Study On Three Dimensional Numerical Simulation Of Process Characteristics Of Draft Mechanical Cooling Tower

In order to ensure the safety of products and production equipment,cooling medium is used to take away part of the heat energy from the production.Cooling tower is one of the most important components in the cooling cycle system.With the development of economy,mechanical ventilation cooling tower is widely used in electric power,chemical,pharmaceutical and other industries because of its small area and short construction period.Domestic and foreign scholars have done a lot of research on the aerodynamic and thermal characteristics of mechanical ventilation cooling towers,but there is little research on the application of high-level water collector in mechanical ventilation cooling towers.Therefore,this paper analyzes the applicability of high-level water collector in mechanical ventilation cooling towers,which has important practical significance.In this paper,a three-dimensional numerical model of mass transfer and heat transfer in a mechanical ventilated cooling tower is established by using FLUENT software.The loss of source terms in the porous media model in the packing area is added by UDF according to the nature of the actual packing.Firstly,the numerical results are compared with the measured results in the actual running state of the cooling tower,and the reliability of the numerical results is verified and analyzed.Then,by installing high-level water collecting device on the basis of ordinary mechanical cooling tower,this paper analyzes the influence of high-level water collecting device on the thermal performance of cooling tower under different inlet water temperature,different inlet water volume and different cross-wind environment,and gives the feasibility analysis of economic efficiency of high-level water collecting device.At the same time,the effects of different wind speeds and row spacing on the thermodynamic performance and the reflux rate of the cooling towers are also analyzed.Without the influence of cross wind,the water temperature of the tower is affected by the high-level water collecting device,and the water level of the tower is slightly lower than that of the ordinary tower.When there is no wind,the flow field in the cooling tower is approximately asymmetrical,and the velocity distribution in the center of the tower is uniform.The water temperature of the high tower is better than that of the ordinary tower at different inlet temperature,different inlet water volume and different ambient temperature.Rain area is cancelled in high position,the wind resistance in tower is lower,the ventilation rate in tower is larger,and the wind conduction effect is produced,so the water temperature of tower is lower.The lateral crosswind has great influence on the water temperature of the tower outlet.When cross wind exists,the symmetry of the air flow field in the cooling tower is destroyed.The air flow produces swirls near the wall of the tower near the leeward side,and produces the phenomenon of "cross wind",which seriously affects the inlet air of the cooling tower.Because there is no transverse resistance in the rain zone,the inlet flow field of the cooling tower is uneven under the action of cross wind,which makes the distribution of temperature and velocity field of steam and water in the tower uneven,and deteriorates the heat and mass exchange process between water and gas phases,resulting in the rise of water temperature out of the tower.For adjacent towers with long axis not in the same straight line and parallel arrangement,the smaller the spacing between towers,the less the ventilation,the longer the residence time of ambient air in the towers,the sufficient heat transfer between air and water,the formation of high temperature zone in the towers,worsening the heat and mass exchange process.With the increase of row spacing,the interaction between towers decreases,the cooling efficiency of cooling towers increases,and the outlet water temperature decreases.In the presence of cross-wind,the interaction between tower rows will be strengthened by the presence of cross-wind,and a turbulent vortex will be generated between tower rows,resulting in an increase in the average return rate of tower rows with the increase of ambient wind speed level;at the same time,the tower exhaust air volume increases first and then decreases sharply with the increase of cross-wind speed.The temperature and ventilation volume of the tower are more susceptible to environmental wind.