A continuous evaporator is operated with a given feed materialunder conditions in which the
concentration of the product remains constant. The feed rate at thestart of a cycle after the
tubes have been cleaned has been found to be 5000 kg/h. After 48 hof continuous operation,
tests have shown that the feed rate decreases to 2500 kg/h. Thereduction in capacity is due to
true scale formation. If the downtime per cycle for emptying,cleaning, and recharging is 6 h,
how long should the evaporator be operated between cleanings inorder to obtain the maximum
amount of product per 30 days?
