CALCULATED by the following formula\(\ETA = \FRAC{m\;\times\;Δ h}{m_{COAL}\;\times\;C.V}\)where, m = water supplied per hour, Δh = rise in enthalpy, mcoal = mass of fuel, CV = calorific valueCalculation:Given:m = 205 kg/hr, mcoal = 23 kg/hr, Δh = 145 kJ/kg, CV = 2050 kJ/kg\(\eta = \frac{m\;\times\;Δ h}{m_{coal}\;\times\;C.V}\) = \(\frac{205\;\times\;145}{2050\;\times\;23}\)η = 0.6304 or 63.04% \(\approx\) 63%