Research On The Determination Method Of Outdoor Design Conditions Of Sun Shading Design

It is the basic principle that architecture should adapt to the local climate.The Windows are the components with weak thermal performance in the building envelope.Excessive solar radiant heat entering the interior through the Windows will cause the interior overheating and constitute the main load of indoor air conditioning in summer.Sun shading is the most effective measure to reduce solar radiation entering the interior,and with the widespread application of transparent envelope,the importance of shading is becoming more and more prominent.Therefore,sun shading has become the most widely used summer heat protection measure by architects in scheme design.However,as sun shading is a passive technology,influenced by the temporal variation of solar radiation,the shading design effect of buildings is closely related to the design period.Sun shading design should include three parts: analysis of outdoor climatic conditions,form design of shading components and effect evaluation of sun shading design.In this paper,from the perspective of building thermal engineering,according to different shading design objectives and requirements,the determination conditions of shading design period for different types of rooms are clarified.Two methods to determine the period of shading design based on outdoor climatic conditions and indoor thermal environment requirements are proposed.The statistical calculation method of the outdoor design conditions of sun shading design is established and the generating program of the parameters is written.The outdoor design conditions set of sun shading design in 10 typical cities in China is established and the evaluation method of sun shading design effect is put forward.The main research works are as follows:(1)Through analyzing the relationship between the climate characteristics of China and sun shading,it is proposed that air temperature and solar radiation are the basic conditions for determining the establishment of sun shading.On the basis of previous studies,it is proposed that "sun shading design should be guided by indoor thermal environment demand,and the determination of shading design period should be based on indoor air temperature".Depending on the room operation mode(natural ventilation,intermittent air conditioning operation,continuous running air conditioning),has been clear about the three kinds of shading design goal: "reduce room solar radiation heat gain,to prevent indoor overheat","to weaken the influence of outdoor temperature,increase the thermal comfort time","less room cooling demand,reduce air conditioning cooling load in summer",and the shading design period determination conditions are determined,put forward the three levels of shading design requirements.(2)Through the hourly transformation of the original outdoor meteorological data,the hourly value of outdoor air temperature and solar radiation over the years are obtained,which provided the data basis for the determination of the outdoor design conditions of sun shading design.It is proposed to use the mean value of hourly average dry bulb temperature every month for years to represent the temperature change of each month,and use the method of "virtual year" to determine the starting and ending date of shading design period.For the specific building scheme,it is proposed to analyze the shading demand and determine the shading design period by calculating the cumulative value of temperature difference according to the outdoor climate conditions,envelope structure and room operation mode.The outdoor design conditions set of sun shading design in 10 typical cities in China is established,which can provide the parameter basis for architects to analyze architectural climate in the project design stage.(3)The calculation method of sun shading coefficient in the current thermal code is improved,and the sun shading coefficient during the whole shading period is calculated to represent the design effect of sun shading.Put forward to intensity of thermal discomfort(ITD),frequency of thermal discomfort(FTD)and fluctuation of thermal discomfort(FD)for indoor thermal environment evaluation index to evaluate the effect of sun shading design on improving indoor thermal environment.Studies have shown that: Under the premise of reasonable design,sun shading can effectively improve the indoor thermal environment.However,although sun shading can weaken the influence of outdoor climate in the overheated season,it can no longer fully meet the indoor thermal comfort demand,that is,active equipment should be used to cool the room.Therefore,the most important effect of the shading design is to fully delay the active device opening time,to extend the time to meet indoor thermal comfort.