环境风影响下直接空冷机组喷雾增湿系统数值模拟

Numerical Simulation of Spray Humidification System in Direct Air-Cooled Units under Environmental Wind Condition

环境风对直接空冷凝汽器的换热性能影响显著,为了更真实地分析喷雾增湿系统对空冷凝汽器换热的影响,基于标准k-ε湍流模型和离散相模型,采用分步建模的方法,对某300 MW直接空冷机组进行了三维数值模拟。模拟过程中考虑风速对喷雾增湿效果的影响,提出增加喷嘴喷水量的方法来改善边缘空冷单元受环境风影响入口风温值偏高的问题。结果表明:主导风向下,风速为9 m/s时,平台边缘空冷单元入口温度平均值高于其他空冷单元6.4℃,其换热器出口温度值也相应高出6.4℃;增加喷嘴的喷水量可以降低边缘空冷单元换热器出口温度,进而提高机组整体换热效率,以风速9 m/s为例,增加喷嘴喷水量后,机组背压值较增加喷水量之前降低了5 kPa。

The environmental wind has significant influence on the heat transfer performance of direct air-cooled condenser. In order to more accurately analyze the influence of spray humidification system on the heat transfer of air-cooled condenser, three-dimensional numerical simulation was carried out on a 300 MW direct air-cooled unit by using two-step modeling method, based on the standard k-ε turbulence model and the discrete phase model. Considering the influence of wind speed on the effect of spray humidification during the simulation process, the method of increasing the nozzle＇ s water spray quantity was proposed to solve the problem that the entry temperature of air-cooled unit was higher because of the environmental wind. The result shows that under the dominant wind direction with wind speed of 9 m/s, the entry temperature of the air-cooled unit at platform edge is 6.4 ℃ higher than those of other air-cooled units. The increase of the nozzle＇ s water spray quantity can lower the exit temperature of the heat exchanger in the air-cooled unit at platform edge, so that the whole exchange efficiency of the unit is increased. Taking the wind of 9 m/s as an example, after the increase of the nozzle＇ s water spray quantity, the back pressure of the unit is 5 kPa lower than before.