Thermal environment in indoor spaces with under-floor air distribution systems: Part 1. Impact of design parameters (1522-RP)

The under-floor air distribution system creates a cleaner indoor environment and provides enough energy saving potential for it to have become increasingly popular in North America. The system also generates thermal stratification in an occupied zone since it supplies cold air directly to the occupied zone of an indoor space. This study identifies the impact of different design parameters on thermal stratification. The investigation used the orthogonal method to identify the most important parameter and to establish a set of test cases for the parametric study. The parametric study used both experimental measurements in an environmental chamber and numerical simulations by computational fluid dynamics. The environmental chamber was used to simulate an office, a classroom, and a conference room with swirl, square, and linear diffusers. The experimental data were used to validate the numerical results by computational fluid dynamics. These results indicate that swirl diffusers created the largest thermal stratification, while linear diffusers provided almost uniform distribution of the air temperature in the occupied zone. The swirl diffuser can create a very good mixing in the occupied zone so the supply air temperature can be lower. The thermal stratification was smaller when the cooling load was higher in indoor spaces such as conference rooms.