Flowmeter Sizing
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All standard flowmeters are calibrated at Standard Temperature and Pressure ("STP" 68°F/ 20°C and 14.7 psia/ 1 ATM). When sizing a flowmeter that will operate at conditions other than "STP", it is important that the maximum flowrates of the fluid be converted to equivalent standard flowrates of air or water. To do this, calculate the equivalent flowrates of air or water at "STP" as shown below, then select the appropriate flowmeter for your application. |
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For Gases: Where: Qair = Equivalent air flow at STP Qgas = Maximum flow of gas G = Specific gravity of gas Tact = Absolute Temperature at flow conditions in deg. K or deg. R To = Absolute temperature at STP, in deg. K (294) or deg. R (530) Po = Pressure at flow conditions (psia) Pact = Pressure at STP (14.7 psia)
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For Liquids: Where: Qwater = Equivalent water flowrate at STP Qliq = Maximum flowrate of metered liquid df = Density of float selected (g/mL) dL = Density of meters liquid (g/mL) dw = Density of water at STP (1 g/mL)
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