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D13.3 — Comparisons of the spectral emissivity measurements at high temperatures of stainless steel AISI 310S List of content
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This document presents the comparison of emissivity measurements for AISI310S at high temperature conducted by CIEMAT and CNRS with 3 different setups.
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In this work an alternative method for emittance determination based on pyrometric measurements is presented. The measurement procedure is limited by the spectral range of the infrared sensors used in this work (1400–5000 nm) and by its working temperature range (500–1000 °C). The measurement procedure has been applied to sintered SiC samples in the Plataforma Solar de Almería solar furnace SF40. The experimental results show that emittance decreases with increasing temperature and wavelength with a main value of 0.80. This behaviour is in agreement with experimental results obtained by other authors. Analysis of tests has revealed a good repeatability (1%) and accuracy (<3%) of this measurement procedure.
ScienceDirect 1876-6102 © 2013 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer review by the scientifi c conference committee of SolarPACES 2013 under responsibility of PSE AG. Final manuscript published as received without editorial corrections. Abstract A new high-flux vertical axis solar furnace has been constructed and is fully operational at Plataforma Solar de Almería (PSA). This new system is able to deliver up to 5 kW power at peak concentration ratios exceeding 6000. It has been designed to perform tests that require high radiant flux, strong gradients and very high temperatures, and will be devoted for materials treatment at high temperature, under vacuum and controlled atmosphere conditions This new solar furnace operates in a vertical axis, i.e. parabolic concentrator and heliostat are vertically aligned on the optical axis of the paraboloid. The main advantage of vertical axis solar furnaces is that the samples are deposited, without the need of any fixation, on a horizontal plane where they can be treated directly in the focus or inside crucibles, avoiding problems of loss of material by gravity in those tests in which pre-deposited powders are used, or when the treatment requires surface melting of the specimens, and preventing the use of re-directional mirrors, with the loss of power involved. The SF5 main components and canting procedures (alignment) of heliostat and concentrator are described, as well as the flux measurement in the focal area.
Surface temperatures are key parameters in many concentrated solar radiation applications. Pyrometric temperature measurement of solar irradiated material surfaces is the alternative to contact measurement techniques, which are inadequate for measuring the temperatures of such surfaces. However, reflected solar radiation is an important uncertainty variable in this non-contact methodology. A promising method for eliminating this solar perturbation is by using centred passband filters on the atmospheric solar absorption bands, creating solar-blind pyrometric systems. A commercial pyrometer has been tested in the wavelength band at around 1.4 µm in the solar furnace at Plataforma Solar de Almería, showing its advantages and limitations. An estimation of temperature measurement uncertainty for a real case is presented with theory and experiment in agreement: the higher the temperature, the lower the uncertainty. Another experiment has shown that the pyrometer measures temperature properly even through quartz windows in this spectral range.
Infrared measurement of the thermal radiation emitted by solar irradiated material surfaces is the most reliable alternative to contact thermometry which is inadequate for measuring surface temperatures. However, reflected solar radiation and the use of windows for material testing in controlled atmosphere or vacuum, can be important sources of error in this non-contact methodology. A promising method for eliminating this solar perturbation is by using centered band-pass filters on the spectral bands where the solar radiation has been attenuated. Two wavelength bands are analyzed in this paper. An IR camera prototype with band-pass filters centered at these two wavelength bands and an analysis of its behavior are presented.
In this paper an emissivity measurement method is proposed; it relies on individual calibration functions, and is based on the spectral response of a specific IR sensor. The reflected temperature is kept constant during the test, and its knowledge is not required. Results of measurements on materials commonly used as emissivity references in quantitative thermography are reported. Computer simulations of indoor and outdoor thermographic inspections show the differentiated influence of emissivity and surroundings temperature on the measurement accuracy. Finally experimental results of absolute and differential temperature measurements are discussed.
An analytical comparison of the accuracy of the most often used methods of emissivity measurements carried out during infrared thermographic studies on electronic microcircuits (thin-, thick-film and hybrid ones, high-density miniature PCBs, microsystems) is the main purpose of this paper. A typical measurement arrangement applied to these studies and main factors influencing the measurement results are presented. A special relationship describing the thermographic camera signal has been formulated. Conventional and unconventional methods of the emissivity measurements together with a detailed analysis of the accuracy of typical methods are presented in the paper. A criterion and a procedure of choosing the emissivity measurement method are also proposed. Similar problems concerning the temperature measurements will be presented and discussed in the next paper.
The emissivity ε of a surface is an essential quantity in i.r. thermography and thermometry. Since very few data are available, in particular for the 5 μm band, a technique has been worked out for the assessment of i.r. emissivities of surfaces at approximately room temperature. The method provides the reflectivity ρ from a differential temperature measurement of the same object in two different environments. This is equivalent to a determination ofϵ through the relationship ϵ + ρ = 1. Measurements have been made in the 5μm band with an AGA 680 camera and in the 10μm band with a Heimann KT4 thermometer. Surfaces studied include leaves of trees and green plants, wood, plastics, paper, human skin, and some other materials. The accuracy of the results is shown to be 0.005 or better for ϵ values of 0.92 or higher. Natural surfaces have emissivities in this range, with ϵ usually slightly higher in the 10μm band. Other materials may have a significantly lower ϵ.
Steel emissivity behaviors were investigated in this study. Experiments were conducted to measure emissivity. Six emissivity models were then applied to examine Multispectral Radiation Thermometry (MRT) on inferring surface temperature. The data show that emissivity decreases with increasing wavelength. For steel containing high chromium, emissivity is usually lower than others because of the chromium oxide protection layer. Two emissivity models provide the best overall compensation for different alloys, number of wavelengths, and temperatures. The results reveal that if the emissivity model can well represent the real emissivity behaviors, the more accurate inferred temperature can be achieved.
Carbon–carbon composites are candidate materials for the conception of the thermal shield of the “Solar Probe” space mission. To understand their behavior under solar aggressions and know the possible interactions with the shipped-in instruments, these materials were tested in a facility that allows to partially simulate the solar environment and to carry out in situ measurements. In this paper, we present the experimental results obtained for the α/ɛ ratio, i.e. the ratio of the solar absorptivity α to the total hemisherical emissivity ɛ that controls the thermal equilibrium of the thermal shield. The objective is to find the lower ratio α/ɛ in order to have the lowest temperature on the shield at 4 solar radii.
Estudio de la incertidumbre en la medida de temperatura superficial de materiales mediante sensores de contacto
- M I Roldán
M. I. Roldán, "Estudio de la incertidumbre en la medida de temperatura superficial de materiales mediante
sensores de contacto", SFERAII-SC-QA-02, (2015).