Measuring the temperature of a flowing stream can be accomplished using various temperature measurement devices and techniques. One common method involves using a temperature sensor installed within a thermowell, which is then inserted into the flowing stream. Here's how it works:

1. Thermowell Installation: A thermowell is a hollow tube typically made of metal (such as stainless steel) or ceramic material, designed to protect a temperature sensor from the harsh conditions of the process fluid. The thermowell is inserted into the flowing stream, allowing the process fluid to flow around it.

2. Temperature Sensor Placement: A temperature sensor, such as a resistance temperature detector (RTD) or a thermocouple, is installed inside the thermowell. The sensor is positioned in such a way that it is in direct contact with the flowing process fluid, allowing it to accurately measure the temperature of the stream.

3. Sensor Wiring: The temperature sensor is connected to a temperature transmitter or temperature monitoring system using wiring that runs through the thermowell. This allows the temperature measurement to be transmitted to a remote location for monitoring and control purposes.

4. Calibration and Verification: Before putting the temperature measurement system into service, it is essential to calibrate the temperature sensor and verify its accuracy against a known reference. Calibration ensures that the temperature measurement is accurate and reliable over the operating range of the system.

5. Monitoring and Control: Once the temperature measurement system is installed and calibrated, it can be used to monitor the temperature of the flowing stream continuously. This temperature data can be used for various purposes, such as process control, safety monitoring, and quality assurance.

Thermowells are essential components in temperature measurement systems for flowing streams because they provide protection to the temperature sensor from the process fluid, which may be corrosive, abrasive, or at high pressure. Thermowells also allow for easy installation and removal of temperature sensors for maintenance or replacement without interrupting the flow of the process fluid.

In summary, measuring the temperature of a flowing stream involves installing a temperature sensor inside a thermowell, which is then inserted into the stream. This setup provides accurate and reliable temperature measurements while protecting the sensor from the harsh conditions of the process fluid.