中庭建筑盐水模型中关键参数的实验研究

中庭建筑利用自然通风，改善室内热环境，可以有效减少建筑能耗。简化数学模型结合盐水实验装置已被用来研究建筑中的热压通风问题。利用盐水模型分析中庭通风规律需要解决羽流卷吸系数的确定、通过开口释放系数的确定以及多羽流作用规律三方面的问题。本项研究针对卷吸系数的选择具有明显分散性的现状，通过改变实验初始条件，结合分层界面高度随时间变化，采用重复迭代的方法，根据源参数与卷吸系数对应关系确定纯羽流卷吸系数。针对流体密度对释放系数的影响，建立non-Boussinesq条件下填充箱体模型，获得羽流流出开口处的释放参数表达式，利用实验结果建立释放系数与释放参数之间关系。针对不同强度羽流对空间分层的影响，在动量、浮力通量方程守恒基础上，分别对较强羽流和较弱羽流进行流量修正，确定分层界面位置和每个分界面内部折减加速度。本项研究工作，为盐水实验中关键参数的确定提供理论依据，也为中庭建筑通风设计提供理论指导。

The atrium is a common architectural feature in modern ventilated buildings for improving the thermal comfort in the room and reducing the building energy consumption. Simplified mathematical models, with salt water experiment, have been developed and used in numerous studies of stack ventilation in atrium buildings. There are three problems to be solved for understanding the basic regulation of ventilation in the atrium, including the entrainment coefficient of plume to determined, the discharge coefficient through a square-edged opening and the dependence of interface height on two-plume located at various positions within the space. For the non-negligible scatter of entrainment coefficient, the salt-bath experiment will be used to give a definite value. The initial boundary condition of the plume will be determined by the nozzle, and the interface change with time in the confined room where the plume will be added. With repeated iteration of entrainment coefficient by assumption and calculation, the coefficient of the pure plume will be determined by a group experiment data of the source parameters and the coefficients. For the influence of the density contrast on the discharge coefficient, steady and unsteady experiment of plume flow will be conducted. In the first, the container will be initially filled with dense saline fluid of a known reduced gravity, which is allowed to drain and the rate of descent of the interface height will be recorded. In the second, a steady two-layer stratification will be established by introducing a localized buoyancy source in the container. The emptying-filling box model will be established in a general non-Boussinesq case, and the discharge coefficient at the vent will be calculated. The dependence of discharge coefficient on the discharge plume parameter will be revealed. For the influence of two sources of unequal strength on the interfaces between the three layers, a theoretical model based on mass conservation and buoyancy fluxes relations will be established. The volume flux of strong plume will be revised when the plume to be considered that of a plume from an area source of finite volume and momentum flux in an environment of uniform density. The entrainment from the top layer by the weaker plume will also be considered and be incorporated into the analysis of the control equations. The position of the interfaces between the three layers and the reduced gravity in the layers can be determined by the salt water experiment for two plumes on the same level or various positions within the space. The research work will provide theory basis for the key parameters and give theory instruction for atrium designers to improve the ventilation in the storey.