Literature was reviewed about underfloor systems and engineers having experienced these systems on completed projects were interviewed. Underfloor air distribution systems improve thermal comfort , indoor air quality and user satisfaction.
A big airport hangar for planes (177x37x92 m) was studied using CFD in cold season conditions. Without nozzle jets for air supply, severe temperature stratification occurs. With nozzle jet fans (17 m/s - 11000 m3/h), the average temperature in the occhupied zone is increased of 2 C.
Numerical simulation (CFD code) was used to optimise the design of the ventilation system of a large underground bus terminal complex near Seoul (Korea). The analysis of air flow patterns and parameters such as NOx and CO concentrations (from diesel engines of 19 buses) allowed to suggest and study modifications of design (change in airflow rates and grilles locations). Changes improve indoor air quality as the mean residual life time of contaminated air decreases.
Five different techniques of tracer gas measurement are reviewed in order to determine the total ventilation airflow rate as well as air distribution in the room, on site or in laboratory. Examples of applications are given insisting on the two most recent techniques.
The study examines the effect of diffuser, buoyancy and surface radiation on flow, in order to better understand the changes in room air flow due to the energy control strategy. Calculations have been applied on one room for two different ceiling air diffusers.
Experimental results on the thermal conditions around a ventilated chair (with air supply openings in its base) are provided. They concern air velocities, temperatures and thermal comfort for a seated person. Results are commented compared to those obtained in a room with displacement ventilation with wall-mounted diffuser.
A simplified methodology for numerical simulation of air flows around and above ventilated chairs in a theater or auditorium has been developed. It uses a simplified method for describing the air diffuser geometry (N-point momentum model), a simplified turbulence model (zero-equation turbulence model) and an error pretreatment method. It has been applied to a room ventilated through air supply openings in the chair bases. Simulation results (air temperature and velocity distributions) show good agreement with experimental data.
The paper gives an explanation of the phenomenon of attachment of a cold air jet to a ceiling, based on a theoretical analysis. A formula to calculate the distance between the blowing slot and the point where the cold air jet will separate from ceiling is given. The results of calculations using this formula show good agreement with experimental data.
This study is to validate a CFD model of displacement ventilation combined with chilled ceiling and determine if this combination may create draught risk or influence badly indoor air quality.
Airflow patterns, temperature and indoor air quality (ventialtion efficiency) are modelized in a room with floor heating. Results show that ventilation efficiency depends directly of diffusers layout.
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