Numerical investigations on the start-up of a dual-tower system under crosswind: Collaborative and competitive effects

Abstract

A three-dimensional numerical model is established to investigate the start-up process of a dual-tower system composed by two natural draft dry cooling towers (NDDCTs) under crosswind from 1 to 10 m/s. The coupled effects of tower spacings (1.5D, 2D and 3D) and incidence angles (0°, 45° and 90°) on the transients of the dual-tower system are checked. A simplified analysis identifies an enhancing factor EN and an impairing factor IM, which mutually determine the start-up duration of the dual-tower system. The numerical results present a general trend of the start-up process for a dual-tower system, i.e., it increases under mild crosswind from 1 to 4 m/s, peaks between 4 and 5 m/s and drops from 5 to 10 m/s. However, the dual-tower system at different tower spacings interacts with crosswind of different incidence angles in different ways during the start-up process. When paralleling with crosswind at 0°, both NDDCTs collaborate via the rising plumes. The collaborative effect accelerates the start-up process and is enhanced at a closer tower spacing. While perpendicular to the crosswind at 90°, both NDDCTs compete for the bottom inlet air via the shared zone. The competitive effect extends the start-up duration but is weakened at a larger tower spacing. While both effects exist simultaneously at a 45° wind incidence angle, leading to an increase of duration from 1.5D to 2D as the collaboration is weakened more, but a decrease of duration from 2D to 3D as the competition is decreased more. These conclusions will be useful for the request of larger cooling capacity and dispatchability on power blocks in hybrid energy systems.