Numerical Simulation Of Gas-liquid Flow,Heat And Mass Transfer Process In Natural Draft Wet-cooling Tower With Flue Gas Injection

Cooling tower is an important equipment in cooling system of power plant,the capacity of cooling characteristic is related to the safety and economy of power plant operation.With the contradiction between development of power industry and lack of water resources,the requirement for cooling efficiency of cooling tower is increased,and the research of cooling tower have deepened.The emerging of NDCT with flue gas injection technology is beneficial to policies about energy saving and emission reduction,and make power plant construction in sky clearance limits area be possible.The writer mainly used CFD software Fluent to 3D-simulated calculation NDCT and NDCT with flue gas injection which used in 300MW grade power plant.These results of 3D-simulated calculation shall be compared with one dimension calculation results.One dimension calculation method is widely used in engineering design area,the method has a lot of hypothesis,the results shall have difference to the actual situation.So we use the results of 3D-simulated calculation to revise and give out safety margin,make sure that the calculation results be safety and steady.Especially in the mixed gas temperature at tower outlet area with one dimension calculation of NDCT with flue gas injection,we need precise results to meet the requirements of the environmental protection.So the major reserach works are as follow:(1)Through analysis of the results which come from one dimension method between NDCT and NDCT with flue gas injection,we found that the flue gas injection in the tower make the outlet water temperature lower than NDCT,the capacity of cooling enhanced.The capacity of cooling enhanced little between these two cooling tower in hot ambient temperature,enhanced obviously in lower ambient temperature and heavy cooling load.(2)The 3D-numerical simulation model for NDCT and NDCT with flue gas injection was established.Through analysis of the results which come from these 3D-numerical simulation calculation,we know that the wind speed higher in design scope the outlet water temperature will be higher.In the same situation,the NDCT with flue gas injection can get lower outlet water temperature the NDCT.(3)Through analysis of the outlet water temperature results which come from one dimension method and 3D-numerical simulation calculation,we know that the results are very close.In the lower ambient temperature,outlet water temperature results which come from one dimension method is lower than 3D-numerical simulation calculation.In the normal and hot ambient temperature the results between these two calculations are nearly the same.But we need consider safety margin in summer 10%meteorology frequency TRL operating situation.The safety margin can choose 1.5 ℃temperature arising to outlet water temperature under the situation that wind design speed below 5m/s,if wind design speed exceed 5m/s,we need choose a higher safety temperature margin.(4)Through analysis of the outlet mixed gas temperature results which come from one dimension method and 3D-numerical simulation calculation,we know that the difference of results are big.In the situation that wind design speed around 3m/s,one dimension method calculation results are reliable.In none wind speed situation,we need consider safety margin in one dimension method calculation results,the outlet mixed gas temperature is suggested to reduce 2.8 ℃ to 4℃ choose lower value when ambient temperature is lower.