Abstract: In windy and dusty areas short of water, with large temperature differences during one year, dry-wet closed cooling tower can be widely used in industry fields in order to achieve the best technical economy and the least water consumption. It operates as wet cooling tower in summer with water sprayed outside of pipes. While in winter, it operates as dry cooling tower without sprayed water. In spring and autumn, the way to save water is the mixed use of both dry and wet closed cooling tower, which can also achieve the cooling performance required.
In this paper, taking a project in Hami of Xinjiang for example, every single closed cooling tower is designed to be counterflow and coil stagger arranged whose structure is designed according to wet operating conditions while size in consideration of dry cooling required. Four different water-saving solutions and corresponding air consumption are given by calculating and clearly described. It is concluded that the fourth solution: four-month use of all cooling towers as dry coolers in winter, one-month use of all cooling towers as wet coolers in July and mixed use of dry and wet closed cooling tower in the rest months in a year leads to the least annual water consumption. The method and example mentioned above provide a reference to design and operation of dry-wet closed cooling towers.

Key words: closed cooling tower, wet cooling, dry cooling, water-saving