Infrared Radiative Properties of Thin Polyethylene Coating Pigmented With Titanium Dioxide Particles

2009 ◽  
Vol 132 (2) ◽  
Author(s):  
Mehdi Baneshi ◽  
Shigenao Maruyama ◽  
Atsuki Komiya
Keyword(s):  
Particle Size ◽  
Volume Fraction ◽  
Near Field ◽  
Field Approximation ◽  
Anisotropic Scattering ◽  
Radiative Properties ◽  
Emission Model ◽  
Tio2 Pigment ◽  
Pigmented Coatings ◽  
Thin Polyethylene

The infrared (IR) radiative properties of TiO2 pigment particles must be known to perform thermal analysis of a TiO2 pigmented coating. Resins generally used in making pigmented coatings are absorbing at IR wavelengths, which means that the conventional Mie solution (MS) may not be adequate in this domain. There are two approaches to evaluating radiative properties in an absorbing medium: far field approximation (FFA) and near field approximation (NFA). In this study, after reviewing these two approaches, we evaluated the radiative properties of TiO2 particles in polyethylene resin as an absorbing matrix in the wavelength range of 1.7–15 μm based on the MS, FFA, and NFA. We then calculated the effective scattering and absorption coefficients for different models. To investigate the effect of the particle size and volume concentration on the transmittance of IR wavelengths, we made a nongray radiative heat transfer in an anisotropic scattering monodisperse pigmented layer, with independent scattering using the radiation element method by the ray emission model. The results showed that all three approaches predicted similar results in the particle size domain and volume fraction range utilized in pigmented coatings.

A Parametric Numerical Study of Radiative Transfer in Thermotropic Materials

2013 ◽  
Author(s):  
Adam C. Gladen ◽  
Susan C. Mantell ◽  
Jane H. Davidson
Keyword(s):  
Particle Size ◽  
Radiative Transfer ◽  
Optical Thickness ◽  
Parametric Study ◽  
Volume Fraction ◽  
Numerical Study ◽  
Anisotropic Scattering ◽  
Index Of Refraction ◽  
Spherical Particles ◽  
Size Parameter

A thermotropic material is modeled as an absorbing, thin slab containing anisotropic scattering, monodisperse, spherical particles. Monte Carlo ray tracing is used to solve the governing equation of radiative transfer. Predicted results are validated by comparison to the measured normal-hemispherical reflectance and transmittance of samples with various volume fraction and relative index of refraction. A parametric study elucidates the effects of particle size parameter, scattering albedo, and optical thickness on the normal-hemispherical transmittance, reflectance, and absorptance. The results are interpreted for a thermotropic material used for overheat protection of a polymer solar absorber. For the preferred particle size parameter of 2, the optical thickness should be less than 0.3 to ensure high transmittance in the clear state. To significantly reduce the transmittance and increase the reflectance in the translucent state, the optical thickness should be greater than 2.5 and the scattering albedo should be greater than 0.995. For optical thickness greater than 5, the reflectance is asymptotic and any further reduction in transmittance is through increased absorptance. A case study is used to illustrate how the parametric study can be used to guide the design of thermotropic materials. Low molecular weighted polyethylene in poly(methyl methacrylate) is identified as a potential thermotropic material. For this material and a particle radius of 200 nm, it is determined that the volume fraction and thickness should equal 10% and 1 mm, respectively.

Control of Radiative Properties of Coatings Pigmented With Fe2O3 Nanoparticles

2011 ◽  
Author(s):  
Hiroki Gonome ◽  
Mehdi Baneshi ◽  
Atsuki Komiya ◽  
Shigenao Maruyama
Keyword(s):  
Near Infrared ◽  
Average Particle Size ◽  
Optimization Method ◽  
Radiative Properties ◽  
Average Particle ◽  
Emission Model ◽  
Properties Of Coatings ◽  
Spectral Behavior ◽  
Pigmented Coatings ◽  
Numerical Approaches

This study describes nanoparticles pigmented coatings used in controlling the radiative properties of surfaces exposed to sunlight. An optimization method that embraces both thermal and aesthetic requirements has been proposed. The proposed coatings maximize the reflectivity of the near infrared (NIR) region to reduce thermal heating, while for aesthetic appeal they minimize the visible (VIS) reflected energy. This spectral behavior can be achieved by controlling the size and concentration of pigment particles and coating thickness. In this study, both experimental and numerical approaches are applied on Fe2O3 pigmented coating samples with 0.2 μm and 1 μm of average particle size and different particle concentrations and coating thicknesses. For numerical part the radiation analysis using the Radiation Element Method by Ray Emission Model (REM2) in a one dimensional parallel plane model is conducted. From the numerical results, it is shown that the optimum size of Fe2O3 particles for our desired spectral behavior is about 0.8 μm. The experimental results also show that the samples made from 1 μm particles have better performance for our objective.

scholarly journals Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Particle Size ◽  
Aspect Ratio ◽  
Power Law ◽  
Volume Fraction ◽  
Inclined Magnetic Field ◽  
Magnetic Field Effects ◽  
Power Law Nanofluid ◽  
Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

scholarly journals A Thermally Conductive Pt/AAO Catalyst for Hydrogen Passive Autocatalytic Recombination

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 491
Author(s):  
Alina E. Kozhukhova ◽  
Stephanus P. du Preez ◽  
Aleksander A. Malakhov ◽  
Dmitri G. Bessarabov
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Combustion Temperature ◽  
Volume Fraction ◽  
Morphological Characteristics ◽  
Al Alloy ◽  
Impregnation Method ◽  
Case Scenario ◽  
Worst Case ◽  
Thermal Distribution

In this study, a Pt/anodized aluminum oxide (AAO) catalyst was prepared by the anodization of an Al alloy (Al6082, 97.5% Al), followed by the incorporation of Pt via an incipient wet impregnation method. Then, the Pt/AAO catalyst was evaluated for autocatalytic hydrogen recombination. The Pt/AAO catalyst’s morphological characteristics were determined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The average Pt particle size was determined to be 3.0 ± 0.6 nm. This Pt/AAO catalyst was tested for the combustion of lean hydrogen (0.5–4 vol% H2 in the air) in a recombiner section testing station. The thermal distribution throughout the catalytic surface was investigated at 3 vol% hydrogen (H2) using an infrared camera. The Al/AAO system had a high thermal conductivity, which prevents the formation of hotspots (areas where localized surface temperature is higher than an average temperature across the entire catalyst surface). In turn, the Pt stability was enhanced during catalytic hydrogen combustion (CHC). A temperature gradient over 70 mm of the Pt/AAO catalyst was 23 °C and 42 °C for catalysts with uniform and nonuniform (worst-case scenario) Pt distributions. The commercial computational fluid dynamics (CFD) code STAR-CCM+ was used to compare the experimentally observed and numerically simulated thermal distribution of the Pt/AAO catalyst. The effect of the initial H2 volume fraction on the combustion temperature and conversion of H2 was investigated. The activation energy for CHC on the Pt/AAO catalyst was 19.2 kJ/mol. Prolonged CHC was performed to assess the durability (reactive metal stability and catalytic activity) of the Pt/AAO catalyst. A stable combustion temperature of 162.8 ± 8.0 °C was maintained over 530 h of CHC. To confirm that Pt aggregation was avoided, the Pt particle size and distribution were determined by TEM before and after prolonged CHC.

Electroacoustic Study of n-Hexadecane/Water Emulsions

2001 ◽  
Vol 54 (8) ◽  
pp. 503 ◽  
Author(s):  
Linggen Kong ◽  
James K. Beattie ◽  
Robert J. Hunter
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Volume Fraction ◽  
Sodium Dodecyl ◽  
Surfactant Solution ◽  
Minimum Size ◽  
Water Mixture ◽  
Concentrated Suspensions ◽  
Minimum Concentration ◽  
Median Diameter

n-Hexadecane-in-water emulsions were investigated by electroacoustics using a prototype of an AcoustoSizer-II apparatus. The emulsions were formed by passing the stirred oil/water mixture through a homogenizer in the presence of sodium dodecyl sulfate (SDS) at natural pH (6–7). With increasing oil-volume fraction, the particle size increased linearly after 5 and also after 20 passages through the homogenizer, suggesting that surface energy was determining particle size. For systems in which the surfactant concentration was limited, the particle size after 20 passages approached the value dictated by the SDS concentration. With ample surfactant present, the median diameter was a linear function of the inverse of the total energy input as measured by the number of passes. There was, however, a limit to the amount of size reduction that could be achieved in the homogenizer, and the minimum size was smaller at smaller volume fractions. Dilution of the emulsion with a surfactant solution of the same composition as the water phase had a negligible effect on the particle size and changed the zeta potential only slightly. This confirms results from previous work and validates the equations used to determine the particle size and zeta potential in concentrated suspensions. The minimum concentration of SDS that could prevent the emulsion from coalescing for the system with 6% by volume oil was 3 mM. For this dilute emulsion, the particle size decreased regularly with an increase in SDS concentration, but the magnitude of the zeta potential went through a strong maximum at intermediate surfactant concentrations.

The Effect of Particle Size on the Electromechanical Properties of PZT/PVDF

2009 ◽  
Vol 66 ◽  
pp. 238-241
Author(s):  
Xiao Fang Liu ◽  
Hua Jun Sun ◽  
Ming Wei ◽  
C.X. Xiong
Keyword(s):  
Particle Size ◽  
Piezoelectric Ceramic ◽  
Electromechanical Coupling ◽  
Piezoelectric Properties ◽  
Volume Fraction ◽  
Relative Dielectric Constant ◽  
Connectivity Pattern ◽  
Conventional Solid State Reaction ◽  
Pressing Method ◽  
Dielectric And Piezoelectric Properties

The Nb modified PZT piezoelectric ceramic was synthesized by conventional solid-state reaction, where all of different particle sizes had the same physical properties. 0-3 modified PZT/PVDF composites were formed by hot-pressing method. The particle size effect of modified PZT on the relative dielectric and piezoelectric properties of the composites were investigated. The relative dielectric constant εr, piezoelectric constant d33 and electromechanical coupling factor kp were higher in the composite containing larger PZT particle size. The microstructures of the composites were studied by SEM, the composite with the finer PZT particle size was more homogeneous, but larger particle size was easy to be contacted. In a high volume fraction particle-loaded composite, some piezoelectric ceramic particle appeared to be in contact, as in a 1-3 connectivity pattern. The larger particle size of modified PZT itself could be seen as the grain of modified PZT contact in a 1-3 connectivity pattern and easy to be contacted each other compared to the finer particle size in the composites, thus reducing the resistance of the composites and the poling process became effective, which led to higher properties. The optimal particle size of PZT is about 100μm, the Nb modified PZT/PVDF (volume fraction 70/30) composite show higher dielectric and piezoelectric properties than the others, εr=156.6, d33=69pC/N and kp=0.358.

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