A: Valtek (now Flowserve) started making a "smart valve" 20 years ago. The current generation of the system has embedded pressure and temperature sensors that allow it to internally calculate flow rates.
A: Flowserve's patented "StarPac-3" intelligent control valve is capable of flow measurement, PID control and diagnostic functionality. You may paste the following link into your browser to download literature for more information: www.flowserve.com/files/Files/Literature/ProductLiterature/FlowControl/Valtek/VLENBR0066.pdf.
A: I recently run across this very thing. It is a Singer Valve accessory (www.singervalve.com/Products/ElectronicControl/1062scmv2062scmv.html). I don't see any specifications on accuracy, though I suspect it is only as good as an orifice plate flowmeter.
A: I used temperature and pressure data at two different times to measure hydrogen leaks in a closed generator system in power plants. When there was no leak, the ratios of (P/T) should be the same at two different times, where both P and T are in absolute values, and the time duration is on the order of 10 hours. When there was a leak, the leak rate was calculated to be (V/R) [(P1/T1) – (P2/T2)] / (t2 – t1) in moles per hour, where (t2 – t1) is the elapsed time, since the volume, V, of the system is constant and the gas constant R, is also constant. For generators, hydrogen leaks are normal, so long as the expression [(P1/T1) – (P2/T2)] / (t2 – t1) is consistent after the casing is put back on each time.
Valtek StarPac control valve has a temperature and a pressure sensor in it, but has no flow sensor. Such a valve has been successfully applied in severe service applications for monitoring both the temperature and the pressure of the process fluid where conventional temperature and pressure tapping points failed.
Gerald Liu, P.Eng.