Related Resources: Fluids Engineering
Thermo-Kinetics Thermowell Excel Calculator Spreadsheet
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Thermo-Kinetics Thermowell Calculation Program Excel Calculator Spreadsheet
These calculations are performed according to the paper "Power Test Code Thermometer Wells" by J. W. Murdock, and also meet the requirements of ASME PTC 19.3-1998. The program supplies results which should only be used as a guide for thermowell design.
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Thermowells are principally used with Thermocouples, RTDs (Resistance Temperature Detectors) and Bimetal Thermometers in applications where it is necessary to measure temperature at high pressure (above 75 psig) or in hostile environments. They are also used for isolation, so a sensor can be replaced without having to shut down the process. Thermowells safe working pressures depend on the well material, operating temperature and the velocity of the flowing medium.
Response to vortex shedding
Vortex shedding is a common phenomenon, frequently visible in wind driven motion of power cables or telephone wires, or the rippling motion of flags, but it also occurs in heat exchanger tube banks and thermowell applications. It was first described by von Karman as a flow induced sound emitted from wires stretched across a duct. Later, Strouhal developed the relationship between the frequency of vortex formation and fluid velocity. Basically these vortices are characterized by flow rate dependent fluctuations in the pressure field surrounding the object. The pressure fluctuations are associated with the initiation and development of vortices that develop and roll-off in alternating fashion to form a series of vortices trailing behind the object.