Mass Flow Meter

What is a Mass Flow Meter? Different Types of Mass Flow Meters

A wide range of flow measurement instruments are available, each tailored to a certain flow type or set of flows. The functions of a flow meter vary depending on the model. There is a suitable flow meter for any application that requires measuring fluid flow or material throughput.

Numerous flow meters are available, making selecting the best one for your company’s needs challenging. Learning more about ICS’s many mass flow meter devices will allow you to pick the one that best suits your needs.

What is a Mass Flow Meter?

Mass flow meters estimate the mass flow rate of fluids traveling via pipes. When comparing mass flow rate to volumetric flow rate, the latter measures volume per unit of time while the former measures mass per unit of time.

Industrial recipe development, material balance calculations, billing, and custody changes all rely on mass flow measurements. Since mass flow rates are typically the most significant flow measurements in a processing plant, their precision and dependability are paramount. 

How Does a Mass Flow Meter Work?

Both inertial and thermal flow technologies can be used to detect mass flow. To determine the mass flow rate, inertia meters using the Coriolis Effect can be used. When mechanically introducing apparent rotation into a pipe, the Coriolis force accelerates the fluid, creating a deflecting force proportional to the fluid’s mass flow rate.

Thermal mass flow meters use a heating element and temperature sensors to calculate the mass flow rate of a fluid or gas according to heat transfer laws.

Mass Flow Meter Principles

Thermal mass flow meter are frequently used for regulating low-flow gas. They work by either adding a given amount of heat to the running stream and measuring the consequent temperature change or maintaining a constant probe and measuring the energy required. A thermal mass flow meter working principle consists of two temperature sensors separated by an electric heater. The heater can be set up either inside the pipe or externally, projecting into the fluid flow.

The amount of energy needed to keep a temperature differential constant is directly related to the mass flow rate. The measured temperature differential (T1 – T2),  the electric heat rate (q), the meter coefficient (k), and the specific heat of the fluid (Cp) are used to get the mass flow (m).

The equation is as follows:

M = Kq (Cp(T1 – T2))

Types Mass Flowmeters

Mass flowmeters are instruments used to determine fluid volume entering a system. When the specific chemical makeup of a product’s ingredients needs to be monitored to maintain quality, a mass flowmeter comes in handy.

The various mass flowmeters are as follows:

Coriolis Mass Flow Meters

In this model, powerful electromagnets were used to cause an oscillation in antiphase between two parallel measurement tubes that contained fluid in motion. The Coriolis forces created in the measurement tubes cause a change in the phase of the oscillations.

When there is no current, the tubes remain stationary.

  •         The mass flow slows the oscillation as it enters the pipelines
  •         speeds it up as it leaves the pipes
  •         As the mass flow rate rises, so does the phase difference (A-B).

Thermal Mass Flow Meters

The mass flow rate of a gas can be determined with the help of a thermal mass flow meter, which operates on the concept of convective heat transfer. A pair of temperature sensors separated by an electric heater make up the fundamentals of a thermal mass flow meter. The heater can be installed either inside the pipe or outside, protruding into the fluid flow.

Historically, the mass flow was calculated by combining the results of a volumetric flow meter and a densitometer. The density was determined using direct measurements and computations based on data from process temperature and pressure transducers.

These mass flow measurements were inaccurate because the relationship between process temperature, pressure, and density was not always precisely known. After all, each sensor contributed to the overall measurement error because the speed of response of such calculations was typically insufficient to detect step changes in flow. 

Impeller-Turbine Mass Flow Meters

This device has two moving parts: an impeller and a turbine. The fluid flowing through the meter is given an angular velocity by an impeller operated by a synchronous motor at a constant speed via a magnetic coupling.

Turbines placed downstream of impellers receive a torque proportionate to the angular momentum of the fluid they are removing. This turbine’s mass flow is represented by the angle of its spring deflection, which is proportional to the torque applied by the fluid.

Dual-Turbine Flow Indicator

Both turbines of this device share a single shaft. Within the twin-turbine assembly, a reluctance-type transducer is installed above each turbine, and a powerful magnet is housed within each turbine.

Due to the fact that each turbine has a unique blade angle, they often rotate at different angular speeds. The function mass flow describes how the two turbines rotate at different velocities when the flow occurs.

Gyroscopic Mass Flow Meter

A circular or square tube is what it is made of. A motor produces a periodic vibration along axis A, with angular velocity held constant.

The displacement of the sensor element can be used to determine the magnitude of the moment of precession that occurs along the B axis as the fluid moves through the loop. It has been demonstrated that the magnitude of this divergence is related to the mass transfer rate.

Typical Uses for a Mass Flow Meter

Recipe development, material balance calculations, and billing/custody transfer activities are examples of mass flow meters used to monitor or regulate mass-related processes (such as chemical reactions) that rely on the relative masses of unreacted constituents. The dependability and precision of mass flow measurements are crucial since these are a processing facility’s most significant flow measurements.

Coriolis mass flow meters can measure corrosive and clean gases and liquids, making them useful in various industries and laboratories. They offer highly precise mass flow, density, temperature, and viscosity measurements. Chemical reactions, which are sensitive to the relative masses of their unreacted constituents, are a common example of mass-related processes that thermal mass flow meter for liquids are used to monitor and regulate.

Thermal mass flow meters are frequently utilized for various applications involving gas flow. Some of these applications include measuring combustion air in large boilers, measuring semiconductor process gas in the petrochemical industries, researching and developing applications, and testing filters and leaks. Pressure and/or temperature changes do not affect mass flow detection for compressible vapors and gases. Measuring very low gas flow rates or very low gas velocities (below 25 feet per minute) is a specialty of thermal mass flow meters. When used in constant-temperature-difference mode, thermal flow meters have a wide usable range (from 10:1 to 100:1).

However, accuracy and dynamic range degrade with steady heat input because of the difficulty in detecting minute temperature changes. The typical error in full-scale measurements is 1-2% at typical flows.

Comparing Mass Flow and Volume Flow

The two most common methods for gauging the flow rate in a system are mass flow measurement and volume flow measurement. Although the two ideas are linked, there are important distinctions between them. The rate of mass transfer through a system, in grams per second, is the primary metric used in mass flow measurement.

Volume flow is measured in units of space occupied by the mass per unit of time, often liters per second. Both are used to determine how fast something is moving through a system, therefore they share that characteristic. In addition, both measurements are often utilized in conjunction with others to gain a more complete picture of the system.

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