A 10 wt% aqueous solution of NaOH at 100°F and a flow rate of 30.000 lb/h is to be concentrated to 50 wt% by evaporation using saturated steam at 115 psia.
(a) If a single-effect evaporator is used with U 400 Btulh-ft2-°F and a vapor-space pressure of 4 in. Hg, determine the heat-transfer area and the economy.
(b) If a double-effect evaporator system is used with forward feed and U = 450 Btu/h-ft2-°F and 112 = 350 Btu/h-ft2-°F, and a vapor- space pressure of 4 in. Hg in the second effect determine the heat- transfer area of each effect, assuming equal areas, and the overall economy.