Study On Influence Of Geometric Characteristic Of Filling Channels On Thermal Performance For Wet Cooling Tower

The cooling tower is used to cool circulating water of high temperature in power plant,the thermal energy of circulating water is diffused to the atmosphere through heat exchange between air and circulating water in the tower.Cooling tower is an important production equipment and its performance has important influence on the effectiveness of whole power plant.Inside the cooling tower,the cooling performance is mainly affected by thermodynamic characteristics of filling,the temperature of the operating system,the feed water quantity,the external wind speed and the drift eliminator,etc.Filling is very important air-water heat transfer element in the cooling tower,and it is of great significance to analyze the heat transfer performance of filling.Liquid film flow patterns affected by many factors,including the properties of liquid,texture and structure of the channel,air speed,water velocity,etc.,and the morphology of liquid film is an important factor influencing the heat transfer,In this paper,the flow and heat exchange of gas liquid in the filling channel are analyzed from the Angle of liquid membrane.In this paper,the numerical models of the heat transfer in air-water two-phase reverse flow in the filling is established by means of the assumption of the wall equivalent method,and the accuracy of the model is validated by comparison with other scholar's computational results.The validated model is then used to calculate the operation of heat transfer in the air-water two-phase flow within the passage of filling,the flow state of liquid film over time is analyzed as well.The variations of temperature distribution,and flow state of liquid film with air speeds,water speeds,air inlet temperature and passage tilt are reported.Through analyzing the simulation results,we found that within the scope of the operation condition of the power plant,it is very effective to improve liquid hold-up,cooling efficiency and reduce the drag coefficient within the passage through improve the air speed.The increase of water inlet speed within the scope of the operation condition of the power plant makes the liquid membrane flows in a poor state,the cooling efficiency of the passage decrease and the drag coefficient increases.In the case of other parameters constant,the decrease of initial air temperature makes the cooling efficiency almost unchanged,but the decrease of water outlet temperature shows the benefit to the heat transfer.This paper analyzes the differences of flow state of liquid film,thermodynamic characteristics of two kinds of tilt angle passage,the result shows that the model of the tilt angle of 45°and 60° is superior to the model of the tilt angle of 30° in cooling efficiency,but in terms of drag coefficient,the model of the tilt angle of 30° is better.According to characteristics of gas-liquid two phase flow within the passage,the three-dimensional numerical computation models of the complex heat transfer in air-water two-phase reverse flow in the filling is established by means of the assumption of the wall equivalent method.The validated model is used to calculate the process of heat transfer and air-water two-phase flow state within the three-dimensional passage of filling,and the relationship of flow and gas-water ratio in the three-dimensional passage.The variations of cooling efficiency,drag coefficient with gas-water ratio are reported in this paper.By analyzing the calculation results we found that the cooling efficiency within the passage is obviously improved with the increase of gas-water ratio,and the drag coefficient is slightly reduced.This paper discusses the filling structure optimized schemes and analyzes the relationship of filling structure and thermodynamic characteristics.The variations of flow state of liquid film,liquid film thickness,liquid hold-up,cooling efficiency,temperature distribution and draft coefficient with aperture size are reported.The factors influencing the difference are analyzed.The results show that the cooling efficiency of the passage improves significantly with the increase of the filling aperture size,it is due to the difference of surface area.The draft coefficient of the structure of little aperture is significantly less than that of previous structure.The cooling efficiency and draft coefficient of three kinds of filling models are presented in this paper,and the factors influencing the difference are analyzed.Because of complex structure and the highest specific surface area of the S corrugated filling,it has the highest cooling efficiency,the most liquid hold-up and the highest draft coefficient.The cooling efficiency of sloping corrugated filling is least because of its minimum specific surface area.Because of the advantage of the tilt angle in structure,the sloping folded corrugated filling has the least draft coefficient.