10% NaOH solution to 50% in a single effect evaporator at 20000 lb/h is concentrated. The pressure of the saturated steam used for heating is 6.09 psig and the evaporator The vapor pressure inside is 2.9 psia. Overall heat transfer coefficient 350 Btu/ft2 .h.F. Feed Since the temperature is 60 F, the amount of steam used, the economy and the heat transfer surface Calculate the area.