Liquid, Steam and Gas - Flow Coefficients Cv
Calculate flow coefficients (Cv) for liquids, saturated steam, superheated steam, wet steam, and gases. The flow coefficient expresses the flow capacity in GPM that a valve will pass for a pressure drop of 1 psi.
| Fluid Type | Formula | Cv Result | Notes |
|---|---|---|---|
| Liquid (Volume - Imperial) | Cv = q √(SG / dp) | =(inputs.liquid_flow_gpm * SQRT(inputs.liquid_sg / inputs.liquid_dp_psi)) | q in GPM, SG relative to water, dp in psi |
| Liquid (Volume - Metric) | Cv = 11.6 q √(SG / dp) | =(11.6 * inputs.liquid_flow_m3hr * SQRT(inputs.liquid_sg / inputs.liquid_dp_kpa)) | q in m³/hr, SG relative to water, dp in kPa |
| Liquid (Weight - Imperial) | Cv = w / (500 √(dp SG)) | =(inputs.liquid_flow_lbhr / (500 * SQRT(inputs.liquid_dp_psia * inputs.liquid_sg))) | w in lb/hr, SG relative to water, dp in psia |
| Liquid (Weight - Metric) | Cv = 5.8 w / (500 √(dp SG)) | =(5.8 * inputs.liquid_flow_kghr / (500 * SQRT(inputs.liquid_dp_kpa * inputs.liquid_sg))) | w in kg/hr, SG relative to water, dp in kPa |
| Saturated Steam (Critical) | Cv = m / (1.61 pi) | =(inputs.steam_flow_lbhr / (1.61 * inputs.steam_pi_psia)) | m in lb/hr, pi inlet absolute pressure in psia |
| Saturated Steam (Critical - Metric) | Kv = m / (12 pi) | =(inputs.steam_flow_kghr / (12 * inputs.steam_pi_bara)) | m in kg/hr, pi inlet absolute pressure in bara |
| Saturated Steam (Non-Critical) | Cv = m / (2.1 √((pi + po) dp)) | =(inputs.steam_flow_lbhr / (2.1 * SQRT((inputs.steam_pi_psia + inputs.steam_po_psia) * inputs.steam_dp_psi))) | m in lb/hr, pi and po absolute pressures, dp = pi - po |
| Superheated Steam | Cv = Cv_saturated (1 + 0.00065 dt) | =(inputs.steam_cv_saturated * (1 + 0.00065 * inputs.steam_dt_degf)) | dt = temperature above saturation in °F |
| Wet Saturated Steam | Cv = Cv_saturated √ζ | =(inputs.steam_cv_saturated * SQRT(inputs.steam_dryness_fraction)) | ζ = dryness fraction (0 to 1) |
| Gas (Critical Pressure Drop) | Cv = q √(SG (T + 460)) / (FL 834 pi) | =(inputs.gas_flow_cfh * SQRT(inputs.gas_sg * (inputs.gas_temp_degf + 460)) / (inputs.gas_fl * 834 * inputs.gas_pi_psia)) | q in CFH, SG relative to air, T in °F, FL pressure recovery factor |
| Gas (Non-Critical Pressure Drop) | Cv = q √(SG (T + 460)) / (1360 √(dp po)) | =(inputs.gas_flow_cfh * SQRT(inputs.gas_sg * (inputs.gas_temp_degf + 460)) / (1360 * SQRT(inputs.gas_dp_psi * inputs.gas_po_psia))) | q in CFH, SG relative to air, T in °F, dp and po in psia |