Strength Design And Heat Transfer Study Of Half-Pipe Jacket Vessels

Jacketed vessels are applied as heat exchange,reaction,and separation equipment in industries such as petroleum,natural gas,chemical,light industry and food processing,etc.Among them,half-pipe jackets are widely used due to their compact structure,high heat transfer efficiency,material saving and other advantages.For the design of a jacketed vessel,it is particularly important to ensure its strength and rigidity and improve its heat transfer efficiency.In this thesis,to solve the design difficulties of some jacketed vessels when using design codes,a new design method was proposed based on limit-load analysis approach.Effects of half-pipe jacket on the strength and rigidity of the vessel shell were investigated.Influences of the section shape of the arcuate-tube jacket on the fluid flow and heat transfer performance inside the jacket were studied.The main contents and conclusions are as follows:(1)ASME Ⅷ-1 and Ⅷ-2 codes have two limitations on the design of half-pipe jacket vessels,one is size limitation and the other is that only internal pressure is considered.To overcome these weaknesses,this thesis proposed a design method based on limit-load analysis,which can be applied to large jacket vessels and comprehensive loads,including the nozzle load and seismic load,etc.Thus,the engineering design difficulties of many half-pipe jacket vessels have been solved.(2)Through limit-load analysis and eigenvalue buckling analysis,the influence of the half-pipe jacket on the strength and rigidity of the vessel was investigated.The limit load analysis found that the jacket increased the strength of the cylinder,but if other areas not covered by the jacket was the first to yield,the jacket had little impact on the limit-load value of the structure.The eigenvalue buckling analysis showed that the critical load of vessels with or without jackets was obviously different.The half-pipe jacket not only changes the buckling mode of the vessels,but also increases critical load of the vessel buckling.Effects of the diameter and thickness of the jacket on the strength and stability of the vessel was also investigated.(3)In turbulent state,using water as the medium,the fluid flow and heat transfer performance in arcuate straight pipe and helical pipe with different cross section center angles were numerically simulated by using Fluent.It was found that when the volume flow rate is constant,the Nusselt number of the straight pipe and the helical pipe increases with the decrease of the center angleα of the cross section,but the flow resistance increases at the same time.According to the comprehensive performance evaluation factor pec,it was found that the comprehensive heat transfer performance of the arcuate tube is better.When α is 90°,the pec can reach 1.68 times that of 180°.To exchange the same heat,the material weight of the arcuate tube varies with the center angle,and the smaller the center angle α is,the less the consumed material is.When α is 90°,the weight of the arcuate pipe jacket can be reduced by 80%compared with that of semicircle pipe jacket.(4)By introducing the parameter α and based on a large number of numerical simulation results,the Nusselt number and friction coefficient calculation correlation formula of the straight pipe and helical pipe jackets of the arcuate section were fitted.The numerical verifications show that the relative errors are all within 10%.The correlation formula provide the basis for the process design of arcuate pipe jacket vessels.