Study On Temperature Calculation Of Boiler's Water Wall And Tube Busting Under Low-load

As an equipment of generating steam and heat energy, boiler plays an important role in regular operation of electric company. The reliability of boiler heating surface depends on temperature operating condition of tubes. When the metal tubes' temperature rises, its permanent intensity falls, and the tubes will burst if the temperature reach a certain value. Working in low load raises security problems of boiler, which is dangerous for heating surface. Therefore, research on temperature distribution of tubes and overheating problems in under loaded condition is significant.Firstly, this paper constructs a temperature model, analyses the heat transfer character of a single tube, considers the dividing points between one-phrase area and two-phrase area, and discusses the influence to water wall by inlet state, density of heat flow and steam ratio. Results indicates that variation of inlet temperature will affect the height of initial point of sub-cooled boiling, but it has less effect to temperature; metal's temperature will be rising along with increase of heat flow density, but there will be different ranges of one-phrase area and two-phrase area; increase of mass velocity will lower temperature; under regular operating condition, variation of steam ratio doesn't have remarkable influence to temperature.With the case of the event of bursting tube of a factory(130t/h), which was in under loaded condition of 23t/h, this paper analyses reasons of the burst event. At first, burning cases in boilers is simulated with FLUENT, distribution of heat stream density is computed; Then, hydrodynamic force model of water circle system is constructed, temperature of water wall in under loaded condition is studied with temperature computing program. As a result, when a boiler runs in under loaded condition of 23t/h, its less heated side wall A is in a low flow rate, circular stagnation and overheating of water wall in a short time will cause burst, it accords with results of rupture sampling's analysis. Moreover, burning in under loaded condition is not steady, partial burning will worsen heat transfer of metal tube.