Study On The Influence Of Stack Effect On High-rise Buildings And The Mitigation Measures

Due to the increasingly shortage of land resources,high-rise buildings with their unique advantages are developing rapidly,however,they are also confronting with many new problems,for example,the stack effect caused by indoor and outdoor temperature difference results in difficulties in the opening and closing of elevator doors and inner doors,noises from elevator shaft,huge energy consumption and so on.In view of this,taking pressure difference across elevator doors as assessment criteria,this paper analyzes the stack effect on high-rise buildings and corresponding measures are found by multi-regional network simulation.Based on the theory of stack effect,this paper introduces the theoretical calculation of the differential pressure,the calculation of air penetration and many other basic principles in detail;taking ideal open high-rise building as research object,this paper verifies the accuracy of CONTAMW software and studies the influences of indoor and outdoor temperature difference and the air tightness of envelop on stack effect;taking a complex high-rise building of 452m high as an example,this paper analyzes pressure differential distribution characteristics of different elevator doors and finds ways to ease the problems relevant to stack effect.The following main conclusions are reached:The ideal open high-rise buildingFirstly,with extreme low temperature in winter,the neutral pressure level lays in the middle of the high-rise building.The pressure difference below the neutral pressure level is positive,therefore,the air flows from the outside into the inside and flows upward along the elevator shaft,while the pressure,above the neutral pressure level,is negative,so the air flows from the inside to the outside.As the temperature is extremely high in summer,the air flows downward in the elevator shaft,which is opposite to that in winter.In general,the stack effect in winter is more serious than that in summer.Secondly,the range of TDC calculated in this paper fluctuates between 0.56 and 0.72,indicating that the envelop bears more than 56%of the total pressure difference,which is higher than the TDC of the high-rise residential buildings--0.42 calculated in literature[25].It can be seen that pressure difference caused by stack effect distribute more across the envelop in ideal open commercial buildings and more across the internal compartmentation in residential buildings.The complex high-rise buildingFirstly,the complex high-rise building has four major functional areas and 37 elevators.Different functional areas are equipped with internal doors of different air tightness,which gives rise to a more complex and changeable pressure difference and air permeability characteristics.Secondly,the interaction between wind pressure and heat pressure are reflected in the following two forms:a.enhanced mode:when wind direction is consistent with airflow direction caused by hot pressing,the pressure difference across the envelop increases with wind speed;b.inhibition mode:when wind direction is opposite to airflow direction caused by hot pressing,the pressure difference across the envelop decreases with wind speed.Thirdly,many measures can be applied to ease stack effect to various extent,including revolving doors,adding elevator front door,improving the air tightness of the elevator front door,cooling elevator shaft,etc.