Study On The Flow And Heat Transfer Of Non-Newtonian Power Law Fluid With Different Cross Sections

With the acceleration of China's urbanization process and the rapid development of urban industry,the energy pressure is becoming more and more serious.Therefore,the use of energy and the energy saving requirements will inevitably continue to improve and the industrial equipment will be more energy-efficient.In the petroleum,coal and power engineering,most of the fluid has the characteristics of non-Newtonian fluid.At the same time,non-Newtonian fluid is also ubiquitous in nature and in the actual production process.The theory of non-Newtonian fluid plays a very important role in the application of all kinds of materials,which involves the flow characteristics of many materials.So the flow characteristics and energy transfer mechanism of non-Newtonian fluid is an important theoretical basis for the practitioners of industrial equipment design.The study on the flow and heat transfer of non-Newtonian power law fluid is of great significance to the economic development and energy consumption reduction,and it has great practical value and practical significance in the fields of water conservancy,chemistry,metallurgy,material,energy,biology and so on.In this paper,the flow and heat transfer of non-Newtonian power law fluid in different sections of pipe are studied.The non-Newtonian fluid mathematical model and the physical model which is divided into structured grids are introduced at first and the rationality of the numerical simulation method is verified by the experimental data.Based on the theoretical analysis,the direct numerical simulation of the laminar flow of non-Newtonian fluid with different power law exponent in different cross sections is carried out.On the basis of discussing the distribution of velocity field and temperature field,the paper analyzes the influence of many parameters,such as tube shape,the power-law index,the Reynolds number,the Peclet number,on the velocity,temperature,entrance length of velocity or temperature,flow resistance and heat transfer characteristics.The results show that the inlet length,flow resistance and heat transfer characteristics are related to these parameters.In this paper,the numerical analysis of the flow and heat transfer of non-Newtonian power law fluid is presented.The numerical simulation results are compared with previous studies or classical formula to verify the correctness of the numerical simulation method and the reliability of the results.Furthermore,the local resistance coefficient of non-Newtonian power law fluid in a 90° bend is studied in the case of turbulent flow,and the paper analyzes the influence of bend diameter ratio,the surface roughness and the Reynolds number on it.In addition,the influence factors of the secondary flow in the 90 ° elbow are explored.And then the paper analyzes the formation of the secondary flow at different angles pipe sections and discusses the effect of Dean number on the formation of secondary flow.The results indicate that the size of Dean number has a certain influence on the center position of Dean vortex and velocity distribution of fluid.The theoretical analysis and numerical simulation of this paper have important guiding significance for the understanding of non-Newtonian power law fluid,and provide a theoretical reference for further research to explore the complex fluid flow law and the mechanism of heat transfer.At the same time,there is also a strong engineering background to study the flow and heat transfer problems of non-Newtonian fluids with different power-law exponents in different cross-section pipes.Therefore,the research of this paper has good application prospects.