Studied On Flow And Heat Transfer Characteristics Of Power-law Fluid In Porous Media

Flow and heat transfer of non-Newtonian fluid in porous media was an universal physical process in nature,industry and agriculture,which had a strong engineering application background.It was of great scientific value and engineering significance to study the flow and heat transfer law of power law fluid in porous media.Because of the unique rheological properties of power law fluid and the complexity of multi-scale behavior in porous media,the present research results in this field had some limitations,and many important problems needed to be studied and explored in depth.For example,the experimental study on the flow and heat transfer of power law fluid in porous media was relatively deficient.The study of flow resistance characteristics of power law fluid in porous media was still lack of in-depth theoretical analysis.The understanding of non-Darcy flow characteristics and viscous dissipation effect for power law fluid in porous media was not inadequate.Based on the above problems,the main research work was divided into the following aspects:First,the polyacrylamide(HPAM)solution with certain rheological parameters was chosen as power law fluid medium,constructing the porous media skeleton model of orderly arrangement of spherical particles.The basic experimental data of flow and heat transfer characteristics of HP AM solutions with different rheological properties in porous media with real physical structure were experimentally measured.The flow and heat transfer law of power law fluid in different porous media model was experimentally analyzed,and the comprehensive heat transfer efficiency was introduced to evaluate its flow and heat transfer characteristics.The experimental data were enriched to reveal the flow and heat transfer mechanism of power law fluid passing through the three-dimensional ordered packing of particles.Secondly,based on the Carman-Kozeny-Blake model and the contracting-expanding channel model,this study developed a new resistance model for predicting power law fluid flow through granular porous medium with homogeneous spherical particles.For the rheological properties of power law fluid,by employing the average hydraulic radius theory and considering the influence of wall effect on the pressure drop,a modified Ergun type equation was expressed as a function of tortuosity,porosity,ratio of throat diameter pore hydraulic diameter to,diameter of particles,wall correction factor,permeability and fluid rheological index.The influence of the above important parameters on the flow resistance characteristics was discussed in detail.Thirdly,based on Darcy-Brinkman-Forchheimer flow model,this study analyzed the flow characteristics during fully developed forced flow in the flat channel filled with a power law fluid saturated porous medium.By assuming the linear and parabolic velocity distribution within the boundary layer,the dimensionless calculation formulas of the boundary layer thickness,the axial velocity and pressure drop were deduced using the boundary layer momentum integral method,and the influences of the Darcy number,integrated inertial parameter,viscosity ratio,porosity and power law index on the dimensionless axial velocity distribution and pressure drop were discussed.The flow characteristics of non-Darcy flow for power law fluid in porous media was clarified.Then,based on Darcy-Brinkman-Forchheimer flow model,the influence of different viscous dissipation on fully developed forced convection heat transfer of a power law fluid in a saturated porous medium channel was compared.The dimensionless calculation expressions of the axial velocity distribution,temperature distribution and convection heat transfer characteristics were deduced,and the viscous dissipation effects under different cases was solved numerically by employing the classical Runge-Kutta fourth order scheme subject to uniform heat flux.The numerical simulation results indicate that the convection heat transfer characteristics related closely to velocity distribution,and the viscous dissipation terms,namely Darcy term and the Forchheimer term would strengthen the convection heat transfer characteristics,while the Al-Hadharami term would weaken the convection heat transfer characteristics.The influence mechanism of characteristic parameters of Brinkman number,Darcy number,Forchheimer inertial parameter and the power-law index on the flow and heat transfer characteristics was clarified.