| Based on the research of enhanced heat transfer technology of insertion tube and special shaped heat exchange tube, a new type of enhanced heat transfer tube with spiral internal rib twisted tube is proposed. The inner unique spiral inner rib structure can cause disturbance to the fluid in the near wall region and the external spiral twist shape can cause the tube to flow out of the spiral flow, which can enhance the degree of mixing between the fluid, also can enhance the heat transfer effect. Using the means of numerical simulation, performance of heat transfer and flow resistance in both the tube side and shell side is analyzed and the research of multi-objective optimization is carried out.The following is the main work and results:(1)By comparing the heat transfer and flow resistance performance of spiral internal rib twisted tube, twisted tube and circular tube, it is concluded that the spiral internal rib twisted tube has the advantages of better heat transfer performance than twisted tube and circular tube. When the Reynolds number Re ranges from 2300 to 50000, the Nusair number Nu increases with the increase of Reynolds number Re, the minimum is 50.87, the maximum is 481.33, and always higher than that of twisted tube and circular tube at the same Reynolds number Re; The drag coefficient f decreases with the increase of Reynolds number Re, the minimum is 0.043, and the maximum is 0.114, but it is higher than that of twisted tube and circular tube at the same Reynolds number Re; The comprehensive evaluation index of the pump work criterion PEC decreases with the increase of Reynolds number Re, the minimum is 1.15, the maximum is 1.62, and always higher than that of twisted tube at the same Reynolds number Re. Thermal potential tolerance decreases with the increase of the Reynolds number, and always higher than that of twisted tube and circular tube at the same Reynolds number.(2)Analysising the single factor variable of spiral internal rib twisted tube, when semi-major axis a rangs from 11 to 14 mm, lead s rangs from 100 to 250 mm, rib height h rangs from 0.6 to 1.2mm, rib angle c rangs from 60° to 120°, the number of ribs n rangs from 4 to 16, the heat transfer performance increases with the increase of the length of the half axis a, decreases with the increase of lead s, increases with the increase of the rib height, decreases with the increase of the rib angle, increases with the increase of the number of ribs.(3)Studying the multi objective optimization based on genetic algorithm for spiral internal rib twisted tube, considering the influence of the heat transfer and flow resistance performance of both the structural parameters of a, s, c and the flow parameters v, then we can get the optimal parameter combination of a semi-major axis of 12.28 mm, lead s of 140.17 mm, rib angle c of 103.15°, inlet velocity v of 2.77m/s, and the nusair number Nu is 661.69, the resistance coefficient f is 0.045, the comprehensive evaluation index PEC is 1.70.(4)The single factor analysis is made on the shell side of spiral internal rib twisted tube heat exchanger which is composed of 7 spiral internal rib twisted tubes, derived in the long axis of 27~33mm for the A, the guide path 100~250mm for the S, the overall heat transfer performance of the shell process increases with the increase of the long axis A, and decreases with the increase of the lead S.(5)Studying the multi objective optimization based on genetic algorithm for the shell side of the spiral internal rib twisted tube heat exchanger, considering the influence of the heat transfer and flow resistance performance of both the structural parameters of a, s and the flow parameters v, then we can get the optimal parameter combination of a semi-major axis of 15.86 mm, lead s of 139.98 mm, inlet velocity v of 1.17m/s, and the nusair number Nu is 128.06, the resistance coefficient f is 0.060, the comprehensive evaluation index η is 326.18. |
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