Enhancement of Forced Convection H检验检疫局英文eat Transfer
Rongzhen You
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竞争力英文Class 1202 of Power Engineering
In my College Students Innovative Project, we are suppod to adopt some methods to enhance the forced convection heat transfer on the plain surface. Although we have taken veral technical methods into consideration, most of them are too difficult for us to apply in our project. Therefore, I would like to make an introduction to the methods here.
Firstly, machining some grooves or dimples on the plain plates is one of important methods to enhance the convection heat transfer. The grooves or dimples can change the flow field of the fluid near the surface, for which the fluid would be turbulent than before. In this way, the Nuslt number of the near surface fluid would be raid, and than the convection heat-transfer coefficient would increa. This method can enhance the convection heat transfer on the plain plate to some extent, but it’s still ineffective for the reason that the improvement
of heat-transfer coefficient of the fluid in the near wall region can not enhance the heat-transfer of the mainstream.
Secondly, some rearchers come up with an idea that using spiral fine ribs (SFRs) in plate channel to enhance the convection heat transfer. They equally placed the SFRs in the channel, which can form a packing layer rembling a kind of quasi-porous media with large porosity and can produce efficient disturbance both to the boundary layer and the mainstream. The operation principle of SFRs is that the multi-longitudinal vortices induced by SFRs can significantly increa the tangential velocity components in the cross ction, which is helpful to promote the micro-fluctuation in the fluid. What’s more, the transport action caud by the longitudinal vortices can improve the mass exchange between the boundary layer and the mainstream. The two factors can not only speed up the heat migration from the channel walls, but also enhance the heat diffusion in the mainstream. This improves the temperature distribution uniformity in channel.
Thirdly, the most efficient way to enhance the convection heat transfer is installing fins on
三年级上册英语直播课免费the plain plate. Ba on this thought, some rearchers have fabricated many different types of fins, such as columned pin fins, conical pin fins, elliptical pin fins, cross-cut pin fins and longitudinal vortex generator arrays (LVG). Nowadays, fins with geometric shape pins have been commonly ud to in the engineering. As for the vortex generator, it can disturb the flow field by the vortex and generate vortex after the generator, which can break the boundary lay on the surface and transfer the heat into mainstream quickly. Nowadays, many rearchers have proved that the LVG effect is much better than the straight fins within a certain limit of Reynolds number, as well as that the multi rows LVG can improve the whole heat transfer effect.
The methods mentioned above sounds pretty advanced, but it’s quiet difficult for us, regular college students, to apply the methods in our project. Becau we couldn’t analysis the complex flow field in the special structure, unless we u the FLUENT software to build up their mathematic model. As the advanced usage of FLUENT is out of our ability, we have no choices but to install the straight fins on the heat transfer surface. Some rearchers have found that the overall thermal resistance of straight fins is lower t
han other geometric pin fins, due to the combination effect of enhanced later conduction along the fins and the lower flow bypass characteristics. At last, our experiment also proved that the straight fin can meet the requirement of the enhancement of forced convection heat transfer.
birthday cakeReferences
1. Christopher L. Chapman, and Seri Lee, Thermal Performance of an Elliptical Pin Fin Heat Sink, Silicon Graphics Computer Systems Mountainview, California, 94039
2. Pradeep Salapakkam, Ri Li, Mehmet Arik, Bill Gerstler, Augmenting Forced Convection Heat Transfer Coupled with an Aerodynamic Surface and a Synthetic Jet, lyncOne Rearch Circle, 四级高频词组Niskayuna, NY 12309
3. Zhang Xiang, Rearch on Forced Convection Heat Transfer of Parallel Plate with Grooves, China 高中历史教学案例Academic Journal Electronic Publishing Hou, TK 123
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4. Tang Yufeng, Rearch on Heat Transfer Enhancement Mechanism and Heat Transfer
Characteristic of Spiral Fine Ribs in Plate Channel, China Academic Journal Electronic Publishing Hou, TK124
5. K.W. Low, and C. Yap,语文课前三分钟演讲 The Enhanced Cooling of IC Chip Arrays On Printed Circuit Boards, Electronics Packaging Technology Conference, Singapore, 119260
