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ENCIT 2020
18th Brazilian Congress of Thermal Sciences and Engineering
MEASUREMENT OF SPECTRAL EMISSIVITY IN METALS FOR LONG INFRARED WAVELENGTHS USING THERMAL IMAGERS
Submission Author:
Matheus de Oliveira Moreira , MG , Brazil
Co-Authors:
Matheus de Oliveira Moreira, Rafael Augusto Magalhães Ferreira, Alexandre Abrao, Matheus Porto
Presenter: Matheus de Oliveira Moreira
doi://10.26678/ABCM.ENCIT2020.CIT20-0247
Abstract
Emissivity is a physical property that relates temperature difference with heat transfer. Emissivity depends on a set of physical properties: molecule/surface temperatures, wavelength, directional dependence (optical properties, rugosity, etc.), and polarization. Spectral dependence in metallic surfaces can not be neglect, and gray body-based models may lead to inaccurate estimates of heat transfer and emissivity. The present study proposes a methodology to estimate long-wavelength spectral emissivity of metallic surfaces, using a thermal imager and mathematical models. We used a 7.5μm to 13μm infrared camera to measure the radiosity of an AISI H13 steel sample, at the same time as temperature was measured using a thermocouple type T. We upload the thermal images in Python, extract a matrix of radiosities, and post-process the experimental results using heat transfer relations and data from the literature, to estimate the spectral behavior of the metal surface. We tested temperatures from 50°C to 250°C, and spectral emissivity of AISI H13 steel ranged from 0.12 to 0.20. The results of spectral emissivity achieved with the proposed procedure were higher than those obtained by applying only theoretical models.
Keywords
thermal radiation, spectral emissivity, longwave infrared, measurement, Metal
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