Radiation thermometry

D. P. DeW itt. Theory and Practice of Radiation Thermometry. New York John Wiley Sons, 1988. J. C. Richmond. Applications of Radiation Thermometry. ASTM Special Technical Publication. American Society for Testing and Materials, 1984. 

At temperatures above the melting point of silver (1234.93 K), radiation thermometry is used. The equation that applies is... 

Radiation thermometers, 24 453 calibration of, 24 454 calibration source for, 24 458 Radiation thermometry, uncertainty of,... 

Radiation thermometry (visual, photoelectric, or photodiode) 500-50,000 Spectral intensity I at wavelength A Planck s radiation law, related to Boltzmann factor for radiation quanta Needs blackbody conditions or well-defined emittance... 

As expected, the effective emissivity reaches unity as A1/A2 approaches zero. The effective absorptivity ttjff is equal to 8 and may be viewed as the ratio of the radiant energy absorbed by the cavity walls to that incident through the opening. Blackbody cavities have important applications in radiometry and radiation thermometry. 

FIGURE 7.17 Radiation thermometry (a) calibration against a blackbody cavity (b) measurement of a real surface. 

Although the concept of radiance is the same as the intensity defined in Equation (7.3), it is commonly used in radiation thermometry. Therefore, both the term radiance and its symbol L are retained here. 

Any device or system that has one or more physical properties (e.g., electrical resistance, electrical potential, length, pressure at constant volume, or volume at constant pressure) that vary monotonically and repro-ducibly with temperature may be used to measure temperature. The science of the measurement of temperature is called thermometry. In the past, the measurement of high temperature was known as pyrometry but now that term usually refers to radiation thermometry at any temperature. Although the accuracy of a measurement refers to the difference between the measured value and the true value of the quantity being measured, and the precision of measurement refers to the degree of agreement among repeated measurements of the same quantity, it follows that a set of measurements of the same quantity, it follows that a set of measurements may be very precise but terribly inaccurate. Since in many instances the word accuracy is used when inaccuracy is meant and the word precision is used when imprecision is meant, perhaps it would be better always to refer to uncertainties of measurement, statistical and systematic, rather than to accuracy and precision. 

Another noncontact technique for measuring high temperatures involves Raman spectroscopy, in particular the nonlinear process known as coherent anti-Stokes Raman spectroscopy (CARS) (Radiation Thermometry, 1982). This technique is finding practical applications in measurements of temperatures of flames (in internal combustion engines, in jet engines) and of hot gases. The imprecision of such temperature measurements is generally a few percent. 

Radiation Thermometry Session (1982), in Temperature Its Measurement and Control in Science and Industry, vol. 5, American Institute of Physics, New York, pp. 575-629. 

D. P. DeWitt, Advances and Challenges in Radiation Thermometry, in G. F. Hewitt (ed.) Heat Transfer 1994 Proceedings of the Tenth International Heat Transfer Conference, vol. 1, pp. 205-222,1994. 

Temperature is undeniably the most important property for all calorimetric measurements, because it is the common denominator. Two different techniques for temperature measurements are used for pulse calorimetry contact thermometry (e.g. thermocouples) and radiation thermometry or pyrometry. Because pulse calorimetry is often used to handle and measure liquid materials, non-contact radiation thermometry is far more common in pulse-heating than contact thermometry. Other reasons for non-contact temperature measurement methods include the fast heating rates and temperature gradients (inertia of the thermocouples), difficulties mounting the contact thermometers (good thermal contact needed), and stray pick-up in the thermocouple signal because the sample is electrically self-heated. 

Literature data [77] definition of the temperature scale, [76] radiation thermometry. 

D. P. DeWitt and G.D. Nutter, Theory and Practice of Radiation Thermometry, Wiley, New York, 1988. 

CD Wen. Investigation of steel emissivity behaviors Examination of multispectral radiation thermometry (mrt) emissivity models. InternationalJournal of Heat and Mass Transfer, 53(9) 2035--2043, 2010. 

Dai, J. M. (1995). The study of multi-wave spectral radiation thermometry. Doctoral dissertation, Harbin Institute of Technology, Harbin. 

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