In this article,the natural-convective flow of an electrically conducting nanofluid adjacent to a spinning down-pointing vertical cone in the presence of transverse magnetic field is studied.The mathematical model has...In this article,the natural-convective flow of an electrically conducting nanofluid adjacent to a spinning down-pointing vertical cone in the presence of transverse magnetic field is studied.The mathematical model has been formulated based on Tiwari-Das nanofluid model.Three different types of water-based nanofluid with copper,aluminum oxide(alumina)and titanium dioxide(titania)as nanoparticles are considered in this investigation.Two cases of heat transfer analysis are discussed.These are:(i)the spinning cone with prescribed surface temperature and(ii)the spinning cone with prescribed surface heat flux.Using appropriate transformations,the system of partial differential equations is transformed into an ordinary differential system of three equations,which is solved numerically using the fourth-order Runge-Kutta method with shooting technique.The current solution demonstrates very good agreement with those of the previously published studies in the especial cases.The effects of the three key thermophysical parameters governing the flow;the nanoparticle volume fraction,the magnetic parameter and the spin parameter on dimensionless velocity and temperature distributions,skin friction coefficient,Nusselt number and entropy generation number are presented graphically and discussed in details.Our results demonstrate that,the enhancement of heat transfer is a function of particle concentration,small fraction of metallic particles leading to significant changes in all three quantities of skin friction coefficient,local Nusselt number and entropy generation number.The results illustrate that selecting alumina and copper as the nanoparticle leads to the minimum and maximum amounts of skin friction coefficient value,and also copper and titania nanoparticles have the largest and lowest local Nusselt number.Moreover,it is observed that the magnetic parameter has a decreasing effect on both skin friction coefficient and local Nusselt number and an increasing effect on entropy generation number.In addition,our computation shows that all three quantities of skin friction coefficient,local Nusselt number and entropy generation number are the increasing functions of spin parameter.Finally,this simulation represents the feasibility of using magnetic rotating body drives in novel nuclear space propulsion engines and this model has important applications in heat transfer enhancement in renewable energy systems and industrial thermal management.展开更多
Heat and mass transfer effects on the unsteady flow of a micropolar fluid through a porous medium bounded by a semi-infinite vertical plate in a slip-flow regime are studied taking into account a homogeneous chemical ...Heat and mass transfer effects on the unsteady flow of a micropolar fluid through a porous medium bounded by a semi-infinite vertical plate in a slip-flow regime are studied taking into account a homogeneous chemical reaction of the first order. A uniform magnetic field acts perpendicular to the porous surface absorb micropolar fluid with a suction velocity varying with time. The free stream velocity follows an exponentially increasing or decreasing small perturbation law. Using the approximate method, the expressions for the velocity microrotation, temperature, and concentration are obtained. Futher, the results of the skin friction coefficient, the couple stress coefficient, and the rate of heat and mass transfer at the wall are presented with various values of fluid properties and flow conditions.展开更多
文摘In this article,the natural-convective flow of an electrically conducting nanofluid adjacent to a spinning down-pointing vertical cone in the presence of transverse magnetic field is studied.The mathematical model has been formulated based on Tiwari-Das nanofluid model.Three different types of water-based nanofluid with copper,aluminum oxide(alumina)and titanium dioxide(titania)as nanoparticles are considered in this investigation.Two cases of heat transfer analysis are discussed.These are:(i)the spinning cone with prescribed surface temperature and(ii)the spinning cone with prescribed surface heat flux.Using appropriate transformations,the system of partial differential equations is transformed into an ordinary differential system of three equations,which is solved numerically using the fourth-order Runge-Kutta method with shooting technique.The current solution demonstrates very good agreement with those of the previously published studies in the especial cases.The effects of the three key thermophysical parameters governing the flow;the nanoparticle volume fraction,the magnetic parameter and the spin parameter on dimensionless velocity and temperature distributions,skin friction coefficient,Nusselt number and entropy generation number are presented graphically and discussed in details.Our results demonstrate that,the enhancement of heat transfer is a function of particle concentration,small fraction of metallic particles leading to significant changes in all three quantities of skin friction coefficient,local Nusselt number and entropy generation number.The results illustrate that selecting alumina and copper as the nanoparticle leads to the minimum and maximum amounts of skin friction coefficient value,and also copper and titania nanoparticles have the largest and lowest local Nusselt number.Moreover,it is observed that the magnetic parameter has a decreasing effect on both skin friction coefficient and local Nusselt number and an increasing effect on entropy generation number.In addition,our computation shows that all three quantities of skin friction coefficient,local Nusselt number and entropy generation number are the increasing functions of spin parameter.Finally,this simulation represents the feasibility of using magnetic rotating body drives in novel nuclear space propulsion engines and this model has important applications in heat transfer enhancement in renewable energy systems and industrial thermal management.
文摘Heat and mass transfer effects on the unsteady flow of a micropolar fluid through a porous medium bounded by a semi-infinite vertical plate in a slip-flow regime are studied taking into account a homogeneous chemical reaction of the first order. A uniform magnetic field acts perpendicular to the porous surface absorb micropolar fluid with a suction velocity varying with time. The free stream velocity follows an exponentially increasing or decreasing small perturbation law. Using the approximate method, the expressions for the velocity microrotation, temperature, and concentration are obtained. Futher, the results of the skin friction coefficient, the couple stress coefficient, and the rate of heat and mass transfer at the wall are presented with various values of fluid properties and flow conditions.
基金Supported in part by the National Natural Science Foundation of China under Grant No. 10431050the foundation of CAEP 2007B09008foundation of LCP 9140C6902010805
