A plant manager has a decision to make. She needs to reduce the concentration of salt in the 8000-gal tank from 30,000 m
Posted: Mon May 16, 2022 1:38 pm
A plant manager has a decision to make. She needs to reduce the concentration of salt in the 8000-gal tank from 30,000 mg/L to 1500 mg/L. She can do it in one of two ways:
(1) she can start flushing it out by keeping the tank well mixed while running in a hose with clean water (zero salt) at a flow rate of 60 gpm (with an effluent of 60 gpm, obviously) or (2) she can empty out some of the saline water and fill it up again with enough clean water to get 1500 mg/L. The maximum rate at which the tank will empty is 60 gpm, and the maximum flow of clean water is 60 gpm. If she intends to do this job in the shortest time possible, which alternative will she choose?
(1) she can start flushing it out by keeping the tank well mixed while running in a hose with clean water (zero salt) at a flow rate of 60 gpm (with an effluent of 60 gpm, obviously) or (2) she can empty out some of the saline water and fill it up again with enough clean water to get 1500 mg/L. The maximum rate at which the tank will empty is 60 gpm, and the maximum flow of clean water is 60 gpm. If she intends to do this job in the shortest time possible, which alternative will she choose?