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A study about the influence of soot particles morphological parameters on their thermophoretic behaviour is presented in this paper. Soot particles with variable morphological parameters were produced using a miniCAST (Combustion Aerosol Standard) JING5120 type C. Ex-situ (TEM) and online (CPMA) techniques were used in order to characterize the generated particles. The TheRmophoretic Annular Precipitator (TRAP) developed in our previous study ( Ait Ali Yahia, Gehin, & Sagot, 2017 ) was used to evaluate the soot particles thermophoretic diffusion coefficient K th . The TRAP is a device where a thermal gradient is created in the 1 mm annular space between two concentric 0.5 m length tubes, the inner tube is cooled and the outer one heated. Particles flowing through the annular space will migrate and deposit by thermophoresis on the cold tube external wall. The thermal gradient was fixed at 46,000 K m −1 and a laminar aerosol flow was applied (Re = 380). The new experimental results obtained in this work confirmed and completed the results presented by Brugière ( Brugière, Gensdarmes, Ouf, Yon, & Coppalle, 2014 ). These results provide also new indications about the influence of the particles size, the primary particles diameter and the presence of organic compound on the soot particles thermophoretic behaviour. [ABSTRACT FROM AUTHOR]

A TheRmophoretic Annular Precipitator (TRAP) aimed to study the thermophoresis of soot particles is presented in this paper. This device consists of two 0.5 m length concentric tubes together with an inner cylinder and an external envelope. The particles flow through the 1 mm gap created between the inner and outer tubes with imposed temperatures, the inner tube is cooled and the outer one is heated. A thermal gradient is thus created, and particles will deposit by thermophoresis on the inner tube cold wall. This device is based on the so-called penetration method, where the deposition rate on the cold wall is obtained by particles concentration measurements upstream and downstream of the test section. A model developed in this study allowed the conversion of the deposition rates into thermophoretic diffusion coefficients K th . In this work, the thermophoretic diffusion coefficient in a vertical laminar flow were measured for mono-dispersed spherical PSL particles with particles diameter ranging from 0.1 to 1 μm, and also for poly-dispersed DEP droplets oil with particles diameter from 0.1 to 0.65 μm. The Reynolds number and the thermal gradient values were fixed respectively at 520 and 60,000 K m −1 in order to avoid convective effects that might appear in a laminar configuration. The thermophoretic diffusion coefficients were compared to the theoretical models and other experimental data from the literature. The good agreement found especially with Beresnev and Chernyak (1995) model together with the experimental data validates the use of the TRAP to the on-line determination of the soot particles thermophoretic diffusion coefficients. [ABSTRACT FROM AUTHOR]

In the last two decades, multidisciplinary research teams worked on developing a comprehensive understanding of the transmission mechanisms of airborne diseases. This article reviews the experimental studies on the characterization of the exhaled airflow and the droplets, comparing the measured parameters, the advantages, and the limitations of each technique. To characterize the airflow field, the global flow‐field techniques—high‐speed photography, schlieren photography, and PIV—are applied to visualize the shape and propagation of the exhaled airflow and its interaction with the ambient air, while the pointwise measurements provide quantitative measurements of the velocity, flow rate, humidity and temperature at a single point in the flow field. For the exhaled droplets, intrusive techniques are used to characterize the size distribution and concentration of the droplets' dry residues while non‐intrusive techniques can measure the droplet size and velocity at different locations in the flow field. The evolution of droplets' size and velocity away from the source has not yet been thoroughly experimentally investigated. Besides, there is a lack of information about the temperature and humidity fields composed by the interaction of the exhaled airflow and the ambient air. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including air pollution control and waste management.

Abstract: The quality of air within factory buildings is controlled by many food manufacturers. Ventilation system hygiene must be regularly cleaning to prevent the build up of dust, product or condensate that may provide a focus for microbial growth. In the present study we predict the particle deposition velocity in ventilation ducts of three different food factories. At these locations, during several days, aerosol particle number and mass size distribution were measured using optical particle counter and cascade impactor, respectively. The concentration of particulate matter of aerodynamic diameters in the size range 0.3–20μm varied from 0.2 to 1.7μgm−3. The measured mass concentration and the predicted particle deposition velocity were used to calculate the deposited particle mass flux (DMF) in the ventilation ducts of each site. The results indicate that the DMF at the floor is about 2–20 times larger than that at vertical walls. Thus, the deposited particle mass on the floor is sufficient to check whether a ventilation duct should be cleaned. According to the chosen cleaning initiation criteria for ducts, ventilation systems would take approximately 1–9years to meet the cleaning time. So, cleaning procedures and maintenance intervals are strongly influenced by several parameters, such as flow conditions, particle concentration, characteristics of the ventilation duct and the filter efficiency. The modeling approach combined with mass concentration measurements enables the analysis and the quantification of the influence of these parameters. [Copyright &y& Elsevier]