| Nowadays with the economic,science and technology and the whole society rapidly developing,as well as people’s living standard constantly getting enhanced,the construction industry is booming as the result,therefore the demand of building energy consumption continues to rise in our country,and the public’s awareness of the importance of building energy conservation are increasing day by day.The building natural ventilation technology,with its excellent ventilation characteristics and energy-saving advantages,has attracted more and more attentions by now.However,when outdoor natural wind goes through the building,which accompanied by a large number of air separation and vortex movement,the flow mechanism is very complex and the process is abstract,so for a long time scholars are looking for a way to make more accurate prediction of the ventilation rate in the natural ventilation process of buildings,and it will be of great significance to the building design work and make great promotion of the building energy conservation.There are many factors influencing the wind-driven natural ventilation in building,including the building body shape,the wind characteristics(wind velocity and direction),the opening structure and the internal resistance partition of the room and etc.This study will be on the basis of previous research,and carry out a series of studies to establish a new model of ventilation rate prediction based on the key of building wind-driven natural ventilation resistance characteristics-the discharge coefficient.This subject adopts CFD method which based on the large eddy simulation,working conditions with different room shapes(aspect ratio),different relative positions of door and window are numerically simulated.The effect of wind-driven natural ventilation and the foregoing influence factors were studied,combined with the flow field situation such as the pressure and the velocity distribution and the ventilation rate.On the basis of this,a method of determining the integrated discharge coefficient of the room is suggested by combining Bernoulli’s equation and the influence of the shape of the room and the relative positions of the door and window are analyzed: in the back of the door model,the empirical formula of the relationship between the integrated discharge coefficient(Cdz)of the room and the relative positions(Θ)of the door and window is obtained.;in the side wall model,the qualitative relation of the room shape and the relative positions of door and window between the integrated discharge coefficient of the room was analyzed.Finally,a model of ventilation rate prediction based on Cdz is presented.By using the above CFD method,the numerical simulation expansion calculation of the single-zone room model with the same aspect ratio but doubled the side length and the two-zone tandem model are conducted,and the resulting ventilation rate values are compared to the results calculated by the prediction model and been made comparative analysis and developed revision.The results show that with a certain size opening,the natural ventilation rates of the doubled single-zone room models are reduced,and the decrease of ratio coefficient K1 is associated with the room aspect ratio—under the condition of three aspect ratio is 0.95,0.96 and 0.97;then the coefficient of correction a of ventilation rate is value for every doubling of the floor area of the room;the correction coefficient K2 is also found in the double zone tandem room to make the ventilation rate prediction model established. |
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