Ultraviolet Germicidal Irradiation Development Method for Transportation Disinfection Modelling

Abstract

How do you continuously sanitise a coach/bus? Travelling on a coach during the COVID 19 pandemic was risky, and still is in some regions. There are many means of viral transfer: fomites, which is via contact after touching an infected surface; through direct droplet ballistics after a cough, and finally through aerosolization of the sputum into the air. Clean hands and masks reduce the former two. Mitigating viral load aerosol accumulation within the bus is of personal, commercial and societal interest. Done correctly, the passengers are safer; the transport organisation maintains hygienic business conditions and the society sees the viral spread reduction. Ultraviolet Germicidal Irradiation (UVGI) has been in use in operating theatres and water plants for over 100 years to reduce viral and bacterial load in the air and water. Valeo’s Thermal Commercial Vehicles (TCV) product group proposed, developed and now manufactures the most powerful coach/ bus UV Purifier module available. If the module is located within direct reach of the main air conditioning inlet, disinfected air is then delivered and entrained into the vehicle HVAC air delivery system. There it is cleanly distributed to the passengers and driver. During development two linked problems emerged:1. Where do you put the module(s) in retrofit?2. How do you keep the UV-C levels sufficiently high enough to kill the SARS Cov-2 virus but then low enough for continuous driver and passenger daily exposure?Computational Fluid Dynamics (CFD) provides the insight necessary to solve them. However, although high and low UV-C limits can be defined for the latter limit problem, devising a suitably representative model presented a novel challenge to Valeo TCV. This paper deals with the introduction of the radiation and viral field modelling into Valeo’s CFD toolset. Reformulating the InfraRed radiation model into essentially monochromatic UV-C band radiation, and with thoughtful design allowed us to develop a very high intensity virus killer that was also perfectly safe in the vehicle cabin. The modules are sold worldwide. Most importantly we use them daily on our team member transportation coaches to keep our employees safe to and from work at our production facilities.