Types of Flow Meters

A volumetric flowmeter with pressure and temperature sensors added can calculate the mass flow. We use vortex flowmeters with pressure and temperature sensing to convert our steam volumetric flow (liters/hr) to mass flow (kg/hr).

You can also use an orifice type differential pressure flowmeter if you don't have or want a vortex flowmeter.

regards,

Vulcan

Thank you for your answer sir, since density of liquid varies with respect to temperature, we use temperature sensor in volumetric flow meter. For what we should use pressure sensor?. Thankyou in advance. What is the calculation , to convert volumetric flow to mass flow, with temp and pressure as variables along with volumetric flow?

For what we should use pressure sensor?. Thankyou in advance. What is the calculation, to convert volumetric flow to mass flow, with temp and pressure as variables along with volumetric flow?

For the answers to your questions, please read craigza's post #4 below.

regards,

Vulcan

Thermal mass flowmeter

Regrads

Jose

Hi there,

There are many mass flow meters on the market.

Radiation type, Angular Momentum type, Impeller-turbine type, twin turbine type gyroscopic type, thermal type, etc etc etc.

For mass flow W

W=Q*Rho

where Q is volumetric flow rate and Rho is density

If you are measuring a liquid flow, then you add a densitometer to the line and you have Rho. Then apply W = Q*Rho

If you are measuring gas flow, then you need temperature and pressure compensation to get the density of the gas.

So you will have:

Rho(g) = (Mwg*Pg)/(10.73*Tg*Zg)

Where Rho(g) = gas density

Mwg = Gas molecular weight

Pg = Gas pressure

Tg = Gas temperature

Zg = Gas compressability Factor

To get Zg

Zg = (P*SG)/(Rho*T*Rair)

Where

Zg = compressability factor

P = operation pressure

SG = specific gravity

Rho = flowing density

T = absolute temperature

Rair = gas constant for air

After this apply W = Q*Rho.

Regards,

Craig

Depending on the fluid you are using, there is a high variety of them. In the case of water the top four are:

Mechanical flow meters

The most popular and cheapest, this meter measures the speed of water running through a pipe with a rotating turbine or piston in it, usually in a propeller, shunt, or paddle wheel design. The volumetric flow rate of the water is proportional to the speed of the rotating blades. Sadly, these meters can clog in dirty or chunky water, which increases maintenance costs. They also don’t work well with low flow.

Vortex flow meters

Vortices are the “swirls” that form as a fluid moves past an object, like river water around a rock or air currents across a wing. In a vortex meter, a sensor tab flexes from side to side as each vortex flows past, producing a frequency directly proportional to the volumetric flow rate. Multivariable vortex meters measure up to five process variables with one connection: volumetric flow rate, mass flow, density, pressure, and temperature. Insertion vortex meters work well on very large pipes since you can insert them by hot tapping with a retractor.

Ultrasonic flow meters

These meters use ultrasound to measure flow. A transit-time ultrasonic meter sends one signal downstream and another upstream. Then the meter compares the travel time for both signals to find the flow velocity. Finally, it uses this calculation to find the volumetric flow rate.

You can also measure energy and temperature using the differences between the hot and cold legs. Clamp-on ultrasonic meters measure water from outside the pipe by sending signals through the pipe walls. This feature makes them ideal for measuring flow in large pipes and a wide range of other processes.

Magnetic flow meters

Last but not least, magnetic meters use a magnetic field and Faraday’s law of induction to measure flow. Liquid flowing through a magnetic field creates a charge. So when the fluid flows faster, it creates more voltage, proportional to the movement of the water. The meter then processes the voltage into the flow rate. Magnetic flow meters don’t have great accuracy, so you can’t use them for custody transfer. They also don’t work on pure water because it has no ions to measure.