Calculate compressible flow pipeline or vessel blow down time through a constant diameter vent for adiabatic and isothermal flow using either the integration method, or the simplified method.
The integration method uses numerical integration to calculate the elapsed time between the initial pressure, and the final blow down pressure. At high pressure the vent exit flow is critical (Mc = 1 for adiabatic flow and 1/√γ for isothermal flow). At lower pressures the vent exit flow is sub critical (M < Mc). The vent entry is subsonic at all conditions. Increase the number of steps to improve the accuracy. Use the minimum number of steps required (the method is reasonably accurate with 16 steps). Using a large number of steps may slow down the calculation, especially on older computers. The accuracy of the integration method decreases at pressure less than 1.1 x ambient pressure (ie 110 kPa or 16.2 psi for atmospheric pressure discharge). The blow down time tends to infinity as the final pressure approaches ambient pressure.
The simplified method calculates the blow down time from the initial pipeline gas moles, and the initial vent mole flow rate. The flow is assumed to be always critical, and the pipeline pressure is assumed to decrease exponentially. The simplified method is reasonably accurate for final pressure ≥ 2 x ambient pressure. At low pressures flow is sub critical and the simplified method underestimates the elapsed time relative to the integration method (both methods are less accurate at very low pressure). The simplified method is not recommended for final pressure less than 1.2 x ambient pressure. The blow down time tends to infinity as the final pressure approaches absolute zero.
Minor losses should include the vent entry valves and bends etc. The vent exit should not be included as the fluid dynamic pressure is included in the calculation. Minor losses can be accounted for by using the minor loss factor K, or the discharge coefficient Cd. The discharge coefficient is used to factor the mole flow rate. The gas in the pipeline is assumed to be stationary (stagnation conditions), ie the pipeline diameter >> the vent diameter. Phase changes are ignored. The Darcy friction factor is calculated from pipe roughness assuming fully turbulent flow.
| Links : ± |
CALCULATOR : Gas Speed Of Sound And Mach Number From Temperature [FREE] ±
Calculate the speed of sound and mach number for an ideal gas. The speed of sound is calculated from the gas temperature, specific heat ratio and gas specific gravity. Either the Mach number can be calculated from a user defined velocity, or the velocity can be calculated from a user defined Mach number. Tool Input- fluidtype : Fluid Type
- γu : User Defined Specific Heat Ratio
- SGu : User Defined Gas Specific Gravity
- zfactype : Compressibility Factor Type
- Zu : User Defined Compressibility Factor
- cctype : Speed Of Sound Type
- Cu : User Defined Sound Velocity
- machtype : Mach Number Type
- Vu : User Defined Fluid Velocity
- Mu : User Defined Mach Number
- T : Fluid Temperature
Tool Output- γ : Specific Heat Ratio
- C : Speed Of Sound
- M : Mach Number
- Rg : Specific Gas Constant
- SG : Gas Specific Gravity Relative To Air
- V : Fluid Velocity
- Z : Gas Compressibility Factor
- mmg : Gas Molar Mass
|
CALCULATOR : Compressible Flow Critical Pressure Relief Vent Flowrate [FREE] ±
Calculate gas vent flow rate and pressure drop for critical adiabatic and isothermal flow. The pipeline is assumed to be at stagnation conditions (M = 0), which is valid when the pipeline diameter is much greater than the vent diameter. The vent exit flow is assumed to be critical flow (Mc = 1 for adiabatic flow and Mc = √(1/γ) for isothermal flow). The vent entry is sub critical for all conditions. Check that the vent exit pressure is greater than or equal to ambient pressure. If the exit pressure is less than ambient pressure the flow is sub critical and the calculation is not valid. Pressure drop is calculated from the pressure loss factor (fld = fd L / D = K). The minor loss K factor should include the vent entry, valves and bends etc. The vent exit should not be included (the fluid dynamic pressure is included in the calculation). The discharge coefficient Cd can be used as a design or safety factor (API 520 recommends Cd = 0.9 for vents with a valve, or Cd = 0.62 for vents with a burst disk). The vent is assumed to be constant diameter. For isothermal flow the inlet temperature should be set equal to the estimated isothermal temperature (eg ambient temperature). The stagnation temperature is constant for adiabatic flow, and varies with Mach number for isothermal flow. Tool Input- flowtype : Flow Type
- Tou : User Defined Adiabatic Stagnation Temperature
- Tiu : User Defined Isothermal Vent Temperature
- Po : Stagnation Pressure
- γ : Specific Heat Ratio
- SG : Specific Gravity
- Z : Compressibility Factor
- Cd : Discharge Coefficient
- ID : Vent Inside Diameter
- fL/ID : Pressure Loss Factor
Tool Output- Me : Vent Exit Mach Number
- Mi : Vent Inlet Mach Number
- Pe : Vent Exit Pressure
- Pi : Vent Inlet Pressure
- Rg : Specific Gas Constant
- Te : Vent Exit Temperature
- Ti : Vent Inlet Temperature
- m : Vent Mass Flowrate
- n : Vent Mole Flow Rate
|
CALCULATOR : Compressible Flow Pipeline Blowdown Time [PLUS] ±
Calculate pipeline or pressure vessel blow down time through a constant diameter vent for either adiabatic flow or isothermal flow, and using either the integration method or the simplified method. The pipeline is assumed to be at stagnation conditions (M = 0), which is valid when the pipeline diameter is much greater than the vent diameter. The pipeline temperature is assumed constant. Select either the simplified method, or the number of steps for the integration method. For the integration method the vent exit flow is critical flow at high pressure (M = 1 for adiabatic flow and M = √(1/γ) for isothermal flow). At lower pressures the vent exit flow is subsonic (M < 1). The vent entry is subsonic at all conditions. The integration method can be slow on older computers. Reduce the number of calculation steps to improve calculation speed (16 steps is reasonably accurate). The calculation is less accurate for final blow down pressure close to ambient (blow down pressure ≤ 1.1 x ambient pressure) because of the low flow velocity. For the simplified method the flow is assumed to always be critical, and the pressure is assumed to decrease exponentially. At low pressure the flow is sub critical, and the simplified method underestimates the blow down time. The simplified method is reasonably accurate down to a final pressure of approximately 2 x ambient pressure (2-5% error relative to the integration method). The simplified method is not recommended for final blow down pressure less than 1.2 x ambient pressure. Minor losses can be included using the minor loss K factor. Minor losses should include the vent entry, valves and bends etc. The vent exit should not be included (the fluid dynamic pressure loss is included in the calculation). The Darcy friction factor is calculated for fully turbulent flow using the rough pipe equation (less accurate at low flow velocity). The discharge coefficient Cd can be used as a design factor or safety factor. Tool Input- schdtypeb : Pipe Schedule Type
- diamtypeb : Pipeline Diameter Type
- ODpu : User Defined Pipeline Outside Diameter
- IDpu : User Defined Pipeline Inside Diameter
- wtntypeb : Pipe Wall Thickness Type
- tnpu : User Defined Pipeline Wall Thickness
- schdtypea : Vent Schedule Type
- diamtypea : Vent Diameter Type
- ODu : User Defined Vent Outside Diameter
- IDu : User Defined Vent Inside Diameter
- wtntypea : Vent Wall Thickness Type
- tnu : User Defined Vent Wall Thickness
- rfactype : Vent Internal Roughness Type
- ru : User Defined Surface Roughness
- rru : User Defined Relative Roughness
- fdtype : Darcy Friction Factor Type
- fdu : User Defined Darcy Friction Factor
- leqtype : Minor Pressure Loss Type
- ku : User Defined Minor Loss K Factor
- lu : User Defined Minor Loss Length
- lodu : User Defined Minor Loss Diameters (L/ID)
- fL/Du : User Defined Pressure Loss Factor
- fluidtype : Fluid Type
- γu : User Defined Specific Heat Ratio
- SGu : User Defined Gas Specific Gravity
- zfactype : Compressibility Factor Type
- Zu : User Defined Compressibility Factor
- cdtype : Discharge Coefficient Type
- Cdu : User Defined Discharge Coefficient
- flowtype : Flow Type
- numsteps : Method Type Or Number Of Integration Steps
- Po : Initial Pipeline Stagnation Pressure
- Pb : Final Pipeline Stagnation Pressure (After Blowdown)
- Pa : Ambient Pressure (At Exit)
- To : Pipeline Stagnation Temperature
- Lv : Vent Length
- Lp : Pipeline Length
Tool Output- γ : Specific Heat Ratio
- Cd : Discharge Coefficient
- IDp : Pipeline Inside Diameter
- IDv : Vent Inside Diameter
- Le : Vent Eqivalent Length
- Rg : Specific Gas Constant
- SG : Gas Specific Gravity Relative To Air
- Tbd : Blowdown Time
- Z : Compressibility Factor
- cvg : Convergence Factor (≅ 1)
- fL/D : Pressure Loss Factor Including Minor Losses
- fd : Darcy Friction Factor
- mf : Pipeline Fluid Mass
- mmg : Gas Molar Mass
- ng : Pipeline Fluid Moles
- rr : Surface Roughness Ratio
- vf : Pipeline Volume
|
CALCULATOR : Compressible Flow Pipeline Blowdown Time (General) [FREE] ±
Calculate pipeline or pressure vessel blow down time through a constant diameter vent for either adiabatic flow or isothermal flow, using the simplified method. The pipeline is assumed to be at stagnation conditions (M = 0), which is valid when the pipeline diameter is much greater than the vent diameter. The pipeline temperature is assumed constant. For the simplified method the flow is assumed to always be critical, and the pressure is assumed to decrease exponentially. At low pressure the flow is sub critical, and the simplified method underestimates the blow down time. The simplified method is reasonably accurate down to a final pressure of approximately 2 x ambient pressure (2-5% error relative to the integration method). The simplified method is not recommended for final blow down pressure less than 1.2 x ambient pressure. Minor losses can be included using the minor loss K factor. Minor losses should include the vent entry, valves and bends etc. The vent exit should not be included (the fluid dynamic pressure loss is included in the calculation). The Darcy friction factor is calculated for fully turbulent flow using the rough pipe equation (less accurate at low flow velocity). The discharge coefficient Cd can be used as a design factor or safety factor. Tool Input- flowtype : Flow Type
- Po : Initial Pipeline Stagnation Pressure
- Pb : Final Pipeline Stagnation Pressure (After Blowdown)
- Pa : Ambient Pressure (At Exit)
- To : Pipeline Stagnation Temperature
- γ : Specific Heat Ratio
- SG : Gas Specific Gravity
- Z : Compressibility Factor
- Cd : Discharge Coefficient
- IDp : Pipeline Internal Diameter
- IDv : Vent Internal Diameter
- Lp : Pipeline Length
- fL/D : Pressure Loss Factor Including Minor Losses
Tool Output- M : Pipeline Fluid Mass
- N : Pipeline Fluid Moles
- Q : Pipeline Volume
- Tbd : Blowdown Time
- cvg : Convergence Factor (≅ 1)
- m : Vent Initial Mass Flowrate
- n : Vent Initial Mole Flowrate
|
CALCULATOR : Compressible Flow Gas Density And Compressibility Factor [FREE] ±
Calculate gas compressibility factor and density from gas temperature and pressure for common gases: argon Ar, n-decane C10H22, ethylene C2H4, ethyl chloride C2H5Cl, ethane C2H6, propene C3H6, propane C3H8, iso-butane C4H10, n-butane C4H10, iso-pentane C5H12, n-pentane C5H12, n-hexane C6H14, n-heptane C7H16, n-octane C8H18, n-nonane C9H20, methyl chloride CH3Cl, methane CH4, chlorine Cl2, carbon monoxide CO, carbon dioxide CO2, hydrogen H2, steam H2O, hydrogen sulphide H2S, hydrogen chloride HCl, helium He, krypton Kr, nitrogen N2, air N2+O2, ammonia NH3, oxygen O2, sulphur dioxide SO2, xenon Xe. The gas compressibility factor is calculated from the critical point temperature, critical point temperature, and the accentric factor using either the Peng Robinson, Soave, Redlich Kwong or Van Der Waals equations of state (EOS). The compressibility factor calculation is valid for gas phase only. Use the Result Plot option to plot compressibility factor versus pressure and temperature, compressibility factor versus pressure and equation of state type, or compressibility factor versus temperature and equation of state type. Tool Input- fluidtype : Fluid Type
- Pcu : User Defined Critical Point Pressure
- Tcu : User Defined Critical Point Temperature
- ωu : User Defined Accentric Factor
- SGu : User Defined Gas Specific Gravity
- eostype : Equation Of State Type
- Zu : User Defined Gas Compressibility Factor
- P : Fluid Pressure
- T : Fluid Temperature
Tool Output- ρ : Fluid Density
- ω : Accentric Factor
- Pc : Critical Point Pressure
- Rg : Specific Gas Constant
- SG : Gas Specific Gravity
- Tc : Critical Point Temperature
- Vm : Molar Volume
- Z : Compressibility Factor
- cvg : Convergence Check
- mmg : Gas Molar Mass
|
CALCULATOR : Compressible Flow Pipe Inside Diameter And Internal Cross Section Area [FREE] ±
Calculate pipe inside diameter and internal cross section area for a circular pipe or duct. The pipe inside diameter and cross section area are calculated from the pipe schedule diameter and wall thickness. Use the Result Table option to display a table of the inside diameter and cross section area versus either outside diameter or wall thickness. Tool Input- schdtype : Schedule Type
- diamtype : Diameter Type
- ODu : User Defined Outside Diameter
- IDu : User Defined Inside Diameter
- wtntype : Wall Thickness Type
- tnu : User Defined Wall Thickness
Tool Output- AX : Pipe Inside Cross Section Area
- ID : Nominal Inside Diameter
- OD : Nominal Outside Diameter
- OD/tn : Diameter Over Wall Thickness Ratio
- tn : Nominal Wall Thickness
|
CALCULATOR : Compressible Flow Pipeline Gas Mass And Mole Volume [FREE] ±
Calculate pipeline fluid volume, mass and mole volume from inside diameter and length for single phase gas. The pipe inside diameter and cross section area are calculated from the pipe schedule diameter and wall thickness. Use the Result Table option to display a table of the inside diameter and cross section area versus either outside diameter or wall thickness. Tool Input- schdtype : Pipe Schedule Type
- diamtype : Pipe Diameter Type
- ODu : User Defined Outside Diameter
- IDu : User Defined Inside Diameter
- wtntype : Wall Thickness Type
- tnu : User Defined Wall Thickness
- sgtype : Gas Specific Gravity Type
- SGu : User Defined Gas Specific Gravity
- Mu : User Defined Gas Molar Mass
- ρu : User Defined Gas Density
- P : Gas Pressure
- T : Gas Temperature
- Z : Gas Compressibility Factor
- L : Pipeline Length
Tool Output- ρ : Gas Density
- ID : Inside Diameter
- M : Gas Molar Mass
- Mf : Gas Mass
- Ng : Gas Moles
- OD : Outside Diameter
- SG : Gas Specific Gravity
- Vf : Gas Volume (At T P)
- tn : Nominal Wall Thickness
- vg : Gas Mole Volume (At T P)
|
CALCULATOR : Compressible Flow Duct Vent Or Header Pressure Loss Factor fL/D From The Von Karman Rough Pipe Equation [FREE] ±
Calculate duct, vent or header Darcy friction factor (fd) and pressure loss factor (fL/D) from the Von Karman rough pipe equation. At high Reynolds numbers the flow is fully turbulent and the Darcy friction factor is dependent on the pipe roughness only. Minor losses can be included in the pressure loss factor, either as a K factor, an equivalent added length, or an equivalent added length over diameter ratio. Tool Input- schdtypea : Vent Schedule Type
- diamtypea : Vent Diameter Type
- ODu : User Defined Vent Outside Diameter
- IDu : User Defined Vent Inside Diameter
- wtntype : Vent Wall Thickness Type
- tnu : User Defined Vent Wall Thickness
- rfactype : Vent Internal Roughness Type
- ru : User Defined Surface Roughness
- rru : User Defined Relative Roughness
- fdtype : Darcy Friction Factor Type
- fdu : User Defined Darcy Friction Factor
- leqtype : Minor Pressure Loss Type
- ku : User Defined Minor Loss K Factor
- lu : User Defined Minor Loss Length
- lodu : User Defined Minor Loss Diameters (L/ID)
- fL/Du : User Defined Pressure Loss Factor
- Lv : Vent Length
Tool Output- ID : Vent Inside Diameter
- Le : Vent Eqivalent Length
- fL/D : Pressure Loss Factor Including Minor Losses
- fd : Darcy Friction Factor
- rr : Surface Roughness Ratio
|
CALCULATOR : Compressible Flow Gas Duct Fanno Line [FREE] ±
Calculate gas duct Fanno lines or flow ratios for adiabatic (constant enthalpy) and isothermal (constant temperature) flow. Fanno lines or flow ratios are calculated for critical flow with friction loss. The inlet Mach number can be calculated from the friction loss factor (fLD), or the friction loss factor can be calculated from the inlet Mach number. Critical flow conditions occur when the exit Mach number equals the critical Mach number and the critical exit pressure is greater than or equal to ambient pressure. For adiabatic flow the critical exit Mach number = 1 (eg sonic flow conditions). For isothermal flow the critical exit Mach number = √γ. Note : Fanno flow is normally calculated for adiabatic duct flow with friction. The calculator also calculates Fanno ratios for isothermal (constant temperature) flow. Use the Result Plot option to plot critical pressure loss factor versus inlet Mach number and either flow type or specific heat ratio; or Fanno lines for pressure ratio, temperature ratio, density ratio, speed of sound ratio, and velocity ratio, versus either Mach number or pressure loss factor, and versus either flow type or specific heat ratio. The plot range is set from the calculated value of either the inlet Mach number, or the pressure loss factor in the main calculation. Change the main calculation values to change the plot range. Tool Input- fluidtype : Fluid Type
- γu : User Defined Specific Heat Ratio
- fldtype : Pressure Loss Factor Type
- Mciu : User Defined Inlet Mach Number
- fL/Du : User Defined Pressure Loss Factor
- flowtype : Fluid Flow Type
Tool Output- γ : Specific Heat Ratio
- ρi/ρ* : Inlet Density Over Critical Exit Density Ratio
- Ci/C* : Inlet Speed Of Sound Over Critical Exit Speed Of Sound Ratio
- M* : Critical Exit Mach Number
- Mi : Inlet Mach Number
- Pi/P* : Inlet Pressure Over Critical Exit Pressure Ratio
- Ti/T* : Inlet Temperature Over Critical Exit Temperature Ratio
- Vi/V* : Inlet Velocity Over Critical Velocity Ratio
- cvg : Convergence Factor (≅ 1)
- fL/D* : Critical Duct Pressure Loss factor
|