Influence of Partial Recirculation on the Build-up of Cabin Carbon Dioxide Concentrations 2019-01-0908
Carbon dioxide exhaled by occupants remains within the cabin during operation of HVAC unit in recirculation mode. The CO2 inhaled by the occupants goes into their blood stream that negatively affects occupant’s health. ASHRAE Standard 62 specifies safe levels of carbon dioxide in conditioned space for humans. The CO2 concentration limit per ASHRAE is 700 ppm over ambient conditions on a continuous basis. In a recent investigation (Mathur, 2017), the author had developed a model to predict cabin carbon dioxide concentrations for recirculation mode as a function of time, number of occupants, vehicle speed, body leakage characteristics, occupant lung capacities and concentrations of the carbon dioxide coming out form occupant’s mouth, blower position and vehicle age. This developed model has been modified to simulate cabin airflows from 100% recirculation mode to 100% outside air mode, i.e., for any percentage of partial recirculation.
In this investigation, the author will present simulated results for a vehicle from D segments. The effect of the partial recirculation is investigated to maintain good air quality per ASHRAE standard 62. Detailed analysis will be presented as a function of partial recirculation. Some experimental validation will also be presented in the paper.
1. ASHRAE/ANSI, Standard 62-1999, Ventilation for acceptable indoor air quality, American Society of Heating Refrigerating and Air Conditioning Engineers., Inc., Atlanta, GA, 1999.
2. Mathur, G.D. “Development of a Model to Predict Build-Up of Cabin Carbon Dioxide Concentrations in Automobiles for Indoor Air Quality”, SAE Paper # 2017-01-0163.