These type of air dryers are used to utilize the heat energy of compressor discharge .In this type of HOC Dryer the hot air at 120 Deg C {Minimum} is directly taken from compressor discharge through insulated pipelines, is passed through one drying vessel where saturated desiccant is regenerated by this hot air.After picking up moisture from desiccant bed, the air is cooled in an intermediate cooler. Here the moisture is condensed and removed by auto drain valve.