Reducing Virus Transmission from Heating, Ventilation, and Air Conditioning Systems of Urban Subways

Abstract

Transmission via virus-carrying aerosols inside enclosed spaces is an important transmission mode for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as supported by growing evidence. The urban subway is one of the most commonly used enclosed spaces. The subway is a utilitarian and low-cost transit system in today’s society. However, studies are yet to demonstrate patterns of viral transmission in subway heating, ventilation, and air conditioning (HVAC) systems. To fill this gap, we performed a computational investigation of the airflow (and the associated aerosol transmission) in an urban subway cabin equipped with an HVAC system. We employed a transport equation for aerosol concentration, which was added to the basic buoyant solver to resolve aerosol transmission inside the subway cabin. This was achieved by considering the thermal, turbulence, and induced ventilation flow effects. Using the aerosol encounter probability over sampling lines crossing the passenger breathing zones, we can detect the highest infection risk zones inside the urban subway under different settings. We proposed a novel HVAC system that can impede aerosol spread, both vertically and horizontally, inside the cabin. In the conventional model, the maximum aerosol encounter probability from an infected individual breathing near the fresh-air ducts was equal to 15%. This decreased to 0.36% in the proposed HVAC model. Overall, using the proposed HVAC system for urban subways decreased the mean value of the aerosol encounter probability by approximately 79% compared to that for the conventional system.

Study on the Ventilation Method to Maintain the PM10 Concentration in a Subway Cabin below 35 μg/m3

“…As shown in Figure 1 b, the supply inlets through which the air from the duct flows into the cabin were simplified. Further, the flow rate of each supply inlet obtained from the duct flow analysis results was applied to the simplified geometry [ 16 , 17 ]. Figure 1 c shows the four exhaust outlets in the center and the 16 supply inlets in the longitudinal direction.…”

“…The buoyancy effect due to heat generation by the passengers was assumed to be negligible [ 19 ]. The continuity equation and the momentum equations were solved for the flow analysis, and the k – ε turbulence model was used for turbulence analysis [ 16 , 17 , 20 ]. QUICK was set as the momentum equation scheme, SIMPLEC—as the pressure-velocity coupling scheme, and PRESTO—as the pressure interpolation scheme.…”

A numerical approach for preventing the dispersion of infectious disease in a meeting room

“…In recent years, with the increase in the incidence of the COVID-19 pandemic, more research has been conducted to examine and assess the behavior of viral microorganisms in indoor environments [19][20][21] . These infections with small particles can occur through various routes, whether direct or indirect pathways involve the susceptible person 19,22 .…”