Effects of Variable-Flow Water Distribution on Cooling Performance of Wet Cooling Towers and Its Optimization

doi:10.12096/j.2096-4528.pgt.23048

Abstract

Abstract:

Objectives When distributing water across the whole tower under different water flow rates, the water distribution uniformity has a significant effect on the cooling performance of wet cooling tower. In order to realize the high efficiency and energy-saving operation of wet cooling tower in the whole process of deep peak-shaving of wet cooling power units, the influence of the variable flow rate of the wet cooling tower on the water distribution uniformity and cooling performance of the whole tower is studied, and the water distribution optimization is carried out. Methods Based on the theoretical calculation model for water distribution in wet cooling tower and the three-dimensional thermal calculation model, the variation characteristics of water mass flow rate, water distribution and its non-uniformity during whole-tower water distribution under single-pump and dual-pump operation are studied. The influence of variable flow water distribution on the surface water temperature and average water temperature of cooling tower pool is analyzed, and the optimization scheme of water distribution is put forward. Results When switching from dual-pump to single-pump operation, the non-uniformity coefficient of water distribution in the inner zone is increased from 3.8% to 6.8% under the scheme only considering the optimization of water distribution in dual-pump operation, and zero spray phenomenon occurs at the end of some water distribution pipes in the outer zone, which weakens the cooling performance of the outer zone when the water distribution of the whole tower is operated by single-pump. Combined with the flow change of circulating water pump under variable operating conditions, an optimization scheme of water distribution in the whole tower integrating single-pump and dual-pump operation is proposed, which can reduce the average outlet water temperature by 0.8 ℃ under the single-pump operation. Conclusions Considering the optimization design of the water distribution uniformity of the whole tower during the variable flow water distribution of the wet cooling tower, the high efficiency and energy-saving operation of the cold end of the wet cooling units under the full working condition of the deep peak-shaving can be realized.

Key words: thermal power generation, cooling tower, variable flow rate water distribution, water distribution uniformity, water distribution optimization, cooling performance, deep peak-shaving, energy-saving

CLC Number:

TK 124

Cheng LUO, Lei WANG, Yang LI, Qingming MENG, Guibin ZHANG, Yuanbin ZHAO. Effects of Variable-Flow Water Distribution on Cooling Performance of Wet Cooling Towers and Its Optimization[J]. Power Generation Technology, 2025, 46(5): 1041-1049.

Figures/Tables 20

Fig. 1 Schematic diagram of water distribution system and zero spray range during single-pump operation

Tab. 1 Dual-pump water distribution

区域	分区总流量/(m³/s)	平均喷头流量/(m³/s)	不均匀性系数/%
内区	0.762 7	0.001 4	1.5
外区	1.009 2	0.001 5	1.7

Fig. 2 Water distribution zones of scheme 1

Tab. 2 Nozzle diameter configuration of scheme 1

区域	内区	外区
喷头直径/mm	26	30

Fig. 3 Nozzle flow rate for dual-pump water distribution pipes of scheme 1

Tab. 3 Dual-pump operation calculation results of scheme 1

区域	淋水密度/[kg/(m²⋅s)]	配水不均匀性系数/%
内区	1.371 6	3.8
外区	2.033 3	7.6

Fig. 4 Nozzle flow rate for single-pump water distribution pipes of scheme 1

Tab. 4 Single-pump operation calculation results of scheme 1

区域	淋水密度/[kg/(m²⋅s)]	配水不均匀性系数/%
内区	1.244 1	6.8
外区	1.124 3(淋水部分)	—

Fig. 5 Water distribution zones of scheme 2

Tab. 5 Nozzle diameter configuration of scheme 2

区域	内区		外区
区域	内区	1	2	3
喷头直径/mm	26	22	26	30

Tab. 6 Dual-pump operation calculation results of scheme 2

区域	淋水密度/[kg/(m²⋅s)]	配水不均匀性系数/%
内区	1.594 2	5.3
外区整体	1.856 2	6.4
外1区	1.435 6	5.5
外2区	1.598 6	4.9
外3区	2.285 5	6.7

Fig. 6 Nozzle flow rate for dual-pump water distribution pipes of scheme 2

Tab. 7 Single-pump operation calculation results of scheme 2

区域	淋水密度/[kg/(m²⋅s)]	配水不均匀性系数/%
内区	1.036 0	6.3
外区整体	1.060 3	9.2
外1区	0.945 4	7.1
外2区	1.036 6	7.6
外3区	1.154 9	8.5

Fig. 7 Nozzle flow rate for single-pump water distribution pipes of scheme 2

Fig. 8 Distribution of water leaching density in the spray zone of cooling tower when single-pump running at scheme 1

Fig. 9 Water surface temperature distribution in cooling tower basin during dual-pump operation of scheme 1

Fig. 10 Water surface temperature distribution in cooling tower basin during single-pump operation of scheme 1

Fig. 11 Water surface temperature distribution in cooling tower basin during dual-pump operation of scheme 2

Fig. 12 Water surface temperature distribution in cooling tower basin during single-pump operation of scheme 2

Fig. 13 Comparison of cooling characteristics between variable flow rate water distribution schemes

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