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Critical (Choked) Pressure Drop. With choked flow and critical pressure drop, the outlet pressure - p o - after the control valve is aprox. 58% of the inlet pressure - p i - before the control valve. The flow coefficient at choked - or critical - flow can be expressed as: C v = m / (1.61 p i) (2) where. m = steam flow (lb/hr)
The adjusted Cv (or Kv) value should be based on the Cv or Kv formula for sub critical gas pressure drop. A simplified version of the Cv formula for sub critical gas pressure drop is shown below: Where: Cv = flow coefficient. SCFH = flow rate in ft 3 /hr (NTP) D n = the gas density in lbs/ft 3 at 0.00 psig. o F = gas temperature
Based on M = 0.96, the critical pressure coefficient was found to be −0.0697. A pressure coefficient below this critical pressure coefficient constitutes the supercritical region or the region of supersonic flow on the surface of the wing.
The flow coefficient of a device is a relative measure of its efficiency at allowing fluid flow. It describes the relationship between the pressure drop across an orifice valve or other assembly and the corresponding flow rate.
Flow for a given Cv is typically calculated from the following formula. Q = Cv x ΔP x 62.4. D. Where: = Valve flow rate in gallons per minute (US GPM) ΔP = Difference between upstream and downstream pressure in pounds per square inch (PSI) 62.4 = Conversion factor for fluids computed in relation to water.
28 sie 2024 · Cv calculation formula. Before exploring how to calculate C v for a valve, let's explain the variables that we will need for the C v flow formula: Specific gravity. SG SG (also known as relative density) measures the density of a liquid compared to the density of water at 4 °C, or 39.2 °F.
Flow Calculation for Gases. The coefficient of flow (Cv) is a formula which is used to determine a valve’s flows under various conditions and to select the correct valve for a flow application. The Cv was designed for use with liquid flows, it expresses the flow in gallons per minute of 60o F water with a pressure drop across the valve of 1 psi.
