Bell & Gossett Circuit Sensor Question

[jcrank]

Hi,

We have Bell & Gossett Circuit Sensor flow meters in our chiller plant on each of the secondary loops. The plan is to connect differential pressure transmitters connected to the BAS system to the flow sensors so we can monitor and trend the chilled water flow.

My question is what formula can I use to convert the differential pressure from the sensors to a flow rate in GPM?

The meters have metal tags on them with a chart that can be used to find the flow using the differential pressure in feet of head, but I need to be able to do this using a formula.

A little more information:
Bell & Gossett Circuit Sensor flow meters Link Documentation

We have
Four - MN: OP-8A
One - MN: OP-6A

Thanks,

[jcrank]

Any Ideas?

[crab master]

I have not worked with one of those, but many sensors have formulas the manufacturer gives, have you called B&G and asked them for help?
This might be better served if it was posted in the hydronics section.
http://hvac-talk.com/vbb/forumdisplay.php?f=41

[ctrlguy]

This is pretty basic stuff. I suggest you try this.

Here, I did it for you:

Qh = C' SQRT(Hw)

where

Qh = liquid flow in gpm
C' = orifice constant (Fb x Fgt x Fr)
Hw = differential pressure in inches of water
Fb = orifice factor. These are tabularized values, depending on the pipe diameter and orifice diameter. They are given in the GPSA, and probably also in Perry's.
Fgt = specific gravity temperature factor for bellows meters. Also a tabularized value
Fr = Reynolds number viscosity factor for liquids. Also a tabularized value.