CFD Simulation Of Fluid Flow And Heat Transfer In The Shellside Of Rod Baffle Multi-tubular Reactor

Multi-tubular reactor (MTR) is an important equipment in chemical industy,which is widely used in highly exothermic catalytic process. Compared toconventional MTR which is strengthened by plate baffle, rod baffle MTR hasexcellent anti-vibration performance, as well as advantages like small pressure drop,small dead zones, and antiflouling performance. According to its structural andflowing characteristics, the periodic unit duct model and the whole inlet section modelwas employed to simulate the flow field and temperature field of the shellside of rodbaffle MTR.By adopting the periodic unit duct model, the performance of rods with differentshapes, arrangements and axial distances was investigated. The results show that rodscan disturb the flowing of the fluid in the duct considerably. The order of the pressuredrop and average heat transfer film coefficient of each structure is as follows: doublesupported with square-rod model> snigle supported with square-rod model> doublesupported with round-rod modle> single supported with round-rod model. Thepressure drop of double supported with square-rod model is too big. The average heattransfer film coefficient of single supported with round-rod model is too small. Thepressure drop of the double supported with round-rod modle is close to the singlesupported with square-rod model, while its average heat transfer coefficient is justnear with single supported with round-rod model. Each of them is not good. Only thesingle supported with square-rod model achived a good balance among the theaverage heat transfer film coefficient, the pressure drop and rod consumption. Thus,the single supported with square-rod model is the optimal structure. On the other hand,the axial spacing of rods should not be less than100mm, otherwise, the pressure dropwould increase significantly. The spacing of100~150mm is recommended.As the axial flow dominates the shellside flow of rod baffle MTR, how to achivethe uniform distribution on the radial direction of the reactor is a problem. The wholeinlet section model was built, and its flow and heat transfer field was simulated. Theresults indicate that it exists many dead zones in the shellside of large MTR withoutany support components, whose radial uniformity problem is extremely serious. Asthe rod baffles were added into the reactor gruadually, the area of dead zones decreased, but the radial uniformity problem still remains significantly. Remove partof the tubes in front of the inlet, and set incident channel at the appropriate location,then the fluid would be guided into the transfer into internal part of the shellside of thereactor, and making the fluid distribut in the reactor uniformly, which would improvethe uniformity of flow and heat transfer greatly. The strip baffle in the entrancechannel and the baffle ring, especially in the shape of zigzag, can avoid short circuitbehavior of the fluid. The distance of the first set of the rods and inlets to the tubesheet may not be too small, otherwise the flow and heat transfer uniformity will bedeteriorated. Overlapping the first and second set of the rod baffle may worsen theflow and heat transfer radial uniformity possibly, which should not be adopted. As thedisturbance of rod baffle is weaker than the plate baffle, the average heat transfer filmcoefficient of rod baffle MTR is smaller than the plate baffle MTR, which has beenoptimized.