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A single-effect forced-circulation evaporator is to be used to evaporate 50,000 lb/hr of 50% NaOH solution to 70% NaOH. The pressure at the vapor space is 3 in. Hg absolute. Saturated steam at 70 psig is to be used as the heating medium. It is estimated that an overall coefficient of 700 BTU/hr-f2-F will be obtained. Determine the heat-transfer surface required and the steam economy if the feed to the evaporator is at 200F. 20 nto A solution is to be concentrated in a single effect evaporator from 20 to 68% solids. The specific heat of the feed, entering at 50F is 0.93. The pressure of the saturated steam to the evaporator is 20 psia and the pressure in the vapor space is 5 in. Hg abs. The steam chest has an overall heat transfer coefficient of 200 BTU/hr-ft- F. Water must be evaporated at the rate of 45,000 lb/hr. Neglecting boiling point elevation, what must be the heating surface required? What is the steam economy? 20 pts