Abstract
The optical constants of a liquid hydrocarbon such as liquid n-octane are basic material properties that may be used to evaluate their thermal radiation transfer capabilities. In this study, the ellipsometry method was used to measure the optical constants of liquid n-octane in the midinfrared wavelength range of 2.0–16.0 μm at temperatures of 20, 50, and 80°C. Experimental analyses indicate the significant effect of temperature on the refractive index, although it has little effect on the absorption index. With increasing temperature, the refractive index shows a linear decrease, and reduced density leads to weaker absorption intensities. The radiative properties of n-octane droplets, including the absorption and scattering efficiency factors of single droplets with droplet radii r = 10, 20, 50, and 100 μm and the absorption and scattering coefficients in a droplets-air system of droplet volume fractions fv = 2%, 3%, and 4%, were calculated using Mie theory. The numerical results indicate that, with increasing temperature, the absorption efficiency factor slightly decreases, and the variation trend of the scattering efficiency factor is more complicated. With increasing droplet radius, the absorption efficiency factor increases within the studied wavelength range, except for certain absorption peaks, but the scattering efficiency factor tends to decrease. While the absorption is greater, the scattering is weaker for a given droplet radius. With an increasing volume fraction of n-octane droplets, the absorption and scattering coefficients increase linearly within the studied wavelength range.
Highlights
Liang Zhao,1 Chaoyu Jing,2 Yu Jin,1 Jiangping Chen,1 Ke Yin,1 Sujun Yang,1 Bingqing Liu,1 Xiao Han,1 and Jianyu Tan 2
With the development of experimental conditions, numerous experimental approaches have been proposed to investigate the optical properties of liquids, such as the attenuated total reflection (ATR) method [16,17,18,19,20], the transmission method [21,22,23,24], the combined transmissionreflection method [25, 26], and the ellipsometry method [27,28,29,30,31,32,33]. e ATR method is suitable for the measurement of absorption indices in strong absorption regions, whereas the transmission method is especially suitable for measuring the absorption indices of liquids in weak absorption regions
The optical constants of liquid n-octane, the absorption and scattering efficiency factors of a single spherical droplet, and the absorption and scattering coefficients of droplets-air systems formed by sprays with various droplet radii and droplet volume fractions were investigated at 20, 50, and 80°C in the midinfrared wavelength range of 2.0–16.0 μm. e absorption and refractive indices of liquid n-octane were obtained experimentally using the improved ellipsometry method. e absorption and scattering efficiency factors of n-octane droplets of various temperatures and radii, together with the absorption and scattering coefficients of droplet-air systems of various volume fractions, were calculated using Mie theory. e following conclusions were drawn
Summary
Liang Zhao ,1 Chaoyu Jing,2 Yu Jin,1 Jiangping Chen,1 Ke Yin,1 Sujun Yang,1 Bingqing Liu,1 Xiao Han,1 and Jianyu Tan 2. The ellipsometry method was used to measure the optical constants of liquid n-octane in the midinfrared wavelength range of 2.0–16.0 μm at temperatures of 20, 50, and 80°C.
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