A convector for air cooling of a fluid flowing in a pipe, comprising: - a path for a cooling air flow comprising an inlet from and an outlet towards the environment, - a heat exchange section comprising at least one tube bundle defining a heat exchange surface, said section being provided in said path for the air flow, - fan means producing said air flow along said path, so that said air flow externally invests said tube bundle on said heat exchange surface, - a humidifying section arranged in said path, upstream of said heat exchange section, where water is atomized to be invested by the air flow, wherein said at least one tube bundle being adequately provided with an entrance side for the fluid to be cooled to enter the at least one tube bundle, and with an exit side, other than the entrance one, for the fluid to exit the at least one tube bundle, so that the cooling fluid is able to have an overall flowing direction from the entrance side to the exit side, said convector comprising a wetting device for wetting directly with water a portion of the heat exchange surface of said at least one tube bundle to further cool said portion of said at least one tube bundle, characterized in that said wetting device comprising adjusting means for regulating the wettable width of said portion of heat exchange surface, so that said portion can be wet from a minimum or null dimension up to a maximum dimension different than the overall dimension of said heat exchange surface of the at least one tube bundle, wherein said wetting device comprises a plurality of nozzles operatively connected to an hydraulic system and directed to wet said portion of said at least one tube bundle, each nozzle being suitable to wet a respective part of said heat exchange surface of the at least one tube bundle and wherein said adjusting means for regulating the wettable width comprise valves to intercept selectively the water flows to said nozzles. - a path for a cooling air flow comprising an inlet from and an outlet towards the environment, - a heat exchange section comprising at least one tube bundle defining a heat exchange surface, said section being provided in said path for the air flow, - fan means producing said air flow along said path, so that said air flow externally invests said tube bundle on said heat exchange surface, - a humidifying section arranged in said path, upstream of said heat exchange section, where water is atomized to be invested by the air flow, wherein said at least one tube bundle being adequately provided with an entrance side for the fluid to be cooled to enter the at least one tube bundle, and with an exit side, other than the entrance one, for the fluid to exit the at least one tube bundle, so that the cooling fluid is able to have an overall flowing direction from the entrance side to the exit side, said convector comprising a wetting device for wetting directly with water a portion of the heat exchange surface of said at least one tube bundle to further cool said portion of said at least one tube bundle, characterized in that said wetting device comprising adjusting means for regulating the wettable width of said portion of heat exchange surface, so that said portion can be wet from a minimum or null dimension up to a maximum dimension different than the overall dimension of said heat exchange surface of the at least one tube bundle, wherein said wetting device comprises a plurality of nozzles operatively connected to an hydraulic system and directed to wet said portion of said at least one tube bundle, each nozzle being suitable to wet a respective part of said heat exchange surface of the at least one tube bundle and wherein said adjusting means for regulating the wettable width comprise valves to intercept selectively the water flows to said nozzles.