自然通风计算基础—表面风压系数和开口流量系数

Basis of Natural Ventilation Calculation: Local Wind Pressure Coefficient and Opening Discharge Coefficient

表面风压系数和开口流量系数是多区域模型的自然通风计算基础。本文通过文献综述系统梳理两系数的研究结果。综述表明,流态变化与两系数密切相关,伯努利原理是理解两系数变化的重要依据。建筑体型与设计、风向、上游地貌和周边建筑遮挡是影响表面风压系数的关键因素。小开口具有恒定的静止空气流量系数。大开口热压通风下的流量系数与室内外温差、开口的垂直位置、宽度和厚度有关,风压通风下的流量系数与开口率、风向和进出风口面积比有关。房间内部流动阻力对流量系数有一定影响。

The local wind pressure coefficient and opening discharge coefficient are the basis of the natural ventilation calculation using a multi-zone model. The present paper systematically reviews the study of these two coefficients. The review shows that the coefficients are closely related to the airflow pattern and that the Bernoulli principle is the key to understanding it. The local wind pressure coefficient depends on the building shape and design,wind direction,terrain features and the influence of nearby buildings. The still-air discharge coefficient for a small opening is constant. However,the discharge coefficient for a large opening for buoyancy-driven ventilation depends on the indoor and outdoor temperature difference and the vertical position,width and depth of the opening.It also depends on the porosity,wind direction and inlet to outlet area ratio for wind-driven ventilation. The internal resistances also have an influence on the discharge coefficient.