Rack Power Density and Cooling Airflow
Converts rack kW to heat and required airflow at an entered equipment temperature rise.
Example
You enter
- Rack load (kW) 8
- Temperature rise across equipment (deg F) 20
- Standard tile delivery (cfm) 500
- Higher-density rack load (kW) 15
- High-flow tile delivery (cfm) 900
- Alternative temperature rise (deg F) 30
You get
- Required rack airflow 1,264 cfm (158 cfm/kW)
- Standard tiles required 2.53
- Higher-density rack 2,369 cfm; 4.74 standard tiles
- With high-flow tiles 2.63
- Alternative airflow reduction (%) 33.3333
Checked against published worked examples from: Upsite Technologies; Tate Access Floors.
Details, formula, and sources
ScopeConverts rack kW to heat and required airflow at an entered equipment temperature rise, then expresses the demand as standard and high-flow floor outlets. The worked 15 kW rack needs about 2,369 cfm at 20 degF, nearly 5 standard perforated panels; equipment and cooling-system limits govern.
Formula or tableheat = rack kW x 3,412 Btu/hr per kW; airflow = heat/(1.08 x delta-T); tile count = airflow/tile delivery.
Source and editionThe standard air-side sensible-heat relation and ASHRAE TC 9.9 thermal guidance. Equipment airflow and cooling-unit data govern.
Free accessA public sensible-heat balance using the conventional 1.08 air constant.
What governsEstimate. AHJ and licensed professional govern.
API field namesrack_load_kw, equipment_delta_t_f, standard_tile_cfm, comparison_rack_kw, high_flow_tile_cfm, alternative_delta_t_f, required_cfm, standard_tiles_required, comparison_required_cfm, comparison_high_flow_tiles_required, alternative_airflow_reduction_pct
- Air constant 1.08 Btu/hr per cfm-degF at ordinary standard-air conditionsASHRAE Fundamentals
- Tile delivery entered from measured or manufacturer performance at the actual plenum pressuretile manufacturer / commissioning