Researchers from North China Electric Power University investigated the local flow and heat transfer performances of the cooling deltas
The natural draft-dry cooling system (NDDCS) is used in thermal and nuclear power plants throughout the world due to its advantages such as significant water conservation compared to wet-cooling system. NDDCS cools the air flowing through the heat exchanger finned tube bundles to take away the heat rejection of circulating water. However, crosswinds can have a significant impact on the productivity of NDDCS as they can strongly impair the thermo-flow performances of the system. Therefore, several studies are focused on understanding the impact of wind and finding the relevant approaches to enhance the thermo-flow performances with the help of computational fluid dynamics (CFD) method.
Now, a team of researchers from North China Electric Power University developed 3D overall outlet temperature fields for a large-scale air-cooled heat exchanger. The team also developed a macro heat exchanger model and compared the quantitative thermo-flow performances at various wind speeds. The team found that the air mass flow rate and heat rejection for the frontal sector increases with increase in wind speed. However, no significant variation was observed for the middle-front sector. The thermo-flow performances differ significantly with the wind speed for the middle and middle-rear sectors and these sectors are highly deteriorated at a wind speed of 12 m/s. However, the rear sector received the best performance at a wind speed of 12 m/s.
The team also assessed the local thermo-flow characteristics for the cooling deltas in various air-cooled sectors. The team found that the thermo-flow performances deteriorated along the circumferential angle for the frontal and middle-front cooling deltas and the middle deltas demonstrated extremely deteriorated performances at high wind speeds. This can be attributed to the hot-flow recirculation and the air-flow vortices. Majority of the middle-rear deltas demonstrate reduced thermo-flow performances at the wind speed of 12 m/s. However, the sixth to 11th deltas showed best performances at 16 m/s. The best flow and heat transfer performances for rear deltas were at 12 m/s. The research was published in the journal MDPI Energies on March 22, 2019.
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