Is the noise from the cooling tower too loud? 3 Practical Tips to Help You Solve the "Disturbance Problem"

In the vicinity of industrial plants, commercial complexes or large office buildings in cities, the operating sounds of cooling towers sometimes become a disturbing "background noise". This continuous low-frequency noise not only may affect the daily life of the surrounding residents, but also poses a potential threat to human health when exposed to a noisy environment for a long time. In fact, the noise from cooling towers is not uncontrollable. As long as the source of the noise is accurately identified and targeted measures are taken, the decibels can be effectively reduced and the problem of disturbing the residents can be solved.

First, figure out: Where does the noise from the cooling tower come from?

The noise from the cooling tower does not come from a single source but is the superposition of multiple sounds. To solve the noise problem, the first step is to identify who the "enemy" is.

Fans are one of the main noise sources of cooling towers. When a fan is in operation, the blades rub against the air at high speed, generating aerodynamic noise. This kind of noise has a high frequency and a wide propagation range. Meanwhile, the mechanical vibration of the fan motor will also generate low-frequency noise, which is conducted to the surrounding environment through the metal supports of the cooling tower and the ground.

The sound of flowing water should not be ignored either. When hot water is sprayed onto the packing through the water distributor, a "swish swish" sound of water falling will be produced. When water flows through the gaps of the packing, it will also generate continuous water flow noise due to friction and impact. If the water distribution is uneven and the water volume in some areas is too large, the sound of water falling will be more obvious.

In addition, equipment vibration can also cause noise. When a cooling tower is in operation, the vibrations of equipment such as fans and water pumps will be transmitted to the building through pipes and foundations, thereby generating structural sound transmission. Especially for old equipment, due to the wear and tear of components, the vibration intensifies, and the noise problem becomes more prominent.

The noise performance varies among different types of cooling towers. For instance, the water distribution height of cross-flow cooling towers is relatively low, and the noise of water drop is relatively small. The fans of counter-flow cooling towers are usually installed at the top, and aerodynamic noise is more likely to spread to high altitudes. Only by understanding these characteristics can a more precise noise reduction plan be formulated.

Technique One: Give the fan a "noise-reducing package" to cut off airborne sound transmission

Fan noise is the most prominent noise source in cooling towers. Noise reduction treatment for it can produce immediate results. Specifically, it can be approached from three aspects:

Choosing a low-noise fan is the foundation. The new type of axial flow fan adopts a streamlined blade design, which can reduce the noise generated by air vortices. For instance, a certain brand of low-noise fan, by optimizing the blade Angle and increasing the number of blades, reduces noise by 8 to 10 decibels compared to traditional fans while ensuring air volume. When selecting a fan, it is necessary to take into account the heat dissipation requirements of the cooling tower to avoid the situation of "a big horse pulling a small cart" - overly pursuing high-power fans not only consumes energy but also increases noise.

Installing sound insulation covers on fans is an effective auxiliary measure. The sound insulation cover adopts a double-layer sound insulation board structure, with sound-absorbing cotton filled in the inner layer, which can absorb most of the aerodynamic noise. It should be noted that the sound insulation cover should reserve sufficient heat dissipation holes and install small cooling fans to prevent the fan from affecting its operating efficiency due to poor heat dissipation. In a case of cooling tower renovation in a certain shopping mall, after installing a custom sound insulation cover on the top fan, the noise level within a 10-meter radius was reduced from 75 decibels to 62 decibels, achieving a remarkable effect.

The installation details of the fan can also affect the noise level. Installing vibration isolators (such as rubber vibration isolators or spring vibration isolators) between the fan base and the cooling tower support can reduce the noise transmitted from vibration to the shell. At the same time, regular maintenance and servicing of the fan should be carried out. Dust and debris on the blades should be cleaned in a timely manner, and the tightness of the belt should be adjusted to prevent increased noise caused by component wear or imbalance.

Tip Two: Optimize the water flow design to reduce the noise of falling water

Although the decibel level of water flow noise is not as high as that of a fan, the continuous "sound of running water" is more likely to make people feel irritable. By optimizing the water distribution and packing structure, this kind of noise can be effectively reduced.

Reasonable design of the water distribution system is the key. Change the traditional single-point water distribution to multi-point uniform water distribution to reduce the concentrated drop of water flow. For instance, by using a rotary water distributor, water can be evenly sprayed onto the filler material through multiple tiny water outlet holes, thus avoiding the formation of a "waterfall-like" water drop. A certain factory reduced the noise of water falling from 68 decibels to 55 decibels by modifying the water distributor, and the effect was very obvious.

Choosing high-efficiency sound-absorbing fillers can achieve two goals at once. High-quality honeycomb packing not only has a high heat dissipation efficiency but also can absorb water flow noise through its porous structure. Laying an elastic cushion layer (such as polyurethane foam) under the packing can further buffer the impact of water flow and reduce the impact sound. It should be noted that the packing material needs to be cleaned regularly to prevent uneven water distribution due to blockage, which may instead increase local noise.

It is also very important to control the water level drop. If the water level in the collection pool of the cooling tower is too low, the height of the water flow will increase, and the noise will increase significantly. By adjusting the water replenishment device, the water level in the sump can be kept stable and the water flow drop can be reduced, which can lower the noise of water falling from the source. Meanwhile, deflector plates are set up in the water collection pool to ensure the water flows in smoothly and avoid the generation of vortices and impact sounds.

Technique Three: Properly carry out vibration reduction treatment to prevent sound transmission through the structure

Structural sound transmission caused by vibration is often overlooked, but it can spread to more distant places through the ground and buildings. Vibration reduction treatment for equipment vibration and pipeline vibration can effectively cut off this transmission path.

Vibration reduction of the equipment foundation is the first step. Installing vibration isolators, such as spring vibration isolators or rubber vibration pads, between the concrete foundation of the cooling tower and the tower body can reduce the transmission of vibration to the ground. The selection of shock absorbers should be determined based on the weight and vibration frequency of the cooling tower to ensure a matching load-bearing capacity. By replacing high-performance vibration isolators with cooling towers in a certain office building, the vibration noise in the surrounding residential buildings has been reduced from 45 decibels to 38 decibels, meeting the noise standards for residential environments.

Vibration reduction at pipe connection points cannot be ignored. The connection between the inlet and outlet pipes of the cooling tower and the water pump and equipment should use flexible joints (such as rubber flexible joints) to avoid vibration transmission caused by rigid connections. Meanwhile, vibration isolation pads should be installed at the pipe supports to reduce the impact of pipe vibration on the wall. For longer pipes, elastic hangers can also be added to further absorb vibration energy.

Regular inspection and maintenance can prevent the intensification of vibration and noise. After the cooling tower has been in operation for a period of time, problems such as loose components and worn bearings can lead to increased vibration. Therefore, it is necessary to regularly check whether the fixing bolts of the fans and pumps are loose, whether the bearings need lubrication or replacement, and promptly eliminate potential faults. A certain industrial park has established a quarterly maintenance system to keep the vibration and noise of the cooling towers within a stable range, thus avoiding a sudden increase in noise caused by equipment aging.

Verification and continuous optimization of the noise reduction effect

After the noise reduction measures are implemented, it is necessary to detect the noise values through professional instruments to verify whether the effect meets expectations. The detection should be carried out at night when the environmental noise is relatively low. Measurements should be taken at 1 meter, 5 meters and 10 meters around the cooling tower respectively to ensure that the noise level from residential areas complies with the "Environmental Noise Quality Standard" (for example, the noise level in residential areas during the day should be ≤55 decibels and at night ≤45 decibels).

If the noise reduction effect does not meet expectations, the cause should be investigated in a timely manner. For instance, if the gap of the sound insulation cover is too large, it may cause noise leakage. At this time, sealant needs to be used to fill the gap. If the shock absorber is not properly selected, a suitable model should be replaced. During the renovation of the cooling tower in a certain hotel, the noise was not significantly reduced after the initial installation of the sound insulation cover. After inspection, it was found that the sound-absorbing louvers were not installed in the heat dissipation holes. After supplementary treatment, the noise was reduced by another 6 decibels.

In addition, the installation location of the cooling tower will also affect the noise reduction effect. When planning new projects, cooling towers should be placed in corners far from residential areas as much as possible, or buildings, fences, etc. should be used to block the transmission of noise. For the already built cooling towers, lush green plants can be planted around them to further reduce noise by taking advantage of the sound-absorbing effect of the vegetation.

The noise problem of cooling towers, in the final analysis, is a systematic project of "source control + transmission blocking". By specifically addressing the three major noise sources of fans, water flow and vibration, it can not only meet the industrial heat dissipation requirements, but also take into account the tranquility of the surrounding environment. As long as these practical skills are mastered, cooling towers can transform from "noise makers" to "quiet workers", achieving a harmonious coexistence of industrial production and living environments.