| Heat exchanger, as an important heat transfer equipment, whose performanceand efficiency has a great effect on economic benefit is widely used in processindustry. In the type selection and design of heat exchangers, it is difficult to getdetailed information of the internal flow based on the traditional experimentalmethods and process simulation. Therefore, using advanced CFD technology toachieve optimization design of heat exchanger has become a common concern ofacademia and industry. According to the improved design of heat exchanger inindustrial loop reaction, the performance and optimization of heat exchanger arestudied based on CFD simulation. In order to optimize the selection and design ofthe heat transfer exchanger, the detailed flow field information of tube and shell sidein heat exchanger is studied, as well as the influence of different structure andoperation conditions on the heat exchanger performance, based on thethree-dimensional model of the tube and shell side in heat exchanger. In this paper,the methods and the data aim to provide theoretical foundation and model supportfor the structure optimization and engineering amplification of the heat exchanger.(1) According to the CFD simulation of heat exchanger in tube-side, thethree-dimensional model of circular tube and other three different types of enhancedheat transfer tube is established, and the factors affecting the performance andinternal flow field of heat transfer tube are analyzed. The results show that thecomprehensive evaluation factor η of twisted tube and tube with twisted tape insertare more than1, their performance is good. What’s more, the performance of twistedtube and tube with twisted tape insert is better than that of flat tube in terms of highviscosity fluid. The geometric structure has great influence on heat transferperformance. When A/B≤2.6for flat tube, S/de=6~22, A/B=2~2.6for twisted tubeand Y=2, ξ=0.1for tube with twisted tape insert, they show best performances.(2) According to the CFD simulation of the heat exchanger in shell-side, the segmental baffle board heat exchanger with circular tube has dead zone of heattransfer and flow because of the fluid flow in “Z” glyph. The arrangement andstructure of baffle plate has great influence on its heat transfer and flow resistanceproperties. When inlet velocity is1m/s, the number of baffle plate is8, and baffle cutis0.4D, the heat exchanger shows its best performance. The flow mode in segmentalbaffle board heat exchanger with flat tube is similar to that in segmental baffle boardheat exchanger with circular tube. But the latter has bigger vortex speed and higheroutlet temperature in stagnating flow area. The twisted tube heat exchanger withself-support structure has a uniform velocity and temperature distribution while doesnot have dead zone of heat transfer and flow. The fluid is the typicallongitudinal-flow along the spiral tube bundle.According to the analysis of three kinds of heat exchanger under differentconditions of shell side heat transfer and flow resistance characteristics, the pressuredrop and heat transfer coefficient increase with the Re rising up. The shell sidepressure drop of twisted tube with flat tube reduces2~4times than the other twokinds of heat exchanger and it has a minimum of its heat transfer coefficient with thesame Re. Therefore, twisted tube heat exchanger instead of traditional segmentalbaffle board heat exchanger can save energy and improve economic benefit in termsof the demand of heat exchange.(3) An industrial heat exchanger type selection and design improvement arestudied based on CFD simulation results, and the performances of different tubes areanalysed and compared. By comprehensive consideration, tube with twisted tapeinsert replaces circular tube. As result, the heat transfer efficiency in tube side withimprovement is about2.6times higher than that without improvement to illustratethe advantage of tube with twisted tape insert. Finally the preliminary design of anindustrial heat exchanger is given. |
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