Abstract
In air conditioning systems heat exchangers are frequently installed upstream of ventilators. These modules are part of the daily life of humans and should therefore create an environment that is as quiet as possible. The heat exchanger generates increased turbulence, which leads to increased sound emissions of the ventilator. Due to installation space limitations, it is not possible to connect silencers to the heat exchanger module. A novel concept is presented, which allows to reduce the sound emissions of heat exchanger due to plate absorbers without the need of additional installation room. The plates contain sub-millimeter openings. They are integrated into the heat exchanger housing together with back volumes. This arrangement guarantees compactness and generates no additional flow resistance. The emitted sound could be reduced by up to 2.9 dB in the partial load range. The main advantages of the concept presented are individual adjustment, cost-effective design and simple installation.
Highlights
Axial fans are used in many installations for cooling and conveying gases
If axial fans are used together with heat exchangers as heat exchanger modules, such as in air conditioning systems or cooling circuits, a higher sound level is often emitted [1, 2]. This is due to the effect that the heat exchanger interferes with the flow field of the axial fan, amplifying the sound generation mechanisms at the axial fan. To counteract these increased sound emissions, either the flow guidance of the heat exchanger could be optimized, the axial fan could be designed for specific inflow turbulence, sound-reducing modifications to the fan such as serrations, slits or porous materials could be used, or classic silencers could be connected upstream or downstream of the heat exchanger module [3,4,5,6]
These noise reduction measures have so far only been used to a limited extent in industrial applications. This is due to the fact that optimization of the heat exchanger is a costly and time-consuming undertaking, axial fans are used in a variety of systems and cannot be optimized for a specific case, blade modifications often reduce sound emissions and lower the efficiency of the machine
Summary
Axial fans are used in many installations for cooling and conveying gases. These machines have to fulfill high requirements with regard to sound emissions, which is due to their close proximity to people. To counteract these increased sound emissions, either the flow guidance of the heat exchanger could be optimized, the axial fan could be designed for specific inflow turbulence, sound-reducing modifications to the fan such as serrations, slits or porous materials could be used, or classic silencers could be connected upstream or downstream of the heat exchanger module [3,4,5,6] These noise reduction measures have so far only been used to a limited extent in industrial applications. This is due to the fact that optimization of the heat exchanger is a costly and time-consuming undertaking, axial fans are used in a variety of systems and cannot be optimized for a specific case, blade modifications often reduce sound emissions and lower the efficiency of the machine,
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