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，将特别注重交叉通风动态相似性的局部动态相似模型应用于出风口处的交叉通风性能评估，并研究了出风口周围的气流结构。 LES 和风洞实验发现 LES 很好地再现了风洞实验的结果，例如在 P_R^* 值较低的小区域内流量系数大幅增加。 LES 对压力场的评估表明：气流中动压的剩余量和出风口周围压力场的变化对流量系数影响很大。此外，通过识别通风气流流管的结构，发现流量系数随流量的变化而变化。一般情况下，流出开口处壁面切向的动压被认为低于流入侧的动压。通过实际尺寸实验研究了 P_R^* 的出现频率。，并阐明了其次，为了利用CFD（计算流体力学）评估建筑物上的风压分布，通常使用k-ε模型然而，众所周知，使用标准 k-ε 模型存在一些缺点，例如高估了风撞击建筑物的迎风表面上的湍流动能。为了克服这些问题，需要对模型进行各种修改。在本研究中，提出了一些改进的k-ε模型和k-ω模型来估计平行六面体形状的建筑物的风压分布，以及其特征。本研究的结果表明，结合杜宾限制器（模型参数α=0.5）的修正k-ε模型在风压分布的估计方面显示出令人满意的结果。 -ε 模型（包含Durbin 的限制器（α=0.65）、RNG 模型（重正化群理论）和二次模型）提供了良好的结果。最后，通过使用建筑模拟程序 TRNSYS 和 COMIS 结果显示，通过引入交叉通风来减少冷负荷。负荷减少取决于建筑物的特性和窗户的操作方式，通常，较低的参考温度，即较高的内部得热量和较低的热损失系数，也会带来较大的负荷减少量。对于窗户操作，对日本郊区的木制独立式住宅的几种操作方式进行了测试和比较，根据窗户操作方式的不同，降低率从 10% 到 20% 不等。仅通过在有人居住和清醒期间打开窗户来减少对环境条件敏感的频繁窗户操作，尤其是在夜间和无人居住期间，会增加交叉通风的效果。