* Bilinear heat exchanger network problem * Avriel and Williams (1971) SCALAR Tcin inlet temperature of cold stream /100/; SCALAR Tcout outlet temperature of cold stream /500/; SCALAR Th1in inlet temperature of hot stream 1 /300/; SCALAR Th2in inlet temperature of hot stream 2 /400/; SCALAR Th3in inlet temperature of hot stream 3 /600/; SCALAR FCp flowrate-heat capacity of cold stream /100000/; SCALAR U1 heat transfer coefficient for first heat exchanger /120/; SCALAR U2 heat transfer coefficient for second heat exchanger /80/; SCALAR U3 heat transfer coefficient for third heat exchanger /40/; VARIABLES A1 area of first heat exchanger A2 area of second heat exchanger A3 area of third heat exchanger Tc1 temperature of cold stream after first heat exchanger Tc2 temperature of cold stream after second heat exchanger Th1out outlet temperature of stream 1 Th2out outlet temperature of stream 2 Th3out outlet temperature of stream 3 objval objective function variable; FREE VARIABLES objval; EQUATIONS f Objective function f1 f2 f3 f4 f5 f6 ; f .. objval =e=A1 + A2 + A3; f1 .. Tc1 + Th1out - Tcin - Th1in =l= 0; f2 .. -Tc1 + Tc2 + Th2out - Th1in =l= 0; f3 .. Th3out - Tc2 - Th3in + Tcout =l= 0; f4 .. A1 - A1*Th1out + FCp/U1*Tc1 - FCp/U1*Tcin =l= 0; f5 .. A2*Tc1 - A2*Th2out - FCp/U2*Tc1 + FCp/U2*Tc2 =l= 0; f6 .. A3*Tc2 - A3*th3out - FCp/U3*Tc2 + FCp/U3*Tcout =l= 0; * Bounds A1.LO = 100; A1.UP = 10000; A2.LO = 1000; A2.UP = 10000; A3.LO = 1000; A3.UP = 10000; Tc1.LO = 10; Tc1.UP = 1000; Tc2.LO = 10; Tc2.UP = 1000; Th1out.LO = 10; Th1out.UP = 1000; Th2out.LO = 10; Th2out.UP = 1000; Th3out.LO = 10; Th3out.UP = 1000; * Starting point (global solution) * A1.L = 1026.94; * A2.L = 1000.00; * A3.L = 5485.28; * Tc1.L = 265.06; * Tc2.L = 280.59; * Th1out.L = 134.94; * Th2out.L = 284.47; * Th3out.L = 380.59; MODEL test /ALL/; SOLVE test USING NLP MINIMIZING objval;