Question 38General Subjects - Assistant Engineer

The correct answer is D) The towers are shifted, and heat is applied to the off-going tower. In a twin-tower desiccant type air dryer, the desiccant (typically silica gel) in one tower becomes saturated with moisture while the other tower is in use. To rejuvenate the saturated tower, the towers are shifted, and heat is applied to the off-going tower. This allows the heat to drive off the moisture from the desiccant, effectively regenerating it for future use. The other options are incorrect because: A) refrigerating the off-going tower would not drive off the moisture, B) applying heat to the tower on service would disrupt the drying process, and C) refrigerating the tower on service would not rejuvenate the desiccant.