Abstract
The operating conditions of axial flow fans are closely related to the thermo-flow characteristics of the mechanical draft direct dry cooling system. Moreover, the uneven distribution of cooling air driven by axial flow fans may lead to the deterioration of the heat transfer capacity of air-cooled condensers (ACCs). Therefore, developing energy-saving operating methods for axial flow fans is very meaningful. In this work, two kinds of adjustment strategies to make the flow field more uniform are proposed for a 2 × 300 MW direct dry cooling power-generating unit. The performance of ACCs in the prevailing wind direction is predicted with the help of the macro heat exchanger model. It is found that the inlet air temperatures of fans are significantly reduced by proposed strategies, especially at high wind speeds. Moreover, the minimum cooling air can meet the cooling demand of ACCs for the strategy which made the air flow rates of all fans consistent. Compared with the case without adjustment of fans, the total power consumption of the fan array was cut down effectively, up to 13.94% at the wind speed of 12 m/s. In conclusion, the energy efficiency of ACCs can be improved by the uniform flow field.
Highlights
For saving water resources and protecting the environment, the direct dry cooling system (DDCS) due to its low investment and flexible regulation has received a lot of attention and developed rapidly in the past several decades, especially in areas with water shortage
Duvenhage and Kröger [1] revealed the effects of ambient wind in different directions for air-cooled condensers through numerical simulation, which mainly include the reduction in flow rates of upward fans and hot air recirculation
Yang et al [3,4] pointed out that the performance of the upwind air-cooled condensers (ACCs) cells is poor under windy conditions, and adjusting the upwind axial flow fans or optimizing the structure of condenser cell is meaningful to improve the cooling capacity of ACCs; the deterioration of the upwind condenser cell performance and the hot air recirculation are the main adverse reasons in the wind directions of 90◦ and 0◦, respectively
Summary
For saving water resources and protecting the environment, the direct dry cooling system (DDCS) due to its low investment and flexible regulation has received a lot of attention and developed rapidly in the past several decades, especially in areas with water shortage. The flow rate of cooling air through each condenser cell varies greatly with ambient wind, which adversely affects the cooling performance of ACCs. the regulation of axial flow fans with considerable power consumption is accepted as an effective method to improve the energy efficiency of direct dry cooling power plants. Chen et al [20] put forward various adjustment strategies of fans for ACCs and compared their performance under different ambient conditions, concluding that accelerating the speed of windward fans in the first row alone is disadvantageous for DDCS He et al [21] found that increasing the installation angle of fans properly can improve the net power of the direct day cooling power plant.
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