(a) Explain the terms: forced draft, induced draft and balanced draft, and discuss their relative merits and demerits. What is the role of a chimney in a boiler? Why no chimney is provided in a locomotive boiler? 20
(b) An oil fired boiler used 52 kg/hr of oil having a higher calorific value of 44900 kJ/kg and composition/kg C = 0.847, H2 = 0.13, S = 0.0125 and generates 635 K. The flue gases having dry gas analysis / unit volume O2 = 0.043. CO2 = 0.124, N2 = 0.833 and specific heat 1.005 kJ/kg-K, leave the boiler at 635 K. The pressure and temperature of steam after throttling 1.15 bar and 398 K respectively. Taking the partial pressure of steam in flue gases as 0.07 bar and the specific heat of superheated steam = 2.1 kJ/kg-K, determine – (i) the equivalent evaporation / kg of fuel;
(ii) boiler efficiency
Draw up a complete heat balance sheet. Take boiler room temperature = 234 K.