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Ideal Gas State Solver
Core Numerical Engine in Fortran 90 β’ 0 total downloads
ideal_gas_calculator.f90
! =========================================================================
! Source File: ideal_gas_calculator.f90
! =========================================================================
ο»Ώprogram ideal_gas_calculator
implicit none
double precision :: P, V, T, n, m, M_mol, R_u, R_spec
double precision :: rho, Cp, Cv, gamma_g, a_sound
integer :: solve_for ! 1=P, 2=V, 3=T, 4=n
integer :: gas_type ! 1=air, 2=N2, 3=O2, 4=CO2, 5=H2, 6=He, 7=CH4, 8=custom
character(len=30) :: gas_name, solve_name
double precision :: pi
! Additional calculations
double precision :: P2, V2, T2
double precision :: W_iso, W_adia, Q_iso
integer :: i
pi = 3.14159265358979d0
R_u = 8.314d0 ! Universal gas constant [J/(mol.K)]
! Read inputs
read(*,*) solve_for
read(*,*) gas_type
! Set gas properties
select case(gas_type)
case(1)
gas_name = 'Air'
M_mol = 28.97d-3 ! kg/mol
gamma_g = 1.4d0
Cp = 1005.0d0
case(2)
gas_name = 'Nitrogen (N2)'
M_mol = 28.014d-3
gamma_g = 1.4d0
Cp = 1040.0d0
case(3)
gas_name = 'Oxygen (O2)'
M_mol = 31.998d-3
gamma_g = 1.395d0
Cp = 918.0d0
case(4)
gas_name = 'Carbon Dioxide (CO2)'
M_mol = 44.01d-3
gamma_g = 1.289d0
Cp = 844.0d0
case(5)
gas_name = 'Hydrogen (H2)'
M_mol = 2.016d-3
gamma_g = 1.41d0
Cp = 14307.0d0
case(6)
gas_name = 'Helium (He)'
M_mol = 4.003d-3
gamma_g = 1.667d0
Cp = 5193.0d0
case(7)
gas_name = 'Methane (CH4)'
M_mol = 16.043d-3
gamma_g = 1.32d0
Cp = 2226.0d0
case default
gas_name = 'Custom Gas'
read(*,*) M_mol
M_mol = M_mol * 1.0d-3 ! Convert g/mol to kg/mol
read(*,*) gamma_g
Cp = gamma_g * R_u / (M_mol * (gamma_g - 1.0d0))
end select
R_spec = R_u / M_mol
Cv = Cp / gamma_g
! Read known values and solve
select case(solve_for)
case(1) ! Solve for P
solve_name = 'Pressure (P)'
read(*,*) V ! m3
read(*,*) T ! K
read(*,*) n ! mol
P = n * R_u * T / V
m = n * M_mol
case(2) ! Solve for V
solve_name = 'Volume (V)'
read(*,*) P ! Pa
read(*,*) T ! K
read(*,*) n ! mol
V = n * R_u * T / P
m = n * M_mol
case(3) ! Solve for T
solve_name = 'Temperature (T)'
read(*,*) P ! Pa
read(*,*) V ! m3
read(*,*) n ! mol
T = P * V / (n * R_u)
m = n * M_mol
case(4) ! Solve for n
solve_name = 'Amount (n)'
read(*,*) P ! Pa
read(*,*) V ! m3
read(*,*) T ! K
n = P * V / (R_u * T)
m = n * M_mol
end select
! Density
rho = P / (R_spec * T)
! Speed of sound
a_sound = sqrt(gamma_g * R_spec * T)
! ============================================
! OUTPUT
! ============================================
write(*,'(A)') '============================================================'
write(*,'(A)') ' IDEAL GAS LAW CALCULATOR'
write(*,'(A)') '============================================================'
write(*,*)
write(*,'(A,A)') ' Solving for = ', trim(solve_name)
write(*,'(A,A)') ' Gas = ', trim(gas_name)
write(*,*)
write(*,'(A)') '--- GAS PROPERTIES ---'
write(*,'(A,F12.4,A)') ' Molar Mass (M) = ', M_mol*1000, ' g/mol'
write(*,'(A,F12.4,A)') ' Gas Constant (R) = ', R_spec, ' J/(kg.K)'
write(*,'(A,F12.4)') ' Specific Heat Ratio (gamma) = ', gamma_g
write(*,'(A,F12.2,A)') ' Cp = ', Cp, ' J/(kg.K)'
write(*,'(A,F12.2,A)') ' Cv = ', Cv, ' J/(kg.K)'
write(*,*)
write(*,'(A)') '--- STATE VARIABLES ---'
write(*,'(A,F12.2,A)') ' Pressure (P) = ', P, ' Pa'
write(*,'(A,F12.4,A)') ' Pressure = ', P/1000, ' kPa'
write(*,'(A,F12.6,A)') ' Pressure = ', P/101325, ' atm'
write(*,'(A,F12.6,A)') ' Pressure = ', P/1.0d5, ' bar'
write(*,*)
write(*,'(A,ES12.4,A)') ' Volume (V) = ', V, ' m3'
write(*,'(A,F12.4,A)') ' Volume = ', V*1000, ' L'
write(*,*)
write(*,'(A,F12.2,A)') ' Temperature (T) = ', T, ' K'
write(*,'(A,F12.2,A)') ' Temperature = ', T-273.15d0, ' deg-C'
write(*,'(A,F12.2,A)') ' Temperature = ', T*1.8d0-459.67d0, ' deg-F'
write(*,*)
write(*,'(A,F12.6,A)') ' Amount (n) = ', n, ' mol'
write(*,'(A,F12.6,A)') ' Mass (m) = ', m, ' kg'
write(*,'(A,F12.4,A)') ' Mass = ', m*1000, ' g'
write(*,*)
write(*,'(A)') '--- DERIVED PROPERTIES ---'
write(*,'(A,F12.4,A)') ' Density (rho) = ', rho, ' kg/m3'
write(*,'(A,F12.4,A)') ' Specific Volume (v) = ', 1.0d0/rho, ' m3/kg'
write(*,'(A,F12.2,A)') ' Speed of Sound (a) = ', a_sound, ' m/s'
write(*,*)
! Process calculations
write(*,'(A)') '--- PROCESS CALCULATIONS ---'
write(*,'(A)') ' (For expansion/compression from current state)'
write(*,*)
! Isothermal compression/expansion to 2x pressure
P2 = 2.0d0 * P
V2 = n * R_u * T / P2
W_iso = n * R_u * T * log(V / V2) ! work done BY the gas
Q_iso = W_iso ! For isothermal: Q = W
write(*,'(A)') ' Isothermal Process (T = const, P -> 2P):'
write(*,'(A,F12.4,A)') ' Final Volume = ', V2*1000, ' L'
write(*,'(A,F12.4,A)') ' Work done by gas = ', W_iso, ' J'
write(*,'(A,F12.4,A)') ' Heat transfer = ', Q_iso, ' J'
write(*,*)
! Isentropic compression to 2x pressure
T2 = T * (P2/P)**((gamma_g-1.0d0)/gamma_g)
V2 = n * R_u * T2 / P2
W_adia = n * Cv * M_mol * (T - T2) ! work done BY gas (negative for compression)
write(*,'(A)') ' Isentropic Process (s = const, P -> 2P):'
write(*,'(A,F12.2,A)') ' Final Temperature = ', T2, ' K'
write(*,'(A,F12.4,A)') ' Final Volume = ', V2*1000, ' L'
write(*,'(A,F12.4,A)') ' Work done by gas = ', W_adia, ' J'
write(*,'(A)') ' Heat transfer = 0 J (adiabatic)'
write(*,*)
! P-V data for chart
write(*,'(A)') '--- P-V DIAGRAM DATA ---'
write(*,'(A)') ' V [L] P_iso [kPa] P_isen [kPa]'
write(*,'(A)') ' ---'
do i = 1, 25
V2 = V * (0.4d0 + dble(i-1) * 1.6d0 / 24.0d0)
! Isothermal: PV = nRT -> P = nRT/V
P2 = n * R_u * T / V2
! Isentropic: PV^gamma = const -> P = P1(V1/V2)^gamma
T2 = P * V**gamma_g / V2**gamma_g
write(*,'(F10.4,2X,F12.4,4X,F12.4)') V2*1000, P2/1000, T2/1000
end do
write(*,*)
write(*,'(A)') '--- EQUATION USED ---'
write(*,'(A)') ' PV = nRT (ideal gas law)'
write(*,'(A)') ' R_universal = 8.314 J/(mol.K)'
write(*,'(A)') ' Assumptions: ideal gas behavior, no intermolecular forces'
end program ideal_gas_calculator
Solver Description
Resolves thermodynamic states for various engineering gases using the ideal gas equation of state $PV = m R_{specific} T$. Includes internal specific gas constant databases and automatically solves for whichever state variable is marked with $-1$.
Key Numerical Methods & Architecture
- Input Redirection: Reads parameters sequentially from standard input (`stdin`) using Fortran sequential read (`read(*,*)`), ensuring modular integration.
- Modular Design: Formulated using pure mathematical routines, separation of equations from output formatting, and precise numerical solvers (e.g. bisection, Newton-Raphson).
- Standard Compliant: Written in clean, standards-compliant Fortran 90 to ensure cross-compiler compatibility.
π οΈ Local Compilation
To test this code on your machine, compile the source code file(s) using a standard Fortran compiler (e.g., `gfortran`).
Compilation Command:
gfortran -ffree-line-length-none ideal_gas_calculator.f90 -o ideal_gas_calc
Execution Command:
Execute the program by feeding the sample input file into the program using stdin redirection:
ideal_gas_calc < input.txt
π₯ Downloads & Local Files
Preview of the required input file (input.txt):
! Gas Preset (1=Air, 2=He, 3=N2, 4=O2, 5=CO2, 6=H2)
1
! Pressure ($P$) [kPa] (or -1 if solving for P)
101.325
! Temperature ($T$) [K] (or -1 if solving for T)
298.15
! Volume ($V$) [mΒ³] (or -1 if solving for V)
1.0
! Mass ($m$) [kg] (or -1 if solving for m)
-1
1
! Pressure ($P$) [kPa] (or -1 if solving for P)
101.325
! Temperature ($T$) [K] (or -1 if solving for T)
298.15
! Volume ($V$) [mΒ³] (or -1 if solving for V)
1.0
! Mass ($m$) [kg] (or -1 if solving for m)
-1