What is the Principle of Operation of Thermal Control Flow Meters?

Posted by Proteus Industries Inc. on May 21st, 2019

A flow meter that measures either the flow of a fluid flowing through a closed conduit like a pipe or a duct using the thermal properties of that fluid is known as a thermal control flow meters. While most of these are used to measure the gas flow, some of it is also used to measure the fluid flow. It is used in various industries with a broad variety of functions. It is essential to understand the working standards of a thermal control flow meters in order to decide if it will be suitable for your application. Below is a comprehensive principle of operation of it:

 The working principle of the thermal control flow meter is based on the King’s Law that suggests how the heated wire when dipped in a fluid flow determines at a point in the flow the mass velocity. It is based on the theory of conductive and convective heat transfer.

 Two sensors are supported either using in-line flow bodies or insertion style probes of the meter. These sensors are then interfaced with the fluid being measured. The popular of these sensors is the Resistance Temperature Detectors (RTD), consisting of tremendously sturdy winding that is clad in a protective sheath. Heat is introduced into the flow stream of the fluid. A large amount of heat is lost with the increase in the flow of the fluid and the amount of heat dissipation is measured by using one or both of these temperature sensors.

An integrated circuit heats up one of the sensors and it functions as the flow sensor, while the other sensor acts as the reference detector, and finds out the fluid temperature. A continuous overheat is maintained by the circuit between the flow and reference sensor. As fluid flows via the heated sensor, flowing fluid molecules transfer heat away from the sensor. This results in the cooling of the sensor and there is a considerable loss in energy.

The circuit balance is then disrupted, and the temperature difference between the heated Resistance Temperature Detector (RTD) and the reference sensor gets distorted. The energy lost in this process is restored in the circuit within a second by heating the flow sensor to regulate the overheat temperature. The electrical power required to maintain this overheat represents the mass flow signal.

Thermal properties of the fluid and the flow meter design are the factors that decide the amount of total heat loss during the process. The fluid’s thermal properties can vary based on the difference in temperature and pressure, but these changes are relatively small in most of its applications. Fluids with steady thermal properties remain constant during the actual operations and Thermal Control Flow Meters can be used to measure the mass flow of the fluid.

Even though fluid’s thermal properties don’t have noteworthy effects on the measurement process, but somehow, fluid composition is responsible for the change in a degree of measurement. In such cases, a varying fluid composition during the real operations affect the measurement of the thermal flow. Thus, proper regulation factor should be used to define the flow rate.

If you are looking for the best thermal mass flow meter or Standalone Liquid Flow Meters, Proteus Industries Inc should be the preferred choice. They are pioneer in the industry and assure quality products to help your business perform better.