Radiation noise control of a 90° rectangular elbow in ventilation and air conditioning systems

Abstract

The elbow noise is an important part of indoor radiated noise of ventilation and air conditioning (VAC) systems. A technique to reduce the radiated noise of the elbow by adding guide vane is proposed. The models of elbow with/without guide vane were established respectively. Based on the experimental verification, the influence of the guide vane on the flow field of the elbow and the indoor radiated sound field is analyzed. The radiated noise of the elbow was predicted by LES simulation and FW-H equation. The results show that after adding the guide vane, the maximum resistance loss of the elbow can be reduced by about 17%, and the radiation noise can also be significantly reduced in the frequency range of 10–1000 Hz. However, the local turbulent dissipation slightly increases in the elbow due to the guide vane, causing an increase in the peak sound pressure level in the low frequency range of 10–200 Hz. In addition, in the proper position of the guide vane, the influence of elbow radiated noise on standing, sitting and lying posture is also significantly reduced. The maximum radiated total sound pressure level at the design point is reduced by about 5 dB.