Pyrometry optical

Figure 4.25. Experimental configuration for optical pyrometry of shock temperatures induced in transparent minerals. Upon impact of projectile with driver plate, a shock wave is driven into the driver plate and then into the sample. Optical radiation from the sample is detected via six lens/interference filter channels and an array of six photodiodes. Signals from photodiode circuits are recorded on oscilloscopes operating in single sweep model. (After Ahrens et al. (1982).)...

Finally, it is to be expected that the evaporation coefficient of a very stable compound, such as alumina, which has a large heat of sublimation resulting from the decomposition into the elements, will be low. Since the heat of evaporation must be drawn from the surface, in the case of a substance with a low thermal conductivity such as an oxide, the resultant cooling of the surface may lead to a temperature gradient in and immediately below the surface. This will lower the evaporation rate compared to that which is calculated from the apparent, bulk, temperature of the evaporating sample as observed by optical pyrometry, and thus lead to an apparently low free surface vaporization coefficient. This is probably the case in the evaporation of alumina in a vacuum,... 

In optical pyrometry the size of the luminous object must meet a certain minimum, and the radiant energy output must be uniform over the area observed, lest the apparent temp be low. Moreover, temp readings will be low if radiant energy is absorbed in the colder outer gas envelope. The role of smoke and other debris in the study of expls was alluded to in an earlier article ( Spectroscopy of Energetic Materials in this Vol). There, too, was referenced rapid scan spectroscopy for the resolution of pyrot phenomena, and of the energetics of fuel-air expins. For more extensive discussions of high temp measurement techniques, see Ref 6a... 

The transport of thermal energy can be broken down into one or more of three mechanisms conduction--heat transfer via atomic vibrations in solids or kinetic interaction amongst atoms in gases1 convection - - heat rapidly removed from a surface by a mobile fluid or gas and radiation—heat transferred through a vacuum by electromagnetic waves. The discussion will begin with brief explanations of each. These concepts are important background in the optical measurement of temperature (optical pyrometry) and in experimental measurement of the thermally conductive behavior of materials. 

The error introduced by use of the Wien equation is less than 1 percent when XT < 3000 pm K. The Wien equation has significant practical value in optical pyrometry for T < 4600 K when a red filter (X = 0.65 pm) is employed. The long-wavelength asymptotic approximation for Eq. (5-102) is known as the Rayleigh-Jeans formula, which is accurate to within 1 percent for XT > 778,000 pm-K. The Raleigh-Jeans formula is of limited engineering utility since a blackbody emits over 99.9 percent of its total energy below the value of XT = 53,000 pm-K. 

Andreev, V. A., Mal tsev, N. M., and Seleznev, V. A., Study of the combustion of hafnium-boron mixtures by optical pyrometry. Combust. Explos. Shock Waves, 16,374 (1980). 

Several other procedures for a precise temperature control of the filament are also available, such as the use of optical pyrometry or thermocouples [13, 14]. 

The actual temperature acquired by the sample during pyrolysis can be monitored using optical pyrometry or can be standardized between different pyrolyzers using a model compound. The procedure is based on the dependence of the composition of the pyrolysis products on temperature. One such compound chosen as a standard is an isoprene/styrene copolymer, trade name Kraton 1107 [15] (see Section 4.2). 

The true temperature of a sample heated using a filament pyrolyzer can be quite different from the above profile temperature, significantly lower temperatures being recorded inside the samples [4]. In order to obtain a correct Teq, modern equipment uses a feedback controlled temperature system (see e g. [5] for a more detailed description of this type of pyrolyzer). Several other procedures for a precise temperature control of the filament are available, such as the use of optical pyrometry or thermocouples [6, 7], Special pyrolysis systems that allow programmed heated rates at different time intervals also are available [8]. 

Waidner and Burgess, Optical Pyrometry, Bureau of Standards, Sci. Paper 11, 1905. Waidner and Burgess, Platinum Resistance Thermometry, Bureau of Standards, Sci. Paper 124, 1909. 

Often temperature measurements are made using thermocouples or optical pyrometry. However, in situations where rapid motion or reciprocating equipment is present at high temperatures, it is best to use other techniques. For many phosphors, the prompt fluorescence decay time (t) varies as a function of temperature and is defined by ... 

The pyrolysis filament may be shaped for convenience of sampling and may be a flat strip, foil, wire, grooved strip, or coil. In the case of the coil, a small sample tube or boat is inserted into the filament so that the sample is not heated directly by the filament, but is in effect inside a very small, rapidly heating furnace. The pyrolysis filament must be connected to a controller capable of supplying enough current to heat the filament rapidly, with some control or limit since the materials used for filaments are not self-limiting. The temperature of the filament may be monitored using the resistance of the material itself or some external measure, such as optical pyrometry or a thermocouple. ... 

Bab] Laser surface alloying (LSA), optical pyrometry and microscopy Fe rich comer... 

A main part of characterization is knowing the temperature at which the characterization is occurring. There are two ways to know the temperature thermocouples (TC) and optical pyrometry. Both of these approaches were used by the authors in characterization and testing but the vast amount of the work has been with thermocouples. Due to the maximum temperature... 

Crivello, J.V. (2005) Investigation of the photoactivated frontal polymerization of oxetanes using optical pyrometry. Polymer, 46, 12109-12117. 

Nordine PC (1986) The accuracy of multi-color optical pyrometry. High Temp Sd 21(2) 97-109... 

The ITS-90 is defined over a very wide temperature range, from 0.65 K up to at least 1358 K. There is a specified procedure for each measurement of T90, depending on the range in which T falls vapor-pressure thermometry (0.65-5.0 K), gas thermometry (3.0-24.5561 K), platinum-resistance thermometry (13.8033-1234.93K), or optical pyrometry (above 1234.93 K). For vapor-pressure thermometry, the ITS-90 provides formulas for T90 in terms of the vapor pressure of the helium isotopes He and He. For the other methods, it assigns values of several fixed calibration temperatures. The fixed temperatures are achieved with the reproducible equilibrium systems listed in Table 2.3 on the next page. 

Many different methods have been used to monitor the kinetics of cationic ring-opening photopolymerizations. Among the most commonly used techniques are real-time infrared spearoscopy, differential scanning photocalori-metry, " thin-film calorimetry, and optical pyrometry. ... 

An important probe of carbon surface functionality is mass spectrometry, in monitoring the nature of the gaseous phase produced from heated carbon fibers by temperature-programmed desorption (TPD). In the author s group TPD has been applied by heating the Fibers electrically while monitoring the temperature by optical pyrometry and the gaseous phase by mass spectrometry XPS data were recorded at the same time [8],... 

The non-invasive requirement for the hot leg temperature sensor must therefore be evaluated against impacts on reactor control response time. Other factors affecting sensor placement include sensor accuracy and resolution, temperature tolerance, sensor size, and feasible attachment methodologies. The sensor technologies under consideration for measuring the hot gas temperature were ultrasonics, thermocouples, resistance temperature deviees (RTDs), optical pyrometry, and fiber Bragg grating. 

Infrared pyrometry Determination of the temperature of a surface by measuring the IR radiation emitted from it. Useful in temperamre ranges below those at which optical pyrometry (color temperature) is used. See also Optical pyrometry. 

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