JPH10253277A - Tube group structure and waste heat recovery boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tube group structure, capable of preventing noise sufficiently by a method wherein the structure of the tube group is simplified to prevent air columnar resonance between vortex, discharged out of fluid around tubes, and gas existing in a vessel. SOLUTION: A tube group structure is constituted of a tube group, in which a plurality of heat transfer tubes 1 are arrayed regularly and integrated by a supporting structure, supporting the heat transfer tubes 1, and a box type vessel, receiving the tube group, while the heat transfer tubes 1 are provided with disc type thin sheet protuberances 2 on the outer surfaces thereof. In such a tube group structure, the thin sheet protuberance 2 is provided with a plurality of pieces of radial slits and the slit is formed asymmetry with respect to a tube axis in the parallel direction of the flow 3 of medium, which flows along the surface of the tube, or irregularly in the peripheral direction of the tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tube bank structure and an exhaust heat recovery boiler, and more particularly to a tube bank structure and an exhaust heat recovery boiler used in a thermal and nuclear power plant.

[0002]

2. Description of the Related Art In a waste heat recovery boiler of this type, which is conventionally employed in thermal and nuclear power plants, when a fluid flows through a tube bundle of heat transfer tubes, a vortex as shown in FIG. Is released to the rear of the tube at regular intervals. The period (frequency) of the released vortex mainly depends on the representative length such as the diameter of the tube, the flow velocity around the tube, the shape of the tube surface, and the like.

On the other hand, in a tube bank structure such as an exhaust heat recovery boiler, a box-shaped container is required to house the entire tube bank and form a flow path through which a fluid flows in the tube bank. When the fluid is a gas, these containers have a plurality of natural column frequencies corresponding to their dimensions. The natural air column frequency is a frequency that continues to vibrate without damping when a gas filling a certain container vibrates.

[0004] The frequency characteristics of the vortex discharged to the rear of a tube group composed of tubes of the same shape are the same for all tubes. Therefore, the vortices emitted are strengthened as they flow through the tube bank, and certain frequency components become dominant. Here, when the dominant frequency of the vortex coincides with the natural air column frequency of the container that houses the entire tube group, the air column resonates, generating more noise than in the container.

[0005] When the generated sound pressure is large, intense vibration of the pipe is induced, which may lead to breakage. This phenomenon is called an air column resonance phenomenon, and in designing a tube bank structure, it is important to prevent the air column resonance phenomenon from the viewpoint of noise prevention and breakage prevention.

As a conventional technique for preventing the air column resonance phenomenon, a plurality of disk-shaped thin plate projections (fins) are provided on the outer surface of each pipe in the longitudinal direction of the pipe, and radial slits are formed in the circumferential direction of each fin. Some of the vortex emission frequencies attempt to reduce the level of the dominant frequency by providing a plurality. In addition, as a thing related to this kind of tube bank structure, JP-A-55-35867 or JP-T-7-509774 is exemplified.

[0007]

In the prior art described above, as shown in the example of FIG. 2 (b) (illustrating the effect of the depth of the slit on the frequency of the discharge vortex), the vortex of the tube is reduced. The emission only slightly reduced the most dominant frequency components, and could not avoid the column resonance with the gas described above and could not prevent noise.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and it is an object of the present invention to provide a vortex discharged from a fluid around a pipe without changing the configuration of the pipe group, that is, with a simple structure, so that the vortex is present in the vessel. An object of the present invention is to provide a tube bank structure of this kind which can prevent air column resonance with generated gas and sufficiently prevent noise.

[0009]

That is, according to the present invention, a plurality of heat transfer tubes are regularly arranged, and a tube group integrated by a support structure for supporting these heat transfer tubes, and a box-type housing for accommodating them. In the tube group structure comprising the container of the above, and the heat transfer tube is provided with a disk-shaped thin plate projection on the outer surface thereof, the thin plate projection is provided with a plurality of slits in the pipe radial direction, The shape is formed so as to be left-right asymmetric with respect to the pipe axis parallel to the flow of the medium flowing on the pipe surface so as to achieve the intended purpose.

[0010] Further, the present invention comprises a tube group in which a plurality of heat transfer tubes are regularly arranged, a tube group integrated by a support structure for supporting these heat transfer tubes, and a box-shaped container for accommodating them. In the tube group structure in which the heat transfer tube has a disk-shaped thin plate projection on its outer surface, the thin plate projection is provided with a plurality of slits in the radial direction of the tube, and the shape of the slit is not changed in the circumferential direction. It is to be formed uniformly.

Further, a plurality of heat transfer tubes are regularly arranged,
It consists of a tube group united by a support structure that supports these heat transfer tubes, and a box-shaped container that stores them, and the heat transfer tubes have a disk-shaped thin plate projection on the outer surface thereof. In the tube bank structure, a plurality of slits in the radial direction of the tube are provided on the thin plate projection, and the depth of the slits, the width of the slits, or the interval between the slits are formed to be uneven in the circumferential direction. is there. Further, this tube bank structure is provided in an exhaust heat recovery boiler.

That is, in the exhaust heat recovery boiler thus formed and the tube bank structure used therein, the slit shape of the disk-shaped thin plate projection provided on the outer surface of the heat transfer tube flows on the tube surface. Since it is formed asymmetrically with respect to the pipe axis in the direction parallel to the flow of the medium, or non-uniformly in the circumferential direction, the vortex discharge form from the heat transfer tube becomes non-uniform and discharges from a disk-shaped thin plate projection. The dominant frequency component of the vortex is dispersed and suppressed. As a result, the intensity of the most dominant vortex emission frequency component can be made lower than the threshold value of the occurrence of resonance, and the occurrence of resonance can be prevented and noise can be prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 and FIGS. 1 (a) and 1 (b) show a horizontal cross section of a heat transfer tube group structure in a heat recovery steam generator and a horizontal cross section of a heat transfer tube used in the heat recovery boiler in a thermal power plant which best illustrates the present invention. Example 1) is shown, and FIG. 3 shows an outline of an exhaust heat recovery boiler in a thermal power plant to which the present invention is applied.

The exhaust heat boiler includes a duct 10, a superheater 11, a drum 12, a reheater 13, a denitration device 14, a economizer 15, an evaporator 16, and the like. The superheater 11, the reheater 13, the economizer 15, and the evaporator 16 are a group of tubes in which the heat transfer tubes 1 each having a disk-shaped thin plate projection (fin) 2 on the outer surface thereof are arranged in a plurality of rows.

In the first embodiment shown in FIG. 1 (b), a slit of a disk-shaped or spiral thin plate projection (fin) 2 provided on the outer surface of the tube 1 and provided with a slit in the radial direction of the tube. Is set unevenly in the circumferential direction. Since the discharge behavior of the vortex is affected by the depth of the slit, by making the depth of the slit non-uniform in the circumferential direction, the discharge frequency of the vortex discharged to the rear of the tube 1 is different for each slit having a different depth. Because of the differences, the dominant frequencies spread over a wide frequency range.

As a result, the intensity of the most dominant vortex emission frequency component is reduced as compared with the case where the slit has a uniform depth. As shown in FIG. 2C, the intensity of a vortex having energy equal to or greater than the attenuation of the sound field in the tube bank is required for generating resonance. According to the embodiment of the present invention, the intensity of the most dominant vortex emission frequency component can be made lower than the threshold value of the occurrence of resonance, thereby preventing the occurrence of resonance and preventing noise. In addition, the amount of slits can be reduced as compared with the conventional fins, and the surface area of the fins increases, so that the heat recovery efficiency also increases.

FIGS. 4 and 5 show a second and a third embodiment according to the present invention. In the second embodiment, the width of the slit of the fin 2 in the pipe circumferential direction is set to be non-uniform. In the third embodiment, the intervals between the slits of the fins 2 in the pipe circumferential direction are set to be non-uniform. Since the discharge behavior of the vortex affects the width and interval of the slit, by making the slit circumferential width and interval non-uniform, the emission frequency of the vortex emitted to the rear of the tube 1 can be changed by the slits having different depths. The dominant frequency spreads over a wide frequency range because it varies from one frequency to another. This allows
The same effects as those of the first embodiment can be obtained, and resonance can be prevented, and noise can be prevented.

FIG. 6 shows a fourth embodiment according to the present invention. Now, in the pipe section, an angle θ is defined clockwise with reference to a point (A) in the upstream direction of the flow on the pipe axis 4.
The vortex emitted from the tube is near θ = 90 degrees and θ = 27
Peel from near 0 degree. In the fourth embodiment, since the slit width and depth near θ = 90 degrees and near θ = 270 degrees are different, the vortex emitted near θ = 90 degrees and the vortex emitted near θ = 270 degrees are different. The frequencies are different. Therefore, as compared with the case where the slits of the fin 2 are the same near θ = 90 degrees and the same near θ = 270 degrees, the dominant vortex emission frequency is dispersed, and the strength is also reduced. Therefore, resonance can be prevented,
Noise can be prevented.

FIG. 7 shows a fifth embodiment according to the present invention. In the fifth embodiment, the depth and the circumferential width of the slit of the fin 2 are made non-uniform, and the slit of the fin 2 is set to be asymmetric with respect to the tube axis 4 in the direction parallel to the flow. Thereby, a plurality of effects caused by the first, second, third and fourth embodiments can be obtained. Therefore,
Resonance can be prevented, and noise can be prevented.

Although the present invention has been described assuming a heat recovery steam generator provided with a heat transfer tube provided with thin plate projections having the same shape in the longitudinal direction of the tube, the first to fifth embodiments will be described in the longitudinal direction of the tube. An exhaust heat recovery boiler provided with a heat transfer tube in which a plurality of the thin plate projections are arranged, or a tube bank structure used for an exhaust heat recovery boiler may be used.

As described above, according to the tube bank structure formed in this manner, the disk-shaped or spiral-shaped thin plate-shaped projections 2 disposed on the outer surface of the tube 1 have slits extending in the radial direction of the tube. Make the depth uneven in the circumferential direction. Further, slits having uneven widths and uneven intervals in the circumferential direction are provided in the pipe radial direction. This makes it possible to suppress the most dominant frequency component of vortex shedding and prevent resonance. Furthermore, since the amount of slits can be reduced, the heat recovery efficiency can be increased. Further, by setting the slit of the fin 2 so as to be asymmetrical with respect to the tube axis 4 in the direction parallel to the flow,
The dominant frequency component of the emitted vortex can be dispersed and suppressed, and resonance can be prevented. Thus, noise can be sufficiently prevented.

[0022]

As described above, according to the present invention, the structure of the tube group is not changed, that is, the structure is simplified, and the vortex discharged from the fluid around the tube and the gas existing in the container are formed. This type of tube bank structure that can prevent air column resonance and sufficiently prevent noise can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a tube group structure having a disk-shaped thin plate projection and a radial sectional view of a heat transfer tube (Example 1).

FIG. 2 is a characteristic diagram showing characteristics of a vortex discharge form and a vortex discharge frequency in a single tube.

FIG. 3 is a perspective view showing an exhaust heat recovery boiler in the thermal power plant.

FIG. 4 is a sectional view showing another embodiment of the present invention (Embodiment 2).
It is.

FIG. 5 is a sectional view showing another embodiment of the present invention (Embodiment 3).
It is.

FIG. 6 is a sectional view showing another embodiment of the present invention (Embodiment 4).
It is.

FIG. 7 is a sectional view showing another embodiment of the present invention (Embodiment 5);
It is.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heat transfer tube, 2 ... Disc-shaped thin plate projection (fin), 3 ...
Air flow direction, 4 ... Tube axis parallel to flow, 10 ...
Duct, 11: superheater, 12: drum, 13: reheater,
14: denitration equipment, 15: economizer, 16: evaporator.

Claims (4)

[Claims] 1. A heat transfer tube comprising a plurality of heat transfer tubes arranged regularly, a tube group integrated by a support structure for supporting the heat transfer tubes, and a box-shaped container for accommodating the tube groups. However, in a tube bank structure provided with a disk-shaped or spiral-shaped thin plate projection on the outer surface thereof, a plurality of slits are provided in the thin plate projection in the radial direction of the tube, and the shape of the slit is changed to the surface of the tube. A tube bank structure which is formed so as to be left-right asymmetric with respect to a tube axis parallel to a flow of a flowing medium. 2. A heat transfer tube comprising a plurality of heat transfer tubes arranged regularly, a tube group integrated by a support structure for supporting these heat transfer tubes, and a box-shaped container for accommodating the tube groups. However, in a tube bank structure provided with a disk-shaped or spiral-shaped thin plate projection on the outer surface thereof, a plurality of slits are provided in the thin plate projection in the radial direction of the tube, and the shape of the slit is not changed in the circumferential direction. A tube bank structure characterized by being formed uniformly. 3. A heat transfer tube comprising a plurality of heat transfer tubes arranged regularly, a tube group integrated by a support structure for supporting these heat transfer tubes, and a box-shaped container for accommodating them. However, in a tube bank structure having a disk-shaped or spiral-shaped thin plate projection on the outer surface thereof, the thin plate projection is provided with a plurality of slits in the pipe radial direction, and the depth of the slit or the slit is A tube bank structure wherein a width or a gap between slits is formed to be uneven in a circumferential direction. 4. An exhaust heat recovery boiler provided with the tube bank structure according to claim 1.