please dont post an answer from pervious solutions most of them were kinda wrong.Evaporation in Double$-$Effect Reverse$-$Feed Evaporators. A feed

containing $2wt\%$ dissolved organic solids in water is fed to two

double$-$effect evaporators with reverse feed. The feed enters at $100F$

and is concentrated to $25\%$ solids. The boiling$-$point rise can be

considered negligible, as can the heat of solution. Each evaporator has

a $1000-f{t}^2$ surface area, and the heat$-$transfer coefficients are $U_1=$

$500$ and $U_2=700bt\frac{u}{h}*f{t}^2*F.$ The feed enters evaporator number

$2$ and steam at $100$ psia is fed to evaporator number $1.$ The pressure in

the vapor space of evaporator number $2$ is $0\mathrm{.}98$ psia. Assume that the

heat capacity of all liquid solutions is that of liquid water. Calculate

the feed rate $F$ and the product rate $L_1$ of a solution containing $25\%$

solids. $($Hint: Assume a feed rate of$,$ say, $F=1000l\frac{b_m}{h}$ and a value

of $T_1.$ Calculate the area and $T_1.$ Then, calculate the actual feed rate

by multiplying $1000$ by $1000/$calculated area.$)$

Ans. $F=133800l\frac{b_m}{h}(60691k\frac{g}{h}),L_1=10700l\frac{b_m}{h}(4853k\frac{g}{h})$