In most buildings, occupants are the main source of indoor Carbon Dioxide (C02) due to exhalation. Exhaled breath is a vehicle for the release of airborne infectious particles and thus contributes to the risk of airborne transmission of disease. Although CO2 is not considered to pose serious health risks to occupants, elevated levels of CO2 may serve as an indicator of insufficient ventilation. It is assumed that when there are high concentrations of CO2, internally, other pollutants can also build-up to high levels. This research examines how CO2 is distributed within a room and how this distribution is affected by different ventilation strategies, occupant movement and heat source distributions. Measuring CO2 concentrations at a single location or height may not act as a true representation of an entire space, unless it is measured in a very small confined space. However, in a classroom, the complex indoor environments are influenced by many factors . . CO2 concentrations vary from location to location due to gravitational settling and a non- uniform air flow field which are all interrelated. Therefore, the sampling strategies in any room monitoring need to consider the spatial concentration gradient when choosing representative locations. Overall, this research is performed by the integration of four significant techniques that consist of peer review/questionnaire, field measurements, laboratory experiment and numerical modelling. These tools were used because they complement and enhance the results obtained from each other. In literature, different opinions on the CO2 measurement strategies were found, but there were similarities between all the techniques used by researchers. Most researchers preferred measurements in the middle of the room at a height between 1 m to 1.2 m. However in this research, it was observed that higher concentration values were found at higher levels, i.e. at a height of 1.8 m. Therefore, if CO2 concentration levels varied significantly, deviations from the average measured values would be large. In a naturally ventilated classroom, samplers would need to be strategically distributed both horizontally and vertically (preferably at a height of 1.2 and above) due to the non-uniform mixing of room airflow. However, in large rooms that are naturally ventilated, mechanical ventilated and ventilated by a windcatcher, spreading the sensors horizontally would be more beneficial. To complement the experimental results, Computational Fluid Dynamics (CFD) simulations were used and the results obtained are of significance as they enable detailed analysis and visualisation of spatial distribution of CO2 concentration and other effects to be predicted. The overall findings presented represent useful contribution for future researchers to efficiently and strategically design experimental set ups with well-organised positioning of sensors for CO2 monitoring purposes.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553054 |
| Date | January 2011 |
| Creators | Mahyuddin, Norhayati |
| Publisher | University of Reading |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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