Air change effectiveness in laboratory tests of combined chilled ceiling and displacement ventilation.

Radiant chilled ceilings (CC) with displacement ventilation (DV) represent a promising integrated system design that combines radiant systems energy efficiency with the opportunity for improved ventilation performance typical of DV. The purpose of this study was to conduct laboratory experiments to investigate how the radiant surface temperature and the ratio of cooling load removed by CC over the total cooling load affects the air change effectiveness (ACE) measured according to ASHRAE Standard 129. Three experiments were carried out in a climatic chamber equipped with radiant panels covering 36.7% of the suspended ceiling, representing a typical installation of metal radiant panels. The results showed that ACE higher than one is maintained in the occupied zone even when more than half (54 percent) of the heat load is removed by a CC and the radiant surface temperature is 18.7°C.