Abstract: An apparatus which dries compressed air by cooling it substantially to around its dew point. The apparatus includes at least a first heat exchanger, for the direct cooling of the compressed air, selectively associated with a refrigeration unit by a first refrigeration circuit. The first heat exchanger is immersed in a chamber containing a cooling liquid suitable to act as a thermal mass to accumulate the excess thermal energy generated by the refrigeration unit with respect to the energy needed to take the compressed air to dew point temperature. The apparatus also includes a second heat exchanger also immersed in the cooling liquid and suitable to intervene mainly during a momentary de-activation of the refrigeration unit. The apparatus is intended to dry compressed air with a high thermal yield and to substantially correlate energy consumption to the quantity of compressed air actually required.