How To Choose a Mass Flow Meter For Your Application


How To Choose a Mass Flow Meter For Your Application

Image source - pixabay.com

Chemical and industrial processes varying from brewing to polymerization, rely on the transmission of exact quantities of gases or liquids. The delivery rates can be gauged by either volume per unit time or mass per unit time.

Picking between them relies upon the application. In many instances, volumetric flow measurement is enough, mainly if pressure and temperature are stable and known. But as mass flow measurement precisely specifies the number of molecules existing, it’s resistant to density variation.

The majority of engineers and experts know the different ways to calculate the volumetric flow. However, mass flow measurement is less understood and well-known. For a little help, this post will tackle the different mass flow meter types, their operating principles, factors affecting accuracy, and tips on how to choose one for your application. Read on!

Types Of Mass Flow Meter And Their Operating Principles

Below are the generally known mass flow meter types:

Coriolis Mass Flow Meter. This mass flow meter type calculates mass using inertia. A dense gas or liquid moves through a vessel. And through a small actuator, it gets vibrated. This acceleration generates a quantifiable twisting force on the pipe or vessel relative to the mass.

Without knowing the fluid traversing inside, the mass flow rate is specified. More advanced Coriolis mass flow meters use dual-curved tubes for lower pressure drop and higher sensitivity.

Thermal Mass Flow Meter. This mass flow meter type is available in two designs, which are inserted-probe and heated sample tubes. Both models measure mass from the fluid’s heat capacity. Thus, this particular property must be identified. 

Thermal meters are best for applications with low gas flow rates. In heated sample meters, all or some of the flow travels through a precision tube. When heat is subjected to the tube, the difference in temperature measured.

The temperature change amidst two points shows how much energy the liquid has taken in, which relies on the mass passing through the pipe. On the other hand, inserted probe meters employ the same idea.

However, with two resistance temperature detector (RTD) probes placed in the flow. The first sensor gauges the temperature of the fluid. The second sensor is heated to a higher temperature than the first RTD. Heat is then transported from the second RTD to the fluid at a specific rate relative to the mass flow rate.

Differential Pressure Flow Meter (DP). With this kind of mass flow meter, a disc or any obstruction with a hole of known diameter is placed into a laminar flow region. And on each side, fluid pressure is measured.

On the upstream side, the pressure will be higher, with the contrast in readings being relative to the pipe diameter, the span between two reading points, viscosity, and volumetric flow rate, as outlined in Poiseuille’s equation.

Factors Affecting Accuracy

Three factors are influencing the accuracy of the DP mass meter. First, pressure and temperature infer the measurement. Thus, any mishaps in these manifest in the final result. Second, the orifice might wear, getting bigger in the long run. Therefore, minimizing the pressure drop.

Third, there are suspicions about the point to which the laminar flow is attained and the viscosity. Also, relying upon the fluid flowing through, there’s a possibility of partial blockage.

Moreover, in thermal mass meters, it’s essential to think of the possible effect of the following:


  • Particulate accumulation
  • Error in particular heat capacity assumption
  • Moisture condensing on the temp detector


Additionally, thermal meters require ample time to achieve a stable operating temperature. As such, readings must not be obtained as soon as the flow meter is powered-up. When using Coriolis meters, although deemed as the most precise, are prone to errors developing bubbles in the liquid.

These bubbles splash inside the tube, producing noise and altering the energy required for tube vibration. Also, the liquid and gas separator creates a damping impact on tube vibration.

Applications

DP flow meters can be, for the most part, applied almost anywhere, particularly where the fluid has an unchanging temperature and consistent viscosity. This type of mass flow meter is helpful when a flow rate should be obtained once the meter is powered-up.

Thermal meters work well with gases and liquids. They can be used in filter and leak detection, chemical processing, and semiconductor process gas measurement. Furthermore, Coriolis meters can measure both clean and corrosive liquids and gases. They can be used in wastewater handling, chemical processing, petroleum and oil, and pulp and paper processing.

Takeaway

Mass flow meters are one of the generally known gas measurement technologies applied today. The primary advantage of this flow meter for gas streams is its capability to disregard changing and fluctuating pressures and temperatures. Moreover, the three common mass flow meters are Coriolis flow meters, Thermal flow meters, and DP Flow meters.

Author Bio
Sylvia Hopkins is a content writer and copywriter, specializing in sales pages, email marketing campaigns, and ghost blogging. She can be found developing, designing, and writing all kinds of great content. When not working, Slyvia dabbles in oil and charcoal paint.