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+// Display mode

+mode(0);

+// Display warning for floating point exception

+ieee(1);

+clear;

+clc;

+disp("Engineering Thermodynamics by Onkar Singh Chapter 8 Example 18")

+W_net=50*10^3;//net output of turbine in KW

+disp("from steam tables,at inlet to first stage of turbine,h1=h at 100 bar,500oc=3373.7 KJ/kg,s1=s at 100 bar,500oc=6.5966 KJ/kg")

+h1=3373.7;

+s1=6.5966;

+disp("Due to isentropic expansion,s1=s6=s2 and s3=s8=s4")

+s2=s1;

+s6=s2;

+disp("State at 6 i.e bleed state from HP turbine,temperature by interpolation from steam table =261.6oc.")

+disp("At inlet to second stage of turbine,h6=2930.572 KJ/kg")

+h6=2930.572;

+disp("h3=h at 10 bar,500oc=3478.5 KJ/kg,s3=s at 10 bar,500oc=7.7622 KJ/kg K")

+h3=3478.5;

+s3=7.7622;

+s4=s3;

+s8=s4;

+disp("At exit from first stage of turbine i.e. at 10 bar and entropy of 6.5966 KJ/kg K,Temperature by interpolation from steam table at 10 bar and entropy of 6.5966 KJ/kg K")

+disp("T2=181.8oc,h2=2782.8 KJ/kg")

+T2=181.8;

+h2=2782.8;

+disp("state at 8,i.e bleed state from second stage of expansion,i.e at 4 bar and entropy of 7.7622 KJ/kg K,Temperature by interpolation from steam table,T8=358.98oc=359oc")

+T8=359;

+disp("h8=3188.7 KJ/kg")

+h8=3188.7;

+disp("state at 4 i.e. at condenser pressure of 0.1 bar and entropy of 7.7622 KJ/kg K,the state lies in wet region.So let the dryness fraction be x4.")

+disp("s4=sf at 0.1 bar+x4*sfg at 0.1 bar")

+disp("from steam tables,at 0.1 bar,sf=0.6493 KJ/kg K,sfg=7.5009 KJ/kg K")

+sf=0.6493;

+sfg=7.5009; 

+disp("so x4=(s4-sf)/sfg")

+x4=(s4-sf)/sfg

+x4=0.95;//approx.

+disp("h4=hf at 0.1 bar+x4*hfg at 0.1 bar in KJ/kg ")

+disp("from steam tables,at 0.1 bar,hf=191.83 KJ/kg,hfg=2392.8 KJ/kg")

+hf=191.83;

+hfg=2392.8;

+h4=hf+x4*hfg

+disp("given,h4=2464.99 KJ/kg,h11=856.8 KJ/kg,h9=hf at 4 bar=604.74 KJ/kg")

+h4=2464.99;

+h11=856.8;

+h9=604.74;

+disp("considering pump work,the net output can be given as,")

+disp("W_net=W_HPT+W_LPT-(W_CEP+W_FP)")

+disp("where,W_HPT={(h1-h6)+(1-m6)*(h6-h2)}per kg of steam from boiler.")

+disp("W_LPT={(1-m6)+(h3-h8)*(1-m6-m8)*(h8-h4)}per kg of steam from boiler.")

+disp("for closed feed water heater,energy balance yields;")

+disp("m6*h6+h10=m6*h7+h11")

+disp("assuming condensate leaving closed feed water heater to be saturated liquid,")

+disp("h7=hf at 20 bar=908.79 KJ/kg")

+h7=908.79; 

+disp("due to throttline,h7=h7_a=908.79 KJ/kg")

+h7_a=h7;

+disp("for open feed water heater,energy balance yields,")

+disp("m6*h7_a+m8*h8+(1-m6-m8)*h5=h9")

+disp("for condensate extraction pump,h5-h4_a=v4_a*deltap")

+disp("h5-hf at 0.1 bar=vf at 0.1 bar*(4-0.1)*10^2 ")

+disp("from steam tables,at 0.1 bar,hf=191.83 KJ/kg,vf=0.001010 m^3/kg")

+hf=191.83;

+vf=0.001010; 

+disp("so h5=hf+vf*(4-0.1)*10^2 in KJ/kg")

+h5=hf+vf*(4-0.1)*10^2

+disp("for feed pump,h10-h9=v9*deltap")

+disp("h10=h9+vf at 4 bar*(100-4)*10^2 in KJ/kg")

+disp("from steam tables,at 4 bar,hf=604.74 KJ/kg,vf=0.001084 m^3/kg ")

+hf=604.74;

+vf=0.001084;

+h10=h9+vf*(100-4)*10^2

+disp("substituting in energy balance upon closed feed water heater,")

+disp("m6=(h11-h10)/(h6-h7)in kg per kg of steam from boiler")

+m6=(h11-h10)/(h6-h7)

+disp("substituting in energy balance upon feed water heater,")

+disp("m8=(h9-m6*h7_a+m6*h5-h5)/(h8-h5)in kg per kg of steam from boiler")

+m8=(h9-m6*h7_a+m6*h5-h5)/(h8-h5)

+disp("Let the mass of steam entering first stage of turbine be m kg,then")

+disp("W_HPT=m*{(h1-h6)+(1-m6)*(h6-h2)}")

+disp("W_HPT/m=")

+{(h1-h6)+(1-m6)*(h6-h2)}

+disp("so W_HPT=m*573.24 KJ")

+disp("also,W_LPT={(1-m6)*(h3-h8)+(1-m6-m8)*(h8-h4)}per kg of steam from boiler")

+disp("W_LPT/m=")

+{(1-m6)*(h3-h8)+(1-m6-m8)*(h8-h4)}

+disp("so W_LPT=m*813.42 KJ")

+disp("pump works(negative work)")

+disp("W_CEP=m*(1-m6-m8)*(h5-h4_a)")

+h4_a=191.83;//h4_a=hf at 0.1 bar

+disp("W_CEP/m=")

+(1-m6-m8)*(h5-h4_a)

+disp("so W_CEP=m* 0.304")

+disp("W_FP=m*(h10-h9)")

+disp("W_FP/m=")

+(h10-h9)

+disp("so W_FP=m*10.41")

+disp("net output,")

+disp("W_net=W_HPT+W_LPT-W_CEP-W_FP ")

+disp("so 50*10^3=(573.24*m+813.42*m-0.304*m-10.41*m)")

+disp("so m=W_net/(573.24+813.42-0.304-10.41)in kg/s")

+m=W_net/(573.24+813.42-0.304-10.41)

+disp("heat supplied in boiler,Q_add=m*(h1-h11) in KJ/s")

+Q_add=m*(h1-h11)

+disp("Thermal efficenncy=W_net/Q_add")

+W_net/Q_add

+disp("in percentage")

+W_net*100/Q_add

+disp("so mass of steam bled at 20 bar=0.119 kg per kg of steam entering first stage")

+disp("mass of steam bled at 4 bar=0.109 kg per kg of steam entering first stage")

+disp("mass of steam entering first stage=36.33 kg/s")

+disp("thermal efficiency=54.66%")

+disp("NOTE=>In this question there is some caclulation mistake while calculating m6 in book,which is corrected above so some answers may vary.")