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The thermal conductivity detector (TCD), also known as a katharometer, is a bulk property detector and a chemical specific detector commonly used in gas chromatography. [1] This detector senses changes in the thermal conductivity of the column eluent and compares it to a reference flow of carrier gas. Since most compounds have a thermal ...
The heat generated dissipates into the sample on both sides of the sensor, at a rate depending on the thermal transport properties of the material. By recording temperature vs. time response in the sensor, the thermal conductivity, thermal diffusivity and specific heat capacity of the material can be calculated.
Pirani was aware of the gas thermal conductivity investigations of Kundt and Warburg [4] (1875) published thirty years earlier and the work of Marian Smoluchowski [5] (1898). In 1906 he described his "directly indicating vacuum gauge" that used a heated wire to measure vacuum by monitoring the heat transfer from the wire by the vacuum environment.
The transient hot wire method has advantage over the other thermal conductivity methods, since there is a fully developed theory and there is no calibration or single-point calibration. Furthermore, because of the very small measuring time (1 s) there is no convection present in the measurements and only the thermal conductivity of the fluid is ...
The thermocouple temperature is limited also by other materials used. For example beryllium oxide, a popular material for high temperature applications, tends to gain conductivity with temperature; a particular configuration of sensor had the insulation resistance dropping from a megaohm at 1000 K to 200 ohms at 2200 K. At high temperatures ...
The electron–phonon thermal conductance is strongly temperature-dependent, and hence the thermal conductance can be tuned by adjusting T c. [ 3 ] [ 4 ] Other devices use mechanical means of controlling the thermal conductance such as building the TES on a sub-micrometre membrane over a hole in the substrate or in the middle of a sparse ...
The thermal contact conductance coefficient, , is a property indicating the thermal conductivity, or ability to conduct heat, between two bodies in contact. The inverse of this property is termed thermal contact resistance .
More robust sensors for use in high risk environments may have solid steel housing with a gas port of sintered metal granules. [2] Both of these work in a manner similar to the Davy safety lamp; gas may percolate through the permeable mesh, but the passages are too long and narrow to support the propagation of a flame.
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