A study of wind effects and wind barriers on the performance of natural draft cooling towers in a power station

Publication Type:
Thesis
Issue Date:
2007
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NO FULL TEXT AVAILABLE. Access is restricted indefinitely. ----- A study of wind effects on the performance of natural draft wet cooling towers has been performed. The results are based on the prototype tower testing of a cooling tower at a power station, scale model testing in a wind tunnel by fixing the plant building models around the turntable and the numerical simulations of the wind flow patterns around the towers and the buildings. The prototype test results showed that the approach temperature of the tower decreased significantly when the wind was blowing from the direction of the plant building sides. This decrease of 3 K in approach temperature was obtained when the wind speed increased from 0 to 6 m/s from the plant building side. The tower approach increased to 2 K for a wind speed of 4 m/s when it was blowing from the second cooling tower side. The scale model testing showed that as the wind direction changes relative to the obstruction, the tower performance coefficient varied. The major performance drop was observed when the wind was blowing from the second tower side. Wind tunnel tests indicated that curative devices improve the tower performance coefficient (Cpi) by 10 to 28 percent depending on the wind direction and the obstructions near the tower. The 10 percent improvement was obtained when the wind was blowing from the building sides and up to 28 percent when it was from the second tower side. The numerical simulations carried out on the wind flow pattern around the towers and buildings showed the reduction in wind speed as it approached the cooling towers after obstructed by buildings. The wind loses up to 70 percent of its magnitude when it reached the vicinity of the cooling towers down stream of the buildings. The second tower became directly exposed to the wind when it was blowing from that side with the large building on one side and the first tower behind it. The curative devices installed around the towers diverted the wind from directly affecting the both sides of the tower. This resulted in a high velocity wind stream created at the windward section and a decrease in suction causing adverse affect otherwise on both sides (at ±90°) on the tower circumference. This phenomenon will improve the airflow inside the tower due to decrease in suction on both sides and an increase in airflow at the windward side of the tower compared to the tower with no curative devices. This study has discovered that natural draft cooling tower performance heavily depends on the type of wind barriers. The plant buildings have been found to provide the most efficient means of wind barriers for cooling towers in power stations. A limited potential for improvement in tower performance exists for wind barriers to be installed around the cooling towers in those power stations where buildings already provide efficient sheltering from wind prone directions. There will be good potential for wind barriers for those power stations where cooling towers are directly exposed to wind or if there is a partial sheltering produced by buildings. That is, in general local geographic effects have to be considered in evaluating cooling tower layouts in new power stations.
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