Impact of the primary particle polydispersity on the radiative properties of soot aggregates

The radiative properties of numerically generated fractal soot aggregates were studied using the numerically accurate generalized multi-sphere Mie-solution method. The fractal aggregates investigated in this study contain from 10 to 600 primary particles of 30 nm in diameter. These fractal aggregates were numerically generated using a combination of the particle-cluster and cluster-cluster aggregation algorithms with fractal parameters representing flame generated soot. Ten different realizations were obtained for a given aggregate size measured by the number of primary particles. The wavelength considered is 532 nm and the corresponding size parameter of primary particle is 0.177. Attention is paid to the effect of different realizations of a fractal aggregate with identical fractal dimension, prefactor, primary particle diameter, and the number of primary particles on its orientation-averaged radiative properties. Most properties of practical interest exhibit relatively small variation with aggregate realization. However, other scattering properties, especially the vertical-horizontal differential scattering cross section, are very sensitive to the variation in geometrical configuration of primary particles. Orientation-averaged radiative properties of a single aggregate realization are not always sufficient to represent the properties of random-oriented ensemble of fractal aggregates.

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Radiative Properties of Numerically Generated Fractal Soot Aggregates: The Importance of Configuration Averaging

Journal of Heat Transfer ◽

10.1115/1.4000245 ◽

2009 ◽

Vol 132 (2) ◽

Cited By ~ 20

Author(s):

Fengshan Liu ◽

Gregory J. Smallwood

Keyword(s):

Primary Particle ◽

Particle Diameter ◽

Practical Interest ◽

Aggregate Size ◽

Small Variation ◽

Radiative Properties ◽

Fractal Aggregates ◽

Cluster Aggregation ◽

Fractal Parameters ◽

Primary Particles

The radiative properties of numerically generated fractal soot aggregates were studied using the numerically accurate generalized multisphere Mie-solution method. The fractal aggregates investigated in this study contain 10–600 primary particles of 30 nm in diameter. These fractal aggregates were numerically generated using a combination of the particle-cluster and cluster-cluster aggregation algorithms with fractal parameters representing flame-generated soot. Ten different realizations were obtained for a given aggregate size measured by the number of primary particles. The wavelength considered is 532 nm, and the corresponding size parameter of primary particle is 0.177. Attention is paid to the effect of different realizations of a fractal aggregate with identical fractal dimension, prefactor, primary particle diameter, and the number of primary particles on its orientation-averaged radiative properties. Most properties of practical interest exhibit relatively small variation with aggregate realization. However, other scattering properties, especially the vertical-horizontal differential scattering cross section, are very sensitive to the variation in geometrical configuration of primary particles. Orientation-averaged radiative properties of a single aggregate realization are not always sufficient to represent the properties of random-oriented ensemble of fractal aggregates.

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Influence of primary particle polydispersity and overlapping on soot morphological parameters derived from numerical TEM images

Powder Technology ◽

10.1016/j.powtec.2018.02.008 ◽

2018 ◽

Vol 330 ◽

pp. 67-79 ◽

Cited By ~ 6

Author(s):

J. Morán ◽

J. Cuevas ◽

F. Liu ◽

J. Yon ◽

A. Fuentes

Keyword(s):

Primary Particle ◽

Morphological Parameters ◽

Particle Polydispersity

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Characterizing the convective heat exchange with plastic shading nets under natural arid conditions

International Journal of Energy Technology ◽

10.32438//ijet.11415 ◽

2019 ◽

pp. 11-20

Author(s):

Ahmed M Abdel-Ghanya ◽

Ibrahim M Al-Helal

Keyword(s):

Wind Speed ◽

Thermal Radiation ◽

Convective Heat ◽

Convective Heat Transfer Coefficient ◽

Convective Heat Exchange ◽

Radiative Properties ◽

Wooden Frame ◽

Arid Conditions ◽

Air Temperatures ◽

Radiation Fluxes

Plastic nets are extensively used for shading purposes in arid regions such as in the Arabian Peninsula. Quantifying the convection exchange with shading net and understanding the mechanisms (free, mixed and forced) of convection are essential for analyzing energy exchange with shading nets. Unlike solar and thermal radiation, the convective energy, convective heat transfer coefficient and the nature of convection have never been theoretically estimated or experimentally measured for plastic nets under arid conditions. In this study, the convected heat exchanges with different plastic nets were quantified based on an energy balance applied to the nets under outdoor natural conditions. Therefore, each net was tacked onto a wooden frame, fixed horizontally at 1.5-m height over the floor. The downward and upward solar and thermal radiation fluxes were measured below and above each net on sunny days; also the wind speed over the net, and the net and air temperatures were measured, simultaneously. Nets with different porosities, colors and texture structures were used for the study. The short and long wave’s radiative properties of the nets were pre-determined in previous studies to be used. Re and Gr numbers were determined and used to characterize the convection mechanism over each net. The results showed that forced and mixed convection are the dominant modes existing over the nets during most of the day and night times. The nature of convection over nets depends mainly on the wind speed, net-air temperature difference and texture shape of the net rather than its color and its porosity.

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