Falling water high frequency noise control

Governance is relatively easy, but pay attention to sound insulation and avoid affecting the performance of heat dissipation. Although muffler and muffler can greatly reduce noise, it should be rationally designed and designed with thermal and dynamic performance in mind. If the structure is unreasonable, the purpose of noise reduction will not be achieved. If the flow resistance is too large, it will affect the cooling tower work and reduce the cooling capacity. If the power performance design is not good, it will increase the resistance and even generate reverberation noise. Therefore, the management process should be considered comprehensively.

Cooling tower several common cooling tower noise reduction methods

Acoustic guide film method (muffling elbow)

The method of sound-absorbing and baffle is installed in the air inlet of the cooling tower, and the noise-reducing effect of the cooling tower is reduced by the muffling effect of the sound-absorbing baffle. It is also called the muffler method. The theory and experiments show that the noise reduction can reach 35dB(A) or even higher; when the noise reduction is 15-2OdB(A), it is equivalent to the sound barrier, and it is the only noise reduction above 20dB(A). Optional plan; compact structure, does not occupy additional sites of the building, basically no maintenance.

Damping guide method (muffling elbow)

The sound insulation barrier is generally designed such that the distance from the air inlet of the cooling tower is greater than the height of the air inlet of the cooling tower, and the height of the barrier is equal to the distance from the barrier to the air inlet. The noise reduction effect is generally 10-15dB(A), and the theoretical noise reduction can be about 2OdB(A), but there is a problem of acoustic wave diffraction. The noise reduction is better in the range of the sound shadow area, and the diffraction area and the sound area are bright. The noise reduction effect of the area is poor, so it is difficult to reduce the noise in the affected area by 20dB(A) in actual engineering; it has little effect on ventilation and is relatively simple to maintain; the technical requirements for building sound barriers are not high, but the structural requirements are quite high. And the investment cost increases exponentially with height;

Sound insulation barrier method and characteristics:

The structure of the sound insulation barrier can be divided into two parts: the above ground and the underground. The ground part is a giant, continuous plate façade (including diagonal bracing) with a shielding sound wave of about 20 cm thick, and the top is a fan-shaped sound absorber or an inward-facing concealer; The underground part is the basis for load bearing and anti-overturning (wind load).

The noise reduction effect of the sound barrier The diffraction phenomenon of the sound wave encountering the barrier will weaken the sound insulation effect of the sound barrier, and the diffraction ability is related to the frequency of the sound wave, so the noise reduction effect of the sound barrier is related to the frequency of the sound wave, that is, the wavelength. Very big. The sound barrier has a very significant shielding effect on high-frequency waves with short wavelengths and difficult to be diffracted, and can form a long sound-image area behind the barrier. The shielding effect on wavelengths and low-frequency waves with strong diffraction ability is very limited. Of course, it is also possible to weaken the effect of the diffracted sound waves on the sound receiving point by increasing the barrier. Since the sound barrier has a significant effective shielding effect on high-frequency sound waves, and the spectrum of the cooling tower falling water noise is mainly composed of medium and high frequency components, the sound barrier can achieve a certain noise reduction effect.

The noise reduction effect of the sound insulation barrier is as good as the local area of the sound barrier area close to the barrier, and the Zui height is up to 25 db.

The noise reduction level outside the sound shadow area rebounds due to the arrival of the intermediate frequency diffracted sound wave, but for high frequency waves, the attenuation amount can generally reach 10-15 dB.

However, since the cooling tower water noise still contains the intermediate frequency component, its noise reduction effect will be discounted. For the sound receiving point outside the building, in order to obtain a satisfactory noise reduction effect, the barrier height should be adjusted by not increasing the air intake.

When installing the sound insulation barrier, the main concern is that the distance between the sound insulation barrier and the louver air inlet of the cooling tower is about 1m to ensure that the cooling air inlet of the cooling tower is unobstructed, so that the cooling tower has better cooling effect.

In order to prevent the noise from being diffracted and affecting the acoustic effect of the muffler, a certain length of sound barrier can be installed in the vicinity of the muffler to assist in noise reduction.

Falling water muffling method and characteristics: Install the falling water energy-reducing noise-reducing material above the water surface at the bottom of the cooling tower to reduce the noise source from the source. The noise reduction effect is generally 6-10dB(A); the initial investment is less, and it has no effect on ventilation and heat dissipation; the disadvantage is less noise reduction, parts are easy to damage, maintenance workload is large, continuous investment is required, and condensation may also be caused. The problem of blockage of the tube.

The "water-falling energy-reducing noise reducer" is mainly composed of hexagonal honeycomb inclined tube, with a height of 18cm, consisting of four functional sections: vertical lead-in section, silent wiping diagonal section, viscous deceleration ramp section, and evacuation and pick-up section. .

Spring shock absorber selection method:

1. Spring shock absorber load range selection

Equipment operating weight M * 130% / shock absorber installation number N = spring shock absorber load range;

Example: The operating weight of the fan is: 5 tons; a single fan needs to install 4 spring dampers; what is the load of a single spring damper?

According to the formula: 5000 kg * 130% / 4 = 1625 kg

According to the parameters of the spring damper, the spring damper specifications can find the spring damper specifications suitable for the cooling tower.

2. Determination of the number of spring shock absorbers installed on the equipment:

Specific measures If the equipment manufacturer provides this data, it is subject to the factory regulations; under normal circumstances, the installation interval of the shock absorber does not exceed 2M, according to which the number of spring shock absorbers can be calculated, taking into account the stability of the equipment, each The cooling tower has four shock absorption designs.

3. Selection of spring shock absorber type:

In most cases, the function and function of the spring damper are the same. The difference between the different types of dampers is that the shape is different. The limited spring damper is briefly introduced as follows:

The structural feature of the limited-type spring damper is that it has a device for limiting the height of the damper. This feature is beneficial to the equipment that has a large change in the weight of the machine, and avoids a large change in the height of the machine after the damper is installed. , causing damage to certain structures of the device. Example: Large equipment such as cooling towers and water-cooled units.

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