BTU Meters

[russmech]

Can anyone give me a quick summary of their experience with BTU meters? Is a turbine flow meter better than electromagnetic or vice versa? Which is more reliable? Which is more accurate?

My application will be heating loops only with propylene or ethylene glycol.

Thanks.

 

[jsummerfield]

You are confusing me just a bit. I have experience with BTU or heating value meters in fuel gas. If you are using PG or EG as hot-oil you can use differential temperature for a linear representation of the heating duty. Turbine meters are not well known for use in hot services. A magnetic meter works with conductive fluids. I doubt that either is well suited for ethylene or propylene glycol in a heat transfer application. Do you want to measure flow, btu or what?

John

 

[russmech]

I want to measure the BTU transfer of a pumped glycol solution in the range of 170F to 180F with a delta T of approximately 20 degrees.

 

[btrueblood]

In our experience as a manufacturer of HVAC water/glycol valves, turbine and similar (rotating element) meters will tend to jam/bind over time due to buildup of debris on the magnetic pickups. Electromag meters are much more robust and have better turndown and accuracy. You can also get good results with an orifice meter, and it too will be much more reliable than the turbine meter.

Or, you could buy one of my company's pressure-independent valves, and know the flow within +/-5% from the actuator feedback signal.

 

[russmech]

Thanks for the replies. What about ultrasonic meters? How would they rate against the electromagnetic meters?

Which ones are more reliable (installations are very remote locations); maintenance or the lack of it is an important issue.

And how do they rate for expense; I'm guessing turbine meters would be the least expensive, but what about the other technologies out there?

The customer needs to be able to bill from this meter, so accuracy is important; I don't think +/- 5% would be acceptable.

Thanks again to everyone who replies; plague on you who know and don't.

 

[quark]

Building your own BTU meter is rather cheap and if you already have any control system things become much easier. In the past I did it with magmeters(for chilled water) and the accuracy is as good as 1%. I have no experience with Ultrasonics but I read that they will operate with a better turndown ratio. If variation in BTUs is mainly due to temperature difference and with a nearly constant flowrate, you can go for cheaper meters. I used smart transmitters for flow and temperature as well and it was handy for me to trap the data.

Regards,