| With the mature application of NDCT with flue gas injection,three incorporate towers emerged on the basis of it.Desulfurization tower is placed inside air cooling tower,so NDCT with flue gas injection turns into three incorporate towers.Three incorporate towers can save energy,reduce consumption and reduce environmental pollution.In the form of energy conservation and emissions reduction,it will be widely used in the thermal power industry.In the three incorporate towers,smoke and hot gases will mix.And they also transfer heat between each other.Desulfurization tower and chimney will influence the gas flow in the tower.These factors make the flow field more complex.So the influencing factors of heat transfer characteristic are more complex.The installation of radiator,high temperature and high speed flue gas,desulfurization tower and chimney,the structural parameters which determine the tower shape all influence the heat transfer characteristic in different degrees.It is necessary to study the influence rule of these factors on the heat transfer characteristic to find the optimal heat transfer characteristic.The conclusion can provide reference for the optimal operation of this kind of composite tower.This paper takes a 600 MW indirect air cooling tower with three incorporate towers as the research object.Three-dimensional numerical model was established above all,and its correctness was confirmed based on corresponding measured data.Then on the basis of this model,the difference of flow field and heat transfer characteristic of indirect air cooling tower with three incorporate towers and conventional indirect air cooling tower was studied under different environment wind speed,when the radiator is installed outside the tower vertically and installed in the tower horizontally.The influence of the installation of radiator on the heat transfer characteristic of indirect air cooling tower with three incorporate towers was also studied in details.Smoke parameters,structure parameters of Desulfurization tower and chimney,structural parameters which determine the tower shape type are respectively selected as a single variable finally.The influence rules of these parameters on the heat transfer characteristic were studied in details with appropriate evaluation index using numerical calculation.The results indicate: when there is no wind,the difference of heat transfer characteristic of two kinds of structure with the radiator installed outside the tower vertically or installed in the tower horizontally can be negligible.When there is wind,with the increase of environmental wind speed,the difference of heat transfer characteristic increases gradually.In the simulated environment wind speed range,the heat transfer characteristic of indirect air cooling tower with three incorporate towers is consistently better than that of conventional indirect air cooling tower,the heat transfer characteristic of radiator installed outside the tower vertically is consistently better than that of radiator installed in the tower horizontally.The influence of smoke exhaust temperature,smoke exhaust speed,smoke flow,the height and diameter of chimney on the heat transfer characteristic can be negligible.With the increase of the diameter of desulfidation tower,the heat transfer characteristic continues to decrease.When outlet diameter or throat diameter increases,the heat transfer characteristic will increase first,but as outlet diameter or throat diameter increasing to some value,the heat transfer characteristic begins to decrease.When there is no crosswind,the heat transfer characteristic will increase firstly and then decrease with the increase of throat height,as there is crosswind,the change law is opposite.With the increase of tower height,the heat transfer characteristic continues to increase.While the ratio of outlet diameter to base diameter R1/R2=0.8~0.85,and the ratio of throat diameter to base diameter R0/R2=0.6~0.65,the optimal heat transfer characteristic is achieved. |
