Research On The Relationship Between Air-cooled Island Platform Heights And Its Thermal Performance In Diesel Power Station

The air cooled island is widely used in the cooling system of the diesel engine power station.In an air cooler cell,The cooling water cools the diesel engine body and then becomes high-temperature water discharged into the tube-and-fin heat exchanger(air cooler),while cooling air is drawn upward across the fins by a fan that is mounted underneath the platform.The heat is rejected by cooling air,causing the water to be cooled.However,hot air recirculation is prone to occur in the process.The hot air reciculation phenomenon is defined as a part of the hot exhaust air above the air cooler sucked to the inlet region of the fan.If a large amount of hot air recirculation takes place,a significant increase in the fan inlet air temperature will result,greatly reducing the efficiency of the air cooler.Considering the effects of ambient wind speed and air-cooled platform height,numerical simulation of the thermal flow characteristics and heat transfer performance was made of a 10×10339 kW air-cooler in the diesel engine power station.A simplified physical model of the air cooler combined with the designed data as input parameters was used in the simulation.In this paper,based on the SIMPLE algorithm and the k-? turbulence model,the air-cooled island was studied by utilizing the computational fluid dynamics software FLUENT under the conditions of ambient temperature 33 ? and dominant wind direction(west winds)with the hot air recirculation rate as the evaluation standard.The wind speed effects on the hot air recirculation rate for different platform heights are obtained.The flow and temperature field distribution around the air-cooled island are attained through the Post-Processing.Theoretical reference is provided for the design of the air cooling system of a diesel engine power station.The results are as follows:(1)The change of the heights of the air-cooled island and the ambient wind speed is likely to cause hot air recirculation under the prevailing wind direction;(2)When the wind speed is constant and the platform heights varies within a certain range(4.8 m ~ 8.8 m),the hot air recirculation rate decreases as the heights increases.The hot air recirculation rate drops by a large margin while the heights was increased from 4.8 m to5.8 m.(3)The dominant factor which causes the change of the hot air recirculation rate is wind speed with the constant heights.The hot air recirculation rate rises first and then declines with the augmentation of the wind speed.There is a greater impact on the hot air recirculation rate with the wind speed exceeding 3 m/s.Under the prevailing wind direction,the greater the ambient wind speed is,the more obvious would the hot air recirculation be improved,and the greater would the impact on the air cooler cell be apparent.(4)Affected by the hot air recirculation,the air temperature on the fan inlet region located at the edge of the air cooler platform is higher than that of other fans.(5)It can be seen that the optimal platform height should be mounted at 7.8 m approximately.The wind temperature at the fan inlet would not vary much when the heights of the air-cooler increases continuously.