With the aid of a sketch discuss the design of a hydro cyclone showing all the relevant design equations. [6] The size distribution by mass of the dust carried in a gas, together with the efficiency of collection over each size range, is as follows: Size range (um) 0-5 5-10 10-20 20-40 40-80 80-160 Mass (per cent) 10 15 35 20 10 10 Efficiency (per cent) 20 40 80 90 95 100 Calculate (1) the overall efficiency of the collector (ii) percentage by mass of the emitted dust that is smaller than 20 um in diameter (iii) If the dust burden is 18 g/m' at entry and the gas flow 0.3 m/s, calculate the mass flow of dust emitted. [10]