【作者】 马宏涛；

【导师】 陈梅倩；

【作者基本信息】 北京交通大学 ， 动力机械及工程， 2011， 硕士

【摘要】 空冷机组以环境空气作为冷却介质,在运行时受环境影响较大,风机的进风量和空冷单元的换热效率对环境变化十分敏感,在有风情况下通过改变空冷岛的结构来改善其外部流场,达到提高换热效率的目的变得十分必要。本文以数值模拟软件FLUENT作为基本的研究工具,对某600MW直接空冷机组空冷岛外部流场进行了详细的数值模拟研究,主要内容及结论如下：1.分析了在不同环境条件下空冷岛的换热特性,即环境风速、风向、环境温度对每个空冷单元换热量的影响,对流场的影响。风速小于3m/s时,风不会对空冷岛外部流场形成较大的干扰；当环境风风速大于3m/s时,开始出现少量回流,随着风速的增大回流量增加；在不同风向条件下时,炉后风对空冷岛的换热效率影响最大；另外空冷岛的换热效率对环境温度十分敏感。2.使用正交试验的方法对空冷岛的整体结构进行研究,分别对空冷平台高度、上挡风墙高度、下挡风墙高度以及空冷单元管排安装角进行了详细研究,得出了在不同结构组合下,空冷岛的换热量,以此为标准得出空冷岛的最佳结构。研究表明在上挡风墙高度为9m、空冷平台高度为47m、下挡风墙高度为7m和人字排夹角为55°时在炉后风影响下,空冷岛的换热效率最高。3.由于空冷岛周圈单元无论是通风量还是换热量都较小,因此本文提出了一种新型的空冷岛结构,也就是抬高了两侧单元的高度,改善了风机的进口条件,使得整个空冷岛的换热效率有明显的提高,这对未来空冷岛的建设有积极的指导意义。更多还原

【Abstract】 The air cooling unit used the air as cooling medium, its performance was greatly influenced by the external environment factors, the gas fluxes and the heat transfer efficiency of the air cooling unit were sensitive to the environment conditions. Therefore, it was of great necessity to enhance the heat exchange efficiency through the approach of modifying the structure of air-cooled islands thus improving their external flow fields.Based on the platform of numerical simulation software FLUENT, this paper carried out extensive numerical simulation study on the external flow field of a 600MW direct air-cooled unit, and the main contents and conclusions were listed below:1. Analyzing the heat transfer characteristic of the air-cooled island under different environment conditions, that was the effect of factors including ambient wind velocity, wind direction and ambient temperature on heat transfer amounts and the flow field of the air-cooled island. This study found that the flow field would not be obviously interrupted when ambient wind velocity was below 3m/s, however, when the ambient wind velocity exceeds 3m/s, a few recirculation emerged and increased with the increasing wind speeds. In the case of various wind directions, the wind behind the furnace had greatest effect on the heat exchange efficiency of the air-cooled island which was found to be easily influenced by environment temperature.2. Studying on the overall structure of the air-cooled island via Orthogonal Test method. Based on the analyzing results that the total heat transfer amounts of the air-cooled islands with various combinations of the air-cooled platform, up-windbreak height, down-windbreak height and the arrangement angel of the tunes, this study revealed the optimal structure. The results showed that the air-cooled island displayed the highest heat exchange efficiency, when the up-windbreak height was 9m, the air-cooled platform was 47m, the down-windbreak was 7m, the angel was 55°and the wind behind the furnace was present..3. Considering the fact that the units adjacent the air-cooled island exhibited small ventilation and low heat transfer efficiency, this study present a modified air-cooled island structure whose adjacent units were heightened to improve entry conditions of fans, so the heat transfer efficiency of the whole air-cooled island was enhanced evidently. This would provide instructions for the design of air-cooled islands.更多还原