News

More common Coriolis mass flow meter product types?

Indirect
There are three main types of indirect mass flow meters: a combination of a speed flow meter and a densitometer, a combination of a throttle (or target) flow meter and a volumetric flow meter, and a throttle (or target) flow meter. Densitometer combination.
There is also a volumetric flow rate that is converted to a standard state based on the working pressure and temperature of the fluid. However, when the type or composition of the medium changes, it does not give an accurate mass flow. Strictly speaking, it is not a mass flow meter. Output density, specific gravity, volume flow, mass flow, mass energy flow, etc., with indication, analog output, printing, over-limit alarm, instrument fault alarm and many other functions.
Direct
There are many types of direct mass flow meters, such as calorimetric, angular momentum, gyro, and dual impellers. The meter is suitable for measuring small flow gas. The disadvantage is that the inertness is large, and the measured value is related to the constant pressure of the gas. The measuring element is in contact with the medium and is easily stained and corroded. It is a two-hole differential pressure mass flowmeter. Install two identical orifice plates at conduits A, B. Two equal flow pumps are provided in the split line that produce a constant volume flow q in the opposite direction. The pressure difference between the two orifice plates is ΔP=P1-P3=4KρQq, which is proportional to ρ and Q. Where K is the constant coefficient, ρ is the density, Q is the pipe volume flow, and ρQ is the mass flow. The double impeller mass flowmeter is equipped with two impellers with inclination angles x1 and x2 on the same straight line, and the two impellers are connected by a torsion spring. When the fluid passes, an offset angle x is generated between the two impellers, then two The inter-impeller torque difference ΔM is related to the mass flow rate Qm, the flow velocity u, the inclination angle x1, and the x2 is ΔM=Qm*u*(k1*tgx1-k2*tgx2) (k1 and k2 are the blade structure size constants), ΔM =k3*u*Qm,(k3=k1*tgx1-k2*tgx2). Offset angle x=k4*△M=k4*k3*Qm*u; and the impeller group rotation speed U is proportional to the flow velocity of the fluid, U=k6*u, the time required for the entire impeller group to rotate through the two impeller angles x Δt=x/U=k7*Qm. The mass flow rate Qm can be obtained by measuring Δt by a dedicated counter.
Hot
The basic principle of a thermal mass flow meter is to use an external heat source to heat the measured fluid in the pipeline. The thermal energy flows with the fluid and reflects the mass flow of the fluid by measuring the change in heat (temperature) caused by the fluid flow.
When the fluid composition is determined, the constant pressure specific heat of the fluid is a known constant. Therefore, it can be seen from the above equation that if the heating power is kept constant, the mass flow rate can be obtained by measuring the temperature difference; if the constant temperature difference method is used, that is, the temperature difference between the two points is kept constant, the mass flow rate can also be obtained by measuring the heating power. Since the constant temperature difference method is simple and easy to implement, it is practically used. This type of flow meter is often used for the measurement of large gas flows.
In order to avoid contamination and corrosion of the temperature measurement and heating elements due to direct contact with the fluid to be measured, a non-contact measurement method can be used, that is, the heater and the temperature measuring element are installed outside the thin-walled tube, and the fluid is made inside the thin-walled tube. by. Non-contact measurement method for small flow measurement of small diameter pipes. When used for large flow measurement, the shunt method can be used, that is, only the flow of the split flow is measured, and then the total flow is obtained to expand the range.
Coriolis force mass flowmeter is superior to general flowmeter products in measurement accuracy and stability. The whole industry of mass flowmeters is also making breakthroughs in continuous research and development of new products. It is believed that in the near future, the mass flow meter will have more and more product types and will be applied in more fields.

PREVIOUS：Principles and methods for the selection of mNEXT：Calibration points for mass flow meters - foc