Chilled ceilings put under test.

Chilled ceilings.

Displacing air conditioning.


Indoor air quality in rooms with cooled ceilings. Mixing ventilation or rather displacement ventilation?

Experimental investigations and practical experiences in Europe have proved that hydronic cooled ceilings are able to remove high cooling loads without impairing thermal comfort. As hydronic cooled ceilings cannot remove latent loads and pollutants, e.g., C02, VOCs, odors, additional ventilation has to be applied. Often, displacement ventilation is used, which is able to provide lower pollutant levels in the occupation zone than mixing flow systems, if the occupants are causing most of the pollution.

Measurement of personal exposure using a breathing thermal manikin.

When a person is located in a contaminant field with significant gradients the contaminant field will be modified locally due to the entrainment and transport of contaminated air in the human boundary layer as well as due to the effect of the person acting as an obstacle to the flow field, etc. In this paper personal exposure measurements are performed by means of the Breathing Thermal Manikin. Contaminant concentration is measured in a number of locations in the breathing zone and in the inhaled air.

Displacement ventilation forming at different air flow rates.

The paper presents the results of the tests of two-zone airflow pattern forming in a room with displacement ventilation where various heat sources and various airflow rates were tested. The position of the interface layer between the zones was determined experimentally - on the basis of tracer gas concentration measurement and on the way of calculation - on the basis of the plume model above a point heat source complemented with experiment. The following heat sources were used: a plume simulator, a desk lamp, a computer, a round plate and a human body.

Performance evaluation of a displacement ventilation system for improving indoor air quality: a numerical study.

To evaluate the performance of a ventilation system, the local mean age of air has usually been used to estimate how efficiently fresh air is diffused to a desired location. However, this index alone is often not sufficient to assess the local air quality that is also associated with the property of the contaminant source in a ventilated space. Several new indices have been proposed recently, which enable the use of numerical simulation and appear to be appropriate scales for assessing mixing ventilation systems.

The effectiveness of displacement ventilation.

The effectiveness of ventilation related to the two primary tasks of ventilation, (I) the supply of fresh air, and (ii) removal of contaminants, is investigated. To allow a quantitative description of ventilation performance, several effectiveness numbers are discussed, and their dependence on air flow characteristics is explained. The effectiveness of displacement ventilation regarding renewal of the internal air population is analysed both experimentally and by means of Computation Fluid Dynamics simulations.