Coincident Design Day Selection Method Based On Meteorological Daily Ordinal Number

Air-conditioning system design day is the basis of air-conditioning system design cooling load calculation.The design day is composed of 24-hour dry-and wet-bulb temperatures and solar irradiation.The coincidence of meteorological parameters is not taken into account for traditional constructed design day,so that the design cooling load calculated by the traditional constructed design day is significantly different from the actual peak cooling load.At present,it is a common problem that the air-conditioning design cooling loads of buildings are overestimated in China,which leads to oversized air-conditioning system equipment and excessive operating energy consumption.Considering the coincidence of meteorological parameters of the deign day,the coincident design day is selected from long-term measured meteorological parameters.And it can truly reflect the risk level of the indoor thermal environment.However,there is a strong coupling between room characteristics and coincident design day selected by the existing methods,which makes it difficult to select a coincident design day that calculates the design cooling load of all kinds of characteristic parameters rooms with great accuracy.In addition,since the coincident design day is selected from long-term measured meteorological parameters,its hourly meteorological parameter distribution may be extreme.In order to select the coincident design day with great accuracy of design cooling load of most rooms and reasonable hourly distribution of meteorological parameters,a method based on the meteorological daily ordinal number is proposed.In this method,the conception of meteorological daily ordinal number is initially defined.Then the dynamic cooling load of room is calculated using long-term measured meteorological data and dynamic cooling load calculation mode.And a general meteorological daily ordinal number set is selected according to indoor thermal environment risk level and dynamic cooling load of rooms.At last,a multi-dimensional and multi-parameter clustering analysis method is proposed to select the coincident design day with representative hourly distribution of meteorological from the general meteorological daily ordinal number set.This method is applied to select the coincident design day of eight typical orientations of rooms in Hong Kong Changsha and Beijing from their long-term measured meteorological data.The comparison results of coincident design day selected by this method and constructed design day show that the meteorological parameters of the coincident design day are real,and the hourly distribution of meteorological is reasonable,while the hourly distribution of the dry and wet bulb temperatures on the constructed design day is unreasonable.Compared with the coincident design day,the direct solar radiation and horizontal total radiation of constructed design day are larger,and the solar scattered radiation of constructed design day is smaller;the coincident design day selected by this method has higher accuracy of calculating design cooling load of rooms in each building thermal zone than constructed design day.The accuracy of calculating the rooms design cooling load by using the constructed design day varies in different facing rooms.The design cooling of rooms of most orientations are overestimated by using constructed design day.As the latitude of the city increasing,the accuracy of calculating the rooms design cooling load by using the constructed design day will drop significantly.The applicability of calculating the design cooling load of buildings by using coincident design day is analyzed,and the accuracy of calculating buildings design cooling load by using coincident design day and constructed design day is compared.The results show that the coincident design day is suitable for calculating buildings design cooling load;the coincident design day is more accurate in calculating buildings design cooling load than the constructed design day;Buildings design cooling load are overestimated by using constructed design day.