Browsing by Author "Tsai, C-J"

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Effect of Free Electrons on Nanoparticle Charging in a Negative Direct Current Corona Charger
(2009)
Aliat, A.
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Tsai, C-J
;
Hung, C-T
;
Wu, J-S
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機械工程學系
A 2D numerical model is proposed to study the electric charge that will provide nanoparticles within a cylindrical corona discharge with a wire along the axis. The wire-tube electrical charger is subjected to a negative DC voltage and filled with air at atmospheric pressure at ambient temperature. A numerical application is given by considering spherical nanoparticles with a diameter of 65 nm within a wire-tube charger with a radius of 2 cm and 26cm in length. Numerical results obtained are in very good agreement with the experimental data. These results show that free electrons contribute greatly to the electrical charging efficiency mechanism of the corona charger in particular at high Nt-product, which explains very well the large discrepancy found in earlier models which not considered electrons.
The Effect of Nanoparticle Morphology on the Measurement Accuracy of Mobility Particle Sizers
(2013-09-01)
Awasthi, A.
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Wu, B-S
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Liu, C-N
;
Chen, C-W
;
Uang, S-N
The influence of particle morphology on the accuracy of nanoparticle size distributions measured by the engine exhaust particle sizer spectrometer (EEPS, TSI Model 3090) was studied using the scanning mobility particle sizer (SMPS, TSI Model 3936) as a reference. The EEPS shows higher total number concentrations with the maximum relative difference up to 67 % and smaller number median mobility diameters for polydisperse silver nanoparticles generated in the laboratory. To provide a quantitative explanation of the difference, generated polydisperse nanoparticles were classified as monodisperse particles with the initial equivalent mobility diameter (d (m1)) and sintered in the second furnace at different temperatures (room temperature to 600 A degrees C), to change their morphologies for the comparison tests. Without sintering (room temperature), results show that the measured mobility diameter (d (m2)) of the EEPS is smaller than that measured by the SMPS when d (m1) is larger than 30 nm and the difference increases as d (m1) is increased from 30 to 300 nm. But the difference decreases as the morphology of particles is changed from branched chain agglomerates to spheres for d (m1) less than 80 nm and the sintering temperature higher than 200 A degrees C. Theoretical analysis shows that the mean charge per agglomerates is more than that of spheres resulting in overestimation of the electrical mobility and underestimation of the d (m2) by the EEPS.