Numerical study regarding cooling capacity for non-equidistant fillings in large-scale wet cooling towers

Abstract

Fillings are the core part of wet cooling towers, and generally speaking, the fillings are arranged in an equidistant pattern, which actually hampers the heat and mass transfer process. So the non-equidistant fillings which is the combination of large-spacing and small-spacing fillings are adopted to enhance the thermal performance. In this study, numerical simulation was conducted on one real wet cooling towers equipped for a 600 MW unit to study the relatively optimal combination of 26 mm and 30 mm spacing fillings (30 mm fillings are arranged in the inner zone and 26 mm fillings are stalled in the outer zone). The simulation results indicated that, compared with conventional equidistant fillings, the thermal and resistance performance improve partly under the non-equidistant fillings pattern. After adopting non-equidistant fillings, the aerodynamic field and the temperature field improve significantly. Furthermore, with the increase of the inner zone radius R1, the water temperature drop Δt, cooling efficiency η and Merkel number N rise first and then decline, and the relatively optimal inner radius is 47.5 m in this case. When R1 = 47.5 m, compared with 26 mm equidistant fillings condition, Δt, η, and N increase about 0.13 °C, 0.8%, and 0.03. And the ventilation rate G increases by about 751.32 kg/s at most. While the ambient air temperature changes, the non-equidistant fillings can also improve the cooling performance. Under the summer typical conditions, compared with all 26 mm and 30 mm equidistant fillings, the Δt with the relatively optimal non-equidistant fillings rises by 0.17 °C and 0.2 °C, respectively.