Topic: Thermodynamics
In a boiler, feed water supplied per hour is 205 kg while the coal fired per hour is 23 kg. Net enthalpy rise per kg of water is 115 KJ for conversion to steam. If the calorific valve of coal is $2050~KJ/kg.$ find the boiler efficiency.
- A. 75%
- B. 40%
- C. 50%
- D. 60%
Answer: C. 50%
Explanation: Heat utilized in steam generation = $m_{water} \times \Delta h = 205~kg \times 115~KJ/kg = 23575~KJ$.
Heat supplied by fuel = $m_{coal} \times CV = 23~kg \times 2050~KJ/kg = 47150~KJ$.
Boiler efficiency = $\frac{\text{Heat utilized}}{\text{Heat supplied}} = \frac{23575}{47150} = 0.50 = 50\\%$.