Title and Link to Calc:

Fluid Properties : Peng and Robinson (1976) Equation of State : FP-POLI-0030

Description:

Calculates gas state molar volumes per the Peng and Robinson (1976) equation of state and per the ideal gas law. The Peng Robinson constants are generated from the critical temperature, critical pressure and the acentric factor (omega factor) that are required as inputs.

Alternative Descriptors:

Molar Specific volumes per Peng and Robinson (1976) equation of state, Molar specific volume per ideal gas law, Compressibility, Mass specific volumes, Generalized Peng and Robinson (1976) based on critical state - critical temperature, critical pressure, acentric factor (omega)

Calc Number:

FP-POLI-0030

Calc Status:

Beta

Reference:

Properties of Gases and Liquids, Poling, Prausnitz, O'Connell, 5th Edition, pgs. 4.17 - 4.24

Reference Example(s) Modeled/Generalized:

Example 4-3 of the above reference

Calc Origination Date:

03/30/2006

Calc Originator:

RBC

Calc Revision History:

Calc Guidelines:

Solves the Peng and Robinson (1976) cubic equation of state as indicated in the above reference on pg. 4.18 , eq. 4-6.2. Determines if equation has multiple by analyzing the derivative of the cubic equation (a quadratic equation). If the existence of three real roots are detected. The calc finds the large and small root (ignores the middle root) between the limits specified below for the compressibility factor (ZCOM). Otherwise, the calc searches for only one root between the specified limits below. Several typographical errors were noted in the reference above. A right bracket, ], is missing in equation 4-6.3. The exponent, 2, is missing in the epsilon prime equation on the same page.

Access:

Activating this calc requires entry of the correct access code. Contact eng-calc@eng-calcs.com

Variables:

Variable Description - Description of the variable
Variable Label Description - The description of the variable as it appears in the calc.
Variable Calc Name - The calc internal variable name
Variable Units - The units for the variable
Variable Calc Upper Limit - The highest allowed value in the calc.
Variable Calc Lower Limit - The lowest allowed value in the calc.
Variable Type - Either "Output" or "Input"
Variable Format - Real Number, Text, or Integer
Variable Notes - Other comments about the variable

Variable Description: Peng and Robinson (1976) Molar specific volume in cubic feet per pound-mole - based on the greatest or only root to the cubic equation.
Variable Label Description: Peng and Robinson (1976) Molar Specific Volume [Major]
Variable Calc Name: MOLA
Variable Units: CUFT/LBMOL
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes: If the cubic equation has three real roots, this value is based on the largest root between the searched compressibility limits. This is also the value if the cubic equation has only one real root. This value, in most cases, is assumed to be the specific molar volume of the vapor/gas.

Variable Description: Peng and Robinson (1976) Molar specific volume in cubic feet per pound-mole - based on the lowest of multiple roots to the cubic equation.
Variable Label Description: Peng and Robinson (1976) Molar Specific Volume [Minor]
Variable Calc Name: MOLB
Variable Units: CUFT/LBMOL
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes: If the cubic equation has three real roots, this value is based on the smallest root between the searched compressibility limits. This value, in most cases, is assumed to be the specific molar volume of the liquid if multi-phases are present.

Variable Description: Mass specific volume in cubic feet per pound based on Peng and Robinson (1976) equation of state an input molecular weight
Variable Label Description: Peng and Robinson (1976) Mass Specific Volume [Major]
Variable Calc Name: MASA
Variable Units: CUFT/LBM
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes: This is the molar specific volume, MOLA, converted to mass units using the input molecular weight, MW.

Variable Description: Mass specific volume in cubic feet per pound based on Peng and Robinson (1976) equation of state an input molecular weight
Variable Label Description: Peng and Robinson (1976) Mass Specific Volume [Minor]
Variable Calc Name: MASB
Variable Units: CUFT/LBM
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes: This is the molar specific volume, MOLB, converted to mass units using the input molecular weight, MW.

Variable Description: Compressibility Factor at input temperature and pressure based on Peng and Robinson (1976) equation of state - large or major value. This is the largest or only value based on the solved cubic equation.
Variable Label Description: Peng and Robinson (1976) Compressibility Factor [Major]
Variable Calc Name: ZCOM
Variable Units:
Variable Calc Upper Limit: 3
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes: This is the largest or only value based on the solved cubic equation.

Variable Description: Compressibility Factor at input temperature and pressure based on Peng and Robinson (1976) equation of state - smallest or minor value.
Variable Label Description: Peng and Robinson (1976) Compressibility Factor [Minor]
Variable Calc Name: ZCOI
Variable Units:
Variable Calc Upper Limit: 3
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes: This is the value based on the lowest root when multiple real roots are present in the solved cubic equation.

Variable Description: Molar specific volume in cubic feet per pound-mole based on the Ideal Gas Law
Variable Label Description: Ideal Molar Specific Volume
Variable Calc Name: IDMO
Variable Units: CUFT/LBMOL
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes:

Variable Description: Mass specific volume in cubic feet per pound based on ideal gas law an input molecular weight
Variable Label Description: Ideal Mass Specific Volume
Variable Calc Name: IDMA
Variable Units: CUFT/LBM
Variable Calc Upper Limit: 100000
Variable Calc Lower Limit: 0
Variable Type: Output
Variable Format: REAL
Variable Notes:

Variable Description: Comments
Variable Label Description: Comments
Variable Calc Name: COM
Variable Units:
Variable Calc Upper Limit:
Variable Calc Lower Limit:
Variable Type: Output
Variable Format: TEXT
Variable Notes: Displays "Input(s) out of range." if an entered input variable(s) are out of range. Displays "Output(s) out of range." if an output variable exceeds its range. The "out of range" variable(s) are displayed in yellow. The limited range values are used in the calculation, not the "out of range" value(s). See the ZCOM variable above for additional comments.

Variable Description: Pressure of Fluid in PSIA
Variable Label Description: Fluid Pressure
Variable Calc Name: PRES
Variable Units: PSIA
Variable Calc Upper Limit: 20000
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Temp of Fluid in Rankine
Variable Label Description: Fluid Temperature
Variable Calc Name: TEMP
Variable Units: R
Variable Calc Upper Limit: 20000
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Molecular Weight of fluid
Variable Label Description: Fluid Molecular Weight
Variable Calc Name: MW
Variable Units:
Variable Calc Upper Limit: 20000
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Critical Pressure of Fluid in PSIA
Variable Label Description: Fluid Critical Pressure
Variable Calc Name: CPRE
Variable Units: PSIA
Variable Calc Upper Limit: 20000
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Critical Temperature of Fluid in Rankine
Variable Label Description: Fluid Critical Temperature
Variable Calc Name: CTEM
Variable Units:
Variable Calc Upper Limit: 20000
Variable Calc Lower Limit: 0.001
Variable Type: Input
Variable Format: REAL
Variable Notes:

Variable Description: Acentric Factor (Omega)
Variable Label Description: Acentric Factor
Variable Calc Name: ACEN
Variable Units:
Variable Calc Upper Limit: 1.5
Variable Calc Lower Limit: 0
Variable Type: Input
Variable Format: REAL
Variable Notes:

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