基于扭带或锥形环的管内强化传热的数值模拟

发布时间：2018-01-05 01:26

本文关键词：基于扭带或锥形环的管内强化传热的数值模拟　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：管内强化传热技术是工业中一种常用的节能技术手段,广泛运用于能源、化工、电子、医药、材料等领域。因此,开发新的强化传热技术,提高设备的换热效率对于节能和经济的发展都具有重要作用。本文在前人对窄边扭带研究的基础上,设计了交替轴窄边扭带、交替轴窄边中空扭带和交替轴贴壁中空扭带,并对管内内置上述形式的扭带在层流条件下进行了数值模拟,结果表明:对于交替轴窄边扭带和交替轴窄边中空扭带,在较低Re下,Nu随扭带错位角的增大而增大,而Re较高时,不同错位角度之间的差别很小,f随错位角的变化差别不大,PEC最大对应的是90°交错角。对于交替轴贴壁中空扭带,60°交错角下的Nu最大,且不同交错角下f差别明显,90°时f最大,PEC值随错位角的变化而呈现出复杂的变化规律,总体来说,60°的错位角对应的综合性能最好。湍流条件下,不同交错角的交替轴扭带的换热差异不明显,所以对窄边扭带和中空扭带在湍流条件下进行了数值模拟,考察了换热特性、阻力特性及综合性能,并用速度场与温度场进行了分析。通过计算结果可知:窄边扭带的宽度越大,换热越好,阻力也越大,但综合性能依然越好;中空扭带的中空尺寸在较小时换热基本一致,较大时换热削弱,中空尺寸越大,阻力越小,综合性能也越好;传统扭带的换热性能及综合性能始终优于窄边扭带和中空扭带。最后,还对湍流条件下管内内置不同结构形式的锥形环进行了数值模拟,发现固定锥形环小端端径,环大端与管壁间间隙越小换热越好;固定锥形环端径比,对于收缩环环大端与管壁间间隙越小换热越好,对于扩张环环大端与管壁间间隙适当的增大反而会强化传热;扩张环与收缩环相比,在小间隙下阻力大很多,大间隙下阻力反而略小;扩张环的综合性能始终优于收缩环。
[Abstract]:Tube heat transfer enhancement technology is one of the common energy saving technology industry, widely used in energy, chemical, electronics, medicine, material and other fields. Therefore, the development of new technology of heat transfer enhancement, improve the heat exchange efficiency of the device has an important role for the development of energy and economy. This paper based on the study twist the narrow side, the design of alternating narrow shaft twisted tape, alternating narrow and twisting with the hollow shaft shaft wall hollow alternating twisted tape, and the pipe built-in above form twisted tape under laminar flow conditions were simulated. The results show that: for the narrow band and alternating axial torsion alternating narrow shaft the edge of the hollow twisted tape, in low Re, Nu with the increase of dislocation angle twisted tape increases, while the Re is high, the dislocation between the different angle difference is very small, the difference between F changes with the dislocation angle is small, the maximum PEC corresponds to 90 degrees angle. For alternating axis wall hollow twisted tape. 60 Under the angle of Nu degrees, and different stagger angle f was 90 degrees F maximum, PEC value changes with the dislocation angle shows the variation of the complex, in general, the comprehensive performance of misalignment angles of 60 DEG corresponding best. Turbulent flow condition, different stagger angle alternating axial thermal difference for the twisted tape is not obvious, so the narrow side twisted tape and hollow twisted tape under turbulent flow conditions was simulated and investigated the heat transfer characteristics, resistance characteristics and comprehensive performance, and was analyzed with the velocity field and temperature field. The calculation results indicate that: the narrow width of the twisted tape, change the thermal resistance is bigger, better, but still better comprehensive performance; hollow twisted hollow dimension is on the small heat exchanger is basically the same, large heat weakened, the hollow size is larger, the smaller resistance, comprehensive performance is better; the traditional twisted strip with the heat transfer performance and comprehensive performance is always better than the narrow side of the twisted tape The hollow and twisted tape. Finally, the conical ring pipe built-in with different structures under turbulent flow conditions were simulated, found the small end of the tapered end ring diameter, outer ring between the pipe walls and the smaller the gap the better heat transfer; the fixed cone ring end diameter ratio, the contraction between the pipe walls and the ring end gap the smaller the better heat transfer, expansion of the ring and the big end of wall clearance between the appropriate increase but will strengthen heat transfer; compared with expanding ring and shrinkage ring, in the small gap resistance large, large gap resistance but smaller; the comprehensive performance of the expanding ring is always better than the contractile ring.

【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK124

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