Heat exchanger particularly adapted for cooling and dehumidifying air, comprising: - a cooler/heater provided with heat exchange surfaces configured so as to define between them two countercurrent paths that comprise: - a first path for a flow of hot and humid air, which extends between a first inlet line and a first outlet line; - a second path for a flow of cold dehumidified air, which extends between a second inlet line and a second outlet line; - an evaporator provided with heat exchange surfaces configured so as to define between them two countercurrent paths that comprise: - a first path for a flow of partially cooled humid air, coming from said first outlet line of said cooler/heater, which extends between a first inlet line and a first outlet line; - a second path for a coolant fluid (Fr), coming from an external source, which extends between a second inlet line and a second outlet line; - a condensate separator, in which condenser surfaces are provided, configured so as to define between them a path for cooled humid air coming from said first outlet line of said evaporator, which extends between an inlet line and an outlet line, said cooler/heater, said evaporator and said condensate separator being independent units from each other joined by connection means for defining a single-block body on whose outer surface said inlet lines (21i, 22i; 31i, 32i; 41i) and said outlet lines (21u, 22u; 31u, 32u; 41u) are provided, characterised in that it comprises: - a first conduit that places in communication said outlet line of said condensate separator with said second inlet line of said cooler/heater; - a second conduit that places in communication said first outlet line of said cooler/heater with said first inlet line of said evaporator; - a third conduit that places in communication said first outlet line of said evaporator with said first inlet line of said condensate separator, said conduits (5, 6, 7) being arranged projecting externally from said outer surface that delimits said single-block body. - a cooler/heater provided with heat exchange surfaces configured so as to define between them two countercurrent paths that comprise: - a first path for a flow of hot and humid air, which extends between a first inlet line and a first outlet line; - a second path for a flow of cold dehumidified air, which extends between a second inlet line and a second outlet line; - a first path for a flow of hot and humid air, which extends between a first inlet line and a first outlet line; - a second path for a flow of cold dehumidified air, which extends between a second inlet line and a second outlet line; - an evaporator provided with heat exchange surfaces configured so as to define between them two countercurrent paths that comprise: - a first path for a flow of partially cooled humid air, coming from said first outlet line of said cooler/heater, which extends between a first inlet line and a first outlet line; - a second path for a coolant fluid (Fr), coming from an external source, which extends between a second inlet line and a second outlet line; - a first path for a flow of partially cooled humid air, coming from said first outlet line of said cooler/heater, which extends between a first inlet line and a first outlet line; - a second path for a coolant fluid (Fr), coming from an external source, which extends between a second inlet line and a second outlet line; - a condensate separator, in which condenser surfaces are provided, configured so as to define between them a path for cooled humid air coming from said first outlet line of said evaporator, which extends between an inlet line and an outlet line, - a first conduit that places in communication said outlet line of said condensate separator with said second inlet line of said cooler/heater; - a second conduit that places in communication said first outlet line of said cooler/heater with said first inlet line of said evaporator; - a third conduit that places in communication said first outlet line of said evaporator with said first inlet line of said condensate separator, said conduits (5, 6, 7) being arranged projecting externally from said outer surface that delimits said single-block body.