Research Of Flow Characteristics In 300MW Direct Air-cooled Condenser Tubes

Thanks to its remarkable water-saving effect,direct air cooling technology has been widely used in areas rich in coal but short of water,including Northeast China,North China,and Northwest China in recent years.Due to the complexity of the direct air cooling condenser system structure and the uneven distribution of flow during the operation of the steam in the process of flowing,it can increase the difficulty of the operational personnel and render the safety of the unit economic operation under threat,as well.Given that,study of the columns of each unit of heat exchange tube bundle of steam flow of direct air-cooled condensers under various working conditions is of great significance to improving the design and operation of the units.Aiming at the mechanism and characteristics of flow in direct air-cooled condenser,in this paper,the model of the flow in a parallel air-cooled condenser is established,and the influence of the solar radiation on the heat transfer of the air-cooled condenser is considered in the calculation of the heat transfer of the air-cooled unit.Focused on a 300 mw direct air-cooled unit,this Study is intended to come up with a program for flow resistance of heat exchange tube bundle in direct air-cooled condenser compiled by the FORTRAN language.This Study tries to build an internal steam flow model of heat exchange tube bundle of the direct air-cooled condensers by means of integrated modular modeling system,taken into consideration of the solar radiation in the process of heat transfer calculation unit for air-cooled steam condenser heat transfer,and therefore,to reveal the flow status of condensation under different load and heat transfer conditions of steam in the condenser unit each column flows in the tube bundle.This Study researches into the changes of different loads in every column and unit flows of the tube bundle while considering the influence of solar radiation on heat transfer at the same time,and makes a comparison of the flow distribution of tube bundle between the columns before and after the solar radiation conditions.Solar radiation on the influence of different operating mode control flow,under the same condition,varies from each unit control flow.For instance,on the one hand,for higher loads,the flow is affected less by the solar radiation.On the other hand,with the loss of the load,the solar radiation effect on each unit control flow will increase.The solar radiation is studied on the influence of the direct air condensing vapor through pressure,when the full back pressure fluctuation maximum value is 0.134 kpa.With the loss of the unit load,the change of back pressure value accounted for bigger proportion of the back pressure increases,but the maximum percentage is only 0.8%.Therefore,the solar radiation has less effect on the unit back pressure of direct air-cooled condensers.By contrast,the influence of the sun radiation heat transfer on tube condensing flow unit of direct air-cooled steam condensers and its effect on exhaust backpressure is less profound;while they are mainly affected by exhaust steam flow rate and environment factors.