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A Study on the Extreme use of cross-ventilation as a potential energy for air-conditioning purpose

极端利用交叉通风作为空调势能的研究

基本信息

批准号：
15360312
负责人：
KURABUCHI Takashi
金额：
$ 9.6万
依托单位：
Tokyo University of Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

At first, Local Dynamic similarity model giving special notice on dynamic similarity of cross-ventilation was applied to the outflow openings. Cross-ventilation performance at the openings on outflow side was evaluated, and the structure of air flows around the outflow openings was studied by LES and wind tunnel experiment. It was found that LES reproduces the results of the wind tunnel experiment fairly well such as extensive increase of discharge coefficient in a small region where P_R^* value is low. The evaluation of the pressure field by LES revealed that the remainder of dynamic pressure in the air flows and the change of pressure field around the outflow openings give strong influence on discharge coefficient. Also, by identifying the configuration of the stream tube of ventilation air flow, it was found that discharge coefficient is changed depending on how the air flows go out. In general, dynamic pressure tangential to wall surface at the outflow openings is considered to be … More lower than that of the inflow side. The frequency of occurrence of P_R^* was investigated by actual-size experiment, and it was elucidated that the region of P_R^* where discharge coefficient is extensively decreased develops only very rarely.In the second place, to evaluate wind pressure distribution on a building by using CFD (computational fluid dynamics), it has been generally practiced to use k-ε models. However, it is known that the use of the standard k-ε model has disadvantages such as overestimation of wind pressure coefficient and turbulent kinetic energy on the windward surface where wind impinges on the building. To overcome these problems, various modifications of the k-ε model have been proposed. In the present study, a number of modified k-ε models and k-ω model were applied for the estimation of wind pressure distribution on the building, which was designed in parallelepiped shape, and the characteristics in each of these models were confirmed. The results of the present study suggest that the modified k-ε model incorporating Durbin's limiter (model parameter α=0.5) showed satisfactory results for the estimation of wind pressure distribution. In the overall evaluation, the modified k-ε models (incorporating Durbin's limiter (α=0.65), RNG model (renormalization group theory) and Quadratic model) provided good results.At the last, cooling load reduction by introducing cross-ventilation is estimated trough use of building simulation program, TRNSYS with COMIS. Results show the load reduction depends on the building characteristics and way of windows operation. Generally, lower reference temperature, i.e. higher internal heat gain, and lower heat loss coefficient, brings higher load reduction. Larger amount of building thermal capacity also associates the effect. For windows operation, several ways of operations are tested and compared. The reduction rate varies from 10 to 20 % for wooden detached house in suburban area in Japan, depending the way of windows operation. The cooling load is not drastically reduced solely by opening windows during occupied and waking period. Frequent window operations sensitive to ambient conditions especially during night and unoccupied period increase the effect of cross-ventilation. Less

首先采用局部动态相似模型，特别注意交叉通风的动态相似度。利用LES和风洞实验研究了出口侧开口处的对流性能，并对出口开口周围的气流结构进行了研究。结果表明，在P_R^*值较低的小范围内，LES较好地再现了风洞实验的结果，如流量系数大幅度增加。LES对压力场的评估表明，气流中剩余的动压和出口开口周围压力场的变化对流量系数有很大的影响。同时，通过对通风气流流管结构的识别，发现流量系数随气流的流出方式而变化。一般情况下，外流口切向壁面的动压力被认为比流入侧的动压力更低。通过实际尺寸实验研究了P_R^*的出现频率，并阐明了P_R^*中流量系数大幅度降低的区域只很少出现。其次，利用计算流体力学（CFD）来评估建筑物上的风压分布，通常采用k-ε模型。然而，众所周知，使用标准k-ε模型存在过高估计风压系数和风撞击建筑物迎风面湍流动能等缺点。为了克服这些问题，人们提出了对k-ε模型的各种修正。采用k-ε模型和k-ω模型对平行六面体建筑的风压分布进行了修正，并对各模型的特点进行了验证。研究结果表明，加入Durbin限界器（模型参数α=0.5）的k-ε修正模型对风压分布的估计效果较好。在综合评价中，改进的k-ε模型（纳入Durbin's limit (α=0.65)）、RNG模型（重整化群理论）和二次模型均取得了较好的结果。最后，利用COMIS建筑仿真软件TRNSYS对引入交叉通风的冷负荷降低进行了估算。结果表明，减载效果与建筑特点和窗户操作方式有关。一般来说，参考温度越低，即内部热增益越高，热损失系数越低，则负荷降低越高。较大的建筑热容量也与这种影响有关。对于windows操作，对几种操作方式进行了测试和比较。日本郊区的木制独立式住宅，根据窗户的操作方式，减少率从10%到20%不等。仅通过在占用和清醒期间打开窗户，冷却负荷不会急剧减少。频繁的开窗对环境条件很敏感，特别是在夜间和空窗期，会增加交叉通风的效果。少