基于室内空气稳定性的污染物侧送风数值模拟

Numerical Simulation of Lateral Contaminant Ventilation Under Different Indoor Air Stabilities

在室内空气稳定性的概念和判断依据基础上,对其进行数学验证,根据环境温度垂直递减率的正负将其分为稳定型、中性稳定型和不稳定型。建立不同温度梯度下的数学、物理模型,并利用计算流体动力学(CFD)软件对NH3等污染物侧送风条件下,在室内传播的特性进行模拟,得出不同稳定性条件下污染物扩散的规律。在对污染物下进上出的通风方式的研究中发现,污染物在不稳定型条件下能较快到达出口,而稳定型条件下易在室内聚积难以排除室外。不稳定型利于湍流的形成和发展,稳定型抑制湍流的发展,但是在较大的雷诺数下(入口速度3m/s)空气稳定性对污染物扩散规律的影响并不明显。对于不同的污染物气体,与NH3相比,CO2的稳定性更好,不易被排出。同时,减小顺温温差会减弱空气的不稳定性,减小逆温温差同样会降低空气的稳定性。但环境温度梯度对稳定性的影响程度与雷诺数大小密切相关。该研究为室内污染物控制策略提供依据。

The concept and clarifications of indoor air stability are validated by a mathematical method. The indoor air stability is classified into thine types, that is, stable, neutral, and unstable according to the environmental temperature lapse rate after the mathematical derivation. A physieal model is established under different temperature gradients. By use of Computational Fluid I）ynamies （CFD） software, the propagation characteristit s of NH3 and other indoor pollutants are simulated under the condition of lateral ventilation. The diffusion laws of pollutants with different stabilities are obtained through a numerical simulation. The results show that in the unstable conditions, pollutants can quickly get up to the exit with the up-return and down-supply pollutant ventilation. However, pollutants are easy to accumulate indoors and difficult to exhaust in the stal）le conditions. Unstable conditions are eondueive to the formation and development of turbulence; and stable conditions inhibit the development of turbulence. However at large Reynolds number （at the entry speed of 3m/s）, the influence of the stabilities on the dispersal of pollutants is not significant. For different pollutan!s gases, the stability effect of CO, is better than that of NH3, as CO2 can not be easily discharged to the outside. At the same time, the instability can be reduced with the decrease of temperature difference along the vertieal direction. The stability drops down with the decrease of inversion temperature difference. But the effect degree of environmental temperature on stability is closely related to Reynolds number. This work provides a theoretical basis for the indoor pollutant control strategies.