Modulation of apparent optical properties using arrayed mesoscale structures. (November 2022)

• Record Type: Journal Article
• Authors: Simeroth, David L.; Kottke, Peter A.; Kucuktas, Onur A.; Fedorov, Andrei G.
• Is Part Of: Journal of quantitative spectroscopy & radiative transfer. Volume 290(2022)
• Publication Date: 2022-11
• Subjects: Mesoscale structures -- Apparent optical properties -- Net radiosity; Spectrum analysis -- Periodicals; Radiation -- Periodicals; Analyse spectrale -- Périodiques; Rayonnement -- Périodiques; Radiation; Spectrum analysis; Periodicals; 543.0858
• DOI: 10.1016/j.jqsrt.2022.108280
• Languages: English
• ISSNs: 0022-4073

Abstract

Highlights: Opaque, mesoscale surfaces are capable of raising and lowering apparent emissivity. External emitting surfaces raise the apparent emissivity. Reradiating surfaces lower the apparent emissivity. Combining different materials, geometries allows wide range of apparent properties. Analytic relationships well suited to machine learning optimization. Abstract: In this study, a method for using arrays of mesoscale structures to modify the apparent optical properties of an opaque composite surface has been theoretically demonstrated to both raise and lower the apparent emissivity as compared to the intrinsic properties of the constitutive materials. For design problems where thermomechanical and optical material properties are both of importance, mesoscale surface structuring can greatly expand the design space. Analysis via the net radiosity method herein illustrates the ability to achieve a wide range of spectral apparent optical properties. Notably, a hexagonal array of spheres on a planar surface can raise the apparent emissivity of a planar surface by 50%. Conversely, a hexagonal enclosure of reradiating surfaces, realized by thin adiabatic walls, can reduce the apparent emissivity of a blackbody by half. As this method of modifying apparent optical properties utilizes structures much larger than the wavelengths of interest, the relationship between intrinsic planar emissivity, geometry, and apparent emissivity can be computed semi-analytically at low computational expense. Passive solar cooling, thermophotovoltaic cells, aerodynamic surfaces exposed to intense heating, and solar absorbers are presented as case studies that could benefit from the use of mesoscale structures on opaque surfaces to modify the apparent optical properties.