Degree Name

Master of Arts (MA)

Semester of Degree Completion

1979

Thesis Director

Suhrit K. Dey

Abstract

This paper evaluates and improves the performance of the Wu-Koh mathematical model for the prediction of plume dispersion from multiple natural-draft (NDCT) and mechanical-draft (MDCT) cooling towers. The Wu-Koh multiple-tower model was chosen for study due to its advanced treatment of plume merging.

Our evaluation of the Wu-Koh model was carried out by comparing model predictions of field and laboratory data. Comparisons of model predictions of visible plume outlines were made to single- and multiple-tower visible plume data. The sites of the single-tower data were Lunen (300 MWe), Chalk Point (630 MWe) and Paradise (1100 MWe); the sites of multiple-tower comparisons were Neurath (3 towers, 900 MWe total) and Amos (3 towers, 2900 MWe total). These towers represent a significant range in tower capacity. It was found that for single-towers, the model predicted visible plume rise satisfactorily but largely underpredicted visible plume length. The model was noted to predict plumes whose trajectories rose too rapidly and mixed too quickly leading to shorter plumes. Our multiple-tower comparisons revealed that the model underpredicted both visible plume rise and length.

Plume predictions with laboratory data from MDCT plume dispersion (dry plumes) revealed that in addition to the limitation noted above, two other problems existed. First, model/data discrepancies in the MDCT comparisons could be explained by (a) a lack of treatment of downwash caused by the presence of the tower structure itself and (b) a lack of treatment of the shielding of one plume by another during merging.

Model improvement was undertaken in the first of the three areas listed above. A proven model for the prediction of single-tower plumes was inserted into the Wu-Koh computer program to correct the deficiencies seen in the model for single-tower cases. Overall, improved performance of the model resulted. Treatment of downwash and sheltering effects of merging plumes is left for future work.

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