UC Berkeley

Radiant chilled ceilings with displacement ventilation represent a promising system that combines the energy efficiency of both subsystems with the opportunity for improved ventilation performance. Laboratory experiments were conducted for an interior zone office with a very high cooling load (91.0 W/m2) and with two different heat source heights to investigate their influence on thermal stratification and air change effectiveness. The results showed that displacement ventilation with a chilled ceiling is able to provide a stable thermal stratification and improved ventilation effectiveness compared to mixing ventilation for a wide range of configurations. Stratification and air change effectiveness decreases when a larger portion of the cooling load is removed by the chilled ceiling. For every degree decrement of the surface temperature of the radiant ceiling, the stratification decreases by 0.13 K and the air change effectiveness by 0.13. Moving the computer processing units (representing 51% of the total room heat gain) from the floor level to 1.5 m height markedly increased the room median stratification and the median air change effectiveness (from 1.15 to 2.90). Therefore, increasing the height of heat sources has the potential to reduce energy use and improve indoor air quality.