Research On Flow And Heat Transfer Characteristics And Application Of A Kind Of Orthogonal Groove Channel

As 80% of primary energy consumption to experience heat transfer and heat transfer equipment,heat transfer process efficiency will directly affect the efficiency of energy efficiency in various industries.In recent years,it has been shown that chaotic convection can significantly enhance the mixing and heat transfer,which provides a new idea and method for designing efficient and compact mixing and heat exchange equipment.In this thesis,through the combination of computational fluid daynamics(CFD)software numerical simulation,experimental methods and theoretical analysis,the mixing performance and enhanced heat transfer of chaotic convection are studied,and the chaotic convection structure with orthogonal groove is proposed.And its application in plate-fin exchangers and static mixers are further studied.The main work of this thesis is as follows:1.Three-dimensional numerical simulation and comparative analysis of the flow and heat transfer characteristics of L-type chaotic flow channel and ordinary straight channel are carried out.The results show that fluid can generate chaotic convection under small flow velocity in the L-type chaotic channel.The flow pattern can promote the mixing of the fluid in the main flow region and near the wall,and enhance the disturbance of fluid.Consequently,the temperature distribution of each section in the channel is more uniform,which enhances the heat transfer.2.Based on the characteristics of chaotic convection,a novel chaotic channel with orthogonal groove structure in the flow direction is proposed.Furthermore,by means of orthogonal experimental design,the influence of structure parameters such as the width and height of channel,the depth and diameter of groove,and the length of the straight section on the fluid flow and heat transfer performance is analyzed.Meanwhile,the comprehensive performance of the chaotic structure is evaluated and analyzed by the Taguchi method.3.The fluid flow and heat transfer characteristics in the orthogonal channel are studied synthetically.The results show that the inlet effect of the channel is much less than that of the ordinary straight channel under the condition of laminar flow,and the fluid flow and heat transfer in the fully developed section have periodic characteristics.The influence of Reynolds number and Prandtl number on the heat transfer and fluid flow is very different from that of ordinary laminar flow.The correlations of the heat transfer Nu and the friction coefficient f of the calculation model of the orthogonal groove flow are obtained.Also,this thesis briefly introduced several common methods to describe the chaotic performance of fluid in the channel,and proposed a calculation method of modified Lyapunov index.This method can quantitatively calculate the degree of folding and stretching of the flow line in the chaotic convection.4.The relationship and distinction between chaotic convection and mixing is analyzed,and the mixing characteristics of the fluid in the orthogonal groove channel is studied by means of numerical simulation method.The influence of Reynolds number and structural parameters of orthogonal groove channel on the mixing degree was qualitatively and quantitatively analyzed.By comparing the mixing effect and heat transfer performance of fluid in the channel,it can be found that the mixing effect of the parameter change in the channel is consistent with the intensity trend of the heat transfer effect.5.A new plate-fin heat exchanger with the basic structure of the orthogonal groove channel is proposed.A single-row simplified caculation model of the plate-fin heat exchanger is establised to simulate and calculate the fluid flow and heat transfer performance in the channel,which are compared with the flow and heat transfer performance of fluid in a single chaotic channel.The results show that the flow and heat transfer performances can be characterized by the characteristics of a single chaotic channel.The heat transfer factor j and friction factor f ? correlations about the new chaotic plate-fin heat exchanger are obtained.6.According to the measurement requirements and experimental principle,experimental scheme was developed,and a set of cold-model test device for fluid flow and a set of heat-model test device for heat transfer in chaotic convection channel are designed and fabricated.The results of numerical simulation are validated expermentally.It has been shown that the experimental datas agree well with the numerical ones.