A triple-effect evaporator with BACKWARD feed is evaporating aqueous solution with negligible boiling-point rise and containing 10 wt % solids to 50% solids. Fresh saturated steam at 1.02 atm abs (corresponding to 120 C of temperature) is used for heating in the first effect. The pressure in the vapor space of the third effect is 10 cmHg. At given pressure, the boiling point of the solution in the third effect is 51 C. The feed rate 25 000 kg/h and the temperature 21 C. The liquid heat capacity is 4.18 kJ/kgC for all liquid concentrations. The heat-transfer coefficients are U1 = 2250, U2 = 1750, and U3 = 1375 kcal/m2 hC. Calculate the surface area of each effect, the steam, distribution of temperatures in each effect and steam economy of system.