JPH0886587A - Heat exchanger - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent the occurrence of air column resonance in the flow direction of a fluid in a heat exchanger containing a tube group. In a heat exchanger containing a tube group composed of a large number of tubes 2, sound absorbing materials 6, 7a, 7b are attached to the inner walls of the narrowed inlet portion 4 and outlet portions 5a, 5b to form an air column in the fluid flow direction. The generation of resonance was prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger incorporating a tube group used for a boiler, an exhaust / desorption device, a gas heater, an air heater and the like.

[0002]

2. Description of the Related Art There is no technique for reducing air column vibration in the flow direction of a heat exchanger, which is the object of the present invention.

[0003]

As shown in FIG. 2 (a), when a fluid passes at a velocity of Vg between a group of a plurality of tubes 2 having a circular cross section, the frequency from the tube 2 is reduced. f
The regular vortex 3 of is emitted. The emission frequency f of the vortex 3 is
It is characterized by the Strouhal number St = fd / Vg, where d is the diameter of the tube 2, and the Strouhal number St has a constant value. Due to this vortex 3, as shown in FIG. 2 (b), the vortex 3 causes the exciting force Fy of the frequency f and the excitation force Fy of the frequency f in the direction perpendicular to the flow as shown in FIG.
As shown in, the excitation force Fx of the frequency 2f acts in the flow direction. The reaction force of these exciting forces acting on the pipe 2 acts on the fluid, but if the frequency of these exciting forces matches the natural frequency of the sound field in the heat exchanger, a noise problem called air column resonance phenomenon occurs. To do. The excitation force Fy of frequency f excites the air column resonance in the direction perpendicular to the flow, and the excitation force Fx of frequency 2f
Generates a columnar resonance in the flow direction. Note that FIG. 2 (d)
2 (e) is a graph obtained by frequency-analyzing the excitation force shown in FIG. 2 (b) and FIG. 2 (c), respectively.

The present invention relates to a heat exchanger incorporating a tube group for reducing the air column resonance in the flow direction of the frequency 2f.

[0005]

According to the present invention, in a heat exchanger containing a tube group, a sound absorbing material is attached to at least one of the inner walls of the narrowed portions of the inlet and outlet.

[0006]

In the heat exchanger containing the tube group, resonance in the flow direction occurs when the narrowed portions of the inlet and the outlet serve as acoustic reflection ends to form standing waves. Therefore,
By attaching the sound absorbing material to at least one of the inner walls of the narrowed portion of the inlet and the outlet, the sound wave is not reflected, and a standing wave in the flow direction becomes difficult to form.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG.
A fluid having a flow velocity V flows through the heat exchanger 1. Heat exchanger 1
A tube group made up of a large number of tubes 2 having a circular cross section is installed inside the tube so that heat can be exchanged between the external fluid and the internal fluid of the tube 2. The inlet part 4 and the outlet parts 5a, 5b of the heat exchanger 1 are squeezed as shown in FIG.
The sound absorbing material 6 is attached to the inner wall of the narrowed inlet portion 4, and the sound absorbing materials 7a and 7b are attached to the inner wall of the narrowed outlet portions 5a and 5b.

Excitation force is generated in the fluid in the flow direction by the vortex 3 generated on the surface of the tube 2 of the tube group. When the frequency of the exciting force in the flow direction matches the natural frequency of the sound field in the heat exchanger in the flow direction, the air column resonance P in the flow direction occurs. Since the air column resonance P in the flow direction is generated by the standing wave being formed because the narrowed inlet portion 4 and outlet portions 5a and 5b of the heat exchanger serve as sound pressure reflection ends, in the present embodiment, By adhering the sound absorbing materials 6, 7a, 7b to these portions, it is possible to reduce wall reflection of sound waves and make it difficult for standing waves to be formed. As a result, the occurrence of air column resonance in the flow direction can be prevented.

In the above embodiment, the sound absorbing material is attached to the inner wall of both the narrowed inlet and outlet of the heat exchanger, but the sound absorbing material may be attached to either one of them. .

[0010]

According to the present invention, since the sound absorbing material is attached to at least one of the inner walls of the narrowed portions of the inlet and the outlet of the heat exchanger containing the tube group, the wall reflection of sound waves is prevented. By making it small, it is difficult for a standing wave to be formed, and by this, the occurrence of air column resonance in the flow direction can be prevented.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 (a) is an explanatory view of a vortex generation state in a conventional heat exchanger incorporating a tube group, FIG. 2 (b) is a graph of exciting force in a direction perpendicular to a flow due to vortices, and FIG. ) Is a graph of the exciting force in the flow direction due to the vortex, and FIGS. 2D and 2E are graphs obtained by frequency analysis of the exciting forces shown in FIGS. 2B and 2C, respectively.

[Explanation of symbols]

 1 heat exchanger 2 tube 3 vortex 4 inlet of heat exchanger 5a, 5b outlet of heat exchanger 6, 7a, 7b sound absorber P air column resonance in flow direction Fx excitation force in flow direction Fy excitation in right angle direction Force Vg Fluid flow velocity between fluids V Fluid flow velocity f Vortex emission frequency d Pipe diameter

Claims (1)

[Claims] 1. A heat exchanger having a tube group, wherein a sound absorbing material is attached to an inner wall of at least one of a narrowed portion of an inlet portion and an outlet portion.