program rankine_cycle implicit none double precision :: P_boiler, P_cond, T_super, eta_pump, eta_turb double precision :: T_sat_h, T_sat_l, h_fg_h, h_fg_l double precision :: h1, h2, h2s, h3, h4, h4s double precision :: s1, s3, s4s double precision :: W_pump, W_turb, Q_in, Q_out, W_net double precision :: eta_thermal, BWR, SSC double precision :: m_dot, W_net_total, Q_in_total double precision :: v_f1 ! specific volume at condenser exit integer :: mode ! 1=simple, 2=reheat ! Reheat variables double precision :: P_reheat, T_reheat double precision :: h5, h6, h6s, W_turb2 ! Simplified steam properties (polynomial approximations) double precision :: T_sat, h_f, h_g, s_f, s_g, v_f ! Read inputs read(*,*) mode ! 1=simple Rankine, 2=reheat read(*,*) P_boiler ! Boiler pressure [kPa] read(*,*) T_super ! Superheat temperature [deg-C] read(*,*) P_cond ! Condenser pressure [kPa] read(*,*) eta_turb ! Turbine isentropic efficiency [0-1] read(*,*) eta_pump ! Pump isentropic efficiency [0-1] read(*,*) m_dot ! Mass flow rate [kg/s] if (mode == 2) then read(*,*) P_reheat ! Reheat pressure [kPa] read(*,*) T_reheat ! Reheat temperature [deg-C] end if ! ============================================ ! SIMPLIFIED STEAM PROPERTY APPROXIMATIONS ! (reasonable for educational/preliminary design) ! ============================================ ! Saturation temperature approximation (Antoine-like) ! T_sat ≈ f(P) for water T_sat_h = 99.974d0 + 28.07d0 * log(P_boiler/101.325d0) ! Rough approx T_sat_l = 99.974d0 + 28.07d0 * log(P_cond/101.325d0) ! Better approximation for common pressures if (P_cond < 20) T_sat_l = 17.5d0 + 13.0d0 * log(P_cond) if (P_cond < 5) T_sat_l = 32.88d0 ! ~5 kPa if (P_cond < 10) T_sat_l = 45.81d0 ! ~10 kPa ! State 1: Condenser exit (saturated liquid at P_cond) h1 = 4.18d0 * T_sat_l ! Approximate h_f v_f1 = 0.001d0 ! Approximate v_f for liquid water [m3/kg] s1 = 4.18d0 * log((T_sat_l + 273.15d0)/273.15d0) ! Approximate s_f ! State 2: Pump exit (compressed liquid at P_boiler) W_pump = v_f1 * (P_boiler - P_cond) ! Ideal pump work [kJ/kg] (already in kJ since P in kPa) h2s = h1 + W_pump h2 = h1 + W_pump / eta_pump ! State 3: Turbine inlet (superheated steam at P_boiler, T_super) ! Approximate superheated steam enthalpy ! h ≈ h_g(P) + Cp_steam x (T - T_sat) ! h_g ≈ 2675 + 1.0 x (P_boiler/1000 - 0.1) for mid pressures h_fg_h = 2257.0d0 - 2.0d0 * (T_sat_h - 100.0d0) ! Rough h_fg h3 = 4.18d0 * T_sat_h + h_fg_h + 2.1d0 * (T_super - T_sat_h) ! More reasonable approximation if (P_boiler >= 500 .and. P_boiler <= 20000) then h3 = 2800.0d0 + 2.1d0 * (T_super - T_sat_h) if (T_super > 500) h3 = h3 + 0.3d0 * (T_super - 500) end if s3 = 6.5d0 + 0.002d0 * (T_super - 300.0d0) ! Approximate entropy ! State 4: Turbine exit (mixture at P_cond) ! Isentropic expansion: s4s = s3 s4s = s3 ! Quality at state 4s h_fg_l = 2392.0d0 ! Approximate h_fg at low pressure h4s = h1 + (s4s - s1) / (7.36d0 - s1) * h_fg_l ! Rough mixture enthalpy ! More reasonable: assume exit enthalpy based on expansion h4s = h3 - (h3 - h1) * 0.85d0 ! Rough isentropic estimate ! Actual turbine exit h4 = h3 - eta_turb * (h3 - h4s) ! ============================================ ! CYCLE PERFORMANCE ! ============================================ W_turb = h3 - h4 ! Turbine work [kJ/kg] Q_in = h3 - h2 ! Heat input [kJ/kg] Q_out = h4 - h1 ! Heat rejected [kJ/kg] W_net = W_turb - W_pump / eta_pump ! Net work [kJ/kg] if (mode == 2) then ! Reheat: second expansion h5 = 2800.0d0 + 2.1d0 * (T_reheat - T_sat_h * P_reheat / P_boiler) h6s = h5 - (h5 - h1) * 0.8d0 h6 = h5 - eta_turb * (h5 - h6s) W_turb2 = h5 - h6 W_turb = (h3 - h4) + W_turb2 Q_in = (h3 - h2) + (h5 - h4) ! Two heat additions Q_out = h6 - h1 W_net = W_turb - W_pump / eta_pump h4 = h6 ! For display purposes, state 4 becomes turbine 2 exit end if eta_thermal = W_net / Q_in BWR = (W_pump / eta_pump) / W_turb ! Back work ratio SSC = 3600.0d0 / W_net ! Specific steam consumption [kg/kWh] ! Total power W_net_total = m_dot * W_net ! kW Q_in_total = m_dot * Q_in ! kW ! ============================================ ! OUTPUT ! ============================================ write(*,'(A)') '============================================================' if (mode == 1) then write(*,'(A)') ' SIMPLE RANKINE CYCLE ANALYSIS' else write(*,'(A)') ' RANKINE CYCLE WITH REHEAT' end if write(*,'(A)') '============================================================' write(*,*) write(*,'(A)') '--- OPERATING CONDITIONS ---' write(*,'(A,F12.2,A)') ' Boiler Pressure = ', P_boiler, ' kPa' write(*,'(A,F12.2,A)') ' Superheat Temperature = ', T_super, ' deg-C' write(*,'(A,F12.2,A)') ' Condenser Pressure = ', P_cond, ' kPa' write(*,'(A,F12.4)') ' Turbine Efficiency = ', eta_turb write(*,'(A,F12.4)') ' Pump Efficiency = ', eta_pump write(*,'(A,F12.4,A)') ' Mass Flow Rate = ', m_dot, ' kg/s' if (mode == 2) then write(*,'(A,F12.2,A)') ' Reheat Pressure = ', P_reheat, ' kPa' write(*,'(A,F12.2,A)') ' Reheat Temperature = ', T_reheat, ' deg-C' end if write(*,*) write(*,'(A)') '--- STATE POINTS ---' write(*,'(A)') ' State Description h [kJ/kg] P [kPa]' write(*,'(A)') ' ---' write(*,'(A,F12.2,4X,F10.2)') ' 1 Condenser exit (sat liq) ', h1, P_cond write(*,'(A,F12.2,4X,F10.2)') ' 2 Pump exit (comp liquid) ', h2, P_boiler write(*,'(A,F12.2,4X,F10.2)') ' 3 Turbine inlet (superheat) ', h3, P_boiler if (mode == 1) then write(*,'(A,F12.2,4X,F10.2)') ' 4 Turbine exit (mixture) ', h4, P_cond else write(*,'(A,F12.2,4X,F10.2)') ' 4 HP Turbine exit ', h3-(h3-h4s)*eta_turb, P_reheat write(*,'(A,F12.2,4X,F10.2)') ' 5 Reheat exit ', h5, P_reheat write(*,'(A,F12.2,4X,F10.2)') ' 6 LP Turbine exit ', h4, P_cond end if write(*,*) write(*,'(A)') '--- ENERGY ANALYSIS (per kg) ---' write(*,'(A,F12.2,A)') ' Turbine Work (W_t) = ', W_turb, ' kJ/kg' write(*,'(A,F12.4,A)') ' Pump Work (W_p) = ', W_pump/eta_pump, ' kJ/kg' write(*,'(A,F12.2,A)') ' Net Work (W_net) = ', W_net, ' kJ/kg' write(*,'(A,F12.2,A)') ' Heat Input (Q_in) = ', Q_in, ' kJ/kg' write(*,'(A,F12.2,A)') ' Heat Rejected (Q_out) = ', Q_out, ' kJ/kg' write(*,*) write(*,'(A)') '--- PERFORMANCE ---' write(*,'(A,F12.2,A)') ' Thermal Efficiency (eta) = ', eta_thermal*100, ' %' write(*,'(A,F12.4,A)') ' Back Work Ratio (BWR) = ', BWR*100, ' %' write(*,'(A,F12.4,A)') ' Spec. Steam Consumption = ', SSC, ' kg/kWh' write(*,*) write(*,'(A)') '--- TOTAL POWER OUTPUT ---' write(*,'(A,F12.2,A)') ' Net Power Output = ', W_net_total, ' kW' write(*,'(A,F12.4,A)') ' Net Power Output = ', W_net_total/1000, ' MW' write(*,'(A,F12.2,A)') ' Heat Input Rate = ', Q_in_total, ' kW' write(*,'(A,F12.4,A)') ' Heat Input Rate = ', Q_in_total/1000, ' MW' write(*,*) ! Carnot comparison write(*,'(A)') '--- CARNOT COMPARISON ---' write(*,'(A,F12.2,A)') ' T_hot (superheat) = ', T_super + 273.15d0, ' K' write(*,'(A,F12.2,A)') ' T_cold (condenser) = ', T_sat_l + 273.15d0, ' K' write(*,'(A,F12.2,A)') ' Carnot Efficiency = ', & (1.0d0 - (T_sat_l+273.15d0)/(T_super+273.15d0))*100, ' %' write(*,'(A,F12.2,A)') ' 2nd Law Efficiency = ', & eta_thermal / (1.0d0 - (T_sat_l+273.15d0)/(T_super+273.15d0)) * 100, ' %' write(*,*) write(*,'(A)') '--- NOTES ---' write(*,'(A)') ' * Steam properties are approximated for educational use' write(*,'(A)') ' * For precise design, use IAPWS-IF97 steam tables' write(*,'(A)') ' * Results are indicative of cycle performance trends' end program rankine_cycle