Simulation Study On The Effect Of Forced Ventilation On The Performance Of Wet Cooling Towers Under Summer Conditions

The increase of ambient temperature and the presence of crosswind reduce the cooling performance of wet cooling towers.To reduce the adverse effects of high temperature and crosswind on the cooling performance of cooling towers under summer conditions,this paper proposes a coupled operation mode of natural ventilation and forced ventilation for wet cooling towers.The influence of the coupled operation mode on the aerodynamic field,temperature field,cooling per-formance,and economy of forced ventilation inside the tower under different crosswind envi-ronments was studied,which has certain guiding significance for practical applications.Taking the wet cooling tower equipped for a 35MW unit of a biomass cogeneration project as the research object,the geometric modeling of the wet cooling tower was established by DesignModeler,and the grid was divided by ICEM-CFD.Using the UDF in Fluent for programming,a custom function was formed for the coupled operation mode of natural ventilation and forced ventilation of wet cooling towers.A 3-D numerical model for the coupled operation mode of natural ventilation and forced ventilation of wet cooling towers was established,and grid independence and model accuracy verification were completed.By studying the single fan operation pattern,the diameter,power,installation height,number,and radial position of the fan were determined.The effect of single fan operation on the cooling performance and economy of the tower was studied under typical crosswind direction and crosswind speed.The research results indicate that the optimal installation point for the fan is the one closest to the windward point in the crosswind axial position.The circulating water temperature drop and net power increase respectively by 0.455℃ and 213.6kW at lm/s crosswind speed,0.364℃ and 158.9kW at 3m/s crosswind speed,and 0.273℃ and 104.1kW at 5m/s crosswind speed.The uniform variable power operation method of multiple fans was proposed,and the influence of the number and distribution of fan points,and operating power on the aerodynamic and temperature fields inside the cooling tower was obtained.The calculation results show that the cooling performance of the tower is better when the number of fan points increases,the distribution of points is closer to the windward side,and the operating po wer becomes higher.The economy of forced ventilation in the cooling tower first increases and then decreases(under low wind speed)or gradually decreases(under high wind speed)with the increase of the total power of the ac-tive fan.From the economic perspective,under optimized fan locations and operation power,the circulating water temperature drop and net power increase by 0.621 ℃ and 283.4kW at 1m/s crosswind speed,0.496℃ and 208.1kW at 3m/s crosswind speed,and 0.310℃ and 141.2kW at 5m/s crosswind speed,respectively.The non-uniform variable power operation method of multiple fans was put forward,and the influence of fan point distribution and power distribution on the aerodynamic and temperature fields inside the cooling tower was acquired.The calculation results state that the cooling performance of the tower is better when the fan point distribution is closer to the windward side,and the proportion of better performance fan power to the total power of active fans increases.For the case of constant total power of active fans,the higher the proportion of better performance fan power to the total power of active fans,the better the economy of forced ventilation in the cooling tower.Considering the economic benefits,under optimized fan locations and power distribution,the circulating water temperature drop and net power increase by 0.657℃and 305.0 kW at 1m/s crosswind speed,0.528℃ and 227.7 kW at 3m/s cross-wind speed,and 0.359℃ and 155.7kW at 5m/s crosswind speed,respectively.The influence of crosswind speed on the cooling performance and forced ventilation economy of cooling towers were investigated.The research results point out that as the cross-wind speed increases,similar to the regular tower,the cooling performance of the tower in each fan operation pattern first decreases and then improves,which is much better than the regular tower.Taking economic benefits into consideration,it gradually decreases with the increase of crosswind speed.