Performance trends of an air-cooled steam condenser under windy conditions

Van Rooyen, J. A. (2007-03)

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2007.


Air-cooled steam condensers (ACSC’s) are increasingly employed to reject heat in modern power plants. Unfortunately these cooling systems become less effective under windy conditions and when ambient temperatures are high. A better understanding of the fundamental airflow patterns about and through such air-cooled condensers is essential if their performance is to be improved under these conditions. For known flow patterns, improved fan designs are possible and flow distortions can be reduced by means of extended surfaces or skirts, windwalls and screens. Spray cooling of the inlet air or the addition of an evaporative cooling system can also be considered for improving performance under extreme conditions. The present numerical study models the air flow field about and through an air-cooled steam condenser under windy conditions. The performance of the fans is modeled with the aid of a novel numerical approach known as the “actuator disc model”. Distorted airflow patterns that significantly reduce fan performance in certain areas and recirculatory flows that entrain hot plume air are found to be the reasons for poor ACSC performance. It is found that the reduction in fan performance is the main reason for the poor ACSC performance while recirculation of hot plume air only reduces performance by a small amount. Significant improvements in ACSC performance are possible under these conditions if a cost effective skirt is added to the periphery of the ACSC while the installation of a screen under the ACSC has very little effect.

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