Operational flexibility, such as faster start-up time or faster load change rate, and higher thermal efficiency, have become more and more important for recent thermal power systems. The AHAT (advanced humid air turbine) system has been studied to improve operational flexibility and thermal efficiency of the gas turbine power generation system. AHAT is an original system which substitutes the WAC (water atomization cooling) system for the intercooler system of the HAT cycle. A 3MW pilot plant, which is composed of a gas turbine, a humidification tower, a recuperator and a water recovery system, was built in 2006 to verify feasibility of the AHAT system. In this paper, ambient temperature effects, part-load characteristics and start-up characteristics of the AHAT system were studied both experimentally and analytically. Also, change in heat transfer characteristics of the recuperator of the 3MW pilot plant was evaluated from November 2006 to February 2010. Ambient temperature effects and part-load characteristics of the 3MW pilot plant were compared with heat and material balance calculation results. Then, these characteristics of the AHAT and the CC (combined cycle) systems were compared assuming they were composed of mid-sized industrial gas turbines. The measured cold start-up time of the 3MW AHAT pilot plant was about 60min, which was dominated by the heat capacities of the plant equipment. The gas turbine was operated a total of 34 times during this period (November 2006 to February 2010), but no interannual changes were observed in pressure drops, temperature effectiveness, and the overall heat transfer coefficient of the recuperator.

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