The effects of diffuser type on thermal flow and contaminant transport in high-speed train (HST) cabins – a numerical study

Recalling the previous global outbreaks of diseases including severe acute respiratory syndrome spread in public transportation cabins, the investigation of transport characteristics of containments through the high-speed trains (HSTs) cabin is critical due to the currently fast development of high-speed rail around the world. For quantitatively analysing the effects of diffuser on ventilation and spread of diseases in HST cabins, computational fluid dynamics (CFD) models containing four different diffuser types were developed in this study. The drift-flux model and Lagrangian model were applied. Simulation results indicated that the diffuser type significantly affects overall cabin airflow pattern. Even though all four types of diffusers applied in HST cabins could satisfy the thermal comfort criterion, containments dispersion processes varied. Besides, gaseous contaminants and particle contaminants transport also varied in the same ventilation conditions. Importantly, contaminants had locked-up zones around passengers due to the uprising passengers' thermal plume against the descending ventilation airflow.