Heat recoverer

Abstract

[Problem] To provide a heat recovery device in which the heat exchange function between combustion exhaust gas and combustion air is further improved. [Solution] A heat recovery device (3) that exchanges heat between combustion exhaust gas that flows inside a radiant tube (1) and combustion air for combusting a burner used in the radiant tube (1), in which a plurality of grooves (7) that extend in a zigzag shape in the longitudinal direction of the heat recovery device (3) are formed on the outer surface of the heat recovery device (3).

Description

Technical Field

[0001] The present invention relates to a heat recovery device, wherein in a radiant tube heating device, combustion exhaust gas flowing inside a radiant tube exchanges heat with combustion air used to ignite a burner for the radiant tube. Background Technology

[0002] As a heat recovery device for a radiant tube heating apparatus, conventionally, as shown in Patent Document 1, a structure in which a double-layer tube is provided on the exhaust side of the radiant tube has been disclosed. Existing technical documents Patent documents

[0003] Patent Document 1: Japanese Patent Application Publication No. 2000-146118 Patent Document 2: Japanese Patent Application Publication No. 2018-124050 Patent Document 3: Japanese Patent Application Publication No. 2018-17470 Patent Document 4: Japanese Patent Application Publication No. 2016-205644 Patent Document 5: Japanese Patent Application Publication No. 2013-194977 Summary of the Invention The technical problem that the invention aims to solve

[0004] However, in the structure described above, the portion used to preheat the combustion air using the heat from the exhaust is limited to the outer circumferential surface of the outer tube of the double-layer tube. Therefore, in order to increase the heat transfer area, as shown in Patent Document 2, a structure with spiral, straight, wavy, or other fins provided on the outer circumferential surface of the outer tube is disclosed. However, the main portion for conducting the heat from the fins to the interior of the outer tube is the line contact portion at the junction of the outer tube and the fins.

[0005] To increase the contact area, as shown in Patent Documents 3-5, a structure is disclosed in which a spiral flow path is formed on the outer circumferential surface of the double-layer tube, and heat is transferred from its surface and back. However, even with such a flow path formed on the outer circumferential surface of the outer tube, there is still a problem that the fluid flow within the flow path is too smooth, and heat exchange is not sufficient.

[0006] Therefore, the object of the present invention is to provide a heat recovery device that further improves the heat exchange function between the combustion exhaust gas flowing inside the radiant tube and the combustion air used to ignite the burner used in the radiant tube. Technical solutions adopted to solve technical problems

[0007] This invention relates to a heat recovery device in which combustion exhaust gas flowing inside a radiant tube exchanges heat with combustion air used to ignite the burner in the radiant tube. Multiple grooves extending in a serrated pattern along the length of the heat recovery unit are formed on the outer surface of the heat recovery unit.

[0008] According to the above structure, since multiple grooves extending in a serrated shape along the length direction are formed on the outer surface of the heat recovery unit, the fluid flowing into the grooves, i.e., the combustion exhaust gas, flows while colliding with the heat transfer surface due to the serrated shape of the grooves. Therefore, the heat exchange between the combustion exhaust gas and the combustion air flowing inside the heat recovery unit can be fully carried out. As a result, the heat exchange function of the heat recovery unit can be improved. Invention Effects

[0009] According to the present invention, a heat recovery device can be provided that further improves the heat exchange function between combustion exhaust gas and combustion air. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of a radiant tube heating device having a heat recovery unit according to an embodiment of the present invention. Figure 2 yes Figure 1 AA cross-section view. Figure 3 yes Figure 2 BB section view. Figure 4 This is a side view of the heat recovery unit. Figure 5 yes Figure 3 The CC section is in view. Figure 6 This is a perspective view of a part of the main body of the heat recovery unit. Figure 7 This is a schematic diagram of the protrusion in another embodiment of the present invention. Figure 8 This is a schematic diagram of the protrusion in another embodiment of the present invention. Detailed Implementation

[0011] Figure 1 This is a schematic diagram of a radiant tube heating device 10 equipped with a heat recovery unit according to an embodiment of the present invention. Figure 1 As shown, the radiant tube heating device 10 has a cylindrical radiant tube 1, which is heated from the inside, and the processing material disposed in the furnace is heated by radiant heat from the outer peripheral surface of the radiant tube 1.

[0012] In the radiant tube heating device 10 of this embodiment, a U-shaped radiant tube 1 is used as the radiant tube 1, and the main body 11 of the U-shaped radiant tube is disposed inside the furnace. Both ends of the radiant tube 1 extend through the furnace wall to the outside of the furnace. In addition, the radiant tube 1 is not limited to a U-shape, and may also have a W-shape or I-shape, etc.

[0013] A burner 2 is inserted into one end of the radiant tube 1 to burn fuel gases such as hydrocarbons in combustion air. The burner 2 uses combustion air to burn the fuel gases, thereby generating high-temperature combustion exhaust gas, which heats the radiant tube 1 from the inside by circulating combustion exhaust gas. The temperature of this combustion exhaust gas is preferably 800°C or higher and 1400°C or lower, and particularly preferably 900°C or higher and 1300°C or lower.

[0014] A heat recovery unit 3 is inserted at the other end of the radiant tube 1. The heat recovery unit 3 heats the externally supplied combustion air by exchanging heat between the combustion exhaust gas from the burner 2 flowing through the interior of the radiant tube 1 and the combustion air introduced into the heat recovery unit 3 from the combustion air inlet pipe 4. The combustion air heated in the heat recovery unit 3 is supplied to one end of the radiant tube 1 where the burner 2 is located through the combustion air supply pipe 5. The combustion air supplied to one end of the radiant tube 1 is used for combustion in the burner 2, becoming high-temperature combustion exhaust gas, which flows within the main body 11 of the radiant tube 1 and toward the heat recovery unit 3.

[0015] Combustion exhaust gas, which has undergone heat exchange with combustion air in heat recovery unit 3, is discharged from exhaust port 6.

[0016] Figure 2 yes Figure 1 AA section view, Figure 3 yes Figure 2 The cross-sectional view of BB. Additionally... Figure 4 This is a side view of heat recovery unit 3. Figure 5 yes Figure 3 The cross-sectional view of CC. Additionally, for ease of explanation, Figure 3 The orientation of the exhaust port 6 is such that it is located in relation to... Figure 1 The left and right positions are shown in reverse order. For example... Figures 2-5 As shown, the heat recovery unit 3 includes a main body 31 and a front end 32 connected to the main body 31. The main body 31 has a double-layer tube structure with an outer tube 311 and an inner tube 312. In addition, in order to improve the efficiency of heat exchange, the wall thickness of the outer tube 311 and the inner tube 312 is preferably thinner, but as a structural strength of the main body 31 of the heat recovery unit 3, the wall thickness of the outer tube 311 is preferably 1 mm or more, and the wall thickness of the inner tube 312 is preferably 3 mm or more.

[0017] The front end portion 32 has a hemispherical portion 33 located at the front end 38 of the heat recovery unit 3 and a cylindrical portion 34 connected to the hemispherical portion 33. The cylindrical portion 34 has a double-layer tube structure having an outer tube 341 and an inner tube 342.

[0018] The outer tube 311 of the main body 31 is connected to the outer tube 341 of the cylindrical part 34, and the inner tube 312 of the main body 31 is connected to the inner tube 342 of the cylindrical part 34. The connection or joint can be made by any method such as welding, bonding, insertion, screwing.

[0019] Figure 6 This is a perspective view of a portion of the main body 31 of the heat recovery unit. (See image below.) Figure 4 and Figure 6 As shown, a plurality of grooves 7 extending in a serrated pattern along the length of the heat recovery unit 3 are formed on the outer surface of the outer tube 311 of the main body 31. Each groove 7 extends in a serrated pattern along the length of the heat recovery unit, but no single groove 7 completes a full circumference of the heat recovery unit 3. Specifically, each groove 7 extends in a serrated pattern for less than half a circumference along the circumference of the heat recovery unit 3, and the entire groove 7 can be observed and confirmed from a side view centered on the center line extending axially.

[0020] The groove 7 has multiple bends 71, each bend 71 having a two-stage bending shape. Specifically, the front end of each bend 71 is chamfered. More specifically, the two-stage bending shape is trapezoidal, and between the first-stage bend 71a and the second-stage bend 71b, this portion of the groove extends in a straight line parallel to the axial direction X of the heat recovery unit 3. Furthermore, the width of the groove in the groove 7 widens at the front end 72, communicating with the groove of the adjacent groove 7. Preferably, the width of the bend 71 is greater than the width of the groove in the groove 7.

[0021] The protrusion 8 forming the side of the groove 7 is formed to protrude from the outer surface of the inner tube 312, and the front end 8a of the protrusion 8 is located near the inner surface of the radiant tube 1. An opening 81 extending axially along the heat recovery unit 3 is formed inside the protrusion 8. Combustion air passing through this opening 81 and combustion exhaust gas passing through the groove 7 exchange heat, with the combustion air being heated by the combustion exhaust gas. The groove 7, serving as a flow path for combustion exhaust gas, and the opening 81, serving as a flow path for combustion air, are arranged alternately and extend in a serrated shape along the axial direction of the heat recovery unit 3. Furthermore, as... Figure 5 As shown, the rear end 39 of the heat recovery unit 3 is blocked by the flange 9. The flange 9 has an opening 36a that communicates with the central flow path 36 and an inlet 81a that communicates with the opening 81.

[0022] The main body 31 of the heat recovery unit 3 is formed by joining multiple segments 31a that are divided along the length direction. Moreover, the curved portion 71 is located at the joining portion 31b of the segments 31a. That is, the segments 31a are joined at the upper bottom portion of the trapezoid of the curved portion 71 (the portion that extends parallel to the axial direction of the heat recovery unit 3).

[0023] The main body 31 of the heat recovery unit 3 has segments 31a and a front end portion 32 made of ceramic powder using a 3D printer. Examples of suitable ceramic materials include silicon carbide (SiC), alumina, mullite, silicon nitride, and aluminum nitride; however, silicon carbide, which exhibits excellent heat resistance, thermal shock resistance, and high thermal conductivity, is particularly preferred for use in high-temperature furnaces. The main body 31 is formed by joining the segments 31a, which are made using a 3D printer, together, and then the front end portion 32 is joined to the main body 31. Adhesives are used to join the segments 31a together and to join the main body 31 to the front end portion 32. Alternatively, the heat recovery unit 3 can be manufactured as a single unit without joining the segments 31a together.

[0024] like Figure 3 As shown, an ejector 35 is provided in the inner tube of the heat recovery unit 3 to improve the suction of combustion air into the inner tube. The ejector 35 includes an injector 343 and a reduced diameter section 315. The injector 343 is formed in the inner tube 342 of the cylindrical section 34 and protrudes inward from the inner surface of the inner tube 342 so that the diameter of the central flow path 36 decreases as it passes through the internal space of the inner tube 342 toward the main body 31. The reduced diameter section 315 is inside the inner tube 312 of the main body 31 and bends inward throughout the entire circumference near the cylindrical section 34.

[0025] According to the above structure, by providing an ejector 343 on the inner surface of the inner tube 342, a negative pressure is generated by increasing the flow velocity of the combustion air entering the inner tube 342. As a result, the suction of combustion exhaust gas into the inner tube 342 is promoted. In addition, by providing a reduced diameter section 315 in the inner tube 312 of the main body 31, the suction of combustion air into the inner tube 312 is promoted, increasing the flow velocity from the inner tube 312 to the combustion air supply pipe and improving the efficiency of heat exchange. That is, by providing ejectors 35 in the inner tube 342 of the cylindrical section 34 and the inner tube 312 of the main body 31, the suction of combustion air into the inner tube 342 is promoted, accelerating the flow velocity of the combustion air flowing through the opening 81, thereby improving the efficiency of heat exchange (theoretically, the faster the fluid flow velocity, the better the heat conduction).

[0026] (The flow of combustion air and exhaust gas in a radiant tube heating device) Combustion air introduced from the combustion air inlet pipe 4 is introduced from the inlet 81a on the flange 9 into the opening 81 of the protrusion 8 inside the heat recovery unit 3. The combustion air flowing through the opening 81 of the heat recovery unit 3 is heated by heat exchange with combustion exhaust gas generated by the combustion of the burner 2, and flows through the groove 7 located between the outer pipe 311 and the radiant pipe 1 of the heat recovery unit 3.

[0027] The combustion air flowing through the opening 81 flows in the opposite direction (counter-flow) to the combustion exhaust gas flowing through the slot 7, and they flow side by side in a zigzag pattern, colliding with the heat transfer surface as they move forward. As a result, heat exchange between the combustion air and the combustion exhaust gas is promoted (theoretically, counter-flow has better heat conduction than parallel flow, and collision with the heat transfer plate is better than letting the fluid flow along the heat transfer plate).

[0028] The combustion exhaust gas, after being heated in the heat recovery unit 3, flows in the trough 7 to the rear end 39 of the heat recovery unit 3, impacts the flange 9 to change direction, and is discharged from the exhaust port 6.

[0029] The combustion air, heated by the combustion exhaust gas, passes through the space 37 between the outer tube 341 and the inner tube 342 of the cylindrical section 34 from the opening 81 at the front end 32 of the heat recovery unit 3. It then turns back within the hemispherical section 33 and enters the central flow path 36 within the inner tube 342 of the cylindrical section 34. The combustion air entering the inner tube 342 of the cylindrical section 34 then enters the inner tube 312 of the main body section 31.

[0030] Combustion air flowing within the inner pipe 312 of the main body 31 passes through the combustion air supply pipe 5 and is supplied to one end of the radiant pipe 1 where the burner 2 is located. The burner 2 causes the fuel gas to burn in the combustion air supplied from the combustion air supply pipe 5, generating new combustion exhaust gas.

[0031] The combustion exhaust gas generated by the combustion of fuel air by the burner 2 heats the radiant tube 1 from the inside, and the processing material placed in the furnace equipped with the radiant tube heating device 10 is heated by the radiant heat from the outer peripheral surface of the radiant tube 1.

[0032] The radiant tube heating device 10 with the above structure can achieve the following effects.

[0033] (1) Since multiple grooves 7 extending in a serrated shape along the length direction are formed on the outer surface of the heat recovery unit 3, the fluid flowing in the grooves 7, i.e., the combustion exhaust gas, flows while colliding with the heat transfer surface due to the serrated shape of the grooves 7. Therefore, the heat exchange between the combustion exhaust gas and the combustion air flowing inside the heat recovery unit can be fully carried out. As a result, the heat exchange function of the heat recovery unit 3 can be improved.

[0034] (2) The bending section 71 has a two-stage bending shape, so the number of collisions with the heat transfer surface increases and the bending angle of each stage can be reduced. As a result, heat exchange can be further promoted and the flow of combustion exhaust gas in the groove 7 can be smooth.

[0035] (3) The width of the groove in the groove 7 is widened at the front end, so that the combustion exhaust gas can easily enter the groove 7 from the front end, thereby enabling the combustion exhaust gas in the groove 7 to flow smoothly.

[0036] (4) An injector with an inner tube protrusion protruding from the inner surface of the inner tube is formed in the inner tube to increase the suction force of the fluid into the inner tube. Therefore, the flow rate of the combustion air entering the inner tube can be increased. As a result, by promoting the suction of the combustion exhaust gas into the inner tube and accelerating the flow rate of the combustion air flowing through the opening 81, the efficiency of heat exchange can be improved.

[0037] (5) The heat recovery unit 3 has a double-layer tube structure with an outer tube and an inner tube. The depth of the groove formed in the outer tube extends to the vicinity of the inner tube, thus increasing the flow rate of the combustion exhaust gas flowing through the groove 7. As a result, heat exchange between the combustion exhaust gas and the combustion air can be carried out more effectively.

[0038] (6) The protrusion 8 forming the groove 7 is formed in such a way that it protrudes from the outer surface of the inner tube 312. The front end of the protrusion 8 is located near the inner surface of the radiant tube 1. Therefore, the amount of combustion exhaust gas that does not flow through the groove 7 can be reduced, and the heat exchange between the combustion exhaust gas flowing in the groove 7 and the combustion air flowing in the opening 81 of the protrusion 8 can be carried out more effectively.

[0039] (7) Since the heat recovery unit 3 is constructed by joining multiple segments that are divided along its length, the manufacturability of the heat recovery unit 3 can be improved. Furthermore, by arranging the curved portion with a two-stage bending shape at the joint of the segments, the alignment of the groove becomes easier (since the segments join at portions extending parallel to the axial direction of the heat recovery unit 3), and the joining of the segments can be easily performed. Additionally, by forming segments, the length of the components is shortened, thus facilitating operation and reducing the possibility of component damage.

[0040] (8) The heat recovery unit 3 is made by using a 3D printer with ceramic powder as the material, so it is easy to make the heat recovery unit 3 with the groove 7. In addition, by using SiC powder with particularly high heat resistance as the material, the heat recovery unit 3 can be used even in a furnace at high temperature.

[0041] In the above embodiment, the inner and outer surfaces of the protrusion 8 are flat, but in order to increase the contact area between the combustion air and the combustion exhaust gas, the shape of the inner and / or outer surfaces may be changed. Figure 7 This is a schematic diagram of another embodiment of the protrusion 8, in which the inner surface of the protrusion 8 is wavy. Figure 8 This is a schematic diagram of a protrusion in another embodiment where fins are provided on the inner and outer surfaces of the protrusion.

[0042] like Figure 7 and Figure 8As shown, in order to increase the contact area between the combustion air and the combustion exhaust gas, the inner surface 8b and / or the outer surface 8c of the protrusion 8 can be wavy, and fins 82 can also be provided on the inner surface 8b and / or the outer surface 8c of the protrusion 8.

[0043] In the other embodiment described above, the following effects can be achieved.

[0044] The inner surface 8b and / or outer surface 8c of the protrusion 8 forming the groove 7 are wavy, thus increasing the contact area between the combustion exhaust gas and the combustion air. As a result, the heat exchange function of the heat recovery unit 3 can be improved.

[0045] Fins 82 are provided on the inner surface 8b and / or outer surface 8c of the protrusion 8 forming the groove 7, thereby increasing the contact area between the combustion exhaust gas and the combustion air. As a result, the heat exchange function of the heat recovery unit 3 can be improved.

[0046] Alternatively, unlike the above embodiments, an opening (not shown) may be provided at the front end 32 of the heat recovery unit 3, so that a portion of the combustion exhaust gas is introduced into the heat recovery unit 3 from the front end 32.

[0047] In the heat recovery unit 3, the combustion air is heated (preheated) to a high temperature by the combustion exhaust gas and then guided from the combustion air supply pipe 5 to the burner 2 to burn the fuel gas. At this time, the energy saving effect is improved, but the combustion temperature is too high and the amount of NOx produced during combustion increases. The combustion exhaust gas containing a large amount of NOx is discharged from the exhaust port 6 on the other end of the radiant pipe 1.

[0048] In contrast, within the heat recovery unit 3, combustion air is mixed with a portion of the combustion exhaust gas. The combustion exhaust gas and the heated combustion air are then guided together from the combustion air supply pipe 5 to the burner 2 for combustion. During this process, the oxygen concentration in the combustion air decreases, and the combustion rate within the burner 2 slows down. As a result, excessively high combustion temperatures are prevented, reducing the amount of NOx produced during combustion. Furthermore, preferably, the higher the temperature of the combustion air heated by the combustion exhaust gas, the greater the amount of combustion exhaust gas mixed with it.

[0049] The invention and its implementation methods are summarized below.

[0050] (1) One embodiment of the present invention relates to a heat recovery device in which combustion exhaust gas flowing inside a radiant tube exchanges heat with combustion air used to ignite the burner used in the radiant tube. Multiple grooves extending in a serrated pattern along the length of the heat recovery unit are formed on the outer surface of the heat recovery unit.

[0051] According to the above structure (1), since multiple grooves extending in a serrated shape along the length direction are formed on the outer surface of the heat recovery unit, the fluid flowing into the grooves, i.e., the combustion exhaust gas, flows while colliding with the heat transfer surface due to the serrated shape of the grooves. Therefore, the heat exchange between the combustion exhaust gas and the combustion air flowing inside the heat recovery unit can be fully carried out. As a result, the heat exchange function of the heat recovery unit can be improved.

[0052] (2) In the structure (1), the groove has multiple curved portions. The curved portion has a two-stage bending shape.

[0053] According to the above structure (2), by setting the bending part to a two-stage bending shape, the number of collisions with the heat transfer surface can be increased and the bending angle at each stage can be reduced. As a result, heat exchange can be further promoted, thus making the flow of combustion exhaust gas in the slot smooth.

[0054] (3) In the structure (1) or (2), the width of the groove is widened at the front end.

[0055] According to the above structure (3), by making it easy for the combustion exhaust gas to enter the tank from the front end of the tank, the flow of the combustion exhaust gas in the tank can be made smooth.

[0056] (4) In any of the structures (1) to (3), the inner and / or outer surfaces of the protrusion forming the groove are wavy.

[0057] According to the above structure (4), the contact area between the combustion exhaust gas and the combustion air is increased, thus improving the heat exchange function of the heat recovery unit.

[0058] (5) In any of the structures (1) to (3), fins are provided on the inner and / or outer surfaces of the protrusion forming the groove.

[0059] According to the above structure (5), the contact area between the combustion exhaust gas and the combustion air is increased, thus improving the heat exchange function of the heat recovery unit.

[0060] (6) In any of the structures (1) to (5), the heat recovery unit is a double-layer tube structure consisting of an outer tube and an inner tube. An ejector with an inner tube protrusion extending inward from the inner surface of the inner tube is formed in the inner tube to increase the suction force of fluid into the inner tube.

[0061] According to the above structure (6), by forming an injector in the inner tube, the flow rate of the combustion air entering the inner tube can be increased. As a result, the combustion exhaust gas is drawn into the inner tube. By accelerating the flow rate of the combustion air flowing through the opening 81, the efficiency of heat exchange can be improved.

[0062] (7) In any of the structures (1) to (6), the heat recovery unit is a double-layer tube structure consisting of an outer tube and an inner tube. The depth of the groove formed in the outer tube extends to the vicinity of the inner tube.

[0063] According to the above structure (7), since the flow rate of the combustion exhaust gas flowing through the slot is increased, the heat exchange between the combustion exhaust gas and the combustion air can be carried out more effectively.

[0064] (8) In the structure (7), the protrusion forming the groove is formed in such a way that it protrudes from the outer surface of the inner tube, and the front end of the protrusion is located near the inner surface of the radiating tube.

[0065] According to the above structure (8), the amount of combustion exhaust gas that does not flow through the slot can be reduced, and the heat exchange between the combustion exhaust gas flowing through the slot and the combustion air flowing through the opening of the protrusion can be carried out more effectively.

[0066] (9) In the structure (2), the heat recovery unit is formed by joining multiple segments that are divided along the length direction. The curved portion is located at the joint of the segment.

[0067] According to the above structure (9), the heat recovery unit is constructed by joining the segmented parts, thus improving the manufacturability of the heat recovery unit. Furthermore, by arranging the bent portion with a two-stage bending shape at the joint of the segmented parts, the alignment of the groove becomes easier, and the joining of the segmented parts can be easily performed. In addition, by forming the segmented parts, the length of the components is shortened, thus facilitating operation and reducing the possibility of component damage.

[0068] (10) In any of the structures (1) to (9), the heat recovery unit is fabricated using a 3D printer with ceramic powder as the material.

[0069] Based on the above structure (10), a heat recovery unit with a groove can be easily manufactured.

[0070] (11) In the structure (10), the ceramic powder is SiC powder.

[0071] According to the above structure (11), as a ceramic powder, SiC powder with particularly high heat resistance is used as the material, so that the heat recovery device can be used even in a high-temperature furnace.

[0072] Various modifications and alterations can be made without departing from the spirit and scope of the invention as described in the claims. [Industrial Applicability]

[0073] This invention provides a heat recovery device that further enhances the heat exchange function between combustion exhaust gas and combustion air, thus having high industrial application value. Symbol Explanation

[0074] 1 radiant tube; 11. Main body section; 2. Burners; 3. Heat recovery unit; 31. Main body section; 31a Segment; 31b Joint; 311 outer tube; 312 inner tube; 313 Heat exchange components; 314 Reduction section; 315 diameter reduction section; 32. Front end portion; 33. Hemisphere; 34. Cylindrical section; 341 Outer tube; 342 Inner tube; 343 injector; 35 ejector; 36 center flow path; 36a hole; 37 spaces; 38. Front-end development; 39. Backend; 4. Combustion air inlet pipe; 5. Combustion air supply pipe; 6. Exhaust port; 7. Groove section; 71. Bend; 71a Bend; 71b Bend; 72. Front-end development; 8. Protrusion; 8a Frontend; 8b Inner surface; 8c Outer surface; 81. Opening; 81a Inlet; 82 fins; 9. Flange; 10. Radiant tube heating device.

Claims

1. A heat recovery unit in which combustion exhaust gas flowing within a radiant tube exchanges heat with combustion air used to ignite a burner within the radiant tube, wherein, Multiple grooves extending in a serrated pattern along the length of the heat recovery unit are formed on the outer surface of the heat recovery unit.

2. The heat recovery unit according to claim 1, characterized in that, The groove has multiple bends. The curved portion has a two-stage bending shape.

3. The heat recovery unit according to claim 1, characterized in that, In the groove, the width of the groove is widened at the front end.

4. The heat recovery unit according to claim 1, characterized in that, The inner and / or outer surfaces of the protrusion forming the groove are wavy.

5. The heat recovery unit according to claim 1, characterized in that, Fins are provided on the inner and / or outer surfaces of the protrusion forming the groove.

6. The heat recovery unit according to claim 1, characterized in that, The heat recovery unit has a double-layer tube structure consisting of an outer tube and an inner tube. An ejector with an inner tube protrusion extending inward from the inner surface of the inner tube is formed in the inner tube to increase the suction force of fluid into the inner tube.

7. The heat recovery unit according to claim 1, characterized in that, The heat recovery unit has a double-layer tube structure consisting of an outer tube and an inner tube. The depth of the groove formed in the outer tube extends to the vicinity of the inner tube.

8. The heat recovery unit according to claim 7, characterized in that, The protrusion forming the groove is formed in such a way that it protrudes from the outer surface of the inner tube, and the front end of the protrusion is located near the inner surface of the radiating tube.

9. The heat recovery unit according to claim 2, characterized in that, The heat recovery unit is constructed by joining multiple segments that are divided along the length direction. The curved portion is located at the joint of the segment.

10. The heat recovery unit according to any one of claims 1 to 9, characterized in that, The heat recovery unit was fabricated using a 3D printer with ceramic powder as the material.

11. The heat recovery unit according to claim 10, characterized in that, The ceramic powder is SiC powder.

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