Questions about using differential pressure flow meters to measure gas flow rates
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The gas flow rate is the value under standard conditions, that is, at 0°C and 1 standard atmosphere. Please let me know if this understanding is correct. 1. The density used in calculations is the density corresponding to the design temperature and design pressure, that is, the operating condition density ； 2. The flow rate is the flow rate at standard conditions ； 3. Temperature and pressure correction involves adjusting the values to those corresponding to the operating conditions (design values), thereby ensuring that the density matches the operating conditions.
I’d like to share my personal opinion as well. In my view, a differential pressure flow meter measures volumetric flow rate; the value output by the differential pressure transmitter represents the volumetric flow rate under actual operating conditions. If you want the displayed value to correspond to standard conditions, it is necessary to use a correction device or apply software corrections within the DCS in order to convert it into a flow rate under standard conditions
The standard conditions commonly referred to are 0 degrees Celsius and 1 atmosphere of pressure; some companies use 20 degrees Celsius and 1 atmosphere of pressure in their calculations, which represents a slight difference.
A differential pressure flow meter measures the pressure difference before and after the measuring orifice; there is a quadratic relationship between this pressure difference and the flow rate, and the differential pressure value in the PLC program needs to be squared.