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Fu T.,Tsinghua University | Fu T.,Beijing Key Laboratory of CO2 Utilization and Reduction Technology | Liu J.,Tsinghua University | Tang J.,Tsinghua University | And 3 more authors.
Infrared Physics and Technology | Year: 2014

Temperature measurements inside semi-transparent materials are important in many fields. This study investigates the measurements of interior temperature distributions in a one-dimensional semi-transparent material using multi-wavelength pyrometry based on the Levenberg-Marquardt method (LMM). The investigated material is semi-transparent Zinc Sulfide (ZnS), an infrared-transmitting optical material operating at long wavelengths. The radiation properties of the one-dimensional semi-transparent ZnS plate, including the effective spectral-directional radiation intensity and the proportion of emitted radiation, are numerically discussed at different wavelengths (8.0-14.0 μm) and temperature distributions (400-800 K) to provide the basic data for the temperature inversion problem. Multi-wavelength pyrometry was combined with the Levenberg-Marquardt method to resolve the temperature distribution along the radiative transfer direction based on the line-of-sight spectral radiation intensities at multiple wavelengths in the optimized spectral range of (11.0-14.0 μm) for the semi-transparent ZnS plate. The analyses of the non-linear inverse problem show that with less than 5.0% noise, the inversion temperature results using the Levenberg-Marquardt method are satisfactory for linear or Gaussian temperature distributions in actual applications. The analysis provides valuable guidelines for applications using multi-wavelength pyrometry for temperature measurements of semi-transparent materials. © 2014 Elsevier B.V. All rights reserved. Source


Fu T.,Tsinghua University | Fu T.,Beijing Key Laboratory of CO2 Utilization and Reduction Technology | Duan M.,Tsinghua University | Tang J.,Tsinghua University | Shi C.,China Academy of Safety Science and Technology
International Journal of Heat and Mass Transfer | Year: 2015

A method was developed to simultaneously measure the directional spectral emissivity and the temperature of samples with diffuse surfaces at high temperatures using a radiation heating source with alternating spectral distributions and multiple wavelength measurements. The method avoids the need for direct measurements of the sample surface temperature to determine the spectral emissivity. The inverse problem for the spectral emissivity and the temperature of a sample irradiated by a simulated radiation source was analyzed numerically to illustrate the excellent solution accuracy of the measurement method for various noise levels and spectral emissivities in the near-infrared spectra. The solution uncertainties for the spectral emissivity and temperature were smaller for the sample with a larger spectral emissivity. Measurements with a 99.9% purity graphite sample irradiated by a quartz lamp array as the radiation heating source verified the applicability of the method. The spectral emissivities and temperatures of the graphite sample were calculated using the Levenberg-Marquardt algorithm for two heating conditions with alternating spectral distributions and 30 wavelengths in the spectral range of 1.15-1.60 μm. The uncertainties in the spectral emissivity and temperature were very small. The method is useful for accurately measuring the sample spectral emissivity without direct temperature measurements at high temperatures. © 2015 Elsevier Ltd. All rights reserved. Source


Fu T.,Tsinghua University | Fu T.,Beijing Key Laboratory of CO2 Utilization and Reduction Technology | Liu J.,Tsinghua University | Duan M.,Tsinghua University | Zong A.,Tsinghua University
Review of Scientific Instruments | Year: 2014

Temperature measurements are important for thermal-structural experiments in the thermal radiation heating environments such as used for thermal-structural stress analyses. This paper describes the use of multicolor pyrometry for the measurements of diffuse surfaces in thermal radiation environments that eliminates the effects of background radiation reflections and unknown emissivities based on a least-squares algorithm. The near-infrared multicolor pyrometer had a spectral range of 1100-2400 nm, spectrum resolution of 6 nm, maximum sampling frequency of 2 kHz, working distance of 0.6 m to infinity, temperature range of 700-1700 K. The pyrometer wavelength response, nonlinear intensity response, and spectral response were all calibrated. The temperature of a graphite sample irradiated by quartz lamps was then measured during heating and cooling using the least-squares algorithm based on the calibrated irradiation data. The experiments show that higher temperatures and longer wavelengths are more suitable for the thermal measurements in the quartz lamp radiation heating system. This analysis provides a valuable method for temperature measurements of diffuse surfaces in thermal radiation environments. © 2014 AIP Publishing LLC. Source


Fu T.,Tsinghua University | Fu T.,Beijing Key Laboratory of CO2 Utilization and Reduction Technology | Tan P.,Tsinghua University | Duan M.,Tsinghua University
Measurement Science and Technology | Year: 2015

A method was developed to simultaneously measure the total hemispherical emissivity and the thermal conductivity of samples at high temperatures. The inverse problem to determine the emissivity and thermal conductivity from steady-state high-temperature calorimetric experiments was established based on models for these two quantities. The accuracy of the inverse solution was numerically analyzed for various noise levels for samples with various thermophysical properties. The simulation results illustrate that the calculation accuracies for the emissivity and thermal conductivity strongly depend on the proportions of the radiation and conduction heat fluxes in the strip sample arising from the temperature distributions in the sample. Steady-state high-temperature experiments with nickel samples were used to experimentally verify the method. The inverse solution results for the emissivity and thermal conductivity calculated from the measured data agree well with reported data in the literature. This research provides a useful reference for measuring the total hemispherical emissivity and thermal conductivity of conductive samples at high temperatures. © 2015 IOP Publishing Ltd. Source


Fu T.,Tsinghua University | Fu T.,Beijing Key Laboratory of CO2 Utilization and Reduction Technology | Tan P.,Tsinghua University | Pang C.,Beijing Electro Mechanical Engineering Institute | And 2 more authors.
Review of Scientific Instruments | Year: 2011

A fast fiber-optic multi-wavelength pyrometer was developed for the ultraviolet-visible-near infrared spectra from 200 nm to 1700 nm using a CCD detector and an InGaAs detector. The pyrometer system conveniently and quickly provides the sufficient choices of multiple measurement wavelengths using optical diffraction, which avoids the use of narrow-band filters. Flexible optical fibers are used to transmit the radiation so the pyrometer can be used for temperature measurements in harsh environments. The setup and calibrations (wavelength calibration, nonlinearity calibration, and radiation response calibration) of this pyrometer system were described. Development of the multi-wavelength pyrometer involved optimization of the bandwidth and temperature discrimination of the multiple spectra data. The analysis results showed that the wavelength intervals, CCD 30 nm and InGaAs 50 nm, are the suitable choices as a tradeoff between the simple emissivity model assumption and the multiple signal discrimination. The temperature discrimination was also quantificationally evaluated for various wavelengths and temperatures. The measurement performance of the fiber-optic multi-wavelength pyrometer was partially verified through measurements with a high-temperature blackbody and actual hot metals. This multi-wavelength pyrometer can be used for remote high-temperature measurements. © 2011 American Institute of Physics. Source

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