For which one of the following situations would Kendall’s tau be appropriate? a) The Mohs scale rates the hardness of minerals. If one mineral can scratch another, it is judged….

## Calculate the area and T1. Then, calculate the actual feed rate by multiplying 1000 by 1000/calculated area.)

Evaporation in Double-Effect Reverse-Feed Evaporators. A feed containing 2 wt % dissolved organic solids in water is fed to two double-effect evaporators with reverse feed. The feed enters at 100°F 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-ft ^{2} surface area, and the heat-transfer coefficients are U_{1} = 500 and U_{2} = 700 btu/h · ft ^{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 0.98 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 = 1000 lbm/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.)