Beijing Key Laboratory of CO2 Utilization and Reduction Technology

Beijing, China

Beijing Key Laboratory of CO2 Utilization and Reduction Technology

Beijing, China

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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.


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.


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.


Jiang P.X.,Key Laboratory for Thermal Science | Jiang P.X.,Beijing Key Laboratory of CO2 Utilization and Reduction Technology | Jiang P.X.,Tsinghua University | Xiang H.,Key Laboratory for Thermal Science | And 5 more authors.
Science China Technological Sciences | Year: 2012

The nanoparticle thermal conductivity and nanoscale thermal contact resistance were investigated by molecular dynamics (MD) simulations to further understand nanoscale porous media thermal conductivity. Macroscale porous media thermal conductivity models were then revised for nanoporous media. The effective thermal conductivities of two packed beds with nanoscale nickel particles and a packed bed with microscale nickel particles were then measured using the Hot Disk. The measured results show that the nano/microscale porous media thermal conductivities were much less than the thermal conductivities of the solid particles. Comparison of the measured and calculated results shows that the revised combined parallel-series model and the revised Hsu-Cheng model can accurately predict the effective thermal conductivities of micro- and nanoparticle packed beds. © Science China Press and Springer-Verlag Berlin Heidelberg 2012.


Ruina X.,Key Laboratory for Thermal Science and Power Engineering | Ruina X.,Beijing Key Laboratory of CO2 Utilization and Reduction Technology | Ruina X.,Tsinghua University | Yuli H.,Key Laboratory for Thermal Science and Power Engineering | And 8 more authors.
Science China Technological Sciences | Year: 2012

The internal heat transfer of different gases in microporous media was investigated experimentally and numerically. The experimental test section had a sintered bronze porous media with average particle diameters from 11 μm to 225 μm. The Knudsen numbers at the average inlet and outlet pressures of each test section varied from 0.0006 to 0.13 with porosities from 0.16 to 0.38. The particle-to-fluid heat transfer coefficients of air, CO2 and helium in the microporous media were determined experimentally. The results show that the Nusselt numbers for the internal heat transfer in the microporous media decrease with decreasing the particle diameter, dp, and increasing Knudsen number for the same Reynolds number. For Kn>0.01, the rarefaction affects the internal heat transfer in the microporous media. A Nusselt number correlation was developed that includes the influence of rarefaction. The computational fluid dynamics (CFD) numerical simulation was carried out to do the pore scale simulation of internal heat transfer in the microporous media considering the rarefaction effect. Pore scale three-dimensional numerical simulations were also used to predict the particle-to-fluid heat transfer coefficients. The numerical results without slip-flow and temperature jump effects for Kn<0.01 corresponded well with the experimental data. The numerical results with slip-flow and temperature jump effects for 0.01


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.


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.


Fu T.,Tsinghua University | Fu T.,Beijing Key Laboratory of CO2 Utilization and Reduction Technology | Liu J.,Tsinghua University | Zong A.,Tsinghua University
Applied Optics | Year: 2014

Semitransparent zinc sulfide (ZnS) crystal materials are widely used as the infrared-transmitting windows for optical instruments operating in long wavelengths. This paper describes a temperature measurement method for high-temperature ZnS materials using the one-channel optical pyrometer based on a theoretical model of radiation transfer in semitransparent plates. Numerical analyses of the radiation properties of ZnS plate are used to optimize the spectral band for the optical pyrometry. The optimized measurement spectral band is based on a trade-off between the measurement radiation intensity and the signal-to-noise ratio (SNR) for the ZnS material. The effective waveband emittance of one-dimensional (1D) ZnS plates is analyzed for various experimental conditions (temperatures, thicknesses, and direction angles) for the one-channel infrared pyrometer with the optimized measurement spectral response. The analysis can be used to improve radiation temperature measurements of semitransparent ZnS materials in applications. © 2014 Optical Society of America.


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
Measurement Science and Technology | Year: 2012

A steady-state calorimetric technique was developed for measuring the total hemispherical emissivity of a conductive material. The system uses a thin strip of the conductive sample electrically heated by alternating current to high temperatures in a vacuum chamber. The emissivity was measured in a central region of the sample with an approximately uniform temperature distribution. Considering the influences of the gray body assumption, wire heat losses, effects of residual gas and conductive heat loss from the region to the rest of the strip, the emissivity was accurately determined by solving the inverse one-dimension steady-state heat transfer problem. The emissivities of various metal samples (nickel and 45# steel) were measured to verify the system accuracy. And the results were then analyzed to estimate the relative errors of emissivity arising from the gray body assumption, wire heat losses, effects of residual gas, non-uniform temperature distribution and the measurement uncertainty of emissivity. In the temperature range from 700 to 1300 K, the accuracy is acceptable for practical applications within the total measurement uncertainties of 1.1%. To increase the system applicability, some issues related to sample specifications, heating power control and temperature uniformity of sample test section were discussed. Thus, this system can provide accurate measurements of the total hemispherical emissivity of conductive samples at high temperatures. © 2012 IOP Publishing Ltd.

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