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Blockage Effect of the Centrifugal Cooling Fans

DOI: 10.1615/ICHMT.2004.IntThermSciSemin.640
pages 525-533

Sheam-Chyun Lin
Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43, Sec. 4, Keelung Road, Taipei, Taiwan 106, R. O. C.

Fu-Sheng Chuang
Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43, Sec. 4, Keelung Road, Taipei, Taiwan 106, R. O. C.

Chien-An Chou
Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43, Sec. 4, Keelung Road, Taipei, Taiwan 106, R. O. C.

Chun-Wei Sun
Department of Mechanical Engineering, National Taiwan University of Science and Technology, 43, Sec. 4, Keelung Road, Taipei, Taiwan 106, R. O. C.

Zeng-Hwa Yang
Department of Mechanical Engineering, Nanya Institute of Technology, TaoYuan, Taiwan 106, R. O. C.

Abstract

This paper presents the experimental results showing blockage effects on small centrifugal cooling fans. In the beginning, measurements were taken for fans without a blocking board. Then, a blocking board was added and placed closer and closer to the fan inlet to investigate its effects on the fan performance and noise generation. Comparisons among cases with and without the blocking board were made. These experiments employed AMCA test chamber to evaluate the fan performance and followed CNS-8753 acoustic pressure measurement standard to measure the noise level under semi-anechoic chamber conditions. Experimental results show that large fans can better overcome the flow resistance. For fan thickness, fans with high static pressure are more capable of overcoming overall flow resistance in a system and therefore experience lesser blockage effect. The performance and noise level have the same tendency for various rotational speeds. Although the single-inlet centrifugal fan has a better performance and lower noise level than the double-inlet fans, the latter responses better to the blockage effect. Even if one of the inlets of the double-inlet fans is blocked, it can still draw air through the other inlet which is not blocked. Moreover, between the axial and centrifugal fans, the blockage effect has greater influence on the static pressure of the axial fan than its flow rate but the blocking board provokes almost the same influence on the static pressure and flow rate for centrifugal fans. When the blockage distance is 4 mm, centrifugal fans are capable of maintaining at least 70% of its performance. However, the flow resistance in the axial fan is so great that the flow becomes stagnant. Based on these findings, centrifugal fans are apparently more suitable for environment with high resistance.

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