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Research Papers

# Pyroreflectometry to Determine the True Temperature and Optical Properties of Surfaces

[+] Author and Article Information
D. Hernandez

Procédés, Matériaux et Energie Solaire (CNRS), 7 rue du four solaire, 66120 Font-Romeu, Francedaniel.hernandez@promes.cnrs.fr

J. L. Sans

Procédés, Matériaux et Energie Solaire (CNRS), 7 rue du four solaire, 66120 Font-Romeu, Francesans@promes.cnrs.fr

M. Pfänder

Institute for Technicals Thermodynamics (DLR), Apartado 39, E-04200 Tabernas, Spainmarkus.pfaender@dlr.de

J. Sol. Energy Eng 130(3), 031003 (Jun 13, 2008) (4 pages) doi:10.1115/1.2840575 History: Received September 27, 2006; Revised October 02, 2007; Published June 13, 2008

## Abstract

In this paper, we present a theoretical analysis and experimental results of a pyrometric temperature measurement method based on a two-color pyroreflectometer (working wavelengths of $1.3μm$ and $1.55μm$) equipped with an optical fiber probe. By measuring simultaneously the radiance temperature and the normal reflectivity, the true temperature of the measurement target can be determined without the previous knowledge of the optical properties of the sample. The method is based on the introduction and the definition of the diffusivity factor $ηd$ and the assumption that it is equal for the two wavelengths. Besides the experimental results, the sources of errors and their impact on the method accuracy and the performance of the setup are discussed. The quality of the measurement results demonstrates the utility of the pyroreflectometry in a domain where fundamental parameters, such as the temperature and radiative properties, present the major measurement difficulties. The diffusivity factor appears not only a step to determine the true temperature but also as a parameter very useful to evaluate the diffusing behavior of opaque materials.

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## Figures

Figure 1

MEDIASE test facility diagram

Figure 2

Experimental results obtained with W plasma facing components: measured parameters: Tc=1610K, TRr=1264K, TRb=1309K, ρ0,0(T,λr)=1.005, ρ0,0(T,λb)=0.920; calculated parameters: T*=1454K, ηd(T*)=0.201

Figure 3

Experimental results obtained with Er2O3 plasma coating: measured parameters: Tc=887K, TRr=1319K, TRb=1244K, ρ0,0(T,λr)=0.072, ρ0,0(T,λb)=0.216; calculated parameters: T*=1354K, ηd(T*)=0.742

Figure 4

Examples of thermo-optical material classification versus ε and ηd

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