Compare refrigerated dryer and desiccant dryer in terms of dew point and energy use.

• A. Refrigerated dryers achieve very low dew points but use more energy.
• B. Desiccant dryers remove moisture by cooling; refrigerated dryers achieve very low dew points.
• C. Refrigerated dryers remove moisture by cooling to a moderate dew point with relatively low energy use; desiccant dryers achieve very low dew points but require energy for regeneration.
• D. Desiccant dryers are cheaper to operate and have higher dew points.

Answer: (C)

Dew point tells you how dry the air is—the lower the dew point, the drier the air. Refrigerated dryers use a cooling cycle to condense moisture out of the air, delivering a moderate dew point (typically a few degrees above freezing). Because this method relies mainly on cooling and a fan, its energy use tends to be relatively low. Desiccant dryers, on the other hand, remove moisture by adsorption onto a drying material, which can achieve very low dew points—far drier air. But to keep the desiccant effective, you must periodically regenerate it by heating (and often purge with dry air), which consumes additional energy. So the best description is that refrigerated dryers give a moderate dew point with relatively low energy use, while desiccant dryers achieve very low dew points but require energy for regeneration.