Design and Operating Performance of Mechanical Draft Dry Cooling Tower Pre-cooled with Wet Medium

doi:10.11930/j.issn.1004-9649.202306029

Abstract

Abstract:

In order to solve the problem of insufficient output of mechanical draft dry cooling tower which can’t meet the cooling demand in summer, a mechanical draft dry cooling tower with wet medium pre-cooling inlet air system is designed in this paper. The influence of wet medium thickness, ambient temperature and humidity on the operating performance of the designed dry cooling tower and water-saving performance are carried out by using Matlab program. The results show that 300 mm CELdek7060 medium pre-cooling inlet air system has the best pre-cooling effect and the heat rejection rate of the cooling tower increases by 20.57% at the ambient temperature of 26 ℃ and humidity of 57%; the heat rejection performance of the dry cooling tower decreases with the increases of ambient temperature, and there is a critical temperature of 13.5 ℃; the wet medium pre-cooling system could improve the heat rejection rate of dry cooling tower by 96.96%, and further reduce the outlet water temperature by 2.80 ℃ at the ambient temperature of 35 ℃ and humidity of 57%; the wet medium pre-cooling system could improve the heat rejection rate of dry cooling tower by 81.14%, and reduce the outlet water temperature by 6.81 ℃ at the ambient temperature of 26 ℃ and humidity of 0%. The total annual energy-saving benefit of a single tower is about 138 400 yuan, which has good economic benefits.

Key words: cooling tower, evaporative cooling, wet medium, heat rejection performance, inlet air pre-cooling

Mingwei WANG, Tiantian LIU, Qi GAO, Chunwei WANG, Jiyong SHEN, Shoufu LIU, Suoying HE. Design and Operating Performance of Mechanical Draft Dry Cooling Tower Pre-cooled with Wet Medium[J]. Electric Power, 2024, 57(6): 225-234.

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URL: https://www.electricpower.com.cn/EN/10.11930/j.issn.1004-9649.202306029

https://www.electricpower.com.cn/EN/Y2024/V57/I6/225

Figures/Tables 12

Fig.1 Schematic diagram of finned tube

Table 1 Parameters of finned tube

管的布置间距 S₁/mm		翅片管长 L_T/m		管外径 D_o/mm		管内径 D_i/mm		翅片外径 D_f/mm		翅片厚度 δ_f/mm		翅片高度 H_f/mm		翅片间距 Y/mm
59		12		25		23.4		57		0.4		16		2.5

Fig.2 Design process of heat exchanger

Fig.3 Schematic diagram of dry cooling tower with wet medium pre-cooling inlet air system

Table 2 Design parameters of dry cooling tower with wet medium pre-cooling inlet air system

塔高 H₉/m		风机高度 H₆/m		塔入口高度 H₃/m		塔宽 B/m		气室高度 H_pl/m		换热器上游高度H₄/m		风机直径 d_F/m		风机转速 N_F/rpm		V型换热器夹角θ/(°)		管束数 n_b		管排数 n_r		每排管数 n_tr		管流程 n_p
17		15.6		4		12.5		1.2		14.4		9.145		120		60		8		4		50		4

Fig.4 Flow chart of Matlab iterative process

Fig.5 The influence of different thicknesses wet media on the heat rejection and ventilation performance of dry cooling tower

Fig.6 The influence of with/without wet medium pre-cooling system on heat rejection performance of mechanical draft dry cooling tower (ambient humidity of 57%)

Fig.7 The influence of with/without wet medium pre-cooling system on ventilation performance of mechanical draft dry cooling tower (ambient humidity of 57%)

Fig.8 The influence of with/without wet medium pre-cooling system on heat rejection performance of mechanical draft dry cooling tower (ambient temperature of 26 ℃)

Fig.9 The influence of with/without wet medium pre-cooling system on ventilation performance of mechanical draft dry cooling tower (ambient temperature of 26 ℃)

Table 3 Water consumption and fan power of mechanical draft dry cooling tower with/without wet medium pre-cooling system

类型	出塔水温/ ℃	水蒸发量/ (kg·s^–1)	风机功率/ kW
填料预冷的机械通风空冷塔	30.0	0.78	33.92
机械通风空冷塔	30.0	0	95.69

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