clear; clc; // Illustration 12.4 // Page: 676 printf('Illustration 12.4 - Page: 676\n\n'); // Solution (a) //***Data***// // For rectangular pan: l = 0.7;// [m] b = 0.7;// [m] zS = 0.025;// [m] zM = 0.0008;// [m] d = 0.1;// [m] Y1 = 0.01;// [kg water/kg dry air] TempG = 65;// [OC] v = 3;// [m/s] TempR = 120;// [OC] //*************// // From Table 7.1: (Pg 234) vH = (0.00283+(0.00456*Y1))*(TempG+273);// [cubic m/kg dry air] Density_G = (1+Y1)/vH;// [kg/cubic m] G = v*Density_G;// [kg/square m.s] de = 4*d*l/(2*(l+d));// [m] // From Eqn. 12.20: hc = 5.90*G^0.71/de^0.29;// [W/square m.K] // Assume: e = 0.94; // Estimate: TempS = 38;// [OC] // From Eqn. 12.14: hR = e*5.729*10^(-8)*((273+TempR)^4-(273+TempS)^4)/((273+TempR)-(273+TempS)); A = l*b;// [square m] Am = A;// [square m] As = 4*l*zS;// [square m] Au = Am+As;// [square m] // Thermal Coductivities: kM = 45;// [W/m.K] kS = 3.5;// [W/m.K] // By Eqn. 12.16: Uk = 1/(((1/hc)*(A/Au))+((zM/kM)*(A/Au))+((zS/kS)*(A/Am)));// [W/squre m.K] // From Table 7.1: (Pg 234) Cs = 1005+(1884*Y1);// [kJ/kg] // At estimated 38 OC lambdaS = 2411.4;// [kJ/kg] // From Eqn. 12.18: // (Ys-Y1)*lambdaS*10^3/Cs = ((1+(Uk/hc))*(TempG-Temps))+((hR/hC)*(TempR-TempS)) // On Simplifying: // Ys = 0.0864-(10.194*10^(-4)*TempS) // The eqn. is solved simultaneously with the saturated humidity curve of the psychometric chart for the air water mixture. // From Fig. 12.12: (Pg 677) Ys = 0.0460;// [kg water/kg dry air] TempS = 39;// [OC] // At 39 OC lambdaS = 2409.7;// [kJ/kg] // From Eqn. 12.17: Nc = (((hc+Uk)*(TempG-TempS))+(hR*(TempR-TempS)))/(lambdaS*10^3);// [kg water evaporated/square m.s] printf("The Evaporation Rate: %e kg/s\n",Nc*A); // Solution (b) // When no radiation or conduction of heat through the solid occurs, the drying surface assumes wet bulb temparature of the air. // From Fig. 12.12 (Pg 677) TempS = 28.5;// [OC] Ys = 0.025;// [kg water/kg dry air] lambdaS = 2435;// [kJ/kg] // From Eqn. 12.17: Nc = hc*(TempG-TempS)/(lambdaS*10^3);// [kg/aquare m.s] printf("The Evaporation Rate: %e kg/s\n",Nc*A);