For temperature measurement of a flowing stream which is flowing through a closed pipeline, we use Thermowells. Using Thermowells we need not disturb or shutting down the process to measure the temperature.
Thermowells are inbuilt setup in a pipeline where the temperature of the flowing liquid should be measured. A Thermowell setup is shown below
The above setup is fixed in the pipe walls, fluid flows surrounding the walls of the thermowell. A thermometer or temperature sensing is fixed inside the thermowell.
Heat gets transferred through the wall of the thermowell which is sensed by the thermometer inside the thermowell.
Heat in the surrounding fluid may take time to get transferred to the thermometer.
To reduce the time of transferring time space between the thermowell walls and the thermometer is filled with high heat conducting liquids.
Sometimes the probe is placed in a corrugated aluminium cover to give direct metal contact between the probe and the thermowell.
In case of any complaint in the probe, we can replace the probe alone. But new probe must be in the same size as the original.