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Temperature Measurements
Published in Douglas O. J. deSá, Instrumentation Fundamentals for Process Control, 2019
The calibration of radiation pyrometers enables them to measure radiation correctly when sighted on a blackbody. What, then, is a blackbody? A blackbody is a body, which, at all temperatures, absorbs all radiation falling on it without transmitting or reflecting any. When cold it would appear totally black, since it would absorb all light falling on it and reflect none. It is also found that a blackbody is a perfect radiator, and radiates more energy than any other body at the same temperature. How does one achieve a blackbody in practice? Having a large enclosure whose inner surfaces are not perfectly reflecting, i.e., only partially, and maintained at a uniform temperature does this. One of the surfaces of the enclosure has a small opening, and, provided that the opening is small enough, the interior of the enclosure appears perfectly black. If we consider a single ray of radiation falling on the opening, it passes through to the inside of the enclosure, where it is reflected by the “not perfectly reflecting” interior surfaces of the enclosure, so that it “bounces” from one side to another (losing energy with every bounce) so many times, that for all practical purposes, it is completely absorbed before it can reach the opening again. The only test of a blackbody is that there should be no temperature change in the body for radiations falling on it, which means that the emissive power must equal the absorptive power. The enclosure just described is used to calibrate radiation pyrometers by comparing the emissivity at a given temperature to that of the blackbody at the same temperature.
The measurement of temperature
Published in John Bird, Science and Mathematics for Engineering, 2019
A pyrometer is a device for measuring very high temperatures and uses the principle that all substances emit radiant energy when hot, the rate of emission depending on their temperature. The measurement of thermal radiation is therefore a convenient method of determining the temperature of hot sources and is particularly useful in industrial processes. There are two main types of pyrometer, namely the total radiation pyrometer and the optical pyrometer. Pyrometers are very convenient instruments since they can be used at a safe and comfortable distance from the hot source. Thus applications of pyrometers are found in measuring the temperature of molten metals, the interiors of furnaces or the interiors of volcanoes. Total radiation pyrometers can also be used in conjunction with devices which record and control temperature continuously.
The measurement of temperature
Published in John Bird, Carl Ross, Mechanical Engineering Principles, 2019
A pyrometer is a device for measuring very high temperatures and uses the principle that all substances emit radiant energy when hot, the rate of emission depending on their temperature. The measurement of thermal radiation is therefore a convenient method of determining the temperature of hot sources and is particularly useful in industrial processes. There are two main types of pyrometer, namely the total radiation pyrometer and the optical pyrometer.
Residual stresses and distortions in additive manufactured Inconel 718
Published in Materials and Manufacturing Processes, 2023
Chaitanya Gullipalli, Nikhil Thawari, Prayag Burad, T V K Gupta
A total of 5 laser displacement sensors (LDS, S1 - S5), and 5 non-contact type pyrometers (T1 - T5) are fixed on a fixture shown in Fig. 2. All the sensors are placed in such a way to capture the data at substrate bottom to monitor and record distortion and thermal history. One each of the LDS and pyrometer are placed at four corners of the substrate, and the fifth ones are placed at the center as per the schematic in Fig. 2. The LDS (LE250) with 10 mm range and ±1 μm accuracy, Banner (USA) is used. The pyrometers are of K-type, from Micro-Epsilon, with a measuring range of 0°C − 1030°C and accuracy ±1.5°C. The LDS and pyrometers data are acquired with NI DAQ 9025, NI DAQ 9213 (NI USA), respectively; and processed in LabVIEW software. The additional pyrometer installed to measure meltpool thermal history is from Micro-Epsilon having a range of 450°C − 2000°C and ±0.3% accuracy. The samples for microstructure and mechanical testing were cut from the cuboids deposited, using wire EDM. Samples were prepared as per ASTM-E8 standards, shown in Fig. 3, and tested on a universal testing machine. Hardness was measured using Vickers indentation technique, at a load of 200 g and dwell time of 15 s. Microstructure studies are carried on optical microscope, and scanning electron microscope (JEOL 6380A, W-SEM) with EDS. The samples are further subjected to XRD analysis to identify different phases.
Application of inverse heat conduction calculation method for fast-transient flow boiling heat transfer analysis
Published in Journal of Nuclear Science and Technology, 2022
Yong-Seok Choi, Jong-Kuk Park, Byong Guk Jeon, Dong Hoon Kam, Sang-Ki Moon
A high-speed infrared pyrometer (IGA 6/23 advanced, LUMASENSE Tech.) was adopted to measure the temporal surface temperature of the tube. The pyrometer has a measurable temperature range of 75 to 1,300°C and an applicable wavelength spectrum of 2 to 2.6 μm. Its minimum response time, t90, is 0.5 milliseconds. In this study, the response time was set to 1 millisecond to reduce the noise level in the measured data. Any noticeable measurement lag was not observed during the experiment with this response time. A matte black body paint (Rust-Oleum, Specialty High Heat) was sprayed on the tube surface to get a stable emissivity value of 0.95. The temperature measured by the pyrometer was checked using thermocouples attached on the tube surface. While varying the tube temperature slowly, the temperature difference between the pyrometer and the thermocouple was confirmed to be within ±3°C in the whole experimented ranges.
Two-color pyrometer-based method for measuring temperature profiles and attenuation coefficients in a coal power plant
Published in Combustion Science and Technology, 2018
Milentije Lukovic, Milos Vicic, Zoran Popovic, Ljubisa Zekovic, Becko Kasalica, Ivan Belca
In order to do the formal estimation of the measurement uncertainties and compare them with the other methods, we have assumed the following: The total uncertainty is the combination of the uncertainties in (i) calibration of two-color pyrometer, (ii) standard deviation of measurements, (iii) stability of system (boiler environment), (iv) errors due to the discretization and (v) errors due to the numerical iteration (Levenberg–Marquardt method). The estimation of uncertainties due to (i), (ii) and (iii) is standard and straightforward. The two-color pyrometer is calibrated by comparison method using the laboratory standard and black-body furnace (normal distribution). Stability of the system was measured by secondary two-color pyrometer installed near experimental setup. The uncertainty of this source was calculated from maximum difference of temperatures during measurements (rectangular distribution). The discretization and numerical calculation errors are not straightforward for derivation. We have performed a number of simulations in order to estimate the sensitivity of the results due to the segmentation and the iteration method. It was found that the maximum extended uncertainty of the method does not exceed 24°C. It is worth noting that the highest contribution to the overall uncertainty is due to (iii) (effective temperature in firebox measured by control pyrometer).