Research On Thermodynamic Characteristics Of Air-cooled Array Under Natural Wind Disturbance

The condenser of the direct air-cooling plant is composed of dozens of air-cooled units connected in series and in parallel,and is arranged in an open-air environment elevated platform in an array shape.Therefore the air-cooled island is also known as the "air-cooled array".It is crucial to investigate the transient behaviors of air flowing through the ACA during the natural wind varying speed and direction for the purpose of optimal energy consumption of motor group through sub-zoning fans cluster and designing a robust speed controller.Based on the moving boundary model and sliding grid method,a transient mathematical model to cooling-air flow through a 5 x 6 ACA under the nature wind with time-varying speed and direction was developed and calculated numerically,moreover,the predicted air velocity at the inlet of fans were compared with experimental results to verify the the model.The numerical results show the following.(1)The inlet temperature and velocity of ACA response to wind speed without time delay;under the nature wind with continuous-varying velocity,the air flow of the second-row axial fans in the upwind stream can be classified to a negative proportional object to the wind velocity;the inlet hot wind reflux rate can be classified to a self-balance object with final bias to the pulse of wind velocity.(2)The upwind row moves dynamically in ACA with the changes of wind direction in the range of 360°and 120°;the inlet air flow of upwind row is most affected by the natural wind,and the dynamic movement has a time delay of about 2 s;during the wind direction reverses,the hot reflux phenomenon is observed in the inlet of axial fans on the two side of wind direction,furthermore,these fans transpose in a delay of about 10 s with the wind reversing.According to numerical results,5 recommendations are proposed to the sub-grouping of fans cluster and controlling of fans rotation.(1)Appropriately increase the differential term of the fan speed controller in the sensitive area of the wind speed disturbance or increase the feedforward link to speed up the controller response.(2)Install temperature sensors at the inlet of the fans,and input the inlet temperature as a variable into the fan speed control system.(3)Consider the wind direction angle outputted by the airflow meter over the air-cooled island as a control variable to adjust the control partition strategy online.(4)Appropriately improve the speed of fans in surrounding area to improve the flow performance of the air-cooled array.(5)Reduce the speed of fans seriously affected by the hot air return phenomenon to prevent airflow from re-entering the air condenser.