Subzone control of air distribution to improve thermal comfort and energy efficiency

The conventional method for air distribution (e.g., mixing ventilation and stratum ventilation) controls the averaged thermal condition in the occupied zone to satisfy the averaged thermal preference of a group of occupants. However, since the thermal environment cannot be absolutely uniform, the microclimates of occupants can be distinct from the averaged thermal condition of the occupied zone. Moreover, the thermal preferences of occupants are well recognized to be diversified beyond the averaged value. Thus, the conventional method is unable to ensure thermal comfort and risks energy wastage because of overcooling. The method proposed by this study divides the occupied zone into several subzones, and determines the supply air parameters to optimize the overall performance regarding thermal comfort and energy efficiency of the subzones using the multi-criteria decision-making technique. Thermal comfort is indicated by the thermal deviation of the achieved thermal conditions of the subzones from the respective thermal preferences, and energy efficiency is indicated by the heat removal efficiencies of the subzones. Case studies based on experiments of stratum ventilation have demonstrated the effectiveness of the method proposed. Results show that the method proposed achieves thermal comfort for each subzone, and improves the overall performance by 2.1% to 31.0%.