Thermowell
Thermowells are used in industrial temperature measurement to provide isolation between a temperature sensor (often a thermocouple) and the environment whose temperature is to be measured.
They are intrusive fittings and are subject to static and dynamic fluid forces. These forces govern their design. Vortex shedding is the dominant concern as it is capable of forcing the thermowell into flow-induced resonance and consequent fatigue failure. The latter is particularly significant at high fluid velocities.
The ASME Performance Test Code (PTC 19.3) is the most widely used basis for thermowell design. It is currently being updated to cover a broader range of thermowell designs and fluid conditions.