Electronic Cleanroom Air Conditioning System's Noise Control

The rapid development of the electronics industry has placed stringent demands on the production environment. Production processes in precision electronic components, chip manufacturing, and biopharmaceuticals have strict limitations on background noise and vibration. For operational areas in electronics factories, background noise is typically required to be no higher than 60-65 dB(A). Administrative offices and R&D laboratories typically require even lower background noise levels, generally between 40-55 dB(A). In critical process areas such as photolithography areas, electron microscope rooms, and wafer inspection areas, even minute vibrations and low-frequency noise can cause image blurring and alignment errors. These areas often require noise levels below 55 dB(A).

Electronics factory air conditioning system’s noise mainly from originates from the supply/return air fans, fan filter unit clusters, and exhaust fans within the air conditioning units. Noise is generated due to friction, eddies, and impacts as high-speed airflow passes through duct walls, valves, air vents, and plenum chambers. The compressors, fans, and pumps of chiller units and cooling towers are powerful sources of mid-to-low frequency noise and vibration. Chilled water pumps and cooling water pumps generate mid-frequency noise and vibration during operation. The pulsation and vibration generated by fluid flow within pipes, and the water hammer effect caused by sudden opening and closing of valves.

Noise control measures for air conditioning systems can be categorized into three types: source strength control, propagation path isolation, and design scheme control.

1. Source Control (Most Fundamental and Effective). Select low-noise fans, compressors, and pumps, with their rated operating points close to their maximum efficiency points. For fans, prioritize backward centrifugal fans, and appropriately reduce their speed and increase the impeller diameter. Reasonably reduce the resistance of the air and water systems to avoid operation of fans and pumps under high pressure heads. Strictly control the air velocity within the ductwork. Keep cooling towers away from the factory building or use low-noise, ultra-quiet models.

2. Propagation Path Control. Use soundproof enclosures and soundproof rooms for high-noise equipment. Soundproof the walls and floors of the machine room, and use soundproof doors and windows. Duct penetrations through walls must be sealed with elastic materials to prevent "sound bridges." Install silencers at fan inlets and outlets, main ducts, and branches. Based on spectral characteristics, resistive, reactive, or impedance-reactive composite silencers can be selected. Pay attention to the pressure loss and airflow-generated noise of the silencers. Lay sound-absorbing materials in the air conditioning room, duct inner walls, and upper ceiling space of the cleanroom to reduce reverberation noise. Install flexible foundations and elastic vibration isolators for all rotating equipment. Use flexible joints for equipment-to-pipe connections. Use elastic hangers or brackets for HVAC air duct supports, and install elastic sleeves where pipes pass through structures.

3. Architectural Design Collaboration. Optimize the form and location of supply and return air vents, selecting vents with good diffusion performance and low airflow noise. In the overall building layout, place high-noise refrigeration plants and cooling towers on the side away from precision workshops, and use auxiliary buildings for sound barriers.