Heat reactivated dryers are used when one needs compressed air of very low dew point of (-) 60oC or (-) 80o Deg C. The desiccant is regenerated at higher temperature, along with small quantity of dry air purge. The drying unit has 2-vessels filled with activated alumina or molecular sieves desiccant. Electrical heaters are provided in a central finned stainless steel pipe in both drying vessels. The internal heaters provide maximum heat transfer efficiency resulting in lower power requirement.