Thermal transport in porous media has stimulated substantial interest in engineering sciences due to increasing applications in filtration systems,porous bearings,porous layer insulation,biomechanics,geomechanics etc....Thermal transport in porous media has stimulated substantial interest in engineering sciences due to increasing applications in filtration systems,porous bearings,porous layer insulation,biomechanics,geomechanics etc.Motivated by such applications,in this article,a numerical study of entropy generation impacts on the heat and momentum transfer in time-dependent laminar incompressible boundary layer flow of a Casson viscoplastic fluid over a uniformly heated vertical cylinder embedded in a porous medium is presented.Darcy’s law is used to simulate bulk drag effects at low Reynolds number for an isotropic,homogenous porous medium.Heat line visualization is also included.The mathematical model is derived and normalized using appropriate transformation variables.The resulting non-linear time-dependent coupled governing equations with associated boundary conditions are solved via an implicit finite difference method which is efficient and unconditionally stable.The outcomes show that entropy generation and Bejan number are both elevated with increasing values of Darcy number,Casson fluid parameter,group parameter and Grashof number.To analyze the heat transfer process in a two-dimensional domain,plotting heat lines provides an excellent approach in addition to streamlines and isotherms.It is remarked that as the Darcy number increases,the deviations of heat lines from the hot wall are reduced.展开更多
Air film conveyors equipped with porous pads have been developed to bring the liquid crystal display(LCD) into a non-contact state during transportation process. In this work, a theoretical model including flow proper...Air film conveyors equipped with porous pads have been developed to bring the liquid crystal display(LCD) into a non-contact state during transportation process. In this work, a theoretical model including flow property of porous media and Reynolds equation is established within a representative region in order to optimize the design parameters of a partial porous air conveyor. With the theoretical model, an optimization method using nondominated sorting genetic algorithm – II(NSGA-II) is applied for a two-objective optimization to achieve a minimum air consumption and maximum load capacity. Three Pareto-optimal solutions are selected to analyze the influence of each parameter on the characteristics of the air conveyor, and the results indicate that the position of the porous pads has the most significant impact on the performance and of course must be determined with care. Furthermore, experimental results in terms of the supporting force versus gap clearance show that the optimized air conveyor can greatly improve the load capacity over the normal one, indicating that the optimization method is applicable for practical use.展开更多
Water shutoff through injection wells is one of the most important techniques used for water injection profile control and modification in severely heterogeneous reservoirs,aiming at stabilizing oil production.It has ...Water shutoff through injection wells is one of the most important techniques used for water injection profile control and modification in severely heterogeneous reservoirs,aiming at stabilizing oil production.It has been widely reported that the effectiveness and efficiency of water shutoff using gel is mostly dependent on the gel dynamic sealing properties in the porous media.Firstly the gelation strength and gelation time of polymer gel were evaluated.Then,core flowing experiments were conducted before and after gelation in a 32 m long sand pack.In addition,water flooding core experiments were also carried out in a long core of 80 cm before and after injecting gel system to check the reliability of this evaluation method.The experimental results show that moderate-strength gel can be formed at 65 °C.According to the integrated evaluation of the plugging coefficient,plugging strength and water breakthrough time,the gel particles are capable of migrating to a distance of 7.47 m from the injection point of the 32 m long sand pack during the water injection process after gelation.Based on sands gelation status and effluent analyses,the effective migration distance of the gel particles is 4-14 m.Through the core flooding experiments using the 80 cm heterogeneous core,it is evidenced that the gel can be formed in the deep reservoir(40.63% of total length) with the plugging strength as high as 6.33 MPa/m,which leads to extra oil recovery of 10.55% of original oil in place(OOIP) by water flooding after gel treatment.展开更多
基金DST-INSPIRE (Code No. IF160028) for the grant of research fellowship
文摘Thermal transport in porous media has stimulated substantial interest in engineering sciences due to increasing applications in filtration systems,porous bearings,porous layer insulation,biomechanics,geomechanics etc.Motivated by such applications,in this article,a numerical study of entropy generation impacts on the heat and momentum transfer in time-dependent laminar incompressible boundary layer flow of a Casson viscoplastic fluid over a uniformly heated vertical cylinder embedded in a porous medium is presented.Darcy’s law is used to simulate bulk drag effects at low Reynolds number for an isotropic,homogenous porous medium.Heat line visualization is also included.The mathematical model is derived and normalized using appropriate transformation variables.The resulting non-linear time-dependent coupled governing equations with associated boundary conditions are solved via an implicit finite difference method which is efficient and unconditionally stable.The outcomes show that entropy generation and Bejan number are both elevated with increasing values of Darcy number,Casson fluid parameter,group parameter and Grashof number.To analyze the heat transfer process in a two-dimensional domain,plotting heat lines provides an excellent approach in addition to streamlines and isotherms.It is remarked that as the Darcy number increases,the deviations of heat lines from the hot wall are reduced.
基金Project(51205174)supported by the National Natural Science Foundation of ChinaProject(2014M550309)supported by the Postdoctoral Science Foundation of ChinaProject(GZKF-201407)supported by the Open Foundation of the State Key Laboratory of Fluid Power Transmission and Control,China
文摘Air film conveyors equipped with porous pads have been developed to bring the liquid crystal display(LCD) into a non-contact state during transportation process. In this work, a theoretical model including flow property of porous media and Reynolds equation is established within a representative region in order to optimize the design parameters of a partial porous air conveyor. With the theoretical model, an optimization method using nondominated sorting genetic algorithm – II(NSGA-II) is applied for a two-objective optimization to achieve a minimum air consumption and maximum load capacity. Three Pareto-optimal solutions are selected to analyze the influence of each parameter on the characteristics of the air conveyor, and the results indicate that the position of the porous pads has the most significant impact on the performance and of course must be determined with care. Furthermore, experimental results in terms of the supporting force versus gap clearance show that the optimized air conveyor can greatly improve the load capacity over the normal one, indicating that the optimization method is applicable for practical use.
基金Project(2011ZX05009-004)supported by the National Significant Science and Technology Program of China
文摘Water shutoff through injection wells is one of the most important techniques used for water injection profile control and modification in severely heterogeneous reservoirs,aiming at stabilizing oil production.It has been widely reported that the effectiveness and efficiency of water shutoff using gel is mostly dependent on the gel dynamic sealing properties in the porous media.Firstly the gelation strength and gelation time of polymer gel were evaluated.Then,core flowing experiments were conducted before and after gelation in a 32 m long sand pack.In addition,water flooding core experiments were also carried out in a long core of 80 cm before and after injecting gel system to check the reliability of this evaluation method.The experimental results show that moderate-strength gel can be formed at 65 °C.According to the integrated evaluation of the plugging coefficient,plugging strength and water breakthrough time,the gel particles are capable of migrating to a distance of 7.47 m from the injection point of the 32 m long sand pack during the water injection process after gelation.Based on sands gelation status and effluent analyses,the effective migration distance of the gel particles is 4-14 m.Through the core flooding experiments using the 80 cm heterogeneous core,it is evidenced that the gel can be formed in the deep reservoir(40.63% of total length) with the plugging strength as high as 6.33 MPa/m,which leads to extra oil recovery of 10.55% of original oil in place(OOIP) by water flooding after gel treatment.
