Abstract
Illnesses of many indoor air quality problems occur in office room. Ventilation is one way to control the contaminant transport and to provide better indoor air quality with in the office. In the evaluation of indoor air quality, CO<sub>2</sub> concentration is regarded as a good indicator to estimate the air quality level and to assess the performance of a mechanical ventilation system used by many designers, So the CO<sub>2</sub> concentration was used as the tracer gas in this study, also the humans respiration taken into account as CO<sub>2</sub> sources were the rate of production of carbon dioxide (CO<sub>2</sub>) by human respiration. Experimental measurement and computational fluid dynamics (CFD) simulation methods were applied. The results from this study show that the floor-supply displacement ventilation can improve indoor air quality because the pollutant concentration in the breathing zone is lower than that of mixing system and the risk of cross contamination can be effectively reduced. Nevertheless, the indoor spaces with floor-supply displacement ventilation might have a higher risk of discomfort, because of high temperature stratification between the ankle and head levels when compared to traditional mixing ventilation. The results indicated that the contaminant distribution in a mechanically ventilated office room need to be studied individually according to different cases.
Highlights
The quality of indoor environment and energy performance of ventilation highly depends on airflow patterns generated within a room and airflow distributions from air supply devices
The mixed system or so called mixing ventilation (MV) assumes that fresh air delivered from the HVAC systems will completely mix with the indoors contaminants to reduce the concentration level of the pollutants to an acceptable level
In the evaluation of indoor air quality, CO2 concentration is regarded as a good indicator to estimate the air quality level and to assess the performance of a mechanical ventilation system used by many designers [9], so the CO2 concentration being used as the tracer gas in this study as shown in figure (2) the humans respiration is taken into account as CO2 sources where the rate of production of carbon dioxide (CO2) is considered by human respiration
Summary
The quality of indoor environment and energy performance of ventilation highly depends on airflow patterns generated within a room and airflow distributions from air supply devices. The mixed system or so called mixing ventilation (MV) assumes that fresh air delivered from the HVAC systems will completely mix with the indoors contaminants to reduce the concentration level of the pollutants to an acceptable level. Displacement ventilation (DV) is the most widely used variant of the fully stratified systems in which room air flows provides fresh air directly to the occupied zone. Heated objects, such as the occupants and equipment, will bring the contaminants to the upper zone through the thermal plumes generated by the heat. To compare the performance of mixing and displacement ventilation system in removal of pollutants concentration inside Iraqi offices rooms
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