| Chinese economy is in a stage of rapid development,the total power consumption with economic growth also maintains a sustained growth trend,the economic development is inevitably accompanied by a large amount of energy consumption,and therefore our country put forward the sustainable development of modern energy industry.The traditional way of thermal power station cooling system needs a large amount of water as the cooling medium for cooling the turbine exhaust steam,but in Northwest China it is short of rain and water,the direct air cooling technology is widely applied in China where it is rich in coal but short of water resource.In the direct air cooling system,the exhaust steam is cooled down through air,the water consumption is reduced,nevertheless it consumes a lot of high-grade energy in the direct air cooling system,so the heat transfer performance of air cooling island plays a decisive role in energy saving.In this paper,an air cooling experimental test rig is established,and the flat tube radiator with double louver fin is experimentally studied.The air cooling island radiator of the power station is arranged in inclined form.Different angles of the heat exchanger are set to study the condensation and heat transfer capability of the steam in the tube.The inclination angles of the heat exchangers are 15 degrees,30 degrees,45 degrees,60 degrees,75 degrees and 90 degrees,respectively.The condensation heat transfer performance of air cooling radiator is studied under the condition of prescribed inlet pressure and the inlet steam flow rate.To obtain the condensation heat transfer coefficient in tube side,the heat transfer coefficient of the radiator in air side is obtained in advance by testing the radiator with water inside the tube.Then condensation heat transfer coefficient hs inside the tube can be obtained by heat transfer coefficient of the air side flow ha and total fin efficiency ?.During the experiment,the relative error of heat balance is kept less than 5%.The correlation of the condensation heat transfer coefficient inside the tube with Reynolds can be obtained through the analysis of the Reynolds of the condensate water and the heat transfer coefficient hs data.The variation law of pressure drop P in the tube was obtained by adjusting inclined angles.It is found that the heat transfer ability of the heat exchange is different at different angles of inclination when the steam at inlet and water at outlet are saturated state.Under the same wind side Reynolds number,the thickness of the condensate liquid film is affected by the component force of gravity along the direction of the steam flow.With the increase of the tilt angle,the heat exchange capacity increases gradually,and the heat exchange rate achieves maximum at 90 degrees;the a given inclination angle,the condensation heat transfer coefficient increases with the increase of Reynolds number of condensate water.However,the influence of the inclined angle on the heat transfer coefficient hs in the tube is not obvious when the Reynolds of the condensed water is kept unchanged;In the range of 90 to 180 of condensate water Reynolds number,Shah's correlation is equally applicable to the flat tube heat exchanger experiment of condensation,but it is not suitable for the case where the inclination angle is less than 90;A fitting formula is obtained through the experimental data,the error between the fitting formula and the experimental data is less than 15%;The pressure drop in the pipe increases with the increase of the inclination angle,and the maximum pressure drop is found at 90 degrees;The establishment of experimental model of forced condensation as well as the analysis results of experimental data of forced condensation heat transfer in the pipe can provide a reference for the practical application of the air cooling island. |
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