Apple juice is concentrated in a double$-$effect evaporator. The feed enters the first stage

at $9\mathrm{.}5\%$ solids and leaves the second stage at $35\%$ solids. The feed rate is $15,000k\frac{g}{h}$ at

$30$degC. The temperature in the second stage is $60$deg. The overall heat transfer

coefficients for the first and second stages are $800$ and $600\frac{W}{S}$qmdegC and the

specific heats of the food are $4\mathrm{.}0,3\mathrm{.}0,$ and $2\mathrm{.}0K\frac{J}{K}$gdegC at the beginning, in stage $1$

and in stage $2,$ respectively. Determine the steam economy assuming that steam at $120C$

is available and heat transfer areas and temperature gradients are equal in both effects.

Also given are: at $120$degC : enthalpy of saturated vapor and condensate are $(2706$ and

$504k\frac{J}{K}g$; and at $60$degC : $(2610$ and $251k\frac{J}{K}g.$