Abstract: A heat recovery system for supplementing the exhaust mass flow from a gas turbine with additional flow of preheated air to provide greater steam output from a heat recovery unit such as a steam generator. The supplemental preheated air is ambient ventilation air which is used to cool the outer enclosure of the gas turbine. A diverter valve is employed to selectively add to the mass flow from the gas turbine any appropriate mass flow of the ventilation air between zero and a maximum amount. An eductor may be used to aid a blower for moving the supplemental air. A duct burner upstream from the heat recovery unit is employed to raise the temperature of a mixture of turbine exhaust gases and ventilation air being supplied to the heat recovery unit. In a similar fashion, supplemental preheated air may be taken from air used for cooling a generator or other primary load being driven by the gas turbine.