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ارزيابی پارامترهای موثر برکارایی درطراحی سايلنسرجذبی جهت کنترل صدای ناشی از جريان هوای فن سانتريفوژ Evaluation of Efficiency Effective Parameters in the Design of dissipative Silencer for Control Noise Caused by the turbulent Flow Centrifugal Fan

Rashid, Fathi chesly and Ali, Safari variani and Saeid, ahmadi and Ahmad, Nikpey (2018) ارزيابی پارامترهای موثر برکارایی درطراحی سايلنسرجذبی جهت کنترل صدای ناشی از جريان هوای فن سانتريفوژ Evaluation of Efficiency Effective Parameters in the Design of dissipative Silencer for Control Noise Caused by the turbulent Flow Centrifugal Fan. Masters thesis, Qazvin University of Medical sciences.

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Abstract

Introduction and goal: Sound is one of the most pervasive health risks that effects on the production workers, armed forces and construction workers. The National Institute for Occupational Safety and Health (NIOSH) estimates in 2003 that about 30 million workers are exposed to hazardous workplace noise. The cost of compensating for hearing loss for workers is several hundred million dollars. For transferring and moving air for ventilation, dust collecting, drying operations, etc., fans are used. Fans are an important source of noise. To control the noise from fans, most of the mufflers (silencer) are used that can reduce the sound pressure level and is a type of silencer, an absorbent silencer or a dispersion. The purpose of this study was to investigate the effective parameters of the dispersion silencer function to control the noise of centrifuge fan air flow Materials and Methods: the silencers with an outer shell of aluminum thickness of 1, 1.5 and 2 mm of 100 cm in length and with inter and outer diameter of 15 and 33cm was designed and made. Silencers have polyurethane foam and sponge absorbers with 6 cm thickness and density of respectively 23 and 17.7 kg / m3, and a perforated sheet with ahole diameter of 2, 4 and 6 mm, and Measurements were performed using the ISO 11820 standard and using a sound level meter (Cassella Cell-450). The sound meter was calibrated using (cell-110/2) calibrator. Frequency analysis was performed in octave band and A network. The total pressure was also measured with the AFL71805301 pitot tube and the air flow velocity with the PROVA AVM_305 speedometer. Data were analyzed using Excel, SPSS,vertion24 and paired t-test Findings: The noise around the channel before installing the silencer at the blower fan outlet channel section of an average of 94.50 dBA were measured and the noise after the silencer installing with polyurethane foam and perforated sheet with hole diameter of 2, 4 and 6 mm, and an outer shell of aluminum thickness of 1mm respectively, 82. 6, 82.83 and 82.3 dBA and Silancer with absorber polyurethane foam and with shell thickness of 1.5 mm and perforated sheet with a hole diameter of 2.4 and 6 mm respectively were 83.07, 83.5 and 83.5 dBA, and shell with thickness of 2 mm and perforated sheet with a hole diameter of 2,4 and 6 mm respectively were 85.06, 83.9 and 84.6 dBA, it was measured. and also in the suction condition of 85.97 dBA before the installation of silancer and silancer with polyurethane foam and perforated sheet with hole diameter of 2, 4 and 6 mm, and outer shell of aluminum thickness of 1mm respectively 77.53,77.2 and 76. 7 dBA and silancer with polyurethane foam and perforated sheet with hole diameter of 2, 4 and 6 mm, and outer shell of aluminum thickness of 1.5mm respectively 74.73, 75.43 And 75. 3 dBA and silancer with polyurethane foam and perforated sheet with hole diameter of 2, 4 and 6 mm, and outer shell of aluminum thickness of 2mm respectively 77.2, 75.06 And 76. 3 dBA, it was measured. and also The noise around the channel before installing the silencer at the blower fan outlet channel section of an average of 94.50 dBA were measured and the noise after the silencer installing with sponge absorber and perforated sheet with hole diameter of 2, 4 and 6 mm, and an outer shell of aluminum thickness of 1mm respectively, 66. 67, 66.67 and 67.97 dBA and silencer with sponge absorber and perforated sheet with hole diameter of 2, 4 and 6 mm, and an outer shell of aluminum thickness of 1.5mm respectively, 66.06, 66.57 and 66.33 dBA and silencer with sponge absorber and perforated sheet with hole diameter of 2, 4 and 6 mm, and an outer shell of aluminum thickness of 2mm respectively, 67. 2, 66.9 and 67.7 dBA, at the same time, it was measured. The also noise around the channel before the installation of the silencer in the input section of the suction channel 85.97dBA was measured and the noise after the installation of the silencer with a esponge absorber and perforated sheet with an hole diameter of 2, 4 and 6 m, and an outer shell of aluminum thickness of 1mm respectively, 64.67, 65.23 and 65.1dBA, and silencer with a esponge absorber and perforated sheet with an hole diameter of 2, 4 and 6 m, and an outer shell of aluminum thickness of 1.5mm respectively, 63.5, 64and 63.5dBA, and silencer with sponge absorber and perforated sheet with an hole diameter of 2, 4 and 6 m, and an outer shell of aluminum thickness of 2mm respectively, 64.43, 65.2 and 65.04dBA at the same point was measured. Also, there was no significant relationship between Insertion loss and hole diameter of the perforated sheet and external shell thickness in any of the octave band frequencies, but there was a significant relationship between absorberes and Insertion loss in all octave band frequencies is there(P <0.05) The total pressure loss within Intra-channel flow after the installation of silencer with absorber polyurethane foam in a suction condition of 11.30 pa (0.045 inches of water) at the blower condition of 37.9 pa (0.15 inches of water) and with a sponge absorber in suction condition of 8.5 pa (0.034 inches Water) at the blower condition of 16.56 pa (0.07 inches of water), and the average linear velocity loss of air flow with a sponge absorber in the blower condition1.6m/s and with absorber polyurethane foam1.7m/s was measured. and with a sponge absorber in suction condition2.36m/s and with absorber polyurethane foam2.3m/s was measured. Discussion and Conclusion: The results of this study showed that the sponge absorber has a higher noise reduction performance than the polyurethane foam absorber, and the increase in the hole diameter of the perforated sheet, the thickness of the aluminum shell, installation distance of silencer and wire mesh did not have much effect on the silencer performance, while it has not been completely ineffective, and has a minor impact on the Insertion loss. Also, there is a significant relationship between Insertion loss and adsorbent type in all octave band frequencies (P <0.05). The pressure loss in all of the silencers was negligible. Thus, the study of the data obtained from this study showed that the design and manufacturing of punched absorbent silencer to reduce the noise pollution is a suitable control device. Key words: Sound absorption, Absorption silencer, Fans centrifugal, hole diameter, Noise reduction

Item Type: Thesis (Masters)
Uncontrolled Keywords: Sound absorption, Absorption silencer, Fans centrifugal, hole diameter, Noise reduction
Subjects: R Medicine > RN Health > RN1003 Occupational Health
Divisions: University Thesis > Faculty of Health
Depositing User: Health School Students
Date Deposited: 09 Mar 2019 09:37
Last Modified: 09 Mar 2019 09:37
URI: http://eprints.qums.ac.ir/id/eprint/8578

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