness of the plurality of interspiral channels (T C2 ) can be at least 3 mm, or at least 4 mm, or at least 5 mm, or at least 10 mm, or at least 15 mm, or at least 20 mm, or at least 25 mm, or at least 30 mm, or at least 40 mm. In another aspect, the thickness of the interspiral channels (T C2 ) may be not greater than 50 mm, or not greater than 45 mm, or not greater than 40 mm, or not greater than 35 mm, or not greater than 30 mm, or not greater than 20 mm. Moreover, the thickness of the plurality of interspiral channels can be within a range including any of the minimum and maximum values noted above.

[0024] In a further embodiment, a ratio of the spiral wall thickness T WS of the plurality of spirals to the thickness of the intraspiral channels T C1 can be not greater than 1: 1, or not greater than 1:5, or not greater than 1:10, or not greater than 1:15, or not greater than 1:20.

[0025] In a particular embodiment, the plurality of spirals can be arranged parallel to each other.

[0026] As shown in FIG. 5, each spiral (51) of the plurality of spirals comprises a first straight section (52) at the proximal end and a second straight section (53) at the distal end of the body, wherein the first straight section (52) and the second straight section (53) extend the interspiral channels (54) and are oriented parallel to the length direction of the body.

[0027] FIG. 6 illustrates a cross-cut of a section of a heat exchanger insert in the length direction according to one embodiment. It can be seen that the central cavity 61 is surrounded by a tube 62, and the plurality of spirals (63) can be attached to the tube, wherein the spirals may contain intraspiral channels (65), and the spaces between the spirals are interspiral channels (64).

[0028] The ceramic of the body of the component for the heat exchanger can include silicon carbide, a metal, or a metal alloy. In a particular embodiment, the ceramic can consist essentially of silicon carbide.

[0029] In a further embodiment, a material of the body can consist essentially of silicon carbide and can have an average density of at least 2.50 g / cm 3< , such as at least 2.55 g / cm 3< , or at least 2.57 g / cm 3< , or at least 2.60 g / cm 3< , or at least 2.70 g / cm3. In a further embodiment, the average density of the silicon carbide ceramic body may be not greater than 2.9 g / cm 3< , or not greater than 2.8 g / cm 3< , or not greater than 2.75 g / cm 3< . Moreover, the average density of the material of the body can be within a range including any of the minimum and maximum values noted above.

[0030] In a particular embodiment, the body of the heat exchanger component can be manufactured by a powder pressing process as, for example, described in US 8 162 040.

[0031] The component for a heat exchanger of the present disclosure can comprise a body which may have an exchange ratio ER that is advantages to provide a high heat exchange efficiency. As used herein, the exchange ratio is defined as ER = SA / V, with SA being an outer surface area of the body, and V being the hollow volume of the body. In one embodiment, the Exchange Ratio (ER) of the body can be at least 39 m -1< , such as at least 45 m -1< , or at least 50 m -1< , or at least 60 m -1< , or at least 70 m -1< , or at least 80 m -1< , or at least 90 m -1< , or at least 100 m -1< , or at least 110, or at least 120 m -1< , or at least 130 m -1< , or at least 140 m -1< , or at least 150 m -1< . In another embodiment, the exchange ratio may be not greater than 196 m -1< , or not greater than 185 m -1< , or not greater than 180 m -1< , or not greater than 170 m -1< . Moreover, the Exchange Ratio (ER) of the body can be within a range including any of the minimum and maximum values noted above.

[0032] The body of the component of a heat exchanger of the present invention may withstand a pressure of at least 0.035 MPa at any location of the body without forming cracks or deformation.

[0033] In one embodiment, the Nusselt number of the component for a heat exchanger of the present disclosure can be at least 1000, such as at least 1050, or at least 1100, or at least 1200.

[0034] The body of the heat exchanger component can be adapted to work at a temperature of at least 450°C, such as at least 500°C, or at least 600°C, or at least 700°C, or at least 800°C, or at least 900°C, or at least 1000°C. In another aspect, the body can be adapted to work at a temperature not greater than 1350°C, or not greater than 1300°C, or not greater than 1200°C, or not greater than 1100°, or not greater than 1000°C. Moreover, the body of the heat exchanger can be adapted to work at a temperature within a range including any of the minimum and maximum values noted above.

[0035] In a further embodiment, the component of a heat exchanger of the present disclosure can be inserted into a system to form a heat exchanger. For example, the heat exchanger insert can be inserted into fitting pipe and be connected via a thread to a combustion tube.

[0036] The heat exchanger can comprise at least three flow paths (as described above) and can be adapted that a pressure drop during operation may be not greater than 5 kPa, such as not greater than 4 kPa, not greater than 3 kPa, or not greater than 2 kPa.

[0037] In one aspect, a heat exchanger containing the heat exchanger component of the present disclosure can have an efficiency of at least 70%, or at least 75%, at least 80%, at least 82%, at least 84%, at least 86%, at least 88%, or at least 90%.

[0038] A heat exchanger containing the heat exchanger insert of the present disclosure, by having three flow paths and a varying twist angle of the spirals, can allow maximizing the surface area in relation to a cross-sectional flow area, and thereby may provide a low pressure drop (< 5 kPa) and can reach exceptionally high efficiencies.

[0039] The heat exchanger component of the present disclosure can have further the advantage that by varying the twist angle of the spirals, the size of the internal channels of the spirals (herein called intraspiral channels) can be maintained the same and does not need to be altered throughout the length direction of the body, which can simplify the manufacturing and optimize the efficiency.

Claims

1. A component for a heat exchanger comprising: a body including a ceramic and having: a central cavity (13) extending along a length of the body; a plurality of spirals (11) extending around the central cavity (13); a plurality of interspiral channels (14) disposed between the plurality of spirals (11); wherein at least one spiral of the plurality of spirals (11) has a varying twist angle along a length of the body, wherein each spiral (51) of the plurality of spirals (11) comprise a first straight section (52) at the proximal end (18) of the body and a second straight section (53) at the distal end (19) of the body, wherein the first straight section (52) and the second straight section (53) extend the interspiral channels (14, 54) and are oriented parallel to the length direction of the body, wherein a portion of the fluid in the plurality of spirals (11) is returned at the proximal end (18) and redirected through the central cavity (13).

2. The component for a heat exchanger of claim 1, wherein each spiral of the plurality of spirals (11) comprises one intraspiral channel (14).

3. The component for a heat exchanger of claim 1, wherein each spiral of the plurality of spirals (11) has a varying twist angle along the length direction of the body.

4. The component for a heat exchanger of claim 1, wherein the twist angle is at least 15 degrees.

5. The component for a heat exchanger of claim 1, wherein the twist angle varies by at least 1 degree per 0.1 meter length direction of the body.

6. The component for a heat exchanger of claim 1, wherein the central cavity (13) is surrounded by a tube (12), and the plurality of spirals (11) are attached on an outer surface of the tube (12).

7. The component for a heat exchanger of claim 1, wherein the plurality of spirals (11) includes at least 4 spirals.

8. The component for a heat exchanger of claim 1, wherein each spiral of the plurality of spirals (11) comprises at least 2 turns per meter in a length direction of the body and not more than 10 turns per meter.

9. The component for a heat exchanger of claim 2, wherein an average cross-sectional surface area of each intraspiral channel (14) of the plurality of spirals (11) is at least 245 mm2.

10. The component for a heat exchanger of claim 1, wherein a material of the body comprises silicon carbide and an average density of the material is at least 2.50 g / cm3.

11. The component for a heat exchanger of claim 1, wherein the plurality of spirals (11) includes not more than 12 spirals.

12. The component for a heat exchanger of claim 1, wherein a material of the body comprises silicon carbide and an average density of the material is not greater than 3.05 g / cm3.

13. The component for a heat exchanger of claim 1, wherein the ceramic of the body consists of silicon carbide.

14. A heat exchanger comprising the component of a heat exchanger of claim 1, wherein an average cross-sectional surface area of each intraspiral channel of the plurality of intraspiral channels (14) is at least 245 mm2 and not more than 1470 mm2.

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