Answer to Question #209898 in Thermal Power Engineering for Zeeshan

Question

Two boilers one with superheater and other without superheater are delivering equal 

quantities of steam into a common main. The pressure in the boilers and the main is 16 bar. 

The temperature of the steam from a boiler with a superheater is 350°C and temperature of 

the steam in the main is 200°C. Determine the quality of steam supplied by the other boiler.

Answer 1

From the steam table, at 16 bars, $h= 1959.7 kJ/kg; t_s=195.07 ^0C; k_p=2.1 kJ/kg K$

Let the dryness fraction generated by boiler B be x

Then, moisture in 1 kg of wet steam = $(1-x) kg$

Heat required to evaporate the moisture = $(1-x)L$

Heat required to superheat thedry steam = $k_p(t_2-t_s) kJ/kg$

Heat gained by wet steam of the boiler B $(1-x)L+k_p(t_2-t_s) kJ/kg$

Heat lost by superheated steam of boiler A $k_p(t_2-t_1) kJ/kg$

Heat gained by wet steam of the boiler B= Heat lost by superheated steam of boiler A

$(1-x)L+k_p(t_2-t_s) kJ/kg =k_p(t_2-t_1) kJ/kg$

$(1-x)*1959.7+2.1*(235-195.07) kJ/kg =2.1(350-200) kJ/kg$

$x=0.88204 \implies 88.204 \%$