Energy performance index of air distribution: Thermal utilization effectiveness

•Thermal Utilization Effectiveness is introduced and verified as the energy performance index of air distribution.•Energy Utilization Coefficient ignores relative contributions of occupied and unoccupied zones to energy performance.•Effectiveness of Heat Removal cannot qualitatively distinguish the energy performance of air distribution.•Heat Removal Efficiency cannot quantitatively distinguish the energy performance of air distribution.•Thermal Utilization Effectiveness addresses the drawbacks of the above three energy performance indices. The energy performance index is crucial for the energy-efficient design and operation of air distribution. Heat Removal Efficiency (HRE) is a widely used energy performance index, and Energy Utilization Coefficient (EUC) and Effectiveness of Heat Removal (EHR) are alternatives to HRE. This study justifies that these existing indices are unreasonable and incompetent as energy performance indices. This study also proposes a new index called Thermal Utilization Effectiveness (TUE) and verifies its efficacy as an energy performance index via theoretical analyses and experiments on stratum ventilation, displacement ventilation, and underfloor air distribution. EUC is not a suitable energy performance index since it does not consider the relative contributions of the occupied and unoccupied zones to the energy performance of air distribution. EHR cannot qualitatively distinguish the energy performance of air distribution because of its floating benchmark point. HRE cannot quantitatively distinguish the energy performance of air distribution because it unequally weighs the thermal energy of the air temperature of the occupied zone. TUE accounts for the relative contributions of the occupied and unoccupied zones to the energy performance with the help of the exit air temperature, qualitatively distinguishes the energy performance because of its two fixed benchmark points, and quantitatively distinguishes the energy performance by equally weighing the thermal energy of the air temperature of the occupied zone. Therefore, TUE overcomes the drawbacks of EUC, EHR, and HRE, and is a reasonable and competent energy performance index of air distribution.