A boiler produces 9 kg steam/kg of coal burnt, which hasthe calorificvalue 27 MJ/kg. The enthalpy of feed water and steam at the exit are 300 kJ/kg and 3000 kJ/kg respectively. Its thermal efficiency is
94.2%
55%
83.57%
90%
90%
The thermal efficiency of boiler is calculated as:
Where, Q is steam generated kg/hr
H is steam enthalpy kJ/kg
h is feed water enthalpy kJ/hr
q is fuel quantity used per hour kg/hr
C.V, calorific value of fuel kJ/kg
Now, assuming q to be 1kg/hr and putting the other value from the given data, we get
Hence, the correct option is (D).
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