Raised-Floor Tile Airflow and Plenum Pressure
Estimates standard and high-flow raised-floor delivery from the orifice relation.
Example
You enter
- Tile gross area (sq ft) 4
- Standard tile open area (%) 25
- Discharge coefficient 0.7
- Plenum static pressure (in w.c.) 0.05
- Total supply airflow (cfm) 96000
- Open standard tiles 150
- High-flow grate open area (%) 56
- Reduced plenum pressure (in w.c.) 0.02
- Increased open tile count 200
You get
- Standard tile airflow 627 cfm
- High-flow grate airflow 1404 cfm (2.24x)
- Airflow at reduced pressure 396 cfm (-36.8 %)
- Required current pressure 0.052 in w.c.
- Increased count pressure change (%) -43.75
Details, formula, and sources
Including pressure sensitivity and the redistribution caused by opening more outlets at fixed fan airflow. Manufacturer curves and an under-floor pressure survey govern.
Q = 4,005 x discharge coefficient x free area in sq ft x sqrt(plenum pressure in w.c.); pressure at fixed geometry varies with flow squared.
The standard orifice airflow relation. Tile manufacturer measured flow curves and an under-floor pressure survey govern.
A public orifice relation and square-law inversion.
Estimate. AHJ and licensed professional govern.
Field names used by the API: tile_area_ft2, open_area_pct, discharge_coefficient, plenum_pressure_in_wc, total_supply_cfm, open_tile_count, high_flow_open_pct, reduced_pressure_in_wc, increased_tile_count, tile_airflow_cfm, high_flow_airflow_cfm, reduced_pressure_airflow_cfm, required_plenum_pressure_in_wc, increased_count_pressure_change_pct
- Free area gross tile area times entered open-area fractiontile manufacturer
- Discharge coefficient entered coefficient represents the selected tile geometrymanufacturer curve / field measurement