Urban Transport Vehicles Equipped with HVAC Based on Ceiling-Mounted Air Distribution Systems

This paper presents a numerical study on the airflow and indoor air quality influencing the occupants of an urban transport vehicle equipped with a HVAC (Heating Ventilating and Air Conditioning) system based on ceiling-mounted air distribution systems. This study is carried out in a virtual chamber, which simulates the one that exists in the laboratory, occupied by twenty-four seated occupants. Above each occupant there is located an air inlet directed towards the occupants' breathing zone. The exhaust is also located close to the ceiling between every two occupants seated side by side. Numerical simulation is performed using research software founded on a set of numerical models, one that simulates the vehicle's thermal response, Vehicle Thermal Modelling, and a coupling between one that simulates the airflow around the occupants, Computational Fluid Dynamics, and another that simulates the temperature distribution in occupants, Human Thermal Modelling. The performance of the HVAC system is evaluated for an inlet air velocity of 3 m/s. In this study the air velocity and the carbon dioxide concentration field are presented. The results show that the airflow presents a downward path in the inlet towards the breathing zone. In the area located between the occupants, the airflow presents an upward path towards the exhaust area. In accordance with the air velocity field, the CO2 concentration is removed from the breathing zone and is transferred to the exhaust area.