| Project/Area Number |
12650163
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Fluid engineering
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| Research Institution | Toyohashi University of Technology |
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Principal Investigator |
YANADA Hideki Toyohashi University of Technology, Faculty of Engineering, Associate Professor, 工学部, 助教授 (90166554)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2001: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2000: ¥2,400,000 (Direct Cost: ¥2,400,000)
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| Keywords | Electrostatic filtration / Contaminant particle / A. C. electric field / Coagulation / Electric double layer / Velocity gradient / Zeta potential / 静電気応用 / 静電フィルタ / 粒子 |
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| Research Abstract |
The effect of the velocity gradient on the coagulation of particles in oil under an A.C. electric field was investigated using a Couette flow system consisting of coaxial double cylinders with a small radial gap. The relation between the mean oscillation amplitude of particles and the degree of coagulation was examined under different zeta potentials of silica particles and different electric field strengths. The results obtained are as follows:
1. The value of the velocity gradient that most accelerates the coagulation is a few to 10 s^<-1>.
2. The application of a high electric field is not always advantageous to the coagulation. A certain electric field strength that maximizes the degree of coagulation exists for most test oils.
3. The particles are relatively easily coagulated in oil with a low electric conductivity but are not easily coagulated in oil with a relatively high electric conductivity.
4. The degree of coagulation is not dominated by the oscillation amplitude itself but is dominated by the relative oscillation amplitude to the electric double layer thickness.
5. Considering the results 2 to 4, the following estimation can be made regarding the coagulation mechanism:
(1) The coagulation is most accelerated when particles are moderately polarized in their surrounding double layers.
(2) The double layer thickness in a (relatively) high conductivity liquid is thin and the electric charges in the double layer can follow the particle motion when it oscillates. This leads to a week polarization and hence to a lower degree of coagulation.
6. The mechanical conditions that most accelerate the coagulation are as follows: the velocity gradient is a few to 10 s^<-1>: the electric field strength is 1 to 2 kV/mm: the oscillation amplitude of particles is approximately equal to the double layer thickness.
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