Study On Optimal Design Of Natural Ventilation In Xi’an University Gymnasium

The use function of university gymnasium mainly meets the needs of students’ sports activities,takes into account the daily exercise of surrounding residents,and does not undertake large-scale competitive competitions.It is found that some university gymnasiums lack professional design for indoor thermal environment and have poor thermal comfort.The purpose of this paper is to improve the natural ventilation capacity of the gymnasium and improve the indoor thermal comfort of the university gymnasium in summer by means of natural ventilation.The research object of this paper is mainly the university gymnasium in Xi ’an.13 medium and small gymnasiums of different construction ages in Xi ’an are selected for investigation,and the seating arrangement and spatial organization types are investigated.According to the survey,the fixed seats are generally cancelled in the newly built university gymnasium compared with the old university gymnasium,so the gymnasium without seats is the type of gymnasium that this paper focuses on.The main forms of functional space layout of university gymnasium are: single-layer multi-site layout and multi-layer superimposed layout.Therefore,the gymnasium with singlelayer multi-site layout and multi-layer superimposed layout is the type of gymnasium mainly studied in this paper.According to the mainstream space layout,the field test was carried out in the gymnasium of Yanta Campus and the sports training hall of Caotang Campus of Xi ’an University of Architecture and Science and Technology respectively,and according to the test results,the problems of indoor thermal environment in the two gymnasiums were analyzed.Then,combined with the climate characteristics of Xi ’an region,the gymnasium of Yanta Campus of Xi ’an University of Architecture and Science and Technology and the sports training hall of Caotang Campus of Xi ’an University of Architecture and Science and Technology were taken as the basic simulation model,and CFD software was used for simulation and analysis to study the influence of factors such as roof form,height difference of open sash,and introduction of vertical climate regulation space on indoor natural ventilation.The optimal design strategy is proposed.According to the comparison of the simulation results,the following conclusions can be drawn: For the single-storey multi-venue gymnasium,with the same roof form and the same ratio of open sash to ground area,the average wind speed and the optimization degree of indoor air age at the height of 1.5m also increase with the increase of the height difference of open sash.Under the dominant wind direction of E-N-E in Xi ’an,when the area ratio of open sash to ground is the same and the height difference of open sash is the same,the optimization effect of roof form on indoor natural ventilation is as follows: the single-slope roof form with lower north and higher south is better than the concave roof,and the concave roof is better than the convex roof.When the single-slope roof is low in the north and high in the south,and the height difference of opening the window sash is set reasonably,the indoor average wind speed can meet the dynamic thermal comfort requirements of the population with a metabolic rate of 4MET under the standard of "wind sensation index" above 26℃,and the indoor air age can also reach the ideal degree.Through simulation,it is found that when the height difference of northbound open sash remains unchanged at 4.8m,and when the height difference of southbound open sash is greater than 10.4m,the optimization effect of indoor natural ventilation is no longer obvious.For the multilayer stacked gymnasium,when the outdoor patio is transformed into an indoor vertical climate adjustment space with open window sash at the top to form spatial combined ventilation,the indoor air zero ideal area is the largest,and the average indoor wind speed on the first and third floors meets the dynamic thermal comfort requirements above 26℃ for people with a metabolic rate of 4MET under the standard of "wind sensation index".The design method of optimizing the roof form will interfere with the vertical wind environment of the outdoor patio,generate eddy current zone,and adversely affect the indoor natural ventilation,resulting in all indoor Spaces unable to meet the dynamic thermal comfort requirements of people with a metabolic rate of4 MET above 26℃.According to the above research results,it is suggested that the roof form of singleslope roof should be adopted in the design of single-floor multi-venue university gymnasium in Xi ’an area,with the lower side of the windward roof and the higher side of the leeward roof.The recommended height difference between open sashes on the windward side is 4.8m,and the height difference between open sashes on the leeward side is at least 10.4m.In the design of a multi-layered university gymnasium in Xi ’an,it is suggested to increase the vertical adjustment space with open window sashes at the top to form an optimization mode of spatial combined ventilation,so that the vertical air distribution can be smoother,and the old air and hot air can be more smoothly drained from the roof skylight.If the height of the open window sashes at the top can be reasonably highlighted and the area of the outlet can be increased,More conducive to indoor natural ventilation.