| The freezing of finned tube radiator of indirect air cooling system in cold winter not only affects the safe operation of the unit,but also greatly reduces the economy of the power plant.Therefore,it is important to undertake the research on the anti-freezing characteristics of finned tube radiator in indirect air cooling system.There are two main reasons for the freezing of the intercooling radiator,one is the uneven distribution of the air flow at the air side,the other is the uneven distribution of the circulating water flow at the circulating water side,and the cooling load at the air side and the heat load at the circulating water side do not match,so the research and analysis are carried out from the air side and the circulating water side of the intercooling system,and finally the anti-freezing measures are summarized from the thermal economy of the whole unit.On the air side,the finned radiator and the shutter are numerically simulated.It is concluded that the convective heat transfer coefficient between finned tubes and air increases with the increase of ambient wind speed,independent of ambient temperature.The pressure drop before and after the finned tubes increases with the increase of wind speed,and the air resistance changes significantly.The pressure difference at the inlet and outlet and the wind speed at the outlet are positively correlated with the ambient wind speed,and negatively correlated with the shutter opening.The higher the wind speed is and the smaller the shutter opening is,the faster the pressure drop and the exit speed change.According to the flow field nephogram analysis of the louver,after the air passes through the louver blade,it passes through the diversion effect of the blade and the outlet area shrinks,and the outlet wind speed will accelerate through.The larger the blade Angle is,the more obvious the deflection acceleration of the outlet wind speed will be.At the circulating water side,the flow distribution of different sectors of the air cooling tower,the flow distribution of different cooling columns in the same sector,and the relationship between the temperature of the circulating water outlet of the cooling column and environmental factors,as well as the shutter opening were analyzed by numerical simulation.The flow distribution of different sectors and cooling columns of the air cooling tower and the relationship between the outlet water temperature of the circulating water and the ambient temperature,wind speed,shutter opening and the mass flow of the circulating water are obtained.The analysis of the flow field distribution of the cooling column shows that the air mass flow distribution at different positions on the cooling column surface shows a downward trend in the longitudinal direction,while the air mass flow distribution is also uneven in the transverse direction.The influence of the change of back pressure on the thermal economy of the unit is calculated theoretically.Three operating conditions of the unit are selected for comparative analysis.It is concluded that with the increase of the unit back pressure,the equivalent heat drop of the unit is decreasing,while the heat consumption and coal consumption are increasing.With the decrease of the unit load,the absolute thermal efficiency of the unit is decreasing,and the heat consumption and coal consumption of the unit are increasing.Under the same back pressure,the heat consumption and coal consumption of low-load units are higher than that of high-load units,so it should be appropriate to reduce the back pressure and improve the load of units,so as to increase the effective enthalpy drop of units and improve the thermal economy of units. |
