Title page for etd-0924116-220735


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URN etd-0924116-220735
Author Chien-teng Lin
Author's Email Address No Public.
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Department Mechanical and Electro-Mechanical Engineering
Year 2016
Semester 1
Degree Master
Type of Document
Language zh-TW.Big5 Chinese
Title Construct Ultrasonic Diffusion Field to Enhance Microalgae Biomass Productivity
Date of Defense 2016-10-04
Page Count 108
Keyword
  • Uniformity
  • Directivity
  • Diffusion field
  • Ultrasonic bio-effect
  • Acoustic lens
  • Microalgae
  • Abstract The objective of this study is to develop an ultrasonic diffusion field and improve the uniformity of distributed sound energy while inducing constructive ultrasonic bio-effect. The irradiation efficiency can be increased by such ultrasound irradiation field as described in practical application which reduces individual differences caused by the uneven sound energy distribution. In this study, optimized diffusion field boundaries are adjusted to be non-paralleled to each one and equipped with convex acoustic lens. The traditional diffusion field design is also boundary-adjusted but without the convex lens. The finite element method is utilized to analyze the differences between optimized and traditional diffusion field design, and the solution of Chlorella vulgaris is placed in these diffusion fields in comparison and observe the actual ultrasonic bio-effect of this application. While exciting an ultrasound transducer, the sound energy distribution concentrates in front of the transducer which has strong directivity and forms Gaussian distribution pattern. In this study, a convex acoustic lens made of acrylic is placed in front of the ultrasound transducer which is used to diverge sound energy. The results show that ultrasound reflects for multiple times between non-parallel walls, the sound energy distributes more uniformly and less shadow zone in the optimized diffusion field compared with traditional diffusion field. The sound intensity level deviation of traditional and optimized diffusion field model is 1.46 and 0.76 dB respectively, which is measured by hydrophone. The traditional and optimized ultrasonic diffusion field is utilized to irradiate the algae solution with ultrasound at its resonance frequency which is calculated by Rayleigh-Plesset cavitation theory. The growth rate of Chlorella vulgaris has increased while the microalgae growth stationary phase can be reached about two days in advance for the case with optimized diffusion field and about one day for the case with traditional diffusion field. With regard to enhancement for the biomass yield, the algae biomass has 24.5%, 38.4%, 35.6%, 38.9% greater than the control sample without ultrasonic treatment from the second to fifth day in incubation period, and 18.4%, 35.3%, 20.0%, 18.7%, 14.8% for the case utilizes the traditional diffusion field. An optimized ultrasonic diffusion field is designed in this study, and the sound energy distribution is more uniform in such irradiation field. The enhancement of the Chlorella vulgaris growth rate induced by ultrasonic bio-effect could be a reference for industry applications and increases the productivity.
    Advisory Committee
  • Bor-Tsuen Wang - chair
  • Shao-Yi Hsia - co-chair
  • Jyin-Wen Cheng - co-chair
  • Yi-Cheng Huang - co-chair
  • Shiuh-Kuang Yang - advisor
  • Files
  • etd-0924116-220735.pdf
  • Indicate in-campus at 5 year and off-campus access at 5 year.
    Date of Submission 2016-10-25

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