A Study of Displacement Ventilation
Additional Information
Commercial
Case Studies/Projects
Geothermal Energy
Energy Resource Stations
NBCIP
Lighting Research Center
Grant # 00-03
Principal Investigator: Gregory Maxwell and Kenneth Bryden
Organization: Iowa State University
Mission Area: Energy Efficiency
Background
Displacement ventilation is a relatively new concept used mainly in Northern Europe. Compared to traditional mixing ventilation systems, the displacement ventilation system is thought to improve air quality and energy efficiency. In a displacement ventilation system, the supply air is ducted to the space at floor level and exhausted through a return system located in the ceiling. In order for this system to work, heat sources are required in the ventilation space. These heat sources include the human occupants and heat producing pieces of equipment such as computers and task lighting. The natural convection flows that develop around the heat sources cause room air to flow from near the floor toward the ceiling. Contaminant distribution in the ventilation space can be modeled in two zones: a clean zone at the bottom of the room and a contaminated zone near the top. Even though a person's head may be in the contaminated zone, the natural convection airflow around the person usually has a positive influence on the cleanliness of the air the person breaths because the air quality in the convection flow is better than ambient air. Energy savings is achieved due to the reduced amount of ventilation air supplied
to the space for a displacement ventilation system compared to the traditional mixing ventilation systems.
The objective of this project is to investigate the energy savings associated with a displacement ventilation system while maintaining acceptable thermal comfort and air quality for the occupant. The investigation will consist of computer simulation along with experimental validation of a displacement ventilation system in an office type environment. The experimental work will be performed at the Iowa Energy Center's Energy Resource Station. Following validation, the model will be used to investigate the effects of operating conditions in a room on the air quality at the breathing zone for the occupant as well as occupant thermal comfort. The anticipated results will show the potential energy savings that can result from using less outside air to ventilate the space while maintaining acceptable air quality for the occupant. The results of this study will be visualized using virtual reality techniques and presented on video tape. This will make the results from the numerical analysis readily accessible to users at all levels of technical skills, from engineers to the interested general public.
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