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Thermoanalytical Instrumentation and Applications
Published in Grinberg Nelu, Rodriguez Sonia, Ewing’s Analytical Instrumentation Handbook, Fourth Edition, 2019
Kenneth S. Alexander, Alan T. Riga, Peter J. Haines
Temperature measurement is most commonly accomplished by use of thermocouples. Chromel/alumel thermocouples can be used up to 1100°C, whereas platinum metal alloys can be used up to 1750°C. Beyond this temperature, tungsten/rhenium thermocouples can be used. One must consider the possibility of the thermocouple reacting with the sample, reactant, or decomposition products. The highest signal output is achieved using a base/metal thermocouple with the additional advantage that the chromel/alumel thermocouples’ response to temperature is approximately linear. The platinum/platinum alloy thermocouples have lower sensitivities, and in the higher temperature ranges a nonlinear response. Another temperature sensor that is sometimes employed is the resistance thermometer. The resistance of the furnace winding can be used if it has a high temperature coefficient. Optical and radiation pyrometers are rarely used to measure sample temperature (Terry, 1965).
General Information About Electrical Heating Elements
Published in Thor Hesborn, Integrating Electrical Heating Elements in Appliance Design, 2017
If the average wire temperature of an element is to be found, accurate measurement of the resistance in the hot and cold state and subsequent calculation of the temperature factor may give a good guide. A condition is that the temperature factor of the resistance material is large. A more accurate result can often be achieved by making a special element that is identical to the original one, apart from the metal used for the wire or ribbon. Instead of one of the conventional resistance heating alloys, a metal or an alloy is applied that has a very high temperature coefficient of resistance. Nickel is one possible alternative. If the temperature is high, it may be better to use a more oxidation-resistant alloy like Alumel. Table 2.1 shows the properties of these and other possible metals and alloys for such a test. The voltage has to be altered so that the rating can be the same as for the original element. It may be necessary to find an accurate relationship between the resistance of the element and the temperature, by heating the element to different temperatures in an oven with controlled temperature.
The Measurement of Temperature
Published in John Bird, Newnes Engineering Science Pocket Book, 2012
A copper-constantan thermocouple can measure temperature from –250° Cup to about 400°C, and is used typically with boiler flue gases, food processing and with sub-zero temperature measurement. An iron-constantan thermocouple can measure temperature from –200°C to about 850°C, and is used typically in paper and pulp mills, re-heat and annealing furnaces and in chemical reactors. A chromel-alumel thermocouple can measure temperatures from –200°C to about 1100°C and is used typically with blast furnace gases, brick kilns and in glass manufacture. For the measurement of temperatures above 1100° C radiation pyrometers are normally used. However, thermocouples are available made of platinum-platinum/rhodium, capable of measuring temperatures up to 1400° C, or tungsten-molybdenum which can measure up to 2600°C.
Optimization studies on bio-oil yield using microwave-assisted pyrolysis of bio-sludge
Published in Biofuels, 2022
Meena Chandrasekaran, K. Chithra
The bio-sludge was subjected to microwave-assisted pyrolysis (MAP) process in a domestic microwave oven having different frequency levels. The experimental setup was assembled with a domestic microwave oven, a specially designed quartz reactor, a specially designed thermocouple for microwave application, a nitrogen flowmeter, a nitrogen cylinder, condensers, a bio-oil collector, and an ice bath. The quartz reactor was designed with two ports, one to purge nitrogen and the other to collect the gas generated during the process. The temperature of the sludge mixer was monitored using the thermocouple which is inserted through the gas collection port. Chromel-alumel thermocouple was made specifically for this application. A schematic view of the experimental setup is shown in Figure 1.
Kinetics and mechanism of low-temperature aluminothermic reduction of manganese tantalate
Published in Canadian Metallurgical Quarterly, 2022
Alexander Klyushnikov, Roza Gulyaeva, Sofia Petrova, Lyudmila Udoeva
A sample of manganese tantalate was synthesised from a mixture of manganese oxide (II) (99 mass% MnO, particle size <0.1 mm) and laboratory-obtained tantalum oxide (V) (99.9 mass% β-Ta2O5). For the synthesis of the latter, tantalum powder sample (99.5 mass% Ta, 0.3 mass% O, 0.2 mass% N, particle size <0.1 mm) was placed onto the boat-shaped alundum crucible and kept for 4 h at 1100 °C in a muffle electric furnace with air access. The resulting product was air-cooled, ground in an agate mortar to a size of <0.1 mm, and reheated under similar conditions. The oxide samples taken in a given stoichiometric ratio were mixed, placed onto the boat-shaped alundum crucible and kept for 12 h at a temperature of 1200 °C in a tubular electric furnace; helium (99.995 vol.-% He) was continuously fed into the furnace working chamber, the gas flow rate was 10 cm3 min–1. The temperature was measured with a chromel-alumel thermocouple with an error of ± 10 °C. After a specified time, the resulting product was cooled in a furnace and ground in an agate mortar to a size <0.1 mm.
Effect of substitution of alkaline earth metal ion on the structural and dielectric properties of double perovskite
Published in Phase Transitions, 2020
Nirmal Rout, S. Behera, B. N. Parida, R. K. Parida, R. Padhee
An X-ray diffraction (XRD) pattern of the powder sample was recorded at room temperature using an X-ray powder diffractometer (PAN Analytical XPERT) with radiation (Å) in a wide range of Bragg’s angle (2θ) () at a scanning rate of 3deg./min. For dielectric and electrical measurements the sintered pellets were electroded with high-quality silver paste and dried for 4 h at . JEOL JSM SEM recorded the microstructures of the pellet specimens at room temperature. The dielectric (capacitance, dissipative factor), impedance, and inductance parameters of the sintered pellet were measured as a function of frequency (1 kHz–1 MHz) at different temperatures () using a computer-controlled phase-sensitive meter (PSM LCR 4NL, Model: 1735, UK) with a laboratory-designed and fabricated sample holder and furnace. A chromel–alumel thermocouple and a Rishab digital multimeter were used to record the temperatures. The polarization variation with applied electric field (hysteresis loop) of the material on the poled sample was obtained using a hysteresis loop tracer (M/S Marine India, New Delhi).