Cooling Performance Optimization of Direct Dry Cooling System Based on Partition Adjustment of Axial Flow Fans

Abstract

Axial flow fans play key roles in the thermo-flow performance of direct dry cooling system under windy conditions, so the energy efficiency of a power generating unit can be improved by optimizing the operation strategies of the axial flow fans. In this work, various measures based on the partition adjustment of axial flow fans with constant power consumption of a 2 × 660 MW power plant are studied by computational fluid dynamics (CFD) methods. The results show that increasing the rotational speed of the windward fans is beneficial to reduce the inlet air temperature and increase the mass flow rates of the fans, which enhance the heat rejections of the air-cooled condensers, especially at high wind speeds. Moreover, the turbine back pressures for the optimal and original cases are achieved by iterative methods, with the largest drop of 2.77 kPa at the wind speed of 12 m/s for 110-case 3 in the wind direction of −90°. It is recommended to adopt 110-case 1 and 110-case 3 at low and high wind speeds, respectively, in the wind directions of 90° and −90°, while 110-case 2 is always the best choice in the 0° wind direction.

Operation strategies of axial flow fans in a direct dry cooling system under various meteorological conditions

“…In the experiments, the outlet air temperature of radiator t a2 is measured, and the temperature difference used in the experiments is the difference between the steam temperature t s and t a2 . The polynomial formula of h ' takes the following form 26 where h n is the polynomial factor and N is set to 3.…”

“…The size of grid increases from the center to the boundary for reducing the number of grids and satisfying the calculation accuracy. With the grid numbers of 2,310,748, 3,052,216, and 3,855,109, the mass flow rates of one single fan and the ACCs are obtained at various wind speeds 26 . The largest differences between the two bigger grid numbers are both lower than 0.46%, so the number of grids in the middle is adopted.…”

“…He et al 23–25 found that adjusting the blade angle or the fan rotational speed is helpful to increase the net power of the direct dry cooling power generating unit. Huang et al 26 proposed the method of partition adjustment of fans to reduce the turbine back pressure under windy conditions. Li et al 27 obtained the correlation coefficient between each fan and the back pressure of the turbine by using the gray difference incremental correlation method and pointed out that the operating conditions of the fans with high‐correlation coefficients affect the back pressure more significantly.…”

Multi-Model-Based Predictive Control for Divisional Regulation in the Direct Air-Cooling Condenser

“…Li [17] simulated the flow field and temperature field of the direct air-cooling condenser, calculated the correlation between the rotational speed of each fan and the condenser pressure, and suggested adjusting the fans with a relatively higher correlation with condenser pressure is beneficial to reducing condenser pressure and improving efficiency. Huang [18,19] calculated optimal fan speed adjustment strategies under different meteorological conditions and proposed adjusting the fan speed in different blocks under different wind directions. Through scale-down experiments, we found that fan array divisional regulation can help save about 13% of fan energy consumption [20].…”

Energy-Saving Strategies of Axial Flow Fans for Direct Dry Cooling System

“…Li et al [26] associated fan performance with back pressure, and they found that the regulation of fans with high correlation coefficients can bring more benefits. In our previous research [27], it was concluded that windward fans with high rotational speed usually bring economic benefits to the power-generating unit. Moreover, the optimal rotational speeds of fan array are related to different environmental conditions, and the coal consumption may be decreased by reducing the fan speed appropriately under low temperature and wind speed [28].…”