Ultrasonic thermometers

Ultrasonic Thermometers. These are usually designed to respond to the temperature dependence of sound speed. In special cases where only one particular temperature is of interest, such as the temperature of a phase change, or the recrystallization temperature of a substance, the temperature dependence of attenuation may be utilized, Ultrasonic thermometers have found applications in the range —80 to +250 C, where the so-called quartz thermometer offers resolution of 0,1 millidegree and linear superiority to platinum resistance thermometers. 

As was shown in Figure 3.159, cryogenic temperatures can be detected by integrated circuit diodes types K, T, and E thermocouples (TCs) class A and B resistance temperature detectors (RTDs) acoustic and ultrasonic thermometers germanium and carbon resistors and paramagnetic salts. As TCs and RTDs will be discussed in separate subsections, here the focus will be on the other sensors. 

Sonic and ultrasonic thermometers have a unique role for high-temperature applications that involve detection of the average temperature in harsh and abrasive process environments. These sensors operate on the basis of detecting the speed of sound, which is proportional to temperature (Figure 3.163). When the temperature is detected by the measurement of transit... 

Electrical effects. Electrical methods are convenient because an electrical signal can be easily processed. Resistance thermometers (including thermistors) and thermocouples are the most widely used. Other electrical methods include noise thermometers using the Johnson noise as a temperature indicator resonant-frequency thermometers, which rely on the temperature dependence of the resonant frequency of a medium, including nuclear quadrupole resonance thermometers, ultrasonic thermometers, and quartz thermometers and semiconductor-diode thermometers, where the relation between temperature and junction voltage at constant current is used. 

In a resonant-frequency thermometer, the resonance frequency of the medium serves as the temperature indicator. Included in this category are nuclear quadrupole resonance thermometers, quartz thermometers, and ultrasonic thermometers. These thermometers usually... 

Ultrasonic thermometers [87] measure the temperature based on sound velocity. They are mainly used for measurements at high temperatures (300 up to 2000 K). 

Armed with this knowledge a set of boundary conditions was proposed which offered more hope of success. Results using these from a new set of calculation showed that, althou the test objectives were achievable, uncertainties m shroud properties would necessitate on line control of the power driven to the bundle. This control is based on the temperature measurements inside the bun e with thermocouples and ultrasonic thermometers and, after failure of these components, on estimated temperatures deduced from the shroud temperatures. Hi humidities in the containment were shown to be difficult to achieve without extensive thermal hydraulic testing of the containment vessel so it was dedded to aim for a lower humidity in this... 

The sample holder system used contains six sample apertures. Five samples are maximally placed at the same time in this holder to keep one aperture free for the reference measurement, see Figure 4.9. This whole sample holder system is lifted into a special thermostat bath provided with a liquid nitrogen cooling coil. This cooling possibility extends the lower temperature limit of these measurements from 20°C to about -50°C. The bath is filled with a mixture of water/ethylene glycol (l/l) for measurements between -50°C and 80°C. Silicone oil (100 cS.) is used as medium for measurements between 0eC and 200°C. The sample temperature is measured by a platinum resistance thermometer, placed as close as possible to the sample in the ultrasonic beam. 

Ultrasonic irradiation of volatile organometallics (such as Fe(CO)s or Cr(CO)6) in a low volatility organic liquid produces intense sonoluminescence that corresponds to the known atomic emission lines of the metals, again analogous to flame emission. Hot-spot temperatures are sufficient not only to dissociate all the CO ligands fl om the metal complex, but also to produce excited state metal atoms. Figure 5 shows a typical MBSL spectrum from a metal carbonyl solution (Cr(CO)e in this example). Note the intense line emission from the metal atom excited states as well as bands from excited states of the diatomics, C2 and CH. This metal atom emission provides a useful spectroscopic thermometer, as described later. 

Upon completion, the product was purified by centrifugation (at 5000 rpm for 1 h) and washed with ethanol for three cycles to remove excess y-MPS. The vinylated MH was further modified by in situ copolymerization of styrene. Then, the vinylated MH, deionized water and sodium dodecyl sulfate (SDS) were all charged into the reaction vessel fitted with a mechanical stirrer and a thermometer and the condenser was used as a reactor. The reaction was carried out under nitrogen in a 40 kHz ultrasonic irradiation water-bath, with a stirring rate of 150 rpm. When the mixture was heated to 80 °C, a portion of potassium... 

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