| Air-cooled towers are an important part of thermal power plants.As the complexity of the construction of existing double-curved towers is becoming more and more obvious,the application of cylindrical truncated cone-shaped steel aircooled towers,which are easier and more economical to construct,so it is of great importance to study the influence of both tower types on the flow and heat transfer characteristics of air-cooled towers.In this paper,based on the reduced size physical model towers of cylindrical truncated cone and hyperbolic tower types,experimental measurements of temperature and velocity at different positions in the towers are carried out to analyze the similarities and differences in the flow and heat transfer performance of the two.The experimental optimization of the temperature system selection and the arrangement of measurement points during the experiment was also carried out.The results show that the differences in flow heat transfer performance between the two tower types are not significant,but the cylindrical truncated cone air-cooled tower is slightly worse than the hyperbolic air-cooled tower due to the variable cross-sectional angle of the tower wall,which weakens the flow heat transfer effect.Then,a simplified numerical model of cylindrical truncated cone-shaped aircooled tower with reduced dimensions was established by numerical simulation,and the flow and temperature fields of the cylindrical truncated cone-shaped model aircooled tower used in the experimental bench were calculated under windless conditions.A combination of simulation and experiment was used to compare the numerical simulations with the actual test results,and the relative errors were within the acceptable range,which verified the feasibility of the numerical calculation method used.With reference to the above numerical modeling idea,the cylindrical truncated cone air-cooling tower was scaled up by 100 times as the original size of the cylindrical truncated cone air-cooling tower in the actual project to restore the flow situation in the air-cooling tower in the actual project.Under the condition that the height of the air-cooled tower and the bottom radiator section are the same,the proportional size of the outlet diameter of the chimney section of the cylindrical truncated cone tower is changed,and the numerical models of five outlet diameter ratios of the tower are established.The velocity and temperature fields of the cylindrical truncated cone air-cooled tower are calculated under no wind condition(v=0m/s)and different wind speeds(4m/s,8m/s,12m/s,16m/s),and the performance of the air-cooled tower is evaluated in terms of overall heat transfer,outlet flow rate and suction force,and the key design parameters for tower shape optimization are analyzed.Considering the completeness of the subject,the numerical simulation part of the study is divided into windless and windy conditions as a whole.In the actual project,there is a certain amount of ambient wind around the cooling tower,so the focus on the wind conditions for its performance analysis.The calculation results show that the above three evaluation indicators have different degrees of influence on the overall performance of the cylindrical truncated cone air cooling tower.When using the optimal column height ratio of 0.4 under windy conditions as the basis for the design,theoretically,when the outlet diameter d = 0.9 or so,the cylindrical truncated cone tower flow characteristics and heat transfer efficiency is optimal,while the actual engineering tower structure parameters and also according to the specific construction conditions to choose. |
