Ultrafine particle infiltration into passenger vehicles. Part II: Model analysis |
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| Institution: | 1. Department of Environmental Health Sciences, Jonathan and Karin Fielding School of Public Health, University of California Los Angeles, Los Angeles, CA 90095-1772, USA;2. Department of Civil and Environmental Engineering, Henry Samueli School of Engineering and Applied Science, University of California Los Angeles, Los Angeles, CA 90095-1593, USA;3. Institute of Environment and Sustainability, University of California Los Angeles, Los Angeles, CA 90095-1772, USA;1. School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA;2. Environmental Control Systems, Boeing Commercial Airplanes, Everett, WA 98203, USA;3. School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China;1. Department of Building Science, Tsinghua University, Beijing 100084, PR China;2. Environmental Control Systems, Boeing Commercial Airplanes, Everett, WA 98203, USA;1. Tianjin Key Laboratory of Indoor Air Environmental Quality Control, School of Environmental Science and Engineering, Tianjin University, Tianjin, China;2. The Boeing Company, Seattle, USA;3. Boeing Research & Technology – China, Beijing, China;4. School of Mechanical Engineering, Purdue University, West Lafayette, IN, USA;1. College of Electrical and Electronic Engineering, Shandong University of Technology, Zibo 255086, Shandong, PR China;2. School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, PR China |
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| Abstract: | Experimental studies showed that infiltration and passive ventilation are important air exchange mechanisms inside vehicles but previous mathematical models did not consider either one. In this study, we incorporated infiltration and passive ventilation to advance the existing mathematical models and evaluated how different transport mechanisms affect passenger exposures at increasing speeds. Infiltration was formulated using Bernoulli’s equation and passive ventilation was derived empirically. The new model describes ultrafine particle (UFP) and carbon dioxide (CO2) transport for a wide range of driving speed under any ventilation conditions. Unlike statistical models, this mathematical model can also provide vehicle-specific and transport mechanism-specific information. The model predictions were in a good agreement with data collected from 10 different vehicle models with an average discrepancy of less than 16% for UFPs and less than 3% for CO2. Under outdoor air (OA) mode, when the fan is off, the model simulation showed that the infiltration and passive ventilation can substantially increase the UFP I/O (in-cabin/on-road concentrations) ratio from 0.15 at 0 km/h to 0.57 at 130 km/h. At medium fan setting, mechanical ventilation dominates and UFP I/O stays at 0.58 regardless of driving speed. Under recirculation (RC) mode, infiltration increases and the RC-mode filtration only removed 44% and 69% of the infiltrated particles at the lowest and medium fan settings, respectively. Model simulations under OA mode show that infiltration starts to occur above 115 km/h with the lowest fan setting; whereas, medium and higher fan settings prevent infiltration up to 145 km/h. |
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| Keywords: | Ultrafine particle Model Infiltration In-cabin Passenger Automobile |
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