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Floor-supply displacement ventilation system.
Chen-Q; Lau-J; Kobayashi-N
NIOSH 2004 Dec; 1-120
This report presents the research results on floor-supply displacement ventilation sponsored by the National Institute of Occupational Safety and Health under grant number R01 OH004076. The research was to improve the design of the floor-supply displacement ventilation system for the removal of a high cooling load without draft risk. A displacement system provides fresh air directly to the occupied zone. However, the existing side-wall displacement ventilation systems have some problems. There are slow recirculations in the lower part of the room, which increase the risk of cross-contamination among occupants. Hence, the objective of this research was to improve upon the weaknesses of the current system and to develop a new design for the floor-supply displacement ventilation system by studying the effects of swirl diffusers and perforated panels. The performance of the floor-supply ventilation system was evaluated by using a validated Computational Fluid Dynamics (CFD) program for indoor environment study. The parameters calculated and used to evaluate the indoor environment were the distributions of air temperature, air velocity, percentage of dissatisfied people due to draft (PD), predicted percentage dissatisfied people for thermal comfort (PPD), contaminant concentration, mean age of air, and ventilation effectiveness. Generally, the impacts of a changed parameter are similar for offices and workshops. The parameters studied were cooling load, diffuser types, room size, supply airflow rate (also known as the air change rate), supply air temperature, number of diffusers, partition arrangement, occupant arrangement, furniture arrangement, location and number of exhausts, and location of diffusers. The study found that the air change rate, supply air velocity, supply air temperature, and number of diffusers have a large impact on the air distributions; partition location and exhaust location have a moderate impact on the distributions; and diffuser location, occupant location, and furniture arrangement have little impact on the distributions. When the ventilation effectiveness of a space is higher, the indoor air quality is better and therefore, the risk of cross contamination would be reduced by the increased ventilation effectiveness. The present investigation also compared the energy consumption of the displacement ventilation systems with that of mixing ventilation systems for an individual office and a large industrial workshop in five U.S. climate regions. The investigation accounted for the most important characteristics of a displacement ventilation system, such as air temperature stratification and high ventilation effectiveness. The results showed that the displacement ventilation system may use more fan and boiler energy but less chiller energy than the mixing ventilation system. The total energy used is slightly less with displacement ventilation, although the ventilation rate was increased in order to handle the high cooling loads found in U.S. buildings. Therefore, the displacement ventilation system can save some energy in cooling mode, but not in heating mode. Therefore, the floor-supply ventilation system is a suitable ventilation system for use in .offices and workshops in U.S. buildings for improvement of indoor working environment.
Ventilation-systems; Air-flow; Air-quality; Air-quality-control; Risk-analysis; Risk-factors; Air-contamination; Indoor-air-pollution; Air-temperature; Work-environment; Indoor-environmental-quality
School of Medical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907-2088
Final Grant Report
NTIS Accession No.
Work Environment and Workforce: Indoor Environment
National Institute for Occupational Safety and Health
Purdue University, West Lafayette, Indiana
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division