Thanks to an environmental chamber equipped with a displacement ventilation system, neutral height measurements were carried out with the presence of a heated mannequin and other heat sources.The relationship between the neutral height for air distribution and the ventilation load in a room with displacement ventilation was investigated.
Experimental data for an impinging jet in a room are presented in this paper and non-dimensional expressions for the decay of maximum velocity over the floor are derived. The performance of that system is compared with the one of a wall displacement ventilation.
The current design standard BS EN ISO 7730 is based upon the work of Fanger dated 1995, dealing with a steady-state human heat balance model that leads to a prediction of the sensation of human thermal comfort for a given set of thermal conditions. That model was then developed for "conventional" environments. But is the current standard still applicable to more sophisticated environments such as offices with chilled ceiling, in combination with displacement ventilation ? This paper presents findings from a study that sought to answer that question.
The authors have developed a whole-field measuring technique that allows the visualization of air temperatures and airflow patterns over a large cross-section. For that measurement, an infrared camera and a measuring screen placed in the airflow are used. Thanks to that technique, real-time images within large areas can be recorded and transient events can be captured. The method was applied to a flow from a low-velocity diffuser in displacement ventilation.
This study aims to validate a CFD model (Flovent) for calculation of temperature and particulate concentration in a ventilated room. Measurements were operated in a test room with a heat source and a cigarette source. Good agreement was found with the model for temperatures with a mixed ventilation system in the room as well as with a displacement ventilation system. For particulate concentrations, the model was validated for mixed ventilation and 'borderline validated' with displacement ventilation.
This paper gives information about the design of displacement ventilation systems for telecommunication equipment rooms, which need an increasing cooling load because of higher density and new generations of telecommunication systems.
A validated CFD model was used to generate concentration distribution data for CO2, radon and moisture in a Hong Kong workshop with displacement ventilation.Contaminant concentration distribution depends on the contaminant source type and location. A low concentration may be obtained in the occupied zone when the contaminant source is associated to a heat source whose thermal plume is sufficiently strong to reach the upper zone.
This paper deals with the effect of discharging the air from a diffuser elevated above the floor. The temperatures have been measured and the airflow patterns visualised close to a diffuser for displacement ventilation, results from the whole-field method (using infrared thermography) were images of different colours representing different temperatures of the air close to the diffuser.. The aim of the measurements was to see how the elevations of the diffuser above floor level and the thermal jet length of the supply could affect the near zone.
A poor ventilation in buildings costs considerable amounts of money for hospitals and businesses.10 % of hospital acquired infections are directly due to an airborne route. The quantity and the quality of air supplied is important but also the way it is introduced into spaces. A change of the Wells Riley equation (establishing a link between the likelihood of infection, the infective agent production rate, the exposure time, the pulmonary and room ventilation rate) is proposed to take into account ventilation eefectiveness.
This paper gives the results of a field study in Danish office spaces with displacement ventilation systems. Draught was identified as a serious problem. Half of the 227 occupants were not satisfied with indoor air quality. Occupants counteract draught discomfort in blocking air supply diffusers or asking the maintenance staff to increase the supply air temperature. So a very careful design for displacement ventilation is required in order to perform satisfactorily in practice.
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