喷雾降温效果影响因素的数值模拟分析

采用计算流体力学软件(Fluent)对室外空间喷雾降温过程进行了数值模拟,在不同环境风速、喷雾压力、喷嘴流量工况下,模拟模型区域的温度场、速度场、相对湿度分布。环境风速较小时,局部区域降温幅度大,范围窄,温度梯度大;环境风速增大使液滴飘散效果更好,虽然降温幅度减小,但降温区域分布更广,温度分布更均匀。环境风速较小的地区,可以减小单个喷嘴流量,缩短喷嘴布置间距,使喷嘴作用范围内温度分布更加均匀。环境风速较大的地区,宜适当增加单个喷嘴流量并增大下游喷嘴间距,利用环境风速使液滴飘散。此外,在环境风速较大的情况下还可以适当降低喷嘴高度使人员可感知区域的温降增大。在相同环境风速下,喷雾压力对降温范围与降温幅度的影响较小,可适当降低喷雾压力,以提高喷雾系统运行的经济性。

Numerical Simulation Analysis on Influencing Factors of Mist Cooling Effect

The outdoor mist cooling process is numerically simulated by computational fluid dynamics software （Fluent）. The distributions of temperature field, velocity field and relative humidity in the model area are simulated under the conditions of different am- bient wind speeds, spray pressures and nozzle flow rates. When ambient wind speed is smaller, the cool- ing range in local areas increases with a narrow scale and large temperature gradient, which is not beneficial for personal thermal comfort. Increase of ambient wind speed makes the droplet scattering effect better, while the cooling range reduces, but the cooling area distri- bution is broader, and the temperature distribution is more uniform. In the areas where the ambient wind speed is smaller, the flow rate of single nozzle can be reduced, and the nozzle arrangement spacing can be shortened, which makes the temperature distribution more uniform within the scope of the nozzle function. In the areas where the ambient wind speed is larger, the flow rate of single nozzle should be appropriately increased, and the downstream nozzle spacing should be increased to scatter droplets by ambient wind speed. In addition, the nozzle height can be appropriately reduced to increase the temperature drop in the personal perceived areas under the condition of large ambient wind speed. Under the same ambient wind speed, mist pressure has less effect on the cooling range and scale, so mist pressure can be appropriately reduced to improve the operation economy of the mist system.