两机一塔布局下空冷塔流动换热特性及发电机组热经济性研究

Study on Flow and Heat Transfer Characteristics of Dry Cooling Tower and Thermal Economy of Generating Units under the Configuration of Two Units Sharing One Tower

为了揭示两机一塔布局下空冷塔流动换热特性对两台发电机组运行热经济性的影响,建立空冷塔三维数值计算模型和机组热力系统一维仿真模型并进行耦合求解。在两机一塔布局下,研究了变环境风速、两机变负荷工况运行下空冷塔的流动换热特性及其与机组运行热经济性的关系。结果表明:两机非均等负荷搭配运行会导致空冷塔各方位散热器进气温度冷热不均,削弱静风下空冷塔的通风与散热性能,但会改善中、高风速下塔侧散热器性能并减缓环境风对空冷塔散热的不利影响,且机组负荷越高,机组背压对环境风速的变化越敏感;在全厂热经济性方面,在均等负荷搭配运行下两机的总负荷越高,全厂热经济性越优越,且整体加权标准煤耗率明显低于相同总负荷下两机非均等负荷搭配运行。

In order to reveal the influence of the flow and heat transfer characteristics of the dry cooling tower on the thermal economy of the two generating units under the configuration of two units sharing one tower,a three-dimensional numerical simulation model of dry cooling tower and a one-dimensional ther-modynamic cycle model of power generating unit were developed and coupled in this paper.For the con-figuration of two generating units sharing one dry cooling tower,the flow and heat transfer characteristics of the integrated dry cooling tower and their correlation with thermal economy of two generating units were investigated under different crosswind speeds and unit variable loads.The results show that the uneven load combination of the two units leads to uneven air inlet temperature distribution of the radiators located in various directions of the integrated dry cooling tower,which diminishes the ventilation and heat dissi-pation rates of the tower under windless condition.But the uneven air inlet temperature distribution im-proves the performance of the sideward radiators at the medium-high wind speeds,and thereby mitigates the adverse effect of ambient crosswind on cooling performance of dry coding tower.The higher the unit load,the more sensitive the back pressure is to the change of ambient wind speed;in terms of thermal economy of the whole plant,the higher the total load of two generating units under equal load combination,the better thermal economy of the whole plant,and the overall-weighted standard coal consumption rate at the same total load is obviously lower than that under uneven load combination.