Analysis On Variable Condition Characteristic Of The Condenser And ITD Optimization For 1000MW Direct Air Cooled Unit

In the northern regions of China where have rich coal and short water,water scarcity has become the main factors restricting the development of the local power.Air cooling technology as a resource-saving technology means,it uses air instead of water as the cooling medium,greatly reducing the waste of water resources,has a huge space for development.The biggest difference between the conventional water cooling unit and direct air cooling unit is the cold end,the condenser of direct air cooling unit arranged in the open-air air-cooled platform directly,affected by the ambient wind speed,air temperature and flow field,so its cold end parameter has a big range of variation.Researching the characteristic of variable condition has an important significance to improve the unit's thermal economy and to ensure the safe operation of the unit.In this paper,a 1000MW direct air cooling unit,for example,carried out a detailed study on the characteristic of variable condition of the condenser.The external temperature,face velocity and pressure distributions of the condenser under different conditions are obtained with the numerical simulation software,the external radiator heat transfer and flow characteristics under different head-on wind velocity,ambient temperature,fin spacing,fin thickness and fin height are analyzed.On this basis,the mathematical model of the unit exhaust pressure of variable conditions is built with the way of ?-NTU,the characteristics of the unit exhaust pressure under different heat load,environmental temperature,head-on wind velocity and the inside and outside condenser fouling thermal resistance are analyzed,the range of the exhaust pressure which can ensure the safe and stable operation of the unit is determined,the impact that the inside and outside condenser fouling thermal resistance has on the economy of the unit is compared to identify the fouling resistance range which can reduce unit economy significantly and provide reference for determining condenser cleaning cycle.Finally,on the basis of numerical simulation of external the flow field of the condenser and calculation for condenser variable condition,combined with the specific circumstances of the unit of local,with the way of minimum total annual cost and the establishment of the objective function,the ITD value and face velocity are optimized,a sensitivity analysis for the variation of the best ITD when the coal price,the air cooled condenser tubes price and the environmental temperature change is performed and the changes of the best ITD value,and the face velocity are calculated when the design temperature transforms.