CN105021080A - Abrasion resistance finned tube and heat exchanger - Google Patents

Abstract

The invention discloses an anti-wear fin tube and a heat exchanger, wherein the anti-wear fin tube includes a base tube and fins arranged on the outer surface of the base tube, and is characterized in that: There is a drainage groove with an upper end opening on the surface, the height of the drainage groove is 1/2 to 4/5 of the fin height, and the width of the drainage groove is 1/6~1/4 of the diameter of the base pipe; the fins are Parallel fins or helical fins arranged at intervals. Compared with the prior art, the present invention has little effect on the expanded surface area of the finned tube by slotting the fins on the upstream side of the spiral or circular finned tube, and retains the advantage of the large heat exchange area of the finned tube. By adjusting the height and width of the drainage groove, the wear of traditional spiral finned tubes or circular finned tubes can be effectively improved, and the wear resistance is better than that of H-shaped finned tubes. At the same time, because the fins of the present invention are arc-shaped, the anti-wear performance of the fins is more obvious than that of the H-shaped fin tube.

Description

Wear-resistant finned tubes and heat exchangers

technical field

The invention is applied in the field of boiler flue heat exchangers, and in particular relates to a finned tube which can effectively improve the wear resistance of the heat exchange tube and a heat exchanger with the finned tube.

Background technique

Finned tubes are one of the important heat exchange elements for recovering waste heat and enhancing heat transfer in industry. They are widely used because of their compact structure, increasing the total effective area participating in convective heat transfer, and reducing the thermal resistance of heat transfer outside the tube. . Commonly used finned tubes in the industry include circular finned tubes, H-shaped finned tubes, and spiral finned tubes. When the dust-laden flue gas flows through the heat exchanger to scour the heating surface, the flue gas particles in the air flow collide with the tube wall, which will cause wear to the fin tube over time, and the fin tube wear will affect the heat transfer efficiency of the heat exchanger. In severe cases It will also cause the pipe to leak, forcing the boiler to shut down, bringing huge economic losses and potential safety hazards to production. Since the wear of the finned tube is related to many factors such as the diameter of the flue gas particles, the flue gas flow rate, and the impact angle between the particles and the wall, these factors should be fully considered in the design of the finned tube. When the flue gas flows through different finned tubes, the difference in the shape of the fins causes the difference in the distribution of the flue gas flow field. In the case of the same particle diameter, the higher the local flue gas flow velocity near the tube wall, the greater the particle and wall surface. The greater the angle between the particle velocity and the tangential direction of the wall surface during impact, the greater the wear rate of the particles in the flue gas on the tube wall, and the worse the wear resistance of the finned tube.

At present, measures to improve the anti-wear characteristics of finned tubes from the geometric structure of finned tubes include:

1. Adopt H-type finned tube. Due to the slit of the H-shaped finned tube, the stagnation point on the windward surface of the base tube has a certain velocity, forming an axial scour tube wall, which is essentially different from ordinary tubes. The generation of axial velocity reduces the impact of particles angle, the wear rate decreases accordingly. However, the H-shaped finned tube adopts the intermediate frequency welding process, not only the production cost is high, but also the number of fins arranged in a limited space is relatively small, and the heat transfer efficiency is lower than that of the traditional spiral finned tube.

2. Use double H-shaped finned tubes. The rigidity of the double H-type finned tube is stronger than that of the H-type finned tube. The overall wear resistance of finned tube fins is better than that of H-type finned tubes. The double H-shaped finned tube also has the disadvantages of high production cost and relatively low heat exchange efficiency.

3. Adopt diaphragm tube. Compared with the light pipe, in the case that the number of pipes arranged along the longitudinal direction of the flue gas does not change much, the flue gas circulation area is increased, the flue gas flow rate is reduced, and the anti-wear effect is improved. The diaphragm tube divides the tandem tube bundle into its own independent temperature field, velocity field and concentration field through the serpentine tube and diaphragm connection. The wear resistance mechanism of the diaphragm tube is mainly: the velocity field and the concentration field in the small flue show the characteristics of high middle and low sides. At the same time, a part of the flue gas in the small flue forms several small eddies between the tube and the diaphragm, forming a stable adhesion layer on the metal wall, which reduces the impact ability of the dust particles on the metal. Therefore, the use of the diaphragm tube can reduce wear. However, the rigidity and elastic compensation ability of diaphragm tubes and tubes are lower than those of light tubes, and the finned surface area is far less than that of traditional spiral finned tubes, and the effect of enhancing heat transfer is poor.

In short, most of the existing fin tube designs are at the expense of sacrificing the heat transfer area and reducing the heat transfer efficiency, which seriously affects the advantages of high heat transfer efficiency of the traditional fin tube. Therefore, it is particularly important to develop a new finned tube structure that can not only ensure the heat transfer efficiency but also improve the wear performance.

Contents of the invention

Technical problem: The technical problem to be solved by the present invention is to provide a method aimed at improving the flow characteristics of the flue gas outside the heat exchanger pipe and reducing the local smoke on the premise of ensuring the surface expansion rate of the finned tube. Air flow rate, thereby improving the finned tube of the anti-wear performance of the finned tube and the heat exchanger with the finned tube.

Technical scheme: the technical scheme adopted by the present invention to solve the above problems is as follows:

An anti-wear fin tube, including a base tube and fins arranged on the outer surface of the base tube, is characterized in that: a drainage groove with an upper end opening is arranged on the facing surface of the fin, and the drainage groove The height is 1/2-4/5 of the fin height, and the width of the drainage groove is 1/6-1/4 of the diameter of the base pipe.

The fins are parallel fins or spiral fins arranged at intervals.

The drainage groove is a rectangular groove.

The drainage groove is arranged in the middle of the flow facing surface.

A heat exchanger adopts the finned tube of any one of the schemes above.

In the present invention, drainage grooves are arranged on the facing surface of the fins. Such a finned tube structure can not only ensure the heat exchange efficiency of the finned tubes, but also improve the flow field of the flue gas flowing through the finned tubes, so that the upstream The flue gas on the upper side flows through the slot, and forms a certain axial velocity near the wall when scouring the pipe wall, which is obviously different from the flow around the traditional spiral finned tube or circular finned tube. The movement of the dust particles in the medium is greatly changed accordingly. Part of the particles that originally bypassed the fins and directly hit the wall are scattered at a certain axial velocity at the slot. This movement can significantly reduce the impact of the particles on the wall. wear rate.

Beneficial effect: Compared with the existing fin tube, the present invention has the following advantages:

1. High heat transfer efficiency. Grooving the fins on the upstream side of the spiral or circular fin tube has little effect on the extended surface area of the fin tube, and retains the advantage of the large heat exchange area of the fin tube.

2. In the present invention, under the principle of ensuring the maximum extended surface of the fins, the height and width of the drainage groove can be adjusted according to the size of the base tube. The height is 1/2~4/5 of the fin height, and the width is 1/ of the diameter of the base tube 6~1/4, the particles that directly collided with the wall of the substrate scatter with a certain axial velocity at a certain distance from the upper end of the substrate, so that a deceleration surface with a certain axial velocity is formed near the wall of the substrate. The flue gas passing between the fins hinders and reduces the flow velocity near the wall of the substrate tube. The reduction of the flue gas flow velocity is not only distributed in a planar shape, but also coincides with the circular shape of the substrate tube, so that the flue gas has a large impact on the surface of the substrate tube. The scouring speed is relatively uniform, thus effectively improving the wear of traditional spiral finned tubes or circular finned tubes, and its anti-wear properties are better than those of H-shaped finned tubes. At the same time, because the fins of the present invention are arc-shaped, the anti-wear performance of the fins is more obvious than that of the H-shaped fin tube.

3. The present invention can adopt two types of arrangements, in-line and staggered, in the arrangement of heat exchanger tubes, unlike H-shaped finned tubes, which can only be arranged in-line, with high heat exchange efficiency and more flexible use.

Due to the small fin spacing between different tube rows and thicker fins, H-type finned tubes can only be arranged in line, and the heat transfer performance of the heat exchange surface arranged in line is poor, and the required heat exchange area and layout space Larger, higher equipment costs. Circular finned tubes, spiral finned tubes and the finned tubes with drainage grooves of the present invention can be arranged in parallel like the H-shaped finned tubes, but more often they are arranged in staggered rows. The staggered arrangement of heat exchange surfaces has high heat transfer efficiency, compact equipment, and small layout space. Huge heat can be recovered in a small space. Compared with the arrangement of heat exchange surfaces in parallel, a large amount of steel can be saved, and the equipment cost is lower.

Description of drawings

Fig. 1 is the schematic diagram of C type spiral fin tube of the present invention.

Figure 2 is a cross-sectional view of Figure 1.

Fig. 3 is the schematic diagram of C-type circular fin tube of the present invention;

Fig. 4 is the sectional view of Fig. 3;

Fig. 5 is the schematic diagram of prior art spiral fin tube;

Fig. 6 is the sectional view of Fig. 5;

Fig. 7 is the schematic diagram of prior art H-shaped fin tube;

Fig. 8 is a sectional view of Fig. 7;

Fig. 9 is a schematic diagram of a prior art circular finned tube;

Figure 10 is a sectional view of Figure 9;

Figure 11 is a distribution diagram of the wear rate on the upstream surface of the finned tube in Embodiment 1; wherein: a, spiral finned tube, b, H-type finned tube, c, C-type spiral finned tube;

Fig. 12 is a distribution diagram of the wear rate of the upstream surface of the base pipe in Embodiment 1;

Fig. 13 is a distribution diagram of the wear rate of the upstream fin facing surface of the first embodiment;

Fig. 14 is a velocity distribution diagram of the upstream surface of the base pipe in Embodiment 1;

Figure 15 is a distribution diagram of the wear rate on the upstream surface of the finned tube of Embodiment 2; wherein: a, circular finned tube, b, C-type circular finned tube;

Fig. 16 is a distribution diagram of the wear rate of the upstream surface of the base pipe in embodiment two;

Fig. 17 is a distribution diagram of the wear rate of the fin facing surface of the second embodiment;

Fig. 18 is the velocity distribution diagram of the upstream surface of the base pipe in embodiment two;

In the figure: 1. base pipe, 2. drainage groove, 3. fins.

Detailed ways

Below in conjunction with accompanying drawing, the present invention is described in detail:

The invention is a finned tube mainly used in boiler heat exchangers.

Embodiment one

As shown in Figure 1 and Figure 2. The fin tube of the present invention comprises a base tube 1 and fins 3, wherein 1 is a base tube, and the fin 3 is a spiral fin. A rectangular drainage groove 2 is provided on the facing surface of the spiral fin, which is similar to a C shape. In this embodiment, the height of the drainage groove is 2/3 of the height of the fin, and the width of the drainage groove is 1 of the diameter of the base pipe. /5, welding the slotted spiral fins to the base tube 1, or slotting the fins 3 of the existing spiral fin tubes.

Apply Fluent commercial software to the traditional spiral finned tube of a certain structural size (Fig. 5, Fig. 6), H-shaped finned tube (Fig. 7, Fig. 8) and the slotted spiral finned tube of the present invention (Fig. 1, Fig. 2) Numerical simulation of external flue gas flow:

The flue gas velocity outside the finned tube is 6m/s, and flows along the positive direction of the x-axis. For the traditional spiral finned tube, the H-shaped finned tube and the C-shaped spiral finned tube of the present invention, the simulated wear rate diagram of the upstream surface is shown in FIG. 11 .

It can be seen from Fig. 11 that as the incoming smoke scours the finned tubes, there is a certain degree of wear on the upstream surface of the three tube-type finned tubes. The wear on the base tube of the traditional spiral fin tube is obviously more serious than that of the H-type fin tube and the C-type spiral fin tube, and the area where the wear rate is greater than 1.0×10 ^-10 kg/(m ² ·s) accounts for approximately 2.86% of the total base tube area; the wear rate of the H-type fin tube is greater than 1.0×10 ^-10 kg/(m ² ·s) accounts for about 0.78% of the total area of the base tube, and the wear rate of the C-type spiral fin tube is greater than 1.0× The area of 10 ^-10 kg/(m ² ·s) accounts for 0.71% of the total area of the base tube, which is 75% smaller than the traditional spiral finned tube and about 9% smaller than the H-shaped finned tube.

According to the statistics of the fin wear rate, the area of the H-type finned tube fin with a wear rate greater than 1.0×10 ^-10 kg/(m ² ·s) accounts for about 1.22% of the total fin area; the traditional spiral finned tube fin The area where the wear rate of the sheet is greater than 1.0×10 ^-10 kg/(m ² ·s) accounts for about 0.61% of the total area of the fins, and the wear rate of the fins of the C-type spiral finned tube of the present invention is greater than 1.0×10 ^-10 kg/ The area (m ² ·s) accounts for 0.75% of the total fin area, which is 38.5% smaller than the H-shaped tube.

Further analyze the wear rate of the base pipe, the traditional spiral finned tube, the H-type finned tube and the C-type finned tube of the present invention, the wear rate distribution curve of the center section of the two fins on the upstream side is shown in Figure 12, from which it can be seen that It can be seen that the maximum wear rate of the traditional spiral finned tube is about 1.6×10 ^-10 kg/(m ² ·s), and the maximum wear rate of the H-type finned tube is about 9×10 ^-11 kg/(m ² ·s ), the maximum wear rate of the slotted spiral fin tube of the present invention is about 1.0×10 ^-10 kg/(m ² ·s), about 37.5% lower than the traditional spiral fin tube, and the maximum wear rate of the H-type fin tube About the same.

The wear rate distribution curves on the fins of C-type spiral fin tubes, traditional spiral fin tubes, and H-type fin tubes of the present invention are shown in FIG. 13 . It can be seen from the figure that the maximum wear rate on the fins of the H-type finned tube is about 1.6×10 ^-10 kg/(m ² ·s), and the maximum wear rate on the fins of the traditional spiral finned tube is about 8×10 ^-11 kg/(m ² ·s), while the wear rate of the C-type spiral finned tube of the present invention is similar to that of the traditional spiral finned tube, and is about 50% lower than the maximum wear rate of the H-type finned tube.

Figure 14 shows the velocity distribution along the axial direction of the tube within one fin pitch at the upstream surface along the x-direction (that is, the direction of fluid flow) at a distance of 1 mm from the surface of the substrate tube. As can be seen from Figure 14, the speed distribution between the two fins of the C-type spiral finned tube of the present invention and the traditional spiral finned tube has a trend of being high in the middle and low on both sides, that is, the velocity near the fins is relatively low, and that between the two fins The flow velocity in the central area is high; the maximum flow velocity in the central area of the traditional spiral finned tube is about 1.78m/s, and the maximum flow velocity in the central area of the C-type finned tube of the present invention is about 1.21m/s, which is about 32% lower than the traditional spiral finned tube . The velocity distribution of the H-shaped finned tube is relatively uniform, and there is little difference between the area near the fin and the central area, and the average velocity is about 1.06m/s. It can be seen that the slotting of the C-shaped spiral finned tube of the present invention can significantly reduce the incoming flow velocity, so that the speed at which particles hit the base tube is reduced, thereby reducing the wear of the finned tube.

Therefore, compared with the traditional spiral fins, the C-shaped spiral fin tube of the present invention significantly reduces the wear rate of the base tube on the upstream surface, improves the wear characteristics of the fin tube, and ensures the working stability of the fin tube.

At the same time, compared with the H-type finned tube, the wear rate of the C-type spiral finned tube fin of the present invention is also lower, which combines the advantages of the traditional spiral finned tube fin and the H-type finned tube base tube in terms of wear performance .

Embodiment two

Shown in Figure 3 and Figure 4. The C-shaped circular finned tube of the present invention includes a base tube 1 and fins 3, wherein 1 is a base tube, and the fins 3 are circular parallel fins. A rectangular drainage groove 2 is provided on the facing surface of the spiral fin. In this embodiment, the height of the drainage groove is 4/5 of the height of the fin, and the width of the drainage groove is 1/5 of the diameter of the base pipe. Figure 15 shows the wear rate diagram of the upstream surface of the base tube of the C-type circular finned tube of the present invention and the traditional circular finned tube (Fig. 9, Fig. 10) obtained through simulation.

It can be seen from Fig. 15 that the wear rate of the base tube of the C-type circular finned tube of the present invention is lower than that of the traditional circular finned tube, and the wear area is also smaller than that of the traditional circular finned tube. According to statistics on the wear rate of the base tube, the area of the H-type fin tube with a wear rate greater than 1.0×10 ^-10 kg/(m ² s) accounts for about 0.78% of the total area of the base tube, and the wear rate of the traditional circular fin tube is high. The area of 1.0×10 ^-10 kg/(m ² ·s) accounts for about 1.52% of the total area of the base tube, and the wear rate of the C-type circular finned tube is higher than 1.0×10 ^-10 kg/(m ² ·s) The area accounts for about 0.33% of the total area of the substrate tube. The seriously worn area of the C-shaped circular finned tube of the present invention is only 78.3% of that of the traditional circular finned tube, which is 57.7% smaller than that of the H-shaped finned tube.

According to the statistics of the fin wear rate, the area of the H-type finned tube with a fin wear rate greater than 1.0×10 ^-10 kg/(m ² ·s) accounts for about 1.22% of the total fin area; The area where the sheet wear rate is greater than 1.0×10 ^-10 kg/(m ² ·s) accounts for about 1.66% of the total fin area, and the fin wear rate of the C-type circular fin tube of the present invention is greater than 1.0×10 ^-10 kg/ The area (m ² ·s) accounts for 0.39% of the total fin area, which is 76.51% lower than that of traditional circular finned tubes and 68.03% smaller than that of H-shaped tubes.

Further analysis on the wear rate of the base tube, the wear rate distribution curves of the traditional circular finned tube, the H-shaped finned tube and the C-shaped circular finned tube of the present invention are shown in Figure 16. It can be seen from the figure that the maximum wear rate of the traditional circular fin tube is about 1.51×10 ^-10 kg/(m ² s), and the maximum wear rate of the H-type fin tube is about 9×10 ^-11 kg/(m ² ·s), the maximum wear rate of the C-type circular finned tube of the present invention is about 8.5×10 ^-11 kg/(m ² ·s), about 43.7% lower than the traditional spiral finned tube, and lower than the H-type finned tube The maximum tube wear rate is 5.6% lower.

The wear rate distribution curves on the fins of C-type spiral fin tubes of the present invention, traditional spiral fin tubes, and H-type fin tubes are shown in Figure 17. As can be seen from the figure, the maximum wear rate on the fins of H-type fin tubes It is about 1.66×10 ^-10 kg/(m ² ·s), and the maximum wear rate on the fins of traditional circular finned tubes is about 1.56×10 ^-10 kg/(m ² ·s), while the C-type circular The maximum wear rate on the fin of the finned tube is about 1.25×10 ^-10 kg/(m ² ·s), which is about 24.7% lower than that of the H-type finned tube and about 19.9% lower than that of the traditional circular finned tube.

Figure 18 shows the velocity distribution along the tube axial direction within one fin pitch on the upstream surface along the x-direction (that is, the direction of fluid flow) at a distance of 1 mm from the substrate tube surface. It can be seen from Figure 18 that the flow field velocity of the circular finned tube is small near the fins, and the flow field velocity is relatively high at the center of the two fins, with a maximum flow velocity of about 1.64m/s. The C-type circular finned tube and the H-type finned tube have a relatively uniform flow field distribution near the base tube due to the slotting of the fins. The average velocity of the H-type finned tube at 1mm from the base tube is 1.065m/s. The maximum speed of the circular finned tube is 1.22m/s, which is about 25.6% lower than that of the traditional circular finned tube, which makes the wear rate of the base tube of the C-type circular finned tube lower than that of the traditional circular finned tube.

Therefore, compared with the traditional circular fins, the C-shaped circular finned tube of the present invention significantly reduces the wear rate of the base tube and fins on the upstream surface, improves the wear characteristics of the finned tube, and makes the finned tube work stably Sex is guaranteed.

Claims (5)

1. the extended surface tube that resistance to wears, comprise base tube and be arranged on the fin of described base tube outer surface, it is characterized in that: the drainage trough being provided with a upper end open on the fluoran stream surface of described fin, the height of this drainage trough is that 1/2 to 4/5 wing is high, and the width of drainage trough is 1/6 ~ 1/4 of described base tube diameter.

2. the extended surface tube that resistance to wears according to claim 1, is characterized in that: described fin is spaced apart parallel fins or spiral fin.

3. the extended surface tube that resistance to wears according to claim 1, is characterized in that: described drainage trough is rectangular channel.

4. the extended surface tube that resistance to wears according to claim 1, is characterized in that: described drainage trough is arranged on the center of described fluoran stream surface.

5. a heat exchanger, is characterized in that, comprises the arbitrary described extended surface tube that resistance to wears of claim 1 to 5.