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+clc
+Hfg = 2257 // Latent heat at 100 degree Celsius
+
+ma =  500 // mass flow rate of air in Kg/h
+ch = 1.005 // Specific heat capacity of hot air in kJ/kgK
+ta1 = 260 // Inlet temperature of hot air in degree Celsius
+ta2 = 150 // Inlet temperature of cold air in degree Celsius
+tc1 = 100 // Inlet temperature of steam
+tc2 = tc1 // Exit temperature of steam
+U = 46 // heat transfer coefficient in W/m^2K
+
+printf("\n Example 18.7\n")
+Q = ma*ch*(ta1-ta2)
+m = Q/Hfg // mass flow rate of steam
+te = ta2-tc1 // Exit end temperature difference in degree Celsius
+ti = ta1 - tc2 // Inlet end temperature  difference in degree Celsius
+t_lm = (ti-te)/(log(ti/te))
+A = Q / (U*t_lm*3.6) // Surface are of heat exchanger
+
+printf("\n Surface area of heat exchanger is %f m^2",A)
+
+//The answers vary due to round off error
+