Glass lined thermowell also called glass lined thermometer pocket is used in glass lined reactors or vessels as a protection cover for the RTD thermometer that is installed inside. Typically the thermometer pocket will be filled with heat-transfer oil so that temperature value inside vessel can be conducted to the thermometer sensor.
The glass lined thermometer pocket in a flat shape can be used as a baffle to help to reach a better agitating effect in a glass lined reactor. To obtain a precise temperature value, at the pocket bottom a tantulum tip can be installed.