FE-AGA8-92DC-C

FE-AGA8-92DC-C (Revised: February 26, 2010) is the C source code implementation of:

AGA Report No. 8, Compressibility Factor of Natural Gas and Related Hydrocarbon Gases, 2nd edition 1992, 2nd printing 1992.

FE-AGA8-92DC-C implements AGA8_92DC equation in extended operating ranges (see Table below). The code has been split into two parts (OFF-LINE and ON-LINE) and optimized to speed-up the calculations.
The software is written in C-language and embeds all the restrictions implied by AGA-8:1992. The code is fully re-entrant and ANSI C compatible. The following is a brief description of a function (method), input/output parameters, ranges of applications, errors and an example of a main program in a c-source code.

Description of function, input/output parameters, ranges of application and errors

Function
void aga8x92dc(struct aga8 *);

Input parameters
Data type	Parameter name	Parameter description	Unit of measure
double	aga8.x[0]	molar fraction of Methane	mol
double	aga8.x[1]	molar fraction of Nitrogen	mol
double	aga8.x[2]	molar fraction of Carbon dioxide	mol
double	aga8.x[3]	molar fraction of Ethane	mol
double	aga8.x[4]	molar fraction of Propane	mol
double	aga8.x[5]	molar fraction of Water	mol
double	aga8.x[6]	molar fraction of Hydrogen sulfide	mol
double	aga8.x[7]	molar fraction of Hydrogen	mol
double	aga8.x[8]	molar fraction of Carbon monoxide	mol
double	aga8.x[9]	molar fraction of Oxygen	mol
double	aga8.x[10]	molar fraction of iso-Butane	mol
double	aga8.x[11]	molar fraction of n-Butane	mol
double	aga8.x[12]	molar fraction of i-Pentane	mol
double	aga8.x[13]	molar fraction of n-Pentane	mol
double	aga8.x[14]	molar fraction of n-Hexane	mol
double	aga8.x[15]	molar fraction of n-Heptane	mol
double	aga8.x[16]	molar fraction of n-Octane	mol
double	aga8.x[17]	molar fraction of n-Nonane	mol
double	aga8.x[18]	molar fraction of n-Decane	mol
double	aga8.x[19]	molar fraction of Helium	mol
double	aga8.x[20]	molar fraction of Argon	mol
double	aga8.p	Pressure (absolute)	MPa
double	aga8.t	Temperature	K
Output parameters
double	aga8.mm	gas mixture molar mass	kg/kmol
double	aga8.md	gas mixture molar density	kg⋅mol/m³
double	aga8.density	gas mixture density	kg/m³
double	aga8.zf	gas mixture compression factor	dimensionless
double	aga8.rd	gas mixture relative density	dimensionless
double	aga8.scv	gas mixture superior calorific value	MJ/m³
long	aga8.es	error status	dimensionless

Ranges of application implemented in FE-AGA8-92DC-C
Parameter	Range
Mole fraction of Methane	0 to 1.00
Mole fraction of Nitrogen	0 to 1.00
Mole fraction of Carbon dioxide	0 to 1.00
Mole fraction of Ethane	0 to 1.00
Mole fraction of Propane	0 to 0.12
Mole fraction of Water	0 to 0.10
Mole fraction of Hydrogen sulfide	0 to 1.00
Mole fraction of Hydrogen	0 to 1.00
Mole fraction of Carbon monoxide	0 to 0.03
Mole fraction of Oxigen	0 to 0.21
Mole fraction of butanes (n-Butane + i-Butane)	0 to 0.06
Mole fraction of pentanes (n-pentane + i-Pentane)	0 to 0.04
Mole fraction of hexanes plus (n-Hexane + n-Heptane + n-Octane + n-Nonane + n-Octane)	0 to 0.10
Mole fraction of Helium	0 to 0.03
Mole fraction of Argon	0 to 0.01
Pressure (absolute)	10^-8 to 278.5 MPa
Temperature	144 to 678 K
Relative density	0.07 to 1.52
Superior calorific value	0 to 67.066 MJ/m³

Errors and warnings
"long aga8.es" represents errors and warnings generated during program execution as follows:
Bit 0 =1 (0000001H)	Error: There exist at least one molar fraction < 0 or > 1
Bit 1 =1 (0000002H)	Error: The total sum of molar fractions <0.98 or >1.02
Bit 2 =1 (0000004H)	Warning: Total sum of molar fractions is <0.999999 or >1.000001. If set this bit only warns that the fractions have been normalized to give the total sum of molar fractions exactly equal to 1. If only bit 2 was set during the calculation the results are valid.
Bit 3 =1 (0000008H)	Error: Mole fraction of Methane out of range.
Bit 4 =1 (0000010H)	Error: Mole fraction of Nitrogen out of range.
Bit 5 =1 (0000020H)	Error: Mole fraction of Carbon Dioxide out of range.
Bit 6 =1 (0000040H)	Error: Mole fraction of Ethane out of range.
Bit 7 =1 (0000080H)	Error: Mole fraction of Propane out of range.
Bit 8 =1 (0000100H)	Error: Mole fraction of Water out of range.
Bit 9 =1 (0000200H)	Error: Mole fraction of Hydrogen sulfide out of range.
Bit 10 =1 (0000400H)	Error: Mole fraction of Hydrogen out of range.
Bit 11 =1 (0000800H)	Error: Mole fraction of Carbon monoxide out of range.
Bit 12 =1 (0001000H)	Error: Mole fraction of Oxygen out of range.
Bit 13 =1 (0002000H)	Error: Mole fraction of Butanes) out of range.
Bit 14 =1 (0004000H)	Error: Mole fraction of Pentanes out of range.
Bit 15 =1 (0008000H)	Error: Mole fraction of Hexanes plus out of range.
Bit 16 =1 (0010000H)	Error: Mole fraction of Helium out of range.
Bit 17 =1 (0020000H)	Error: Mole fraction of Argon out of range.
Bit 18 =1 (0040000H)	Error: Pressure (absolute) out of range.
Bit 19 =1 (0080000H)	Error: Temperature out of range.
Bit 20 =1 (0100000H)	Error: Relative density out of range.
Bit 21 =1 (0200000H)	Error: Superior calorific value out of range.
Bit 22 =1 (0400000H)	Unused
Bit 23 =1 (0800000H)	Unused
Bit 24 =1 (1000000H)	Error: OFF-LINE calculation failed.
Bit 25,... All higher order bits are unused
The results are valid if bits 0,...,24 are all cleared, or if only bit 2 was set during the calculation, otherwise the results are invalid, i.e. cleared.

Header file: "aga8x92dc.h"

The following is a header file:


#include "stdio.h"
#include "math.h"
// declaration of the 'aga8' struct
struct aga8
{
    // INPUT PARAMETERS
    double t;     // Temperature [K]
    double p;     // Pressure in [MPa]
    double x[21]; // Natural gas molar fractions
      // MOLE FRACTIONS OF:
      // x[0] Methane, x[1] Nitrogen, x[2] Carbon Dioxide, x[3] Ethane
      // x[4] Propane, x[5] Water, x[6] Hydrogen sulfide, x[7] Hydrogen,
      // x[8] Carbon Monoxide, x[9] Oxygen, x[10] i-Butane, x[11] n-Butane
      // x[12] i-Pentane, x[13] n-Pentane, x[14] n-Hexane, x[15] n-Heptane
      // x[16] n-Octane, x[17] n-Nonane, x[18] n-Decane, x[19] Helium, x[20] Argon

    // OUTPUT PARAMETERS
    unsigned long int es; // Error status
    double scv; // Superior calorific value on a volumetric basis [MJ/m^3]
                // at combustion temperature 298.15 K,
                // metering temperature 273.15K, and
                // combustion and metering pressure 0.101325 MPa
    double rd;  // Relative density at 273.15 K and 0.101325 MPa
    double zf;  // Compression (compressibility factor)
    double d;   // Density [kg/m3]
    double md;  // Molar density [kg-mole/m3]
    double mm;  // Molar mass

    // Temporary parameters
    double Gij, Eij, Bnijx, B, U5, U, G, Q, F, K5, dr, Z, Cnx[58];
    double d1, d2, dk, R, p1, p2, temp, z0, rden, sc;
    int i, j, n;

    // Intermediate results in OFF-LINE calculations
    double K3, M;
    unsigned long int es_off;
    double BB[18];
    double Cnx0[58];

    // Temporary registers
    double tmp[10];
    double RT, SumCnx;

    // Natural gas composition from previous cycle: to be compared with actual
    // composition to see whether the OFF-LINE calculation is necessary or not
    double xx[21];
};

// declaration of the function 'aga8x92dc'
void aga8x92dc(struct aga8 *);

Example of a main program in C code calling the function "aga8x92dc()"

The following example illustrates the call to aga8x92dc() function from a main program. The program prompts for input parameters and then transfers the parameters to the struct. After the execution the program prints both the input parameters and the results on the screen.


/* ******************* */
/* MAIN PROGRAM C-CODE */
/* ******************* */

#include "stdio.h"
#include "conio.h"
#include "aga8x92dc.h"
void main(void)
{
    struct aga8 aga, *agap; /* 'agap' is a pointer to a structure 'aga' */
    unsigned short int i, j, igas;
    char ch;
    /* ISO-12213-2 examples */
    /* Array of gas mixture molar fractions */
    // double twodim[2][3] = { 11, 12, 13, 21, 22, 23 };
    double yy[6][21] = {
        0.965, 0.003, 0.006, 0.018, 0.0045, 0.0, 0.0,
        0.0, 0.0, 0.0, 0.001, 0.001, 0.0005, 0.0003,
        0.0007, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
        0.907, 0.031, 0.005, 0.045, 0.0084, 0.0, 0.0,
        0.0, 0.0, 0.0, 0.001, 0.0015, 0.0003, 0.0004,
        0.0004, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
        0.859, 0.01, 0.015, 0.085, 0.023, 0.0, 0.0,
        0.0, 0.0, 0.0, 0.0035, 0.0035, 0.0005, 0.0005,
        0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
        0.735, 0.1, 0.016, 0.033, 0.0074, 0.0, 0.0,
        0.095, 0.01, 0.0, 0.0012, 0.0012, 0.0004, 0.0004,
        0.0002, 0.0001, 0.0001, 0.0, 0.0, 0.0, 0.0,
        0.812, 0.057, 0.076, 0.043, 0.009, 0.0, 0.0,
        0.0, 0.0, 0.0, 0.0015, 0.0015, 0.0, 0.0,
        0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,
        0.826, 0.117, 0.011, 0.035, 0.0075, 0.0, 0.0,
        0.0, 0.0, 0.0, 0.0012, 0.0012, 0.0004, 0.0004,
        0.0002, 0.0001, 0.0, 0.0, 0.0, 0.0, 0.0
    };
    char *text[29] = {
        "Methane         ", "Nitrogen        ", "Carbon Dioxide  ",
        "Ethane          ", "Propane         ", "Water           ",
        "Hydrogen Sulfide", "Hydrogen        ", "Carbon Monoxide ",
        "Oxygen          ", "iso-Butane      ", "n-Butane        ",
        "i-Pentane       ", "n-Pentane       ", "n-Hexane        ",
        "n-Heptane       ", "n-Octane        ", "n-Nonane        ",
        "n-Decane        ", "Helium          ", "Argon           ",
        "Pressure [MPa]  ", "Temperature [K] ",
        "Molar mass                ",
        "Molar density [kg-mole/m3]",
        "Density [kg/m3]           ",
        "Compression               ",
        "Relative density          ",
        "Superior calorific value  "
    };

    for (j=0; ; ) {
        printf("\nINPUT PARAMETERS\n");
        /* Input molar fractions */
        printf("Mole fraction of:\n");
        for (i=0; i<=20; i++) {
            printf("%s = ", text[i]);
            scanf("%lf", &(aga.x[i]));
        }
        printf("%s = ", text[21]);   /* Enter pressure */
        scanf("%lf", &(aga.p));
        printf("%s = ", text[22]);   /* Enter temperature */
        scanf("%lf", &(aga.t));
        agap = &aga; /* Put the address of 'aga' structure into 'agap' */
        aga8x92dc(agap); /* Call function by passing the pointer to structure */
        /* Print input parameters and results */
        printf("\nI N P U T   P A R A M E T E R S:");
        printf("\n%s%d", "Selected gas = Gas", igas+1); /* Print gas selection */
        printf("\nMole fractions:"); /* Print mole fractions */
        for (i=0; i<10; ++i) { /* Fractions of components 1-20 */
          printf("\n%s = %f, %s = %f",text[2*i], aga.x[2*i], text[2*i+1], aga.x[2*i+1]);
        }
        printf("\n%s = %f",text[20], aga.x[20]); /* Fraction of component 21 */
        printf("\n%s = %f", text[21], aga.p); /* Print pressure */
        printf("\n%s = %f", text[22], aga.t); /* Print temperature */
        printf("\n\nR E S U L T S");
        printf("\nError(Hex) = %x", aga.es); /* errr status */
        /* Print results */
        printf("\n%s = %f",text[23], aga.mm); /* print molar mass */
        printf("\n%s = %f",text[24], aga.md); /* print molar density */
        printf("\n%s = %f",text[25], aga.d); /* print density */
        printf("\n%s = %f",text[26], aga.zf); /* compression */
        printf("\n%s = %f",text[27], aga.rd); /* relative density */
        printf("\n%s = %f",text[28], aga.scv); /* superior calorific value */
        printf("\nPress X to exit or anything else to continue: ");
        ch = getch();
        if (( ch == 'X') || (ch == 'x'))
            break;
    }
}

/* ****************************** */
/* END OF THE MAIN PROGRAM C-CODE */
/* ****************************** */