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不同射流速比对螺旋管内流体传热性能的影响
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作者 刘磊 王宗勇 杨鹏达 《当代化工》 CAS 2023年第10期2434-2439,共6页
为了探究射流对螺旋管内流体传热性能的影响规律,采用数值模拟方法研究了无量纲曲率δ=0.0701、无量纲螺距τ=0.143的螺旋管在不同射流速比(ε=1~6)条件下强化传热的效果。研究结果表明:当射流速比ε>2时,射流流体可穿透螺旋管主流... 为了探究射流对螺旋管内流体传热性能的影响规律,采用数值模拟方法研究了无量纲曲率δ=0.0701、无量纲螺距τ=0.143的螺旋管在不同射流速比(ε=1~6)条件下强化传热的效果。研究结果表明:当射流速比ε>2时,射流流体可穿透螺旋管主流流体冲击到螺旋管外侧壁面,大幅度提高螺旋管外侧壁面的换热能力。在雷诺数Re=19000~26000的条件下,随着ε的增大,螺旋管壁面平均努赛尔数Nu_(m)增大,流动阻力f减小,与单一螺旋管(未加入射流)相比,ε>2时螺旋管的Nu_(m)增大幅度较为显著,当ε=6时Nu_(m)最大,与单一螺旋管相比Nu_(m)提升了25%;螺旋管截面周向努赛尔数Nuc和射流管安装位置处的轴向局部努赛尔数Nua均随着ε增大而增大,且射流在螺旋管内起强化传热作用的距离也随ε增大而增大,当ε>2时,强化传热的螺旋角度距离可达到60°以上;随着ε增大,综合传热性能评价因子PEC增大,且PEC均大于1(PEC=1.03~1.42),PEC的平均值是单一螺旋管的1.23倍,在所研究的范围内,当ε>2时PEC的增大幅度较为明显,当ε=6时PEC最大,具有良好的综合强化换热效果。 展开更多
关键词 螺旋管 射流速比 射流冲击 强化传热
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Mixing times in single and multi-orifice-impinging transverse(MOIT) jet mixers with crossflow 被引量:1
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作者 Peicheng Luo Yuncui Tai +1 位作者 Yi Fang Hua Wu 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2016年第7期825-831,共7页
We study the macromixing behavior of single and multi-orifice-impinging transverse(MOIT) jet mixers with crossflow, in particular, the overall mixing time and the back-splash mixing time of the injected flow with the ... We study the macromixing behavior of single and multi-orifice-impinging transverse(MOIT) jet mixers with crossflow, in particular, the overall mixing time and the back-splash mixing time of the injected flow with the crossflow, using the PLIF technique. It is found that for a given mixer configuration, there is a critical jet-tocrossflow velocity ratio rcat which the back-splash begins to occur. Further increase in the velocity ratio r leads to sharp increase in the back-splash mixing time, which can offset the intensification of the downstream mixing. The dimensionless overall mixing time decreases as r increases to reach either a plateau or a local minimum, and the corresponding r value represents the optimal velocity ratio roptfor the macromixing. The momentum ratio of the two liquid streams is a key factor determining rcand ropt. For a larger scale mixer, a higher momentum ratio is required to achieve the optimal macromixing with the minimum dimensionless overall mixing time. 展开更多
关键词 MixingChemical reactorsMixing timeJet mixerPlanar laser induced fluorescence (PLIF)
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Swirl Jets in Crossflow at Low Velocity Ratios
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作者 Alexandros Terzis Charilaos Kazakos +2 位作者 Anestis I. Kalfas PavIos K. Zachos Peter Ott 《Journal of Mechanics Engineering and Automation》 2012年第4期256-266,共11页
This investigation examines experimentally the behavior of swirled jets produced by axial flow fans blowing into a crossflow at low velocity ratios. The main difference with non-swirl cases is an asymmetry of the domi... This investigation examines experimentally the behavior of swirled jets produced by axial flow fans blowing into a crossflow at low velocity ratios. The main difference with non-swirl cases is an asymmetry of the dominant kidney vortex and a slight distortion of the jet trace downstream of the injection hole. The effect of jet rotation at relatively low swirl numbers and similar velocity ratios is also investigated by a validated computational analysis tool. The numerical results are analyzed by means of various post-processing procedures, aiming to clarify, quantify and analyze the impact of swirl on the characteristics and the flow domain of a jet in crossflow. In general, swirl introduces an asymmetry in all examined quantities and prevents the penetration of the jet into the crossflow, causing the jet to remain closer to the wall surface. The rotation of the injected fluid results in an imparity of the two parts of the Counter Rotating Vortex Pair (CVP) which is no longer symmetric to the axial centerline plane. High swirl numbers result in the destruction of the CVP and the dominant kidney shape vortex is transformed into a comma shape vortex, rotating close to the wall. 展开更多
关键词 Jet in crossflow SWIRL CFD (computational fluid dynamics).
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The step-by-step CFD design method of pressure-compensating emitter
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作者 Wei Zhengying 《Engineering Sciences》 EI 2013年第1期62-67,77,共7页
In order to improve the design and research and development (R & D) efficiency of the pressure- compensating drip irrigation emitter,a step-by-step computational fluid dynamics (CFD) design method was proposed bas... In order to improve the design and research and development (R & D) efficiency of the pressure- compensating drip irrigation emitter,a step-by-step computational fluid dynamics (CFD) design method was proposed based on CFD theory combined with the finite element method. By analyzing its hydraulic performance through the step-by-step CFD method,the prediction pressure-flow curve(p-Q curve) of the pressure-compensating emitter was obtained. Then the test samples were fabricated using rapid prototype and manufacturing(RP & M) technology. The emitters' hydraulic performance experiment was carried out and the experimental p-Q curve was obtained. The step-by-step CFD design method was verified by comparing the experimental p-Q curve with the prediction values,which showed that the prediction values met the experimental results well within the normal range of the emitter's working pressure. On this basis,the effect of the emitter structure on its pressure-compensating performance was studied,which showed that the height of the pressure-compensating region had significant effects on the emitter's pressure-compensating performance. Series products of the pressure-compensating emitter could be designed by changing the region's height. 展开更多
关键词 pressure-compensating drip irrigation emitter step-by-step CFD hydraulic performance experiment
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