Numerical Simulation And Experimental Study Of The Stack Effect On High-rise Buildings

The stack effect of super high-rise building is an important issue that would affect its ordinary operation and energy consumption.Unfortunately,such problem has seldom been considered and studied by local architecture design companies and research units so far.Stack effect in high-rise building and its negative impacts would occur under extreme weather conditions.For example,the uncontrolled air flow caused by stack effect takes away the indoor heat and thereby increases the energy consumption in winter,the excessive stack pressure acting on the elevator doors would result in failures in opening and closing,and wind whistling occurs due to strong stack air flow etc.In this paper,based on the current domestic and foreign researches of stack effect,the following three aspects of problems in this area has been studied:(1)In the numerical modeling of the multi zone network model,the refuge layer of high-rise building is usually designed as a semi open shutter.Because of this,the boundary condition of wind pressure of the refuge story is usually difficult to be determined accurately;(2)In the existing stack effect evaluation system,the combination of the evaluation results and the local meteorological data needs to be improved.Stack effect of high-rise buildings is closely related to the meteorological conditions,and it would cause different degrees of stack effect under different climatic conditions even in the same building.The evaluation of stack effect should be combined with the local meteorological conditions to offer a more scientific and reasonable result.(3)Measurement is the most direct and effective method to study stack effect,however there are few researches related the stack effect of high-rise buildings in this area.Therefore,the measurement data are usual difficult to be obtained.Based on the study of this paper,the main contents and conclusions are listed as followings:(1)Through using the relationship between the wind pressure in the inner and outer zone of the building refuge layer,which is obtained by CFD numerical simulation,to reduce the average wind pressure results on the outer building surface from the wind tunnel test,the problem of the difficulty to determine the boundary condition of the wind pressure of the large pore structure of refuge layer in the multi zone network model can be solved.Thus it is helpful to establish a more reasonable numerical analysis model of the stack effect in high-rise buildings,and improve the accuracy of the results of numerical simulations.(2)Taking a super high-rise building with 340 m height as a case,based on the multi zone network model method,and combined with the wind tunnel test,the simulation analysis of the combined wind and stack effect is carried out.Besides,the measures of improvement are studied.After the simulation analysis of high-rise buildings,the results showed that the improvement of the tightness of curtain wall and the increasing of the elevator front doors are effective measures to relieve the pressure difference of the elevator shaft.(3)Based on the meteorological data,the probability distribution function of the main meteorological factors,including temperature,wind speed,wind direction,and so on,is used to establish a more perfect evaluation system of the intensity of stack effect.The results from the simulation analysis of engineering cases showed that through conducting targeted evaluation of the meteorological conditions in the region,the scientific nature of the evaluation of stack effect and the accuracy of the results can be improved.(4)Through the measurement of the winter stack effect of several high-rise residential buildings in Harbin,we obtained the first-hand data of the pressure distribution law under the natural conditions.The experimental results showed that the distribution of the pressure difference along the height of the elevator door is consistent with the linear variation of the theoretical and numerical models.Through the measurement of the building whose elevator doors would result in failures in opening and closing due to the strong stack effect,it is found that the critical pressure difference of the elevator doors would result in failures in opening and closing is about 50Pa(equivalent to 9m/s).Besides,through comparing the measured data with the theoretical pressure difference,it is found that the contribution of wind pressure to the total pressure difference of stack effect can’t be ignored.