自然通风高位收水冷却塔三维热力特性的数值模拟与收水装置的优化研究

发布时间：2018-11-19 08:34

【摘要】：电厂中自然通风逆流湿式冷却塔的冷却性能直接对整个电站热力系统的性能有重要影响,而其性能由于进风情况不理想而造成出塔水温偏高,高位收水冷却塔较于常规冷却塔取消了雨区,设立高位收水装置将填料下方的冷却水收集起来,降低了进风阻力,提高进风量进而改善冷却塔冷却性能。文献[1]指出高位收水可有效利用冷却水的位能,降低循环水泵扬程15m以上,仅此一项,对于AP1000核电厂,两台机组全年可节省厂用电约1.2亿KW.h,符合国家节能减排的战略方针。本文首先建立了自然通风高位收水冷却塔的计算模型,并通过实验验证了高位收水装置模型的正确性,利用实型高位塔验证了整塔计算模型的准确性。并通过此计算模型对高位塔有无环境自然侧风时进行了具体计算分析,给出了塔内外的空气动力场、温度场、压力场和进风量、各区冷却贡献、出塔温度等重要参数以及其随风速改变的变化规律。通过性能保证工况和冬季工况下的计算分析可知,高位塔配水区和填料区的冷却贡献占整塔主要份额,在风速处于0m/s～10m/s时,随着风速增大,冷却塔出塔水温不断升高,在风速处于10m/s-40m/s时,随着风速增大,冷却塔出塔水温不断降低。建立常规冷却塔计算模型,与自然通风高位收水冷却塔进行对比,给出两者在塔内外空气动力场、温度场以及进风量、出塔水温等参数的不同进而比较两塔的冷却性能,对其中差异的影响因素进行深入分析。由结果可知,由于高位塔收水板间流道的导向作用,高位塔收水塔上部主要传热传质区,特别是填料上方,空气流速基本以塔心最高,而塔壁附近区域空气流速则相对较小。而常规塔最高速度出现在半径的三分之二左右。高位塔内进风径向相对比较均匀。高位塔取消大雨区,可明显降低通风阻力,增大通风量,从而通过填料区和配水区传热传质的加强来弥补雨区取消所带来的不利影响,使得低风速环境自然风下高位塔冷却性能优于常规塔。高速环境风下,大穿透能力侧风也在高位塔迎风侧进风口上缘收水装置下方引起较大的纵向漩涡,大幅弱化了迎风侧填料的冷却能力,高位塔热力性能急剧恶化。通过对收水装置高度为9m时收水板角度为40度、45度、50度和收水板角度为45度时收水装置高度为8m、9m、10m时整塔的计算分析,对比其冷却性能,得出最佳的收水装置高度和收水板角度。并讨论了十字隔墙、导风板对于高位收水冷却塔的冷却效果的影响。
[Abstract]:The cooling performance of natural ventilation counterflow wet cooling tower in power plant has a direct impact on the performance of the whole thermal system of the power plant, and its performance is caused by the high water temperature of the tower due to the unsatisfactory inlet air condition. Compared with the conventional cooling tower, the high intake cooling tower cancels the rain area, sets up the high water collection device to collect the cooling water under the packing, reduces the inlet air resistance, increases the intake air volume, and then improves the cooling performance of the cooling tower. It is pointed out in literature [1] that high water intake can effectively utilize the potential energy of cooling water and reduce the lift of circulating water pump more than 15m. For AP1000 nuclear power plant, two units can save about 120 million KW.h, in the whole year. In line with the national energy conservation and emission reduction strategy. In this paper, the calculation model of the natural ventilation high water intake cooling tower is established, and the correctness of the model is verified by experiments, and the accuracy of the whole tower calculation model is verified by using the real high tower. Based on the model, the paper makes a concrete calculation and analysis on whether there is natural cross wind in the high tower, and gives the aerodynamic field, temperature field, pressure field, inlet air volume and the cooling contribution of each district. The important parameters such as tower exit temperature and its variation with wind speed are discussed. Through the calculation and analysis of the performance assurance and winter conditions, it can be seen that the cooling contribution of the high tower water distribution area and the packing area accounts for the main share of the whole tower. When the wind speed is at 0m/s~10m/s, the cooling contribution increases with the increase of the wind speed. When the wind speed is in 10m/s-40m/s, the water temperature of cooling tower is decreasing with the increase of wind speed. The calculation model of conventional cooling tower is established and compared with that of natural ventilation high water intake cooling tower. The differences of aerodynamic field, temperature field, inlet air volume and water temperature of the two towers are given, and then the cooling performance of the two towers is compared. The influence factors of the difference are analyzed in depth. From the results, it can be seen that due to the guiding effect of the passage between the water intake plates of the high tower, the main heat and mass transfer zone in the upper part of the tower, especially above the packing, the air velocity is basically the highest in the tower center, while the air velocity near the tower wall is relatively small. The maximum velocity of the conventional tower appears at about 2/3 of the radius. The air inlet radial is relatively uniform in the high tower. If the high tower cancels the heavy rain area, it can obviously reduce the ventilation resistance and increase the ventilation volume, thus making up for the adverse effect caused by the cancellation of the rain area through the enhancement of heat and mass transfer in the packing area and the water distribution area. The cooling performance of high tower under natural wind in low wind speed is better than that of conventional tower. Under the high speed wind, the large penetration side wind also causes a large longitudinal vortex under the upper edge of the inlet of the upwind tower, which greatly weakens the cooling ability of the upwind side packing, and the thermal performance of the high tower deteriorates sharply. Through the calculation and analysis of the whole tower when the height of the water collector is 9 m, the water collecting plate angle is 40 degrees, 45 degrees, 50 degrees and 45 degrees, the cooling performance of the tower is compared. The optimum height of the water collector and the angle of the water collecting plate are obtained. The influence of cross-wall and air-guide plate on cooling efficiency of high-rise water-collecting cooling tower is discussed.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM621

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