Research On The Air Conditioning Load And Wind & Thermal Pressure In Megatall Building In Cold Region

The rapid growth of population has globally accelerated the urbanization,resulting the scarcity of construction site,which has promoted more and more highrise buildings constructed in densely populated regions.At the same time,some countries and regions,pursuing the brand effects of the supertall buildings,are planning to construct megatall buildings taller than 800 m.China,as the largest developing country,has the vision to construct a thousand-meter scale megatall building as the next tallest building in the world.In order to satisfy the future development of the urbanization in China,and to provide strong technical reserves for designing a thousand-meter scale megatall building,it is very necessary to study on the main technical difficulties related to its architectural and structural design.The height of the megatall building is the most significant feature,therefore,this study focuses on the effect of the vertical climate variation on the air-conditioning(A/C)load and thermal/wind pressure,and the pertinent researches are carried out based on an actual design case in the cold region.Firstly,the meteorological simulations of a particular site are carried out using the mesoscale meteorological model WRF v3.4.Besides,to validate the performance of WRF model in reproducing meteorological parameters at different levels,comparisons are made between the simulated data and radiosonde sounding data.It is found that the vertical variation trends of the meteorological parameters are well reproduced ranging from 0m to 1000 m above the ground.Further,the vertical profiles for all pertinent meteorological parameters are established based on the simulations.The results indicate that the atmospheric temperature decreases linearly with the height;the atmospheric relative humidity increases with the height at first,and subsequently decreases linearly with the height;the atmospheric pressure decreases linearly with the height;the wind speed increases with the height at first,and subsequently decreases gradually with the height,and finally increases slightly with the height.Secondly,the simulated meteorological parameters are fitted to capture the vertical variation trends of paramters at high levels relative to the ground level,and then we developed the simulation model for A/C load using TRNSYS16,which can be integrated with the aforementioned formulas to correct the outdoor weather conditions.The A/C loads can be calculated for the typical floors at different heights in the thousand-meter scale megatall buildings,including heating/cooling load and ventilation thermal load.Specifically,for the heating/cooling load simulations,we investigate the effect of the room height,the orientation,the thermodynamic properties of building envelope on the heating/cooling load;for the ventilation thermal load simulations,not only the room height,but also the air intake height are considered to investigate the effect of vertical climate variation on the ventilation thermal load.Besides,the height correction coefficients are defined to evaluate the vertical variation of A/C load with room height and air intake height.Further,the air density impact factor and enthalpy difference impact factor are defined to investigate the proportion in the effect of room height and air intake height on the ventilation thermal load.Thirdly,the wind profile,representing the wind meteorology in the building location,can be established based on the simulated wind speed distribution,which can be used as the inlet wind profile in the wind tunnel test.Considering the limitation of blocking ratio in the wind tunnel,two sectional building models,representing the upper section and lower section of the megatall building,are adopted in the wind tunnel test,and the corresponding inlet wind profiles are reproduced using the passive simulation method,and thereby the wind pressure are measured under different wind directions.Besides,to evaluate the deviation from using the traditional atmospheric boundary layer model in the wind pressure tests,comparisons are made in the wind tunnel test from using the aforementioned wind profile and the atmospheric boundary layer model(representing the landform of “B” in the building standard).It is revealed that the wind pressure coefficient is significantly lesser than the actual value in the near-surface levels using the wind speed at the building top for reference,while little difference exists in the upper levels.Finally,based on the wind pressure distribution under different wind directions,we simulated the interior pressure environment in the megatall building using the multi-zone network model CONTAMv3.2,which aims to evaluate the vertical distribution of pressures on the doors in the vertical channels.Besides,further evaluations are conducted to investigate the control effects of various measures based on the qualitative analysis,including vertical partitions and horizontal partitions.The results indicate that the vertical partition,which equals to reduce the building height,has a better control effect on the indoor pressure.In this study,a mesoscale meteorological model WRFv3.4 is adopted to explore the vertical distribution of outdoor meteorology by cross-scale application,and thereby the effect of vertical climate variation on the indoor environment can be evaluated.The methodology in this study is expected to provide useful reference for the researches regarding the interaction between high-rise buildings and the outdoor environment,and the findings in this paper can be exploited to optimize the A/C system design in the megatall buildings constructed in the cold region of China.