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A triple-effect backward-feed evaporator concentrates 5kg/s of liquor from 10 per cent to 50 per cent solids. Steam is available at 375kN/m2 and the condenser operates at 13.5kN/m2. What is the area required in each effect, assumed identical, and the economy of the unit? The specific heat capacity is 4.18kJ/kgK at all concentrations and that there is no boiling-point rise. The overall heat transfer coefficients are 2.3,2.0 and 1.7kW/m2K respectively in the three effects, and the feed enters the third effect at 300K