displacement ventilation

The experiment was conducted by means of a scaled-room wtih floor supply ventilation system, it intended to know the vertical distribution of contaminant concentration emitted from a human body. The validity of the models has been proved in so far as the calculated concentrations were almost equal to the measured values.

Measurements are made first in a full-scale room ventilated with a mixing ventilation, and later with a displacement ventilation. A new method to design mixing ventilation is established. A comparison shows the thermal comfort obtained with the two systems.

Experiment and CFD simulation show the influence of moving person simulator (of cylinder shape) and thermal manikins on air distribution in ventilated rooms.

The impact on thermal comfort of the way of introducing replacement air (to replace air being exhausted by the hood) in a kitchen was analysed using mathematical models and laboratory experiments with a tyhermal mannequin. Results allow to rank systems for replacement air introduction from the most to the least tolerable : displacement ventilation, mixing ventilation with ceiling air diffusers, front-face discharge and backdrop plenum.

96 human subjects (18 years age students from a Swedish high school) were submitted in an experimental room furnished as a classroom to different air flows issued from different ventilation systems : displacement with constant air flow rate, alternating between displacement (floor diffusers) and mixing ventilation (ceiling diffusers) with constant flow rate, mixing ventilation with varying flow rate, displacement with constant flow rate and with ceiling fans to generate air motions alternatively on and off.

The effects of an air conditioning system for office buildings were studied experimentally and computationally. A displacement ventilation system was used as the main air-conditioning system, and a partition with a built-in circular fan was used to deliver the air-conditioned clean air near the floor supplied by the main displacement system to the occupant in the office directly.

In this article, four turbulence models are studied to capture the flow and temperature behavior of the air close to a low-velocity diffuser for displacement ventilation. Turbulence is modeled by means of one zero-equation model and three different two-equation models, i.e. the LVEL, the RNG, the Standard k-e, and the Chen-Kim model. They are evaluated for their performance in predicting the air flow patterns and temperature profiles close to the diffuser.

This paper analyses through CFD simulation results the removal effectiveness in an office cooled by a chilled ceiling combined with either mixing or displacement ventilation. For passive pollutant sources, both systems provide similar air quality. For active pollutants and when a large volume of all fresh air is supplied, displacement ventilation has better performance.

Measurements were carried out in a test chamber with displacement ventilation to know the vertical distribution of airborne particles generated by two human subjects having an activity representative of that of people working in an office. Particle concentration was observed as increasing with height. A threshold size of particles was found at 5 to 10 microns above which the displacement effect of particles by air flow started to decline. Negative concentration gradients were observed for large particles at the lowest ventilation rate, when the air flow does not displace them.

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.