Electric Power Technology and Environmental Protection

【目的】喷雾增湿降温技术是一种有效的强化换热手段，为了有效提升燃煤机组空冷单元的散热性能，缓解夏季高温条件下机组的散热压力，同时降低机组能耗，提高运行经济性，开展了喷雾增湿系统优化设计研究。【方法】本文以某600 MW直接空冷燃煤机组的空冷单元为研究对象，基于离散相模型，建立了喷嘴喷雾蒸发换热过程的数值模型，对喷嘴参数（数量、横向距离、高度、压力及喷射角）进行优化设计，并通过变工况分析探究不同环境温度、风机风量及喷水量对系统散热性能的影响。【结果】研究表明，最佳的喷嘴数为12个，整体的散热量为12.430 MW；最佳的横向距离为喷嘴距离中轴线0.64 m，整体的散热量为12.348 MW；随着喷嘴高度的增加，散热器表面进口平均温度逐渐升高，整体散热量逐渐下降；当喷嘴压力为3 MPa时，换热器进口平均温度达到最低值317.940 K，整体散热量达到最大值13.350 MW；随着喷射角度的增加，整体散热量逐渐增大，喷射角为 45°时，整体散热量为 12.348 MW。随着环境温度的升高，有无喷水的情况下，整体散热量逐渐降低，当环境温度为300.150 K时，无喷水整体散热量为13.05 MW，有喷水整体散热量为13.80 MW；随着风机额定流量比例增加，整体散热量逐渐增加，当风机额定流量比例为107.5%时，整体散热量为12.300 MW；随着喷水量的增加，整体散热量逐渐增加，但增加的幅度逐渐下降，喷水量为0.24 kg/s时，整体散热量为12.182 MW，喷水量为1.20 kg/s时，整体散热量为12.369 MW，应根据实际情况合理确定喷水量。【结论】喷雾增湿降温技术可有效提升燃煤机组空冷单元夏季换热能力，本研究可为燃煤机组空冷单元的喷 雾增湿系统设计与运行提供理论依据。

[Objective] Spray humidification and cooling technology is an effective means of heat transfer enhancement. In order to effectively improve the heat dissipation performance of the air cooling unit of coal-fired units, alleviate the heat dissipation pressure of the unit under high temperature conditions in summer, reduce the energy consumption of the unit and improve the operation economy, the optimization design of spray humidification system was carried out. [Methods] In this paper, the air cooling unit of a 600 MW direct air-cooled coal-fired unit is taken as the research object. Based on the discrete phase model, a numerical model of the spray evaporation heat transfer process of the nozzle is established, and the nozzle parameters ( number, lateral distance, height, pressure and injection angle ) are optimized. The influence of different ambient temperature, fan air volume and water injection volume on the heat dissipation performance of the system is investigated by variable condition analysis. [Results] The results show that the optimal number of nozzles is 12, and the overall heat dissipation is 12.430 MW. The best transverse distance is 0.64 m from the central axis of the nozzle, and the overall heat dissipation is 12.348 MW. As the nozzle height increases, the average inlet temperature of the radiator surface gradually increases, and the overall heat dissipation gradually decreases. When the nozzle pressure is 3 MPa, the average inlet temperature of the heat exchanger reaches the lowest value of 317.940 K, and the overall heat dissipation reaches the maximum value of 13.35 MW. As the injection angle increases, the overall heat dissipation gradually increases. When the injection angle is 45° , the overall heat dissipation is 12.348 MW. With the increase of ambient temperature, the overall heat dissipation gradually decreases with or without water spraying. When the ambient temperature is 300.15 K, the overall heat dissipation without water spraying is 13.05 MW, and the overall heat dissipation with water spraying is 13.80 MW. With the increase of the rated flow ratio of the fan, the overall heat dissipation gradually increases. When the rated flow ratio of the fan is 107.5%, the overall heat dissipation is 12.30 MW ; With the increase of water spray volume, the overall heat dissipation gradually increases, but the increase gradually decreases. When the water spray volume is 0.24 kg/s, the overall heat dissipation is 12.182 MW. When the water spray volume is 1.20 kg/s, the overall heat dissipation is 12.369 MW. The water spray volume is reasonably determined according to the actual situation. [Conclusion] Spray humidification and cooling technology can effectively improve the heat transfer capacity of air cooling unit of coal-fired units in summer. This study can provide a theoretical basis for the design and operation of spray humidification system of air cooling unit of coal-fired units.