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Pressure and Flow Measurement

Pressure and Flow Measurement

Pressure and Flow Measurement

I have a system which conveys powder in an air stream. The air is conveyed by a fan in the middle of the system
The system goes through a number of unit stages and pipework.

I need to develop a number of system curve and understand the pressure profiles and velocity through the system on different powders and at different flowrates.

The system currently has no measurements at all.

What is the best way of measuring pressure throuh the system and then how do I calculate the associated velocity. I am comfortable to do the pressure drop calcs for the pipes, but have no real data to establish pressure drop accross cyclones and filter bags etc. The cheaper solution, the better

I have heard of pitot tubes but not too sure if this would be applicable and how they work and what calcs I would need to do.

Any suggestions?

RE: Pressure and Flow Measurement

You need to get the static pressure at the fan inlet and outlet. From this you can deduce the flow if you know the fan speed and have the fan table from the fan manufacturer.
It is important however that you have straight piping at the inlet and outlet of the fan. Otherwise you may not get an accurate number for your flow.

Measuring static pressure is a matter of drilling a 1/8" hole into the pipe and placing the end of a 1/4" flexible hose over the hole and pressing it against the pipe/duct such that the hose end is sealed up tight to the wall of the pipe/duct. The other end of the hose is connected to a gauge or manometer which can read pressure in inches of water.

Add the static pressure you measure at the inlet to the pressure you measure at the outlet, ignoring whether the pressures you measured are positive or negative. This number is your fan static pressure.

Armed with the fan static pressure and the fan speed which you can measure with a tachometer, you can now enter the fan table to determine the volume of air that is being moved.

I am assuming standard air density for this process. If the temperature or humidity is elevated or your altitude is significantly above sea level you will have to do some additional calculations.

Good luck.

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