CFD Investigation of Vehicle’s Ventilation Systems and Analysis of ACH in Typical Airplanes, Cars, and Buses

Behrouz Pirouz,Patrizia Piro,Domenico Mazzeo,Seyed Navid Naghib,Stefania Anna Palermo,Michele Turco

doi:10.3390/su13126799

Abstract

The simulation of the ventilation and the heating, ventilation, and air conditioning (HVAC) systems of vehicles could be used in the energy demand management of vehicles besides improving the air quality inside their cabins. Moreover, traveling by public transport during a pandemic is a concerning factor, and analysis of the vehicle’s cabin environments could demonstrate how to decrease the risk and create a safer journey for passengers. Therefore, this article presents airflow analysis, air changes per hour (ACH), and respiration aerosols’ trajectory inside three vehicles, including a typical car, bus, and airplane. In this regard, three vehicles’ cabin environment boundary conditions and the HVAC systems of the selected vehicles were determined, and three-dimensional numerical simulations were performed using computational fluid dynamic (CFD) modeling. The analysis of the airflow patterns and aerosol trajectories in the selected vehicles demonstrate the critical impact of inflow, outflow, and passenger’s locations in the cabins. The CFD model results exhibited that the lowest risk could be in the airplane and the highest in the bus because of the location of airflows and outflows. The discrete CFD model analysis determined the ACH for a typical car of about 4.3, a typical bus of about 7.5, and in a typical airplane of about 8.5, which were all less than the standard protocol of infection prevention, 12 ACH. According to the results, opening windows in the cars could decrease the aerosol loads and improve the low ACH by the HVAC systems. However, for the buses, a new design for the outflow location or an increase in the number of outflows appeared necessary. In the case of airplanes, the airflow paths were suitable, and by increasing the airflow speed, the required ACH might be achieved. Finally, in the closed (recirculating) systems, the role of filters in decreasing the risk appeared critical.

Highlights

Many researchers have analyzed the efficiency of air conditioners (AC), the vehicle producers, to reduce energy consumption and greenhouse gas emissions [1].Marshall et al analyzed the thermal management strategies for the vehicle, and their results determined the high impact of HVAC and ventilation on the energy demands, especially in electric vehicles [2]
To define the boundary conditions in our computational fluid dynamic (CFD) models, we evaluated the boundary conditions in different case studies, and we selected the average values of dimension, airflow, and temperature for a typical car, bus, and airplane
The analysis exhibited the critical impact of the inflow, the outflow, and the passenThe analysis exhibited the critical impact of the inflow, the outflow, and the passengers’

Summary

Introduction

Marshall et al analyzed the thermal management strategies for the vehicle, and their results determined the high impact of HVAC and ventilation on the energy demands, especially in electric vehicles [2]. Suárez et al analyzed the ventilation and the HVAC system in a railway vehicle with a CFD simulation. They modeled different scenarios in summer and winter, and the results established the methodology for this type of analysis [3]. Mathai et al analyzed the microclimate inside the cabin. Their findings revealed that open windows could increase or decrease the transmission pathways based on the location of the infection source and the open windows [5].

Methods

Results

Conclusion