In order to verify experimentally acoustic similarity laws for fans, experiments were made with three, dimensionally similar centrifugal fans of 140, 280, and 560 mm impeller diameter. The fans were connected to anechoically terminated discharge ducts. It is shown that the influence of the Reynolds number on the radiated sound pressure is negligible within 1.4•105 ≦ Re ≦ 2.2•106, which is the range covered by the measurements. This is in agreement with earlier studies in which the Reynolds number was varied from 1.4•104 to 4.5•105. From the experimental results it is concluded that fan noise data that are taken on model fans can be extrapolated to other dimensionally similar fans of different size for arbitrary fan speeds and working fluids, provided that the operating condition and the measurement position are the same.

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