A small auditorium that can accommodate 30 people allows smoking. The design engineers of the auditorium assume that the smokers each are responsible for an average of 50 micrograms per minute of tobacco smoke being added to the auditorium space. The volumetric flow rate of recirculated room air is 200 cfm. Outdoor air is also supplied, and is mixed with the recirculated room air. The system has a ventilation effectiveness of 80%. In an effort to maintain the level of particulate matter from the tobacco smoke in the auditorium to no more than 5.5 micrograms per cubic foot, filters with an effective efficiency of 90% are added to the ventilation system downstream of the point in the system where outdoor air and recirculated room air are mixed. a) What is the necessary volumetric flow rate (in cfm) for the supply outdoor air? Assume the outdoor air is clean. b) The outdoor air taken into the system becomes contaminated with tobacco smoke due to a leak in an adjacent building’s ventilation system, such that the concentration of particulate matter from tobacco smoke in the outdoor air is 50% of the concentration of particulate matter from tobacco smoke in the auditorium air. What new volumetric flow rate (in cfm) of outdoor air is needed, and how much greater (in %) is this value than the outdoor air flow rate in part (a)?
A small auditorium that can accommodate 30 people allows smoking. The design engineers of the auditorium assume that the smokers each are responsible for an average of 50 micrograms per minute of tobacco smoke being added to the auditorium space. The volumetric flow rate of recirculated room air is 200 cfm. Outdoor air is also supplied, and is mixed with the recirculated room air. The system has a ventilation effectiveness of 80%. In an effort to maintain the level of particulate matter from the tobacco smoke in the auditorium to no more than 5.5 micrograms per cubic foot, filters with an effective efficiency of 90% are added to the ventilation system downstream of the point in the system where outdoor air and recirculated room air are mixed. a) What is the necessary volumetric flow rate (in cfm) for the supply outdoor air? Assume the outdoor air is clean. b) The outdoor air taken into the system becomes contaminated with tobacco smoke due to a leak in an adjacent building’s ventilation system, such that the concentration of particulate matter from tobacco smoke in the outdoor air is 50% of the concentration of particulate matter from tobacco smoke in the auditorium air. What new volumetric flow rate (in cfm) of outdoor air is needed, and how much greater (in %) is this value than the outdoor air flow rate in part (a)?
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