Cooling performance evaluation for double-layer configuration of air-cooled heat exchanger

For large-scale natural draft dry cooling system in thermal power plants, the double-layer air-cooled heat exchanger is recommended thanks to its lower water flow resistance, while the cooling performance is rarely reported so far. Based on the typical natural draft dry cooling system with double-layer air-cooled heat exchanger, the numerical modeling and solution apporaches are developed, by which the representative variable fields and overall cooling performance are obtained and compared with the conventional system. The results show that at the wind speeds of 4 m/s and 8 m/s, the frontal and middle sectors of lower layer show better heat transfer performances than upper layer, especially for the middle sector. At high wind speeds, the frontal sector of upper layer presents a better performance than that of lower layer, but the cooling performances of the middle sectors for both layers get worse with the lower layer showing a slight recovery. The rear sector of lower layer has a much superior cooling performance to upper layer. With increased wind speed, the cooling performance difference of both layers varies little for the middle front sector. As for the middle and middle rear sectors, the performance gap between two layers increases greatly from 4 m/s to 8 m/s, but changes little at high wind speeds. For the rear sector, the difference between both layers stands always prominent at all wind speeds. Compared with the conventional system, the cooling performance gets improved in the absence of winds and at the wind speeds of 4 m/s and 8 m/s, but deteriorated a little at high wind speeds, so this innovative system could be recommended for power plants in arid places with weak wind all year round. (C) 2020 Elsevier Ltd. All rights reserved.