Numerical Analysis And Structure Improvement Of Flow Field In Microscale And Macroscale

Micromation is not the simply size reduction.A new flow characteristic is presented by micro-scale flow because of its physical factor,which is so different from macro-scale flow. The flow and heat transfer performance of microchannel and routine channel are investigated here,to find out the effective approach to the optimum structure design,manufacture and performance optimization in the macro and micro-channel.The research of the flow and heat transfer in recuperator for micro gas turbine is the main object of study in the field of microscale channel.Numerical simulation modelings are set up by Fluent to investigate flow and heat transfer performance for different corrugation angle and Reynolds under the same pitch to height(P/H) condition.The results show that Nusselt number increases with increasing corrugation angle whenθ＜120°,and it decreases whenθ＞120°.Corresponding P/H for optimum heat transfer performance in different corrugation angle 60°,90°,120°,150°are respectively 3.1,2.7,2.2,1.0.And transition flow from layer to turbulence in microchannel is found appearing ahead of the routine channel.A new multi-layer model of recuperator is proposed in this paper to make the simulation results more reliable,then flow and heat transfer performance of 60°PSR are predicted with this model.The result combined Field Synergy theory with heat transfer performance shows the larger Nu,the smaller synergy angle.The uneven distribution of heat convection intensity of unit is discovered based on the whole average synergy angle.Furthermore,performances of PSR vary regularly with the the increasing of the channel numbers.The outlet temperature varies according to logarithmic curve,the pressure drop varies with linearity,and the heat transfer coefficient varies along hyperbola curve on the whole distance time.Then structure of PSR could be designed by these predited results.With regard to the macro-scale research,numerical analysis and investigation of internal flows of the three specific air passages,which cool the traction motors in locomotives,are conducted in order to attain even-distributed mass flow rate in the three vents.However,the results show that the original inlet area of passage 1 enlarges rapidly,then reduces gradually, and its maximum equivalent expansion angle reaches up to 45°which leads to the excessive diffusion flow and the flow block in the corner of the passage.Having analysed several plans, the best way is to optimize the structure of passage 1 through reducing the equivalent diffusion angle to improve the flow area and create a smooth flowing passage so as to increase the flow rate to meet the design requirements.Comprehensive analysis of the flow characteristics of macro and micro-channel can be seen that the heat convective investigation in micro-channel is mainly emphasized upon the heat flow field,while the pressure field in macro- channel is dorminated because of the flow resistance loss and passages'structure.