Temperature measurement radiation

The noncontact measurement principle, usually called optical or radiation temperature measurement, is based on detecting electromagnetic radiation emitted from an object. In ventilation applications this method of measurement is used to determine surface temperatures in the infrared region. The advantage is that the measurement can be carried out from a distance, without contact with the surface, which possibly influences the heat balance and the temperatures. The disadvantages are that neither air (or other fluid) temperature nor internal temperature of a material can be measured. Also the temper-... 

This equation system with the unknown variables 7ttl = Ta2, T 3 = Ta4, So and Si can be solved analytically. The ambient temperatures are thus calculated indirectly by radiation temperature measurements. The ambient temperature of the calibration chamber or the thermometer need not to be measured. 

Leach S (2012) Why COBE and CN spectroscopy cosmic background radiation temperature measurements differ, and a remedy. Mon Not R Astron Soc 421 1325-1330 Indriolo N, McCall BJ (2012) Investigating the cosmic-ray ionization rate in the galactic diffuse interstellar medium through observation of Ha" ". Astrophys J 745 91-1-17... 

Control Devices. Control devices have advanced from manual control to sophisticated computet-assisted operation. Radiation pyrometers in conjunction with thermocouples monitor furnace temperatures at several locations (see Temperature measurement). Batch tilting is usually automatically controlled. Combustion air and fuel are metered and controlled for optimum efficiency. For regeneration-type units, furnace reversal also operates on a timed program. Data acquisition and digital display of operating parameters are part of a supervisory control system. The grouping of display information at the control center is typical of modem furnaces. 

The deterrnination of surface temperature and temperature patterns can be made noninvasively using infrared pyrometers (91) or infrared cameras (92) (see Infrared technology and raman spectroscopy). Such cameras have been bulky and expensive. A practical portable camera has become available for monitoring surface temperatures (93). An appropriately designed window, transparent to infrared radiation but reflecting microwaves, as well as appropriate optics, is needed for this measurement to be carried out during heating (see Temperature measurement). 

The temperature of the gas leaving the sulfur burner is a good indication of SO2 concentration, even though the thermocouples employed for temperature measurement (qv) frequently read somewhat lower than the tme temperatures, because of radiation and convection errors. A temperature of 970°C corresponds to about 10.0 vol % SO2, 1050°C to 11.0 vol % SO2, and 1130°C to 12.0 vol % SO2. Other temperatures and concentrations are in similar proportion. 

The temperature in the hottest part of the kiln is closely controlled using automatic equipment and a radiation pyrometer and generally is kept at about 1100—1150°C (see Temperature measurement). Time of passage is about four hours, varying with the kiln mix being used. The rate of oxidation increases with temperature. However, the maximum temperature is limited by the tendency of the calcine to become sticky and form rings or balls in the kiln, by... 

Total Radiation Pyrometers In total radiation pyrometers, the thermal radiation is detec ted over a large range of wavelengths from the objec t at high temperature. The detector is normally a thermopile, which is built by connec ting several thermocouples in series to increase the temperature measurement range. The pyrometer is calibrated for black bodies, so the indicated temperature Tp should be converted for non-black body temperature. 

Because indirect-heat calciners frequently require close-fitting gas seals, it is customaiy to support aU parts on a selFcontained frame, for sizes up to approximately 2 m in diameter. The furnace can employ elec tric heating elements or oil and/or gas burners as the heat source for the process. The hardware would be zoned down the length of the furnace to match the heat requirements of the process. Process control is normaUy by shell temperature, measured by thermocouples or radiation pyrometers. When a special gas atmosphere must be maintained inside the cyhnder, positive rotaiy gas se s, with one or more pressurized and purged annular chambers, are employed. The diaphragm-type seal ABB Raymond (Bartlett-Snow TM) is suitable for pressures up to 5 cm of water, with no detectable leakage. 

Figure 4.29. Sample assembly for optical shock temperature measurements. The sample consists of a metal film deposited on a transparent substrate which serves as both an anvil and a transparent window through which thermal radiation is emitted. Rapid compression of gases and surface irregularities at the interface between the sample film and the driver produce very high temperatures in this region. The bottom portion of the figure illustrates the thermal distribution across through the assembly. (After Bass et al. (1987).)...

Boslough, M.B., and Ahrens, T.J. (1989), A Sensitive Time-Resolved Radiation Pyrometer for Shock-Temperature Measurements above 1500 K, Rev. Sci. Instrum. 60,3711-3716. 

Contact temperature measurement is based on a sensor or a probe, which is in direct contact with the fluid or material. A basic factor to understand is that in using the contact measurement principle, the result of measurement is the temperature of the measurement sensor itself. In unfavorable situations, the sensor temperature is not necessarily close to the fluid or material temperature, which is the point of interest. The reason for this is that the sensor usually has a heat transfer connection with other surrounding temperatures by radiation, conduction, or convection, or a combination of these. As a consequence, heat flow to or from the sensor will influence the sensor temperature. The sensor temperature will stabilize to a level different from the measured medium temperature. The expressions radiation error and conduction error relate to the mode of heat transfer involved. Careful planning of the measurements will assist in avoiding these errors. 

The temperature for methane and butane calculated with the isothermal model is a factor 1.4 times greater than the average temperature measured by Lihou and Maund (1982) in their small-scale tests, although higher local maximum temperatures were measured. In this model, combustion is stoichiometric, thus leading to very high fireball temperatures which, in turn, lead to high radiation emissions. Effective surface emissions measured experimentally were one-half the value calculated from this model, because combustion is not stoichiometric and emissivity is less than unity. 

The value of k is determined experimentally by gas temperature measurement. The measurement error of a simple pyrometer can be 250 to 300 K, due to re-radiation to water-cooled surroundings, and the values given below are based on measurement by a Land multi-shielded high-velocity suction pyrometer. Typical values for normal excess air at or near full boiler load are ... 

Infrared (IR) thermography is one of the most advanced non-destructive (NDT) methods based on the fact that all bodies whose absolute temperature is above zero emit electromagnetic radiation over a wide spectrum of wavelengths depending on the temperature. Recently, several researchers have applied it to micro-scale temperature measurement. Hetsroni et al. (2001a) constructed a thermal micro-system... 

Site-specific climatic factors that are important to selection of landfill cover type and to design of ET landfill covers include daily measurements of precipitation, maximum and minimum temperature, relative humidity, total solar radiation, and wind run.6 45 55 If all of the data are not available, one can make useful—but less accurate—estimates of cover performance using only daily precipitation and maximum and minimum temperature measurements. 

A thermopile sensor generates an output voltage that depends on the temperature difference between its hot and cold contacts. For infrared temperature measurement, the hot contacts are normally thermally insulated and placed on a thin membrane, whereas the cold contacts are thermally connected to the metal housing. Infrared radiation, which is absorbed by the hot contacts of the thermopile, causes a temperature difference between hot and cold contacts. The resulting output voltage is a measure for the temperature difference between radiation source and cold contacts of the thermopile sensor. It is therefore necessary to measure also the temperature of the cold contacts by an additional ambient temperature sensor in order to determine the temperature of the radiation source. 

Thermopiles are also used in new ear thermometers or in forehead thermometers to measure the infrared radiation emitted from the skin. This allows quick and reliable temperature measurement and is easy and comfortable to use. 

EXAFS (Extended X-ray Absorption Fine Structure) measurements using synchrotron radiation have been successfully applied to the determination of structural details of SCO systems and have been particularly useful when it has not been possible to obtain suitable crystals for X-ray diffraction studies. Perhaps the most significant application has been in elucidating important aspects of the structure of the iron(II) SCO linear polymers derived from 1,2,4-triazoles [56]. EXAFS has also been applied to probe the dimensions of LIESST-generated metastable high spin states [57]. It has even been used to generate a spin transition curve from multi-temperature measurements [58]. 

An average of temperature records on the earth s surface over a year indicates that the earth s average surface temperature is about 14°C (57°F). But, the earth s 240 watts per square meter of thermal infrared radiation as measured by satellite is equivalent to the radiation emitted by a black body whose temperature is about -19°C (-3°F), not the 14°C (57°F) average measured at the earth s surface. The 33°C (60°F) difference between the apparent temperature of the earth as seen in space and the actual temperature of the earth s surface is attributed to the greenhouse effect. 

The temperature of exposed samples is dependent on both the air temperature in the cabinet and the absorbance of direct radiation. Temperature is usually measured with a black panel thermometer, which gives the surface temperature of a perfectly absorbing material. White panel thermometers are also commonly used which measure the other extreme. The actual temperature reached by a test piece depends on the material and its colour. It will also depend on the air temperature and velocity so that both the air and black panel temperatures should be controlled. ISO 11403-3 [23] defines three sets of conditions in air with the black standard temperature at 65 °C (ISO 4892-2 Method A [27]), behind glass at the same temperature (ISO 4892-2 Method B [27]), and behind glass at 100 °C. 

The reported ESR spectra of polyisobutylene, irradiated with high energy radiation and measured at low temperatures (31, 35, 47, 48, 49, 52) are similar in form, showing a broad doublet with a hyperfine splitting constant of 20 gauss. These spectra have been interpreted as caused by radicals (XIII) formed by hydrogen abstraction from the main chain methylene groups ... 

Two main principles of temperature measurement use thermocouples and the so-called resistance thermometer. In chemical plants both methods were applied because they are easy to fit and to maintain.The accuracy of the measurement is influenced by, for example, radiation, which must be taken into account. Thermocouples can be inserted into the pressure system using special sealing techniques, or they may be mounted within a protective tube which is introduced into the pressurized volume. Thermocouple-wires are usually protected with an isulating input in closed-end capillaries with outer diameters of at least 0.5 mm. Thermocouples are technically well tested for pressures up to 6 kbar and temperatures to approx. 800°C. Above these ranges the exact measurement is negatively influenced by several parameters, and the deviations must be taken into account. The accuracy of the temperature measurement devices is normally better than 1 °C. 

The temperature measurement devices which do not contact the hot surfaces, for example, optical -, radiation pyrometers, and infrared techniques, are not typical for high-pressure application. 

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