دانلود رایگان مقاله لاتین گرفتن ترموفورتیک از ذرات زیر از سایت الزویر
عنوان فارسی مقاله:
گرفتن ترموفورتیک از ذرات زیر - میکرونی توسط یک قطره
عنوان انگلیسی مقاله:
Thermophoretic capture of submicron particles by a droplet
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Particulate matter is a critical pollutant in the atmospheric environment of many countries (Agudelo-Castaneda et al., 2013; Li et al., 2014). Fine particle pollution is becoming more stringent. Wet scrubbing and wet deposition are efficient methods of removing particles from industrial flue gas and from the atmosphere (Park et al., 2005; Queen and Zhang, 2008; Bae et al., 2010; Guo et al., 2014). Particle capture by a single droplet is the foundation of both processes (Jaworek et al., 2006); studies on single droplet capture are significant for developing industrial wet scrubbing technologies and understanding the capacity and mechanisms of wet deposition in the atmospheric environment. In wet deposition and wet scrubbing processes, particlecarrying gas flows around the droplet. Particles can collide with the droplet surface during flow, under inertia, interception, Brownian mechanism, electrostatic mechanism, diffusiophoresis and thermophoresis (Kraemer and Johnstone, 1955; Pranesha and Kamra, 1996; Chate and Murugavel, 2011; Carotenuto et al., 2010). The single droplet efficiency is a basic input parameter in predictingthe efficiency of wet deposition and wet scrubbing (Lee et al., 2006). For the convenience of calculation, the deposition effi- ciencies of single droplets under the effect of different capture mechanisms were organized to the empirical concise formula (Park et al., 2005). Deposition efficiencies are the function of dimensionless numbers in the capture process. The classical deposition efficiency calculation includes the following: the formula proposed by Slinn (1977), which is used for calculating the inertial deposition efficiency, interception deposition efficiency, and Brown diffusion deposition efficiency; and the thermophoretic deposition efficiency formula proposed by Davenport and Peters (1978). The total particle deposition efficiency of single droplets is the sum of the calculated deposition efficiencies under different mechanisms. Both the formulaic and numerical calculations of efficiency show that thermophoresis is the most important mechanism for submicron particle capture by droplets. Bae et al. (2009) estimated the relative contribution of thermophoresis in the wet deposition process through the thermophoretic deposition efficiency formula and found that the removal coefficient of 1-mm particles increased from 107 to 106 at 5 C of temperature difference. In the industrial wet spraying process, a few degrees of temperature difference between the droplets and the gas results in a higher submicron particle deposition efficiency. Pilat and Prem (1976) performed a numerical simulation on the deposition efficiencies of single droplets on particles of different sizes as the temperature difference increases from 5 C to 60 C; the deposition efficiency of 1-mm size particles increased by two orders of magnitude, from 0.001 to 0.25, under the effect of thermophoresis. The thermophoretic deposition efficiency formula proposed by Davenport and Peters (1978) is presently the only empirical formula for predicting the thermophoretic deposition efficiency of single droplets. Through experiments and numerical simulation, Wang et al. (1978) studied the deposition efficiency of droplets of 0.1 mme1 mm size on 0.5-mm particles, under a 3 C temperature difference between the environment and the droplet surface. Comparison between the experimental data and the predicted values by the Davenport thermophoretic deposition efficiency formula showed that the latter overestimated the former by a relative deviation of 24.1%e47.8%. Viswanathan (1999) performed a numerical simulation of the deposition efficiency of droplets on particles of 0.1 mme1 mm size under a temperature difference of 10 Ce80 C and with a droplet Reynolds number (Re) of 1.54e400 (characteristic size is the droplet diameter). The predicted values by the thermophoretic deposition efficiency formula (Davenport and Peters, 1978) were found to overestimate the numerical calculation results by 10%e50%. The classical deposition efficiency calculation is based on specific assumptions, theoretical analysis, and experimental data. Numerical simulation (Wang et al., 2015) of particle capture by single droplets show that the discrepancy between the research hypothesis and the actual process will likely result in deviations in the calculated values by the classical deposition efficiency formula and the actual values. Correction is needed based on the thermophoretic deposition behavior. The thermophoretic deposition efficiency of single droplets is the basis for analyzing industrial spraying and wet deposition process of fine particles. Further discussion should thus be made on the reason for the large deviation in the calculated value by the traditional thermophoretic deposition efficiency formula. A more accurate prediction method of the thermophoretic deposition efficiency of droplets is also urgently needed.
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کلمات کلیدی:
Effects of Heat Transfer on the Dynamics and ... - ACS Publications pubs.acs.org/doi/pdf/10.1021/ie00003a018 by DE Rosner - 1992 - Cited by 49 - Related articles include (a) thermophoretic drift of spherical particles in a gas through which energy is diffusing, ...... evaporation accelerates the capture of submicron dust, i.e.,. Transport Processes in Chemically Reacting Flow Systems https://books.google.com/books?isbn=0486150631 Daniel E. Rosner - 2012 - Technology & Engineering ... we show below that, far from being negligible, thermophoresis is expected to increase the previously estimated submicron particle capture rate by over a factor ... Aerosol Chemical Processes in the Environment https://books.google.com/books?isbn=1420036254 Kvetoslav R. Spurny - 2000 - Nature An example of the rate of aerosol particle capture (cm-3 s-') is given in Figure 5. ... in clouds can take place on submicron particles by means of thermophoresis. Effect of gas temperature on the capture of charged particles by ... www.tandfonline.com/doi/full/10.1080/02786826.2015.1131810 by F Di Natale - 2016 - Cited by 2 - Related articles Dec 29, 2015 - Experimental Analysis on the Capture of Submicron Particles ..... The expression of thermophoretic capture efficiency was (Davenport and ... The John Zink Hamworthy Combustion Handbook, Second Edition: Volume ... https://books.google.com/books?isbn=1439839662 Charles E. Baukal, Jr. - 2013 - Science The capture effectiveness can be enhanced by (1) subcooling saturated flue gas to ... The purpose is to take advantage of thermophoresis and diffusiophoresis ... in the Brownian motion toward the target droplet by these submicron particles. A Mechanistic Investigation of Ash Deposition in Pulverized-coal and ... https://books.google.com/books?isbn=0549884394 Shrinivas S. Lokare - 2008 The particle capture efficiency describes the propensity of these particles to stay on ... Thermophoretic deposits are finer grained (sub-micron particles) and more ...
