program 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