Abstract: Compressor discharge air flows through a heat exchanger in heat exchange relation with cooling water and is supplied at reduced temperature in atomizing air and purge modes to combustors in a dual-fuel gas turbine. The heat exchanger has a pair of bypass passages in parallel with a temperature regulating valve controlling flow of water through the heat exchanger in response to the temperature of the compressor discharge air exiting the heat exchanger. Should the flow control valve close in response to low temperature of the compressor discharge air, in the air atomizing mode, the bypass passages with orifices therein provide a minimum protective flow of cooling water to the heat exchanger. In the purge mode where only half the air flow and heat rejection is required in the heat exchanger and the flow control valve closes, a bypass valve in one of the bypass passages closes to enable reduced flow of cooling water through the heat exchanger.