An air cooler for power plants comprising a pressure vessel, in which is accommodated a coaxial arrangement containing a cylindrical central tube, a helical tube bundle surrounding the central tube and a cylindrical casing surrounding the tube bundle. The central tube extends, at one end of the coaxial arrangement, into a first space adjacent to the tube bundle and closed off outwardly by the casing. The central tube can be acted upon by air from outside the pressure vessel, via an air inlet connection piece, at the other end of the coaxial arrangement through a space adjacent to the tube bundle. Water can be fed into the tube bundle from an end of the coaxial arrangement and steam can be extracted from the tube bundle.