574 / 2019-01-19 14:28:51

Numerical study on the cooling performance of natural draft wet cooling tower with the chip muffler

natural draft wet cooling tower; chip muffler; cooling performance; distance between the chip muffler and cooling tower; numerical simulation

全体主题 > 部件、设备和辅助设备

The chip mufflers are demanded to reduce noise for the natural draft wet cooling towers (NDWCTs), but significantly influence the tower cooling performance. This paper investigates a natural draft wet cooling tower of a 1000 MW unit, around which the chip muffler units are installed. A three dimensional numerical model is established to investigate the effects of the chip muffler on the tower performance. The porous step model is used to simulate the air flow resistance for the chip muffler. The whole computational domain is meshed with 2170000 hexahedral structured grids. The accuracy and credibility of the numerical model are validated by actual work conditions. Some important performance parameters including the ventilation volume G and exit water temperature t2 of cooling tower are computed to quantify the tower performance. To clarify the chip muffler influence on the cooling tower, the distributions of air velocity above the packing surface (z=14 m) and contours of the tower exit water temperature are analyzed. Numerical results indicate the air flow resistance for the chip muffler increases with the increment of air velocity, especially when the air velocity is higher than 4m/s. At no muffler condition, the t2 decreases from the center to the periphery area, which illustrates that the heat transfer between water and air is gradually enhanced along the negative radius direction. For the obstacle of the chip muffler, the inflow air has lower velocity to weaken heat and mass transfer between air and water, resulting in the inefficiency of cooling tower. Compared with that under no chip muffler condition, the air velocity is higher about 0.10 m/s and the t2 in the center of basin goes up 0.5℃ at the chip muffler condition. The distance between the chip muffler and cooling tower L is an important factor for the overall cooling performance and the L of 0 m, 3 m, 4m, 5 m and 6 m are employed to further study the effect mechanism on tower performance. It is found that with the increment of L, the G increases while the t2 decreases. With full consideration of the chip muffler noise elimination, the chip muffler with L of 5 m can lead to an optimum cooling performance, where the G is found to increase by 6% and the t2 reduces by 0.334℃.