Study On The Numerical Simulation Of Tube Heater

The problem of tube coking is related to the operation period and the economic benefits of the plant.In order to reduce the coking rate,the heat flux distribution of the tubes should be uniform,which depends on the combustion performance of burners.Therefore,it is necessary to study the heat transfer outside the tubes in the furnace.With the numerical simulation method,this paper focuses on observing the type of burner,the shape of burner orifice,and the influence of internal and external coupled heat transfer to the distribution of physical field in the furnace tube,flame height and the distribution of heat flux.First,the influence of the distribution of physical field in the furnace tube was investigated with CFD software,by changing the conditions of the distance between the burners,the distance between the burner and the wall,the power of the burner.The purpose is studying the effect on the fuel combustion,gas flow and heat diffusion.Results indicate that the highest negative pressure adopted the burner whose flame is along the wall of the furnace is-104 Pa,and the highest negative pressure adopted the burner whose flame is to the wall of the furnace is-51 Pa.The negative pressures are both in allowed pressure range.Second,the bluff body burner has been used as the experimental model,investigated the effect of the orifice shape on the flame height,the air entrainment quantity and the flame temperature.The standard k-? mode,single step combustion reaction mechanism and the turbulent kinetic energy dissipation combustion reaction model were employed.Results indicate that the flame temperature of nozzle hole using circular,square and triangle are 1393°C,1410°C and 1440°C,respectively.The flame height of 1500°C are 1.1m,0.7m and 0.4m,respectively.Finally,numerical simulation for internal and external coupled heat transfer of the tube has been performed to investigating the distribution of convection heat transfer coefficient in the tube.The results indicate that,as pipe flow has been full developed,the calculation results of the convection heat transfer coefficient of the internal tube are either 1304 W/(m2.K)by the heat transfer film theory or 1269W/(m2.K)by the empirical correlations.On the condition of conventional design furnace tube heat intensity,the difference between the tube temperature and the oil temperature is 35~57°C,the empirical value of 50°C is reasonable.