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New ventilation index for evaluating imperfect mixing conditions - Analysis of Net Escape Velocity based on RANS approach

机译:用于评估不理想混合条件的新通风指标-基于RANS方法的净逸出速度分析

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The concentration of contaminant in a room is not always uniformly distributed and hence it is important to evaluate the ventilation efficiency at various points or domains in the room to optimize and reduce the ventilation rate and the air-conditioning load of the room. Various ventilation indices have been developed to evaluate the ventilation efficiency of a point or a domain based on the contaminant concentration, for example, the age of air, the Scale for Ventilation Efficiency series, Visitation Frequency and Purging Flow Rate. This paper presents a new concept of ventilation index, Net Escape Velocity (hereafter NEV), as an index for ventilation efficiency in an indoor environment. NEV represents the effective velocity at which the contaminant is transported/diluted from a target point. The objectives of the present work are to clarify the definition and concept of NEV on the basis of CFD simulation and to investigate the calculation methods of NEV. NEV is defined by contaminant concentration, convective flux and diffusion flux at a point. Using NEV normalized by the convection velocity at a target point, we can obtain information of the turbulent diffusion effect for removal/dilution contaminant and of the direction of diffusion flux which is the same or not with convective flux. It can be said that NEV is an index of ventilation efficiency that can evaluate the ventilation performance at a point and enable understanding of the forming structure of a contaminant concentration at a point.
机译:房间中污染物的浓度并不总是均匀分布,因此,重要的是评估房间中各个点或区域的通风效率,以优化和降低房间的通风率和空调负荷。已经开发出各种通风指数以基于污染物的浓度来评估一个点或区域的通风效率,例如,空气的年龄,通风效率等级标度,访问频率和吹扫流速。本文提出了一种通风指标的新概念,即净逃逸速度(以下简称NEV),作为室内环境中通风效率的指标。 NEV表示从目标点运输/稀释污染物的有效速度。本工作的目的是在CFD模拟的基础上阐明NEV的定义和概念,并研究NEV的计算方法。 NEV由某一点的污染物浓度,对流通量和扩散通量定义。使用通过在目标点处的对流速度归一化的NEV,我们可以获得有关去除/稀释污染物的湍流扩散效应以及与对流通量相同或不同的扩散通量方向的信息。可以说,NEV是通风效率的指标,可以评估某一点的通风性能,并且可以了解某个点上污染物浓度的形成结构。

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