侧风对冷却塔性能影响的特异性定量分析方法

基于换热平衡方程和空气动力方程的耦合关系,建立无侧风条件下,自然通风湿式冷却塔的热力性能计算模型,并利用MATLAB程序,通过迭代运算方法,对两方程进行联立求解,从而获得与现场测试相同的气象和运行条件下,剔除侧风影响后冷却塔通风量和冷却数的应达值,然后结合现场测试得到的实际通风量和冷却数,提出了可以特异地反映侧风对冷却塔性能影响的新指标。某3500m2冷却塔的计算结果表明,在模型散热量和实测散热量相同的条件下,侧风影响会使得冷却塔的通风量最大减少38.5％,此时体积分数为33.9％的填料没有得到有效利用,侧风还会增加冷却塔的冷却任务,相应的,需要冷却塔具有更好的冷却性能,这对于了解侧风对冷却塔性能的影响以及指导冷却塔的设计与改造有重要意义。

Quantitative analysis method for specific effect of crosswind on performance of natural draft wet cooling tower

Computational model of natural draft wet cooling tower (NDWCT) under no crosswind condition was built based on the coupling equations of heat and aerodynamic balance. The two equations were solved by the method of iteration using MATLAB code, so as to calculate the ideal values of airflow rate and number of transfer unit (NTU), which neglect crosswind effect under the same meteorological and operating conditions as field tests. Then by combining the actual values of airflow rate and NTU of tests, new indexes were recommended to represent the specific effect of crosswind on tower performance. The results of a 3500m2 NDWCT showed that, at the same heat loss of model and test, the airflow rate decreased 38.5％ at most by crosswind, and simultaneously 33.9％ volume fraction of fill was not employed efficiently. Crosswind also increased the cooling duty of NDWCT and hence more cooling capacity was needed, which was of great help to understand the theory of crosswind effect on the tower performance and of significance for cooling tower design and modification.