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+clear;
+clc;
+printf("\t\t\tExample Number 8.12\n\n\n");
+// network for gas radiation between parallel plates
+// Example 8.12 (page no.-422-423) 
+// solution
+
+T1 = 800;// [K] temperature of first plate 
+E1 = 0.3;// emissivity
+T2 = 400;// [K] temperature of second plate
+E2 = 0.7;// emissivity
+Eg = 0.2;// emissivity of gray gas
+tg = 0.8;// transmissivity of gray gas 
+sigma = 5.669*10^(-8);// [W/square meter K^(4)]
+// the network shown in figure 8-39(page no.-419) applies to this problem. all the shape factors are unity for large planes and the various resistors can be computed on a unit area basis as 
+F12 = 1;
+F1g = 1;
+F2g = F1g;
+R1 = (1-E1)/E1;
+R2 = (1-E2)/E2;
+R3 = 1/(F12*(1-Eg));
+R4 = 1/(F1g*Eg);
+R5 = 1/(F2g*Eg);
+Eb1 = sigma*T1^(4);// [W/square meter]
+Eb2 = sigma*T2^(4);// [W/square meter]
+// the equivalent resistance of the center "triangle" is 
+R = 1/[(1/R3)+(1/(R4+R5))];
+// the total heat transfer is then 
+q_by_A = (Eb1-Eb2)/(R1+R2+R);// [W/square meter]
+// if there were no gas present the heat transfer would be given by equation (8-42):
+q_by_A1 = (Eb1-Eb2)/[(1/E1)+(1/E2)-1];// [W/square meter]
+// the radiosities may be computed from q_by_A = (Eb1-J1)*(E1/(1-E1)) = (J2-Eb2)*(E2/(1-E2))
+J1 = Eb1-q_by_A*((1-E1)/E1);// [W/square meter]
+J2 = Eb2+q_by_A*((1-E2)/E2);// [W/square meter]
+// for the network Ebg is just the mean of these values
+Ebg = (J1+J2)/2;// [W/square meter]
+// so that the temperature of the gas is
+Tg = (Ebg/sigma)^(1/4);// [K]
+printf("the heat-transfer rate between the two planes is %f W/square meter",q_by_A);
+printf("\n\n the temperature of the gas is %f K",Tg);
+printf("\n\n the ratio of heat-transfer with presence of gas to without presence of gas is %f",q_by_A/q_by_A1);
+
+