A good understanding of the detailed temperature distribution in the furnace plays an important role in the implementation of operation optimization and design improvement of ethylene pyrolyzer. Numerical simulation o...A good understanding of the detailed temperature distribution in the furnace plays an important role in the implementation of operation optimization and design improvement of ethylene pyrolyzer. Numerical simulation of the turbulent flow, combustion and heat transfer was carried out to investigate the temperature distribution in industrial furnace. Inhomogeneities of the flue-gas temperature distribution were observed in X, Y, and Z direction of the furnace from the simulated results. Along the height of the furnace, the average flue-gas temperature increased initially and decreased afterward, and reached its peak at the height of 5 m. The reactor tube skin temperature varied not only along the height of the furnace, but also around the circumference of the tube. The heat flux profiles from the furnace towards the reactor tubes followed the shape of the average flue-gas temperature profile. The heat flux of the inlet tubes was constantly higher than that of the outlet tubes at the same height in the furnace.展开更多
在200 k W试验台上进行了准东煤的沾污、结渣特性试验,分别比较了管壁金属材质、管壁温度、烟温对沾污和结渣的影响。试验结果表明,管壁金属材质对沾污、结渣的影响不明显;在管壁温度较低时,烟温对管壁表面沾污、结渣的影响更明显,烟温...在200 k W试验台上进行了准东煤的沾污、结渣特性试验,分别比较了管壁金属材质、管壁温度、烟温对沾污和结渣的影响。试验结果表明,管壁金属材质对沾污、结渣的影响不明显;在管壁温度较低时,烟温对管壁表面沾污、结渣的影响更明显,烟温越低沾污和结渣情况减弱;当管壁温度较高时,烟温对管壁表面沾污、结渣的影响弱化,此时壁温越高,管壁沾污、结渣越严重。试验结果可为准东煤在电站锅炉的应用以及锅炉设计提供参考。展开更多
The turbulence kinetic energy and heat transfer performance of air in spirally fluted tube were numerically studied at a constant wall temperature with Reynolds number(Re)between 5000 and 45000.Furthermore,the flow dy...The turbulence kinetic energy and heat transfer performance of air in spirally fluted tube were numerically studied at a constant wall temperature with Reynolds number(Re)between 5000 and 45000.Furthermore,the flow dynamics and heat transfer performance of spirally fluted tubes with five different geometric parameters as well as the effects of separation vortex and swirling wake flow on heat transfer and flow resistance were analyzed.According to the results,heat transfer is enhanced mainly because the fluid hit the windward side of the flute,thus generating a strong turbulence kinetic energy to further reconstruct the boundary layer.The second reason is that the formation of the recirculation zone between the flutes disturbs the boundary layer caused by the flow separation.With the increase of flute depth ratio(L_(d)/D),the separation vortex will become stronger and larger on the leeward side of flute.The separation vortex will break the boundary layer and improve the heat transfer capacity which is accompanied with the increase of fluid resistance.As the flute pitch length ratio(L_(p)/D)decreases,the spiral flow is strengthened,and meanwhile more wake flow is generated.The spiral flow causes little impact on enhancing heat transfer but inhibits the development of the separation vortex and fluid pulsation;in addition,the fluid resistance is reduced at the same time.The maximum value of the average Nusselt number appears when Re=5000,L_(d)/D=0.25 and L_(p)/D=1.00,which is 2.53 times the value of smooth tube.In view of the whole range of Reynolds number,the thermal performance enhancement factor indicates that L_(d)/D=0.15 and L_(p)/D=1.00 are the optimal geometric design parameters.展开更多
文摘A good understanding of the detailed temperature distribution in the furnace plays an important role in the implementation of operation optimization and design improvement of ethylene pyrolyzer. Numerical simulation of the turbulent flow, combustion and heat transfer was carried out to investigate the temperature distribution in industrial furnace. Inhomogeneities of the flue-gas temperature distribution were observed in X, Y, and Z direction of the furnace from the simulated results. Along the height of the furnace, the average flue-gas temperature increased initially and decreased afterward, and reached its peak at the height of 5 m. The reactor tube skin temperature varied not only along the height of the furnace, but also around the circumference of the tube. The heat flux profiles from the furnace towards the reactor tubes followed the shape of the average flue-gas temperature profile. The heat flux of the inlet tubes was constantly higher than that of the outlet tubes at the same height in the furnace.
文摘在200 k W试验台上进行了准东煤的沾污、结渣特性试验,分别比较了管壁金属材质、管壁温度、烟温对沾污和结渣的影响。试验结果表明,管壁金属材质对沾污、结渣的影响不明显;在管壁温度较低时,烟温对管壁表面沾污、结渣的影响更明显,烟温越低沾污和结渣情况减弱;当管壁温度较高时,烟温对管壁表面沾污、结渣的影响弱化,此时壁温越高,管壁沾污、结渣越严重。试验结果可为准东煤在电站锅炉的应用以及锅炉设计提供参考。
基金This work was supported by the National Key Research and Development Program of China(Grant No.2018YFE0196000)IWHR Basic Scientific Research Projects(No.MK2018J09,No.MK2020J06).
文摘The turbulence kinetic energy and heat transfer performance of air in spirally fluted tube were numerically studied at a constant wall temperature with Reynolds number(Re)between 5000 and 45000.Furthermore,the flow dynamics and heat transfer performance of spirally fluted tubes with five different geometric parameters as well as the effects of separation vortex and swirling wake flow on heat transfer and flow resistance were analyzed.According to the results,heat transfer is enhanced mainly because the fluid hit the windward side of the flute,thus generating a strong turbulence kinetic energy to further reconstruct the boundary layer.The second reason is that the formation of the recirculation zone between the flutes disturbs the boundary layer caused by the flow separation.With the increase of flute depth ratio(L_(d)/D),the separation vortex will become stronger and larger on the leeward side of flute.The separation vortex will break the boundary layer and improve the heat transfer capacity which is accompanied with the increase of fluid resistance.As the flute pitch length ratio(L_(p)/D)decreases,the spiral flow is strengthened,and meanwhile more wake flow is generated.The spiral flow causes little impact on enhancing heat transfer but inhibits the development of the separation vortex and fluid pulsation;in addition,the fluid resistance is reduced at the same time.The maximum value of the average Nusselt number appears when Re=5000,L_(d)/D=0.25 and L_(p)/D=1.00,which is 2.53 times the value of smooth tube.In view of the whole range of Reynolds number,the thermal performance enhancement factor indicates that L_(d)/D=0.15 and L_(p)/D=1.00 are the optimal geometric design parameters.