In the world of fluid dynamics and process control, selecting the appropriate flow measurement parameter is crucial for accurate and reliable data. Teledyne Hastings’s uses heat transfer technology to indirectly measure the molecular flow rate of dry gases. Our instruments can be used with volumetric flow units as they are converted to find the mass flow rate.

What is the Thermal Mass Flow Meter Working Principle?

Basic Design:

A mass flow meter consists of four basic components:

1. Electronic Circuit Board
2. Flow Sensor
3. Bypass Shunt
4. Base

*See Figure on right

In the world of fluid dynamics and process control, selecting the appropriate flow measurement parameter is crucial for accurate and reliable data. Teledyne Hastings’s uses heat transfer technology to indirectly measure the molecular flow rate of dry gases. Our instruments can be used with volumetric flow units as they are converted to find the mass flow rate.

There are numerous thermal mass flow sensor designs.  The Teledyne Hastings’ 200 Series sensor is shown in image on left.  This thermal mass flow sensor consists of a small 316SS capillary tube with a heater winding located in the center.  A thermocouple (TC-1) is located on the inlet side and another thermocouple (TC-2) is located on the outlet side.  At zero flow (no gas flow), the heat is transferred through the capillary tube in both directions towards the two thermocouples, each of which has the same temperature (see image on right, ZERO FLOW condition).  As gas flow moves through the capillary tube (inlet to outlet), heat is then transferred downstream by the gas molecules.  The temperature of TC-2 will increase, while the temperature of TC-1 will decrease.  This temperature differential correlates to the molecular flow rate of the gases (mass flow). 

Output:

A majority of thermal mass flow meters provide an analog output signal (0-5vdc, 4-20mA, etc.) that is directly proportional to the gas flow rate.  System integrators can directly acquire this signal for process control.  

If the installation is not configured for data acquisition, Teledyne Hastings offers convenient power supplies with integrated displays (see models THCD-101 and THCD-401 in image on right) and ready-to-use connector cables for quick start-up.

Some mass flow meters offer digital communication to convey the flow rate, while other models have a built-in color touchscreen display (See model HFC-D-302B Vue in image on left).​

Thermal Mass Flow Meter Advantages

Thermal mass flow meters have gained widespread popularity in various industries due to their numerous advantages in measuring the flow of gases. Let's explore some of the key advantages of thermal mass flow meters:

One of the primary advantages of thermal mass flow meters is their ability to directly measure mass flow rate. Unlike other flow measurement methods that may require additional measurements or assumptions about fluid properties, thermal mass flow meters provide a direct and accurate measurement of gas flow.

Thermal mass flow meters are less affected by variations in pressure and temperature compared to some other flow measurement technologies. This robustness allows for accurate measurements even in environments where these conditions may fluctuate, reducing the need for extensive compensation or correction factors.

Thermal mass flow meters can be used across a broad range of gas flow applications. They are suitable for measuring the flow of various gases, including compressed air, natural gas, and specialty gases. This versatility makes them valuable in industries such as pharmaceuticals, petrochemicals, automotive, aerospace, and more.

Thermal mass flow meters typically have a low-pressure drop across the sensor, minimizing the impact on the system being measured.

As technology continues to advance, these instruments are likely to play an increasingly integral role in optimizing processes and improving overall efficiency.