Effect of water temperature on the performance of gas turbine inlet air-fogging systems
27 June 2013
With more than 1,000 fogging systems installed worldwide on a wide range of gas turbines of different types, gas turbine inlet air fogging systems have become a well-established technology used to increase gas turbines power output.
The major benefit of spraying fog droplets in the inlet airflow of the gas turbines is to increase the density of the air entering the gas turbine by evaporative cooling in the inlet air stream. A significant amount of research has been carried out to improve the efficiency of fogging systems. However, the effect of water temperature on the overall efficiency of a fogging system has yet to be addressed. In this paper, a detailed analysis of this effect will be presented, both from an experimental and a theoretical view point.
Due to the small size of the droplets used in this application, the temperature of the droplet converges quickly to the wet bulb temperature, regardless of the initial water temperature. The rapidity at which this convergence occurs depends on the initial droplet size, the water temperature, the air mass flow to mass of injected water ratio, and the ambient psychrometric conditions of the surrounding air.
The present study was carried out using water temperatures between 33° and 140°F (1° and 60°C). Results showed that the water temperature has no significant effect on the droplet size. However, within the range of droplet sizes atomized from nozzles installed in the fogging system, using cold water provides a marginal benefit on the cooling efficiency; using hot water, on the other hand, slightly increases the evaporation efficiency.