There's been a change in the thermowell calculation standard, performance test code (PTC) 19.3. After years of development, PTC 19.3 TW is the new standard.
The new standard—PTC 19.3 TW—features a number of enhancements:
• Inclusion of stem profiles
• More accurate natural frequency equations that reflect real-world effects resulting from installation
• Ideal (or theoretical) natural frequency is corrected for adding a sensor and the mounting style
• The Strouhal number—used to calculate the vortex shedding rate—was set at 0.22 in PTC 19.3 and now is calculated
• Perpendicular and in-line oscillation are considered