Experiment And Simulation Of Anti-freezing Characteristic Of Tube Bundle Of Air-cooled Heat Exchanger

The air cooling technology of power station with remarkable water saving benefits has been developed rapidly in China.However,the severe meteorological conditions in the high and cold regions of northern China pose a severe challenge to the safe operation of the air cooling heat exchanger of the indirect air cooling unit.Especially during the operation in winter,the air cooling heat exchanger finned tube bunds are prone to freeze cracking and other safety accidents.Existing antifreezing measures of indirect air cooling units mainly rely on empirical regulation and conservative strategy of increasing back pressure.Although these methods reduce the freezing risk of air cooling exchanger tube bundle to a certain extent,they sacrifice the economy of the operation of air cooling units in winter,so they are difficult to be widely promoted.In this paper,a sample of the fin tube bundle of the air-cooled heat exchanger was tested for antifreeze performance,and a segmented experiment was carried out on the power plant site to simulate the flow and heat transfer of the air-cooled heat exchanger during the actual operation of the power plant.The working condition parameters of the power plant provide experimental data support for the actual antifreeze operation of the indirect air cooling system of the power plant.At the same time,this paper combines theoretical analysis and numerical simulation,and proposes a theoretical calculation model for anti-freezing of air-cooled heat exchanger tube bundles.By dividing the tube bundle of air cooled heat exchanger into many heat transfer units,the lumped parameter method was used to solve the temperature distribution of circulating water and cooling air in the heat transfer unit iteratively,and the change law of the water side temperature of air cooled heat exchanger was obtained to characterize the freezing state of circulating water.Through mutual verification with the results of anti-freezing performance experiments,the model can be used to simulate a variety of environmental conditions in the actual operation of air-cooled heat exchangers in power plants in winter,and then obtain the critical freezing parameterthe of air-cooled heat exchangers at different ambient temperatures,different tube bundle front wind speeds,and different circulating water inlet temperatures,which breaks through the limitations of experimental research-The distribution law of critical freezing parameters of tube bundle was calculated for the two operating modes of air cooled heat exchanger:cross flow and counter flow.On this basis,the influence of different inlet ways of the header on the anti-freezing operation of the air-cooled heat exchanger in power plant is studied.The results of this paper provide theoretical guidance for the anti-freezing operation of air cooled heat exchangers in winter.