Influencing Mechanisms of a Crosswind on the Thermo-Hydraulic Characteristics of a Large-Scale Air-Cooled Heat Exchanger

Yanqiang Kong, Weijia Wang, Zhitao Zuo, Lijun Yang, Xiaoze Du, Chao Xu and Yongping Yang
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Yanqiang Kong: School of Energy Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China
Weijia Wang: Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China
Zhitao Zuo: Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China
Lijun Yang: School of Energy Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China
Xiaoze Du: School of Energy Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China
Chao Xu: School of Energy Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China
Yongping Yang: School of Energy Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China

Energies, 2019, vol. 12, issue 6, 1-29

Abstract: For the large scale air-cooled heat exchanger of a natural draft dry cooling system (NDDCS) in power plants, its thermo-flow characteristics are basically dominated by crosswinds. Unfortunately however, the detailed mechanisms of the crosswind effects have yet to be fully uncovered. Therefore, in this research, the local flow and heat transfer performances of the cooling deltas, which are also termed as the fundamental cells of the large-scale air-cooled heat exchanger, are specifically investigated with full consideration for the cell structure and the water-side temperature distribution at various wind speeds. A 3D CFD method with a realizable k-ε turbulence model, heat exchanger model, and porous media model is developed, and the accuracy and credibility of the numerical model are experimentally validated. With the numerical simulation, the overall 3D outlet air temperature of the large-scale air-cooled heat exchanger, and the corresponding local air velocity and temperature fields of the cooling deltas are qualitatively analyzed. Furthermore, the air-mass flow rate and heat rejection are also quantitatively studied at both the global and local views. The results depict that with an increase in the wind speed, the air mass flow rate and heat rejection will increase greatly for the frontal deltas; however, they will drop dramatically for the middle-front deltas. As for the middle- as well as the middle-rear deltas, the thermo-flow performances vary markedly at various wind speeds, which behave in the most deteriorated manner at a wind speed of 12 m/s. The rear deltas show the best thermo-flow performances at a wind speed of 12 m/s, but the worst at 16 m/s. A detailed analysis of the variable fields for each cooling delta may contribute to the performance improvement of the large-scale air-cooled heat exchanger of NDDCS.

Keywords: large scale air-cooled heat exchanger; cooling delta; macro heat exchanger model; thermo-flow performances; wind speed (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
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