A Study on the Identification of Noise Source and the Noise Reduction Method of a Turbo Chiller

In this paper, we identify the noise source and the path of a chiller. This chiller is newly developed for R-l34a refrigerant and 250 RT cooling capacity. The measured overall SPL of the developed turbo-chiller is about 100 dBA. Due to the high rotating speed of the centrifugal impeller, the nun noise source of the chiller is the blade passing frequency and its higher harmonics of the centrifugal impeller. This generated soundpropagates through the duct, and then transmits and radiates to the outer field. From the experiment, it is found that the high frequency noise is mostlytransmitted and radiated through the elbow duct, but the low frequency noise is transmitted and vadiated through the condenser wall. Therefore applying the absorbing material is an effective way of reducing the high and low frequency noise simultaneously. Measurement results show that the application of the sound absorbing material to the elbow duct reduced the overall sound pressure level by 4 dB compared to the 9 dBA reduction for the case of full enclosure. In order to control the generated noise, a dissipativetype silencer is also designed and tested. The silencer reduced the radiated noise about 7.5 dBA.

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