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Nov
03

Advanced Temperature Measurement and Control Insight of the Day

To maximize the temperature difference between the thermowell tip and the pipe or equipment wall (minimize thermal conduction error), decrease the thermal conductivity, increase the length of the thermowell, and decrease the diameter of the thermowell (increase thermal resistance between tip and pipe or equipment wall). Swaged or tapered thermowells maximize this temperature difference and minimize the temperature difference between the tip and the process so that you measure the process and not the pipe or equipment wall temperature. These thermowells offer a faster response, lower pressure drop, and less possibility of vibration damage from resonance with wake frequencies. When installed in elbows, swaged or tapered thermowells also reduce the insertion length requirement and the pipe cross sectional temperature profile error from imperfect mixing and viscous flow. The difference in process fluid temperature at the pipe wall and the centerline is particularly large for polymers and jacketed pipes. Source