Covid-19 and Indoor Air Quality: dynamic simulation approach to enhance ventilation system in railway sector

In the last year, the Covid-19 outbreak raised great awareness concerning Indoor Air Quality (IAQ) in confined spaces. Specifically, HVAC system design and operating parameters, such as Air Change per Hours (ACH), air recirculation ratio, and vents location, play a crucial role in ensuring indoor spaces air safety and in reducing the spread of viruses, mold, bacteria, and general pollutants. Concerning the transport sector, due to the impracticability of social distancing and to the low IAQ standards, the SARS-COV-19 outbreak brought a reduction of payload (up to 50%) for different carriers. Specifically, the payload reduction has been particularly severe for the railway sector, where carriages are typically characterized by a high recirculation ratio and low air changes per hour. In this framework, this paper aims at studying the feasibility and the convenience in adopting different solutions for indoor air quality enhancement in railway carriages, such as: increasing Air Change per Hour and reducing air recirculation ratio. Specifically, to carry out the energy-based ventilation analyses, a novel dynamic simulation tool for the complete performance investigation of trains was developed in OpenStudio environment. To prove the capabilities of the proposed approach and to show the indoor air quality improvements potentially achievable with the diverse investigated solutions, a suitable case study related to an existing medium-distance train operating in South/Central Italy is presented. Numerical simulations conducted by the developed models return interesting results providing also useful design criteria.