a) From the data relating to a natural draught flue connected to a gas fire boiler determine I. The natural draught available when the plant is run up to temperature II. The volume rate of flue gas III. The stack diameter Data Stack height 8m, ambient air density at 21C is 1.1kg/m3, mean flue gas temperature 150C, boiler output 180kW, calorific value of natural gas 39.4MJ/m2, boiler thermal efficiency 80%, air fuel ratio by volume 10:1, mean flue gas velocity in the stack 6m/s