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+clear;
+clc;
+
+// Illustration 7.15
+// Page: 267
+
+printf('Illustration 7.15 - Page: 267\n\n');
+
+// solution
+
+//***Data***//
+w = 0.75;// [m]
+OD = 19.05/1000;// [m]
+l = 3.75;// [m]
+n = 20;
+t = 1.65/1000;// [m]
+Ws = 2.3;// [kg/s]
+Wal = 10;// [kg/s]
+Wt = 4;// [kg/s]
+Density = 800;// [kg/cubic m]
+viscocity = 0.005;// [kg/m.s]
+K = 0.1436;// [W/m.K]
+Ct = 2010;// [J/kg.K]
+Cal = 4187;// [J/kg.K]
+Y1_prime = 0.01;// [kg H2O/kg dry air]
+Y2_prime = 0.06;// [kg H2O/kg dry air]
+TempT = 95;// [OC]
+//*****//
+
+Free_area = (w-(n*OD))*l;// [square m]
+Gs_min = 2.3/Free_area;// [kg/square m.s]
+Yav_prime = (Y1_prime+Y2_prime)/2;// [kg H2O/kg dry air]
+// From Eqn. 7.86:
+ky = 0.0493*(Gs_min*(1+Yav_prime))^0.905;// [kg/square m.s.delta_Y_prime]
+// From Fig. 7.5:
+H1_prime = 56000;// [J/kg]
+Ao = 400*%pi*OD*l;// [square m]
+// Cooling water is distributed over 40 tubes & since tubes are staggered
+geta = Wal/(40*2*l);// [kg/m.s]
+geta_by_OD = geta/OD;// [kg/square m.s]
+// Assume:
+TempL = 28;// [OC]
+// From Eqn. 7.84:
+hL_prime = (982+(15.58*TempL))*(geta_by_OD^(1/3));// [W/square m.K]
+// From Eqn. 7.85:
+hL_dprime = 11360;// [W/square m.K]
+// From Fig. 7.5 (Pg 232)
+m = 5000;// [J/kg.K]
+Ky = 1/((1/ky)+(m/hL_dprime));
+ID = (OD-(2*t));// [m]
+Ai = %pi*(ID^2)/4;// [square m]
+Gt_prime = Wt/(n*Ai);// [kg/square m.s]
+Re = ID*Gt_prime/viscocity;
+Pr = Ct*viscocity/K;
+// From a standard correlation:
+hT = 364;// [W/square m.K]
+Dav = (ID+OD)/2;// [m]
+Zm = (OD-ID)/2;// [m]
+Km = 112.5;// [W/m.K]
+// From Eqn. 7.67:
+Uo = 1/((OD/(ID*hT))+((OD/Dav)*(Zm/Km))+(1/hL_prime));// [W/square m.K]
+// From Eqn. 7.75:
+alpha1 = -(((Uo*Ao)/(Wt*Ct))+((Uo*Ao)/(Wal*Cal)));
+alpha2 = m*Uo*Ao/(Wt*Ct);
+// From Eqn. 7.76:
+beeta1 = Ky*Ao/(Wal*Cal);
+beeta2 = -((m*Ky*Ao/(Wal*Cal))-(Ky*Ao/Ws));
+y = deff('[y] = f26(r)','y = (r^2)+((alpha1+beeta2)*r)+((alpha1*beeta2)-(alpha2*beeta1))');
+r1 = fsolve(10,f26);
+r2 = fsolve(0,f26);
+beeta2 = 1.402;
+// From Eqn. 7.83:
+// N1-(M1*(r1+alpha1)/beeta1) = 0............................................(1)
+// N2-(M2*(r2+alpha2)/beeta2) = 0............................................(2)
+// From Eqn. 7.77:
+// At the top:
+x1 = 1;
+// TempL2+(M1*exp(r1*x1))+(M2*exp(-(r2*x1))) = TempL.........................(3)
+// From Eqn. 7.78:
+// At the bottom:
+x2 = 0;
+// H1_star-N1-N2 = H1_prime..................................................(4)
+// From Eqn. 7.80:
+// ((M1/r1)*(exp(r1)-1))+((M2*r2)*(exp(r2)-1)) = (Tempt-TempL)...............(5)
+// From Eqn. 7.81:
+// ((N1/r1)*(exp(r1)-1))+((N2*r2)*(exp(r2)-1)) = (H1_star-H1_prime)..........(6)
+// From Eqn. 7.91 & Eqn. 7.92:
+// Uo*Ao*(TempT-TempL)=Ky*Ao*(H1_star-H1_prime)..............................(7)
+
+// Elimination of M's & N's by solving Eqn. (1) to (4) and (7) simultaneously:
+// and from Fig. 7.5 (Pg 232):
+TempL1=28;// [OC]
+H1_star=(Uo*Ao*(TempT-TempL)/(Ky*Ao))+H1_prime;// [J/kmol]
+// Solving (1) to (4) simultaneously:
+a = [1 -(r1+alpha1)/beeta1 0 0;0 0 1 -(r2+alpha1)/beeta1;0 exp(r1*x1) 0 exp(r2*x1);1 0 1 0];
+b = [0;0;TempT-TempL1;H1_star-H1_prime];
+soln = a\b;
+N1 = soln(1);
+M1 = soln(2);
+N2 = soln(3);
+M2 = soln(4);
+// By Eqn. 5
+delta_Temp = ((M1/r1)*(exp(r1)-1))+((M2*r2)*(exp(r2)-1));// [OC]
+Q = Uo*delta_Temp*Ao;
+TempT1 = TempT-(Q/(Wt*Ct));// [OC]
+H2_prime = Q/(Ws)+H1_prime;// [J/kg]
+printf("Temparature to which oil was cooled: %f OC\n",TempT1); \ No newline at end of file