air preheater

Abstract

The application discloses an air preheater, which comprises a flue gas channel, an air channel and a plurality of heat pipes, each of the heat pipes has a first pipe section located in the flue gas channel and a second pipe section located in the air channel, the first pipe section forms a first included angle a with the horizontal direction, and the second pipe section forms a second included angle β with the horizontal direction, wherein 0°<a<β<30°. When the air preheater is arranged on a vertical flue at an outlet of a boiler, the second pipe section and the first pipe section of the heat pipe both form an included angle greater than 0° with the horizontal line, and the included angle of the second pipe section with the horizontal line is greater than that of the first pipe section with the horizontal line, so that the working medium can flow back at a faster speed after being condensed into a liquid state, and meanwhile, the working medium can flow to the second pipe section at a faster speed after being evaporated into a gaseous state due to the smaller included angle of the first pipe section with the horizontal line, and therefore, the working medium in the heat pipe can circulate at a faster speed, and the heat transfer effect and the heat exchange efficiency are improved.

Description

Technical Field

[0001] This utility model relates to the field of coal-fired power generation technology, and in particular to an air preheater. Background Technology

[0002] Due to space constraints, air preheaters in coal-fired power plants are mostly located on the vertical flue at the boiler outlet. In this arrangement, the working fluid inside the heat pipes of the air preheater moves slowly, resulting in poor heat transfer.

[0003] Therefore, how to ensure that the air preheater arranged on the vertical flue of the boiler outlet has a better heat transfer effect is a technical problem that needs to be solved by those skilled in the art. Utility Model Content

[0004] To solve the above-mentioned technical problems, this application provides an air preheater, which includes a flue gas passage, an air passage, and multiple heat pipes. Each heat pipe has a first pipe section located in the flue gas passage and a second pipe section located in the air passage. The first pipe section forms a first angle with the horizontal direction, and the second pipe section forms a second angle with the horizontal direction. The angle of the first angle is α, and the angle of the second angle is β, wherein 0° < α < β < 30°.

[0005] In one embodiment of the air preheater, the heat pipes are arranged in multiple layers along the flue gas flow direction, with each layer arranged sequentially. The first section of one or more heat pipes near the flue gas inlet is a spiral twisted section, and the cross-section of the spiral twisted section is non-circular.

[0006] In one embodiment of the air preheater, the cross-section of the spiral twisted tube section is elliptical or circular-rectangular.

[0007] In one embodiment of the air preheater, the first section of one or more heat pipes near the flue gas outlet is a first straight pipe section.

[0008] In one embodiment of the air preheater, the cross-section of the first straight pipe section is circular, elliptical, or rectangular, and the major axis of the elliptical cross-section of the first straight pipe section is along the flue gas flow direction. Alternatively, the cross-section of the first straight pipe section is circular; or, the cross-section of the first straight pipe section is elliptical with the major axis of the elliptical cross-section along the flue gas flow direction; or, the cross-section of the first straight pipe section is rectangular with the length of the rectangular cross-section along the flue gas flow direction.

[0009] In one embodiment of the air preheater, the second section of all the heat pipes is a second straight section.

[0010] In one embodiment of the air preheater, the cross-section of the second straight pipe section is circular; or, the cross-section of the second straight pipe section is elliptical with the major axis of the elliptical cross-section along the airflow direction; or, the cross-section of the second straight pipe section is rectangular with the length of the rectangular cross-section along the airflow direction.

[0011] In one embodiment of the air preheater, the air preheater includes a housing and a partition, the partition being located within the housing, the housing and the partition forming the flue gas passage and the air passage, the partition being located between the flue gas passage and the air passage, and the heat pipes being inserted into holes in the partition.

[0012] In one embodiment of the air preheater, a first support portion and a second support portion are provided on opposite sides of the housing, and the heat pipe is inserted into the insertion holes on the first support portion and the second support portion.

[0013] In one embodiment of the air preheater, the heat pipe is provided with a first end cap and a second end cap at both ends. The first end cap is connected to the end of the first pipe segment away from the second pipe segment and is inserted into the insertion hole of the first support. The second end cap is connected to the end of the second pipe segment away from the first pipe segment and extends out of the housing through the insertion hole of the second support.

[0014] When the air preheater provided in this application is arranged on the vertical flue at the boiler outlet, both the second and first sections of the heat pipe have an angle greater than 0° with the horizontal line, and the angle between the second section and the horizontal line is greater than that between the first section and the horizontal line. Therefore, the working fluid can return at a faster speed after condensing into a liquid state. At the same time, since the angle between the first section and the horizontal line is smaller, the working fluid can flow to the second section at a faster speed after evaporating into a gaseous state. Thus, the working fluid in the heat pipe is ensured to circulate at a faster speed, thereby improving the heat transfer effect and heat exchange efficiency. Attached Figure Description

[0015] Figure 1 An internal schematic diagram of one embodiment of the air preheater provided in this application;

[0016] Figure 2 for Figure 1 A schematic diagram of a heat pipe in the middle;

[0017] Figure 3 for Figure 1 A schematic diagram of another heat pipe in the middle;

[0018] Figure 4 for Figure 1 A cross-sectional view at the position of the dashed line C;

[0019] Figure 5 for Figure 1 The cross-sectional view at the position of the dashed line D.

[0020] The annotations in the attached figures are explained as follows:

[0021] 10-Heat pipe, 101-First pipe section, 102-Second pipe section, 103-First end cap, 104-Second end cap;

[0022] 20-Shell, 201-First support part, 202-Second support part;

[0023] 30-partition;

[0024] A - Smoke duct, B - Air duct. Detailed Implementation

[0025] This application provides an air preheater. To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] like Figures 1-3 As shown, the air preheater provided in this application includes a flue gas passage A, an air passage B, and multiple heat pipes 10. Each heat pipe 10 has a first pipe section 101 located in the flue gas passage A and a second pipe section 102 located in the air passage B. The first pipe section 101 forms a first angle with the horizontal direction, and the second pipe section 102 forms a second angle with the horizontal direction. The angle of the first angle is α, and the angle of the second angle is β, where 0° < α < β < 30°. That is, the heat pipe 10 is a variable angle pipe. It should be noted that the horizontal direction refers to the direction perpendicular to gravity. Preferably, 5° < α < 10° and 15° < β < 30°.

[0027] The heat pipe 10 is filled with a low-boiling-point, volatile liquid working fluid. During operation, the first section 101 of the heat pipe 10 is heated, causing the liquid working fluid inside to rapidly evaporate and vaporize. The vapor flows to the second section 102 under the action of thermal diffusion, where it exchanges heat with the air flowing through the second section 102. After heat exchange, it condenses back into a liquid state and then flows back from the second section 102 to the first section 101. In this process, the working fluid absorbs heat from the flue gas during evaporation and heats the air during condensation, thereby transferring the heat from the flue gas to the air.

[0028] In the past, when air preheaters were placed on the vertical flue at the boiler outlet, the heat pipes were basically horizontal. This caused the working fluid inside the heat pipes to condense into a liquid state and could not flow back quickly by gravity. As a result, the working fluid circulation speed inside the heat pipes was slow, leading to poor heat transfer effect and low heat exchange efficiency.

[0029] When the air preheater provided in this application is arranged on the vertical flue of the boiler outlet, both the second section 102 and the first section 101 of the heat pipe 10 form an angle greater than 0° with the horizontal direction. Moreover, the angle between the second section 102 and the horizontal direction is greater than the angle between the first section 101 and the horizontal direction. Therefore, after the working fluid condenses into a liquid state, it can return at a relatively fast speed due to gravity. At the same time, since the angle between the first section 101 and the horizontal direction is small, the resistance to the flow of the working fluid to the second section 102 after evaporating into a gaseous state is small. Thus, the working fluid in the heat pipe 10 is ensured to circulate at a relatively fast speed, thereby improving the heat transfer effect and heat exchange efficiency.

[0030] Specifically, the heat pipes 10 are arranged in multiple layers (two or more layers), with each layer arranged sequentially along the flue gas flow direction. For example, in the illustrated embodiment, as shown... Figure 1 , Figure 4 and Figure 5 As shown, heat pipes 10 are arranged in four layers. In actual implementation, it is not limited to four layers; for example, it can also be two, three, or more than four layers. Adjacent heat pipe layers can be arranged facing each other, that is, the lower layer heat pipe is directly opposite the upper layer heat pipe, or they can be arranged in a staggered manner, that is, the lower layer heat pipe is directly opposite the gap between the upper layer heat pipe.

[0031] In some embodiments, the first segment 101 of one or more heat pipes 10 near the flue gas inlet is a spirally twisted segment. For example, in the illustrated embodiment, the first segment 101 of the two heat pipes 10 near the flue gas inlet in the four-layer heat pipe 10 is a spirally twisted segment. The cross-section of the spirally twisted segment is non-circular, preferably elliptical or rectangular with low flow resistance. The spirally twisted segment is a spiral structure formed by twisting a non-circular cross-section pipe around its central axis. The cross-section of the spirally twisted segment varies and is not exactly the same at different length positions, for example... Figure 4 As shown, when the cross-section of the spiral twisted tube section is elliptical, the major axis of the elliptical cross-section at certain length positions may be along the flue gas flow direction, while the major axis of the elliptical cross-section at certain length positions may be nearly perpendicular to the flue gas flow direction. Therefore, when the flue gas flows through these spiral twisted tube sections, its flow direction will change during the collision with the outer surface of these spiral twisted tube sections, thus enhancing the turbulence of the flue gas, which is more conducive to strengthening heat exchange and reducing ash accumulation on the surface of heat pipe 10.

[0032] In some embodiments, the first segment 101 of one or more heat pipes 10 near the flue gas inlet (referring to two or more layers) is a spirally twisted segment. The number of heat pipe 10 layers with spirally twisted segments in the first segment 101 is less than the total number of heat pipe 10 layers. The first segment 101 of the remaining heat pipe 10 layers is a straight segment, and the cross-section of the straight segment remains uniform at different length positions. For example, in the illustrated embodiment, in the four-layer heat pipe 10, the first segment 101 of the two heat pipe 10 layers near the flue gas inlet is a spirally twisted segment, and the first segment 101 of the two heat pipe 10 layers away from the flue gas inlet is a straight segment. With this design, the upstream spirally twisted segment with high turbulence capability disturbs the flue gas, allowing the flue gas to carry away the ash accumulated on the downstream straight segment when it flows through the downstream straight segment with lower flow resistance. This can more effectively reduce the ash accumulation on the surface of the heat pipe 10. In other words, the downstream low-flow-resistance straight segment combined with the upstream spirally twisted segment with high turbulence capability can more effectively alleviate the ash accumulation on the surface of the heat pipe 10.

[0033] It should be noted that, in actual implementation, the ratio of the number of heat pipe layers in the first section 101 that is a spirally twisted section to the number of heat pipe layers in the first section 101 that is a straight section can be flexibly adjusted according to the flue gas velocity, dust content, etc., to achieve the best dust accumulation prevention effect. For example, the ratio of the number of heat pipe layers in the first section 101 that is a spirally twisted section to the number of heat pipe layers in the first section 101 that is a straight section can be 1:1 to 1:5.

[0034] In some embodiments, the cross-section of the first straight pipe section is preferably a circular cross-section, an elliptical cross-section, or a circular rectangular cross-section with low flow resistance. When it is an elliptical cross-section, the major axis of the elliptical cross-section is preferably along the flue gas flow direction. When it is a circular rectangular cross-section, the length direction of the circular rectangular cross-section is preferably along the flue gas flow direction.

[0035] In some embodiments, the second section 102 of all heat pipes 10 is a second straight section, and the cross-section of the second straight section remains uniform at different length positions. The second straight section preferably has a circular cross-section, an elliptical cross-section, or a circular-rectangular cross-section with low flow resistance. Figure 5 As shown, when the cross-section is elliptical, it is preferable that the major axis of the elliptical cross-section is along the airflow direction. When the cross-section is circular or rectangular, it is preferable that the length of the circular or rectangular cross-section is along the airflow direction. This results in lower airflow resistance and improves heat exchange efficiency.

[0036] In some embodiments, the air preheater includes a housing 20 and a partition 30, with the partition 30 located inside the housing 20. The housing 20 and the partition 30 form a flue gas passage A and an air passage B, with the partition 30 positioned between the flue gas passage A and the air passage B. A heat pipe 10 is inserted into a hole in the partition 30. Thus, the partition 30 serves both to form the flue gas passage A and the air passage B and to support the heat pipe 10.

[0037] In some embodiments, a first support portion 201 and a second support portion 202 are provided on opposite sides of the housing 20, and the heat pipe 10 is inserted into the insertion holes on the first support portion 201 and the second support portion 202. The height of the first support portion 201 may be slightly lower than the height of the second support portion 202 so as to correspond exactly to the two ends of the heat pipe 10 at different heights.

[0038] In some embodiments, the heat pipe 10 has a first end cap 103 and a second end cap 104 at both ends. The first end cap 103 is located at the end of the first pipe segment 101 away from the second pipe segment 102 and is inserted into the insertion hole of the first support portion 201. The second end cap 104 is located at the end of the second pipe segment 102 away from the first pipe segment 101. The first end cap 103 and the second end cap 104 serve to seal the heat pipe 10 and prevent the working fluid inside the heat pipe 10 from flowing out.

[0039] In some embodiments, the second end cap 104 extends out of the housing 20 through the insertion hole of the second support portion 202. This design facilitates the maintenance of the heat pipe 10.

[0040] The above embodiments can be freely combined without conflict.

[0041] The above examples illustrate the principles and implementation methods of this utility model. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of this utility model. It should be noted that those skilled in the art can make various improvements and modifications to this utility model without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this utility model.

Claims

1. An air preheater, characterized in that, The air preheater includes a flue gas passage (A), an air passage (B), and multiple heat pipes (10). Each heat pipe (10) has a first pipe section (101) located in the flue gas passage (A) and a second pipe section (102) located in the air passage (B). The first pipe section (101) forms a first angle with the horizontal direction, and the second pipe section (102) forms a second angle with the horizontal direction. The angle of the first angle is α, and the angle of the second angle is β, wherein 0° < α < β < 30°.

2. The air preheater according to claim 1, characterized in that, The heat pipes (10) are arranged in multiple layers, with each layer arranged sequentially along the flue gas flow direction. The first pipe section (101) of one or more heat pipes (10) near the flue gas inlet is a spiral twisted pipe section with a non-circular cross-section.

3. The air preheater according to claim 2, characterized in that, The cross-section of the spiral twisted tube section is elliptical or circular-rectangular.

4. The air preheater according to claim 2, characterized in that, The first pipe section (101) of one or more heat pipes (10) near the flue gas outlet is the first straight pipe section.

5. The air preheater according to claim 4, characterized in that, The first straight pipe section has a circular cross-section; or, the first straight pipe section has an elliptical cross-section with the major axis of the elliptical cross-section aligned with the flue gas flow direction; or, the first straight pipe section has a rectangular cross-section with the length of the rectangular cross-section aligned with the flue gas flow direction.

6. The air preheater according to claim 2, characterized in that, The second section (102) of all the heat pipes (10) is a second straight section.

7. The air preheater according to claim 6, characterized in that, The cross-section of the second straight pipe section is circular; or, the cross-section of the second straight pipe section is elliptical with the major axis of the elliptical cross-section aligned with the airflow direction; or, the cross-section of the second straight pipe section is rectangular with the length of the rectangular cross-section aligned with the airflow direction.

8. The air preheater according to any one of claims 1-5, characterized in that, The air preheater includes a housing (20) and a partition (30), the partition (30) being located inside the housing (20), the housing (20) and the partition (30) forming the flue gas passage (A) and the air passage (B), the partition (30) being located between the flue gas passage (A) and the air passage (B), and the heat pipe (10) being inserted into a hole on the partition (30).

9. The air preheater according to claim 8, characterized in that, The housing (20) has a first support portion (201) and a second support portion (202) on opposite sides, and the heat pipe (10) is also inserted into the sockets on the first support portion (201) and the second support portion (202).

10. The air preheater according to claim 9, characterized in that, The heat pipe (10) has a first end cap (103) and a second end cap (104) at both ends. The first end cap (103) is connected to the end of the first pipe segment (101) away from the second pipe segment (102). The first end cap (103) is inserted into the insertion hole of the first support part (201). The second end cap (104) is connected to the end of the second pipe segment (102) away from the first pipe segment (101). The second end cap (104) extends out of the housing (20) through the insertion hole of the second support part (202).

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