JPS5912293A - Antivibration baffle for heat exchanger - Google Patents

Abstract

PURPOSE:To absorb and attenuate vibrational energy of a gas column by converting the energy into heat, by a method wherein a baffle is constituted by packing heat-resistant metallic fibers or porous ceramic bodies into a casing composed of a perforated metallic plate. CONSTITUTION:The baffle (a) is constituted by packing metallic fibers or porous ceramic bodies 12 into the casing 11 made of a perforated metallic plate, and is inserted between heat-transmitting pipes 14, 14' provided between outer walls 13, 13'. When a gas colum vibration is generated between the walls 13, 13', the vibrating pressure or vibrating velocity is propagated through the interior of the casing 11 of the fabble (a), the vibrational energy is abosrbed and attenuated through conversion into heat by the frictional resistance of walls of minute and irregular passages (which are formed between the metallic fibers or porous ceramic bodies 12 in the casing 11) and the metallic fibers or the like, and gas colum resonance is prevented.

Description

[Detailed description of the invention] The inside of the heat exchanger is mostly made of metal surfaces to improve the heat transfer effect, and when air column vibration occurs, there is no object to absorb and attenuate the energy. .

Therefore, in order to prevent air column resonance, a vibration isolation baffle is generally inserted into the tube group in order to increase the natural frequency of air column resonance between the outer walls.

Figures 1 to 4 show a part of the heat exchanger in which the vibration-proof baffle is installed. Figure 2 shows an example in which one vibration-proof baffle (3) is inserted in the middle of the heat exchanger tubes, and Figure 2 shows an example in which three baffles (3) are inserted in each group of heat exchanger tubes.
In Figure 6, if it is impossible to insert one anti-vibration baffle,
This is an example in which this is divided into two pieces and some of them are overlapped with each other. Note that ■O shown in each of the above figures represents the average flow velocity of the fluid flowing into the heat exchanger tube.

Figure 5 explains the vortex generated on the downstream side of a single tube placed in a flow velocity of . The frequency f is f
= St V(+ given by /d.

Note that the Strovall number St depends on the arrangement of the tube group, the viscosity of the fluid,
It varies depending on the flow rate, etc., but is determined experimentally.

FIG. 6 shows an example of the resonance mode of the air column vibration occurring between the outer walls (1) (1') and its fundamental wave.

p is the mode of pressure amplitude, V is the mode of velocity amplitude, and the fifth
A vortex as shown in the figure is generated, and its frequency f is the natural frequency fu(u21,
2, 3, ...), it includes a group of tubes,
Outer wall (1) in the direction perpendicular to the fluid flow and the axial direction of the tube
(1'), air column resonance with a frequency frL=f occurs.

In order to prevent such air column resonance, a vibration-proof baffle is inserted into the heat exchanger tube group as described above, but depending on the structure of the heat exchanger, it is not possible to insert a single continuous baffle. It was difficult to install two baffles (as shown in Figure 3 above).
3) (3') is used, but the equivalent baffle (3)
(3'), it is difficult to make the natural frequency of the air column higher than the frequency of the vortex at the maximum flow rate used. Further, even if a temporary anti-vibration Z-tuffle is inserted, the damping capacity inside the heat exchanger cannot be improved because the normal anti-vibration Z-tuffle is made of a metal plate.

The present invention was proposed to solve these problems, and is composed of a plate-like structure in which heat-resistant metal fibers or ceramic porous bodies are encased in a housing made of a porous metal plate. This invention relates to a vibration-proofing problem in a heat exchanger characterized by the following.

As described above, in the baffle according to the present invention, heat-resistant metal fibers or porous ceramic bodies are encased in a housing made of a porous metal plate, so that when air column vibration occurs between the outer walls, the air column When the accompanying vibration pressure or vibration velocity acts on the baffle, the vibration pressure and velocity propagate inside the housing made of a porous metal plate with ventilation, but the interior of the housing is made of heat-resistant metal fibers as described above. Alternatively, since the ceramic porous body is ringed and minute passages are arranged irregularly, the vibration energy of the air column is converted into heat and absorbed and attenuated by the frictional resistance of the passage walls and metal fibers.

Further, by reducing the porosity of the metal fiber or ceramic porous body and increasing the bulk density, the effect of blocking the air column vibration mode and the effect of absorbing energy can be simultaneously satisfied.

Furthermore, the metal fibers and porous ceramics constituting the sound absorber have heat resistance and can be sufficiently used in the heat exchanger, and since they are enclosed in a housing made of a porous metal plate, The vibration-proof baffle is kept in a predetermined shape.

The present invention will be described below with reference to the illustrated embodiments.

(α) is constructed by enclosing metal fibers or porous ceramic bodies 0 in a porous metal plate casing αυ with a baffle. (1
4') is inserted between.

When air column vibration occurs between the outer wall (131), the vibration pressure or vibration velocity accompanying the air column is
) is propagated inside the porous metal plate casing 0υ, and due to the frictional resistance of the walls and metal fibers of minute and irregular passages formed between the metal fibers or ceramic porous body α4 inside the casing 0υ. The vibration energy of the air column is converted into heat and absorbed and attenuated, thereby preventing air column resonance when air column vibration occurs.

Although the present invention has been described above with reference to embodiments, the present invention is of course not limited to these embodiments, and may be modified in various ways without departing from the spirit of the present invention. be.

[Brief explanation of drawings]

Figures 1 to 3 are cross-sectional plan views of the baffle arrangement portion of a conventional heat exchanger, Figure 4 is a view taken along arrows IV-IV in Figures 1 to 6, and Figure 5 shows one baffle. FIG. 6 is an explanatory diagram showing an example of the resonance mode of air column vibration occurring between the outer walls of the heat exchanger, and FIG. 1 is a partial cross-sectional plan view of a heat exchanger used in one embodiment; FIG. (al...baffle, 0υ...perforated metal plate housing, 0υ...metal fiber or ceramic porous body Sub-agent Patent attorney Shige Okamoto 2 outsiders 7I = 3rd ward O6 Kasumiya 4 Zo No. 51 Break')'I-4 Off F/'2 417 JV.

Claims (1)

[Claims] A vibration-proof baffle for a heat exchanger, characterized in that it is constituted by a plate-like structure in which heat-resistant metal fibers or ceramic porous bodies are packed into a porous metal plate casing.