In this design there is NO LOSS of compressed air. Time cycle is 4+4 hours with (-) drying towers filled with SILICA GEL desiccant. For regeneration, a centrifugal air blower and an electrical heater is provided. Desiccant is heated upto 200oC by hot air for complete regeneration. These dryers are bulky in size and the power consumption is almost double as compared to "INTERNALLY HEAT REACTIVATED TYPE DRYER". In capacities less than 500 NM3/hr these are uneconomical and not recommended. Also, since regeneration of the desiccant is by atmospheric air, these dryers give Dew Point only upto (-) 40oC. Cost wise these Airdryers are 100% more costly as compared to "Internally Heat Reactivated Type Dryers". One should go for this type of Dryer only when loss of compressed air during regeneration is not acceptable and Dew Point required is not critical. These are recommended for capacities above 500 NM3/hr only. Operating pressure can be from 1 kg/cm2g to 50 kg/cm2g.