More than 130 underfloor air distribution (UFAD) systems are installed in North America today, and that number is growing. In comparison to classical displacement ventilation (DV) systems that deliver air at low velocities, typical UFAD systems deliver air through floor diffusers with higher supply air velocities. Ina addition to increasing the amount of mixing (and therefore potentially diminishing the ventilation performance compared to DV systems), these more powerful supply air conditions can have significant impacts on room air stratification and thermal comfort in the occupied zone.
Tests were conducted to determine the impact of room airflow and supply air temperature (SAT) on the thermal stratification in interior spaces, and the effect of blinds in perimeter spaces for UFAD systems. Room airflow was varied over the range of 0.7-5.1 (L/s)/m^2 (0.3-1.0 cfm/ft^2) and SATs over 15-19°C (60-67°F) for constant nominal interior heat input of 55-59 W/m^2 (5.2-5.5 W/ft^2). Results show that spaces can be highly stratified when the airflow is reduced for a given load. When SAT is varied, the shape of the temperature profile does not change; it only moves to higher or lower temperatures. Perimeter space tests conducted at a heat load of 116 W/m2 (10.7 W/ft^2) and constant room airflow of 5.1 (L/s)/m^2 (1.0 cfm/ft^2) with blinds opened or closed showed that room load is reduced when blinds are closed due to bypassing of window gains directly to the ceiling return via a convective plume.
Cookie SettingseScholarship uses cookies to ensure you have the best experience on our website. You can manage which cookies you want us to use.Our Privacy Statement includes more details on the cookies we use and how we protect your privacy.
