Numerical investigation of flow deflectors for the improvement of condensing air flux through the air-conditioning unit on high-speed trains

• Published in: Building and environment Vol. 215; p. 108949
• Main Authors: Li, Xueliang, Wu, Fan, Tao, Yu, Yang, Mingzhi, Xu, Renze, Vainchtein, Dmitri
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.05.2022; Elsevier BV
• Subjects: Aerodynamic drag; Air conditioning; Air conditioning equipment; Condensing air flux; Cooling rate; Deflectors; Detached eddy simulation; Eddy simulation; Flow deflector; Fluctuations; High speed rail; High-speed train; Locomotives; Mathematical models; Overheating; Shear flow; Trains; High-speed train; Detached eddy simulation; Condensing air flux; Flow deflector; Air-conditioning
• ISSN: 0360-1323; 1873-684X
• DOI: 10.1016/j.buildenv.2022.108949

It has been observed that the condensing air flux through the air-conditioning (AC) unit on a running high-speed train significantly decreases due to the shear stream flowing over the train roof. Insufficient condensing air may put the AC under a risk of overheating. In this study, four shapes of flow deflectors that are able to alleviate the flux drop are designed and investigated using experimentally validated Delayed Detached Eddy Simulation (DDES). Numerical results show that the air flux drop mainly depends on the cross-sectional shape of deflectors, which changes the flow conditions above AC condensing outlets, including the properties of the negative pressure region and the incident angle of the high-speed shear flow produced by the train operation. Meanwhile, the extra aerodynamic drag brought by the installation of deflectors is computed and analyzed. The results presented in this paper can be applied to the design of the AC system, as well as other equipment requiring active convective cooling, on higher speed trains. •Established a numerical model that couples the slipstream of train and the condensing airflow driven by condensing fans.•Analyzed 4 types of flow deflectors that may alleviate the flux decrease while the fans are exposed to slipstream.•Presented the detailed flow characteristics in the vicinity of train and AC units.•Isolated the aerodynamic drag contributed by train body, AC operation, deflectors, and momentum change of condensing flow.