An exploratory research on performance improvement of super-large natural draft wet cooling tower based on the reconstructed dry-wet hybrid rain zone

Abstract

The ambient cold air cannot reach the center area of the super-large natural draft wet cooling towers (S-NDWCTs) due to the large diameter and the large water droplets resistance in the rain zone. In order to solve this issue, the reconstructed dry-wet hybrid rain zone was proposed to improve the performance of S-NDWCTs in this paper. Some split-flow plates were arranged inside the rain zone which can divide the conventional rain zone into the dry zones and wet zones, and then produced the dry-wet hybrid rain zone. The 3D numerical model of S-NDWCTs was established and validated by the actual design data, and then the ventilation and thermal performance of the S-NDWCTs with the reconstructed dry-wet hybrid rain zone were investigated. The numerical simulation results demonstrated that, after adopting the reconstructed dry-wet hybrid rain zone, the airflow velocity inside the tower becomes larger significantly, and the high temperature areas of both the moist air and the circulating water in the central area of the tower disappear. Additionally, by comparing with the S-NDWCTs with a conventional rain zone, it was discovered that, under the conditions of split-flow plates dimension parameters used in this paper, the ventilation rate and the Merkel number increase by about 2.38% and 9.89% at most, respectively; the outlet water temperature decreases by approximately 0.48 °C at most. The investigations in this paper could provide a new idea and a novel method for the in-depth energy-saving research and structural optimal design of the S-NDWCTs.