Computational fluid dynamics has been used for assessing the thermal comfort and air quality in an office ventilated with a displacement system for a range of supply air conditions. Thermal comfort is predicted by incorporating Fanger's comfort equations in the airflow model. Indoor air quality is assessed according to the predicted contaminant concentration and local mean age of air. The performance of the displacement ventilation system is then evaluated based on the predicted thermal comfort and indoor air quality.
A design guide for displacement ventilation (thermally induced ventilation ) has been prepared. It is based on quasi stationary experiments carried out in the Sulzer Infra laboratory in Winterthur. The significant design parameters identified by factorial analysis are the air flow rate, the internal load, the convective part of the internal load and to a lesser extent the room height. Using a linearized polynom representation for the temperature increase near the floor as well as for the vertical temperature gradient in the occupied zone a design nomogram has been obtained.
This paper compares the practice of dilution ventilation (DILVENT), which ideally requires perfect mixing, with displacement ventilation (DISPVENT), which involves fresh air displacing contaminated air without mixing. Keeping DILVENT as a reference the approach of intervention was used to estimate the potential of DISPVENT for improving environmental conditions in a garment sewing plant. Air exchange efficiency of DILVENT came to 49%. DISPVENT improved the efficiency lo a level of 57%. At workstation level DISPVENT improved air renewal by a factor of 1 .3.
Unlike conventional ventilation systems, the displacement ventilation system supplies air in the low region of a room, while the exhaust opening is usually placed near the ceiling. When partitions are used in the occupied zone, the diffusion of supply air may be obstructed; thus, the existence of the partition may present important effects on air diffusion, retarding the removal of a contaminant. The present study considers the effects of office partition layout on air diffusion and indoor contaminant control in a large partitioned office equipped with a displacement ventilation system.
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