Aboiler is capable of generating 8 kg steam per kg of fuel at 400 °c. feed water is supplied at pressure of 30 bar, 40 °c and leaves economiser at 150°c for entering to evaporator. steam leaves evaporator with dryness fraction of 0.98 and enters the superheater. fuel used has calorific value of 29000 kj/kg. considering no pressure loss inside the boiler determine boiler efficiency and fraction of heat given to steam in each section of boiler.

At steady state, air at 200 kpa, 325 k, and mass flow rate of 0.5 kg/s enters an insulated duct having differing inlet and exit cross-sectional areas. the inlet cross-sectional area is 6 cm2. at the duct exit, the pressure of the air is 100 kpa and the velocity is 250 m/s. neglecting potential energy effects and modeling air as an 1.008 kj/kg k, determine ideal gas with constant cp = (a) the velocity of the air at the inlet, in m/s. (b) the temperature of the air at the exit, in k. (c) the exit cross-sectional area, in cm2