The experimental data of nanometer size particle penetration through a series of screens SS40 (Tetko Inc., Elmsford, NY) at three different temperatures (295 K, 316 K and 337 K) are presented in this work. Aerosols of tungsten oxide and molybdenum oxide in the size range from 3.1 to 15.4 nm were studied. The data are compared with the theoretical model developed for a screen-type diffusion battery (Cheng and Yeh, 1980).
EXPERIMENTAL
Penetration of nanometer particles in the size range from 3.1 to 15.4 nm through a series of wire screens has been studied experimentally. A stainless steel screen SS40 (Tetko Inc., Elmsford, NY) was tested. The experimental system used in the study consisted of an aerosol generator, an electrostatic classifier with a short column of 11.11 cm (EC TSI Model 3071A), a thermal chamber with two identical filter holders inside and an ultrafine condensation particle counter (UCPC 3025A, TSI Inc.). Monodisperse aerosols of molybdenum oxide and tungsten oxide were obtained in the following way. Polydisperse aerosols were first produced by a photochemical aerosol generator (Baklanov et al., 1995). The aerosols were introduced into the EC at a volume flow rate of 2 l/min. Aerosol particles were separated according to their mobility, creating a monodisperse aerosol at the outlet of the classifier. (The most probable state of the oxides obtained by oxidation of carbonyls are MoO3 and WO3 but the composition of aerosol particles has not been checked).
We measured the penetration of monodisperse aerosols through 8 stages of wire screen which were placed in a filter holder with a diameter of 3.81 cm. An identical holder was mounted in parallel to the first one and could be switched into the line by means of a three way valve. Both holders, in turn, were housed in a thermal chamber in which we could stabilize and control the temperature of the aerosol flow. The temperature was measured by two thermocouples that were located in the rear part of the holders. During experiments the temperature inside the thermal chamber was varied from 295 to 337 K. The volume flow rate through the holders was kept at a constant value of 2 l/min, which corresponds a mean flow velocity 2.92 cm/s at temperature 21°C. The penetration was calculated as the ratio of particle fluxes after and before the holder. The concentration of aerosol particles was measured by the ultrafine condensation particle counter.
RESULTS AND DISCUSSION
The results of the measured penetration versus particle size for the studied substances at different temperatures of the thermal chamber are presented in Figs. 1 and 2. The dotted lines
right; padding-left:5px">mg src="/scidirimg/btn_xclose.gif" alt="Close" title="Close" onmouseover="javascript:this.src='/scidirimg/btn_xclose_hov.gif';" onmouseout="javascript:this.src='/scidirimg/btn_xclose.gif';"> mg border=0 src="/scidirimg/jrn_nsub.gif" alt="You are not entitled to access the full text of this document" title="You are not entitled to access the full text of this document" width=12 height=14"> ref="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6B-4NYJ0XN-1&_user=10&_coverDate=07%2F31%2F2007&_rdoc=1&_fmt=high&_orig=article&_cdi=5810&_sort=v&_docanchor=&view=c&_ct=39&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=1eaa82dd9a473672805fe2f553c31308">Penetration of 4.5 nm to mg src="http://www.sciencedirect.com/cache/MiamiImageURL/B6V6B-4NYJ0XN-1-19/0?wchp=dGLbVtz-zSkWb" class="charImg" alt="image" title="image" height="16" width="42"> aerosol particles through fibrous filtersr>Journal of Aerosol Science, Volume 38, Issue 7, July 2007, Pages 719-727r>Sheng-Hsiu Huang, Chun-Wan Chen, Cheng-Ping Chang, Chane-Yu Lai, Chih-Chieh Chenr>r>Abstractr>mlktScroll"> r>ref="http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6V6B-4NYJ0XN-1-1F&_cdi=5810&_user=10&_orig=article&_coverDate=07%2F31%2F2007&_sk=999619992&view=c&wchp=dGLbVtz-zSkWb&md5=2e7d0b58ecc991f002719fcc583e11e3&ie=/sdarticle.pdf">mg name="pdf" style="vertical-align:absmiddle;" border="0" src="http://www.sciencedirect.com/scidirimg/icon_pdf.gif" alt=""> Purchase PDF (460 K)This study presents the experimental results of penetration of aerosol particles with diameters between 4.5 nm and mg src="http://www.sciencedirect.com/cache/MiamiImageURL/B6V6B-4NYJ0XN-1-1B/0?wchp=dGLbVtz-zSkWb" class="charImg" alt="image" title="image" height="16" width="42"> through fibrous filters. Three particle size spectrometers: the TSI 3080 electrostatic classifier equipped with nano- or long differential mobility analyzer, and the TSI 3321 aerodynamic particle sizer, were used to measure nanometer, submicron, and micron-sized particles. NaCl aerosol particles were generated by using spray-drying methods. To eliminate electrostatic charges, filters were dipped in isopropanol for 5 min and allowed to dry. These dipped filters, along with controls of each filter type, were then tested to determine the aerosol penetrations in the size range of 4.5 nm–mg src="http://www.sciencedirect.com/cache/MiamiImageURL/B6V6B-4NYJ0XN-1-1C/0?wchp=dGLbVtz-zSkWb" class="charImg" alt="image" title="image" height="16" width="42">. The experimental results demonstrated that almost all particles with sizes below 10 nm or exceeding mg src="http://www.sciencedirect.com/cache/MiamiImageURL/B6V6B-4NYJ0XN-1-1D/0?wchp=dGLbVtz-zSkWb" class="charImg" alt="image" title="image" height="17" width="35"> were collected in the filters, and the filter charge density did not significantly affect the penetration values. The results also suggested that there is no thermal rebound of particles in the size range down to 4.5 nm in fibrous filters. |
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