New design-day method for building cooling load calculation in China

Design days are the fundamental parameters for design cooling load calculations. At present, the coincidence and coupling relationship of meteorological elements are ignored by the design-day selection methods provided in the current standards, which results in conservative and unreasonable designs. This research proposes a method of selecting design days for design cooling load calculation that considers the coincidence and correlation of meteorological elements. First, a joint distribution function is constructed; on this basis, the coincident near-extreme meteorological parameters are selected. Then three meteorological elements from a 30-year meteorological record are integrated into one single normalization parameter. Finally, a design day reflective of the variation trend of near-extreme climate conditions is selected from the meteorological record. This paper uses Tianjin in China as an example to generate the research design day. It was found that the outdoor non-guaranteed rate of the research design day is roughly consistent with the corresponding indoor thermal environment risk level. Compared with the standard Chinese design day, the peak values of the research design day are reduced effectively, and the gap between the indoor thermal environment risk level and the outdoor non-guaranteed rate is narrowed.