Heat Transfer Characteristics Of Large MGGH And Optimization Design Of Flue System

Based on project of th coal-fired power plant MGGH in China,the influence of inlet flue distribution on heat exchanger performance was studied by numerical simulation and empirical formulae.Numerical simulation software was used to simulate the flow field in MGGH flue system.Based on the simulation results,the problems in the flow field in the flue are analyzed,and designed the flow field optimization scheme for MGGH flue system.The main contents and conclusions are as following:(1)The flow field of MGGH flue system was simulated by porous medium model and Standard k-ε turbulence model.The results show that the elbow and the special-shaped flue structure cause flow direction rapid change of flue gas,and the generation of vortex and secondary flow.The generation of vortex and secondary flow also will cause the decrease of flow field uniformity at the entrance of MGGH and desulfurization tower.(2)Choosed three different velocity distribution pattern,the influence of those velocity distribution patterns on the heat exchanger performance was analyzed by numerical simulation and empirical formulae.The results showed that the uneven distribution of flue deteriorates the uniformity of flow field and temperature field in the heat exchanger,when the three velocity distribution patterns were distributed along the perpendicular direction of heat exchange tube.When the non-uniform factor at 0-0.1,multi-strand turbulence can slightly improve the overall performance of the heat exchanger,and the heat exchange rate increases by 0.5%.The integrity performance of heat exchanger deteriorates with the increase of the non-uniform distribution factor.In the range of 0.4-0.5,the heat transfer of the heat exchanger maximally decreased by5.5%,and the pressure drop of the heat exchanger increased by 6.5%.And,when the three velocity distribution patterns are distributed along the tube length direction,heat transfer of heat exchanger in the declining trend,the pressure drop of the heat exchanger shows an increasing trend.The integrity performance of heat exchanger shows a tendence of deterioration.(3)The flow field of desulfurization tower and MGGH and relevant flue was optimized based on Fluent software.As the results showed,though the way of adding splitters,the uneven velocity of the inlet of desulfurization tower,raw gas flue and clean gas flue heat exchanger at-0.2～+0.2,and the velocity deviation coefficient is lower than 10%.The reasonable design of flow guide plate can effectively eliminate the eddy and flow field separation that caused by elbow and variable section,and make the flue gas flow into the heat exchanger and desulfurization tower more evenly.