The main objective of this work is to investigate analytically the steady nanofluid flow and heat transfer characteristics between nonparallel plane walls. Using appropriate transformations for the velocity and temper...The main objective of this work is to investigate analytically the steady nanofluid flow and heat transfer characteristics between nonparallel plane walls. Using appropriate transformations for the velocity and temperature, the basic nonlinear partial differential equations are reduced to the ordinary differential equations. Then, these equations have been solved analytically and numerically for some values of the governing parameters, Reynolds number, Re, channel half angle, α, Prandtl number, Pr, and Eckert number, Ec, using Adomian decomposition method and the Runge-Kutta method with mathematic package. Analytical and numerical results are searched for the skin friction coefficient, Nusselt number and the velocity and temperature profiles. It is found on one hand that the Nusselt number increases as Eckert number or channel half-angle increases, but it decreases as Reynolds number increases. On the other hand, it is also found that the presence of Cu nanoparticles in a water base fluid enhances heat transfer between nonparallel plane walls and in consequence the Nusselt number increases with the increase of nanoparticles volume fraction. Finally, an excellent agreement between analytical results and those obtained by numerical Runge-Kutta method is highly noticed.展开更多
The fluid flow characteristics of the single bunch inclined jet impingement were investigated with different jet flow velocities,nozzle diameters,jet angles and jet-to-target distances for ultra-fast cooling technolog...The fluid flow characteristics of the single bunch inclined jet impingement were investigated with different jet flow velocities,nozzle diameters,jet angles and jet-to-target distances for ultra-fast cooling technology.The results show that the peak pressure varying significantly from nearly 0.5 to above 13.4 kPa locates at the stagnation point with different jet diameters,and the radius of impact pressure affected zone is small promoted from 46 to 81 mm in transverse direction,and 50 to 91 mm in longitude direction when the jet flow velocity changes from 5 to 20 m/s.However,the fluid flow velocity is relatively smaller near the stagnation point,and increases gradually along the radius outwards,then declines.There is an obvious anisotropic characteristic that the flow velocity component along the jet direction is about twice of the contrary one where the jet anlge is 60°,jet diameter is 5 mm,jet length is 8 mm and jet height is 50 mm.展开更多
Numerical analysis was performed to investigate flow and heat transfer characteristics in spiral coiled tube heat exchanger. Radius of curvature of the spiral coiled tube was gradually increased as total rotating angl...Numerical analysis was performed to investigate flow and heat transfer characteristics in spiral coiled tube heat exchanger. Radius of curvature of the spiral coiled tube was gradually increased as total rotating angle reached 12n. As the varying radius of curvature became a dominant flow parameter, three-dimensional flow analysis was performed to this flow together with different Reynolds numbers while constant wall heat flux condition was set in thermal field. From the analysis, centrifugal force due to curvature effect is found to have significant role in behavior of pressure drop and heat transfer. The centrifugal force enhances pressure drop and heat transfer to have generally higher values in the spiral coiled tube than those in the straight tube. Even then, friction factor and Nusselt number are found to follow the proportionality with square root of the Dean number. Individual effect of flow parameters of Reynolds number and curvature ratio was investigated and effect of Reynolds number is found to be stronger than that of curvature effect.展开更多
文摘The main objective of this work is to investigate analytically the steady nanofluid flow and heat transfer characteristics between nonparallel plane walls. Using appropriate transformations for the velocity and temperature, the basic nonlinear partial differential equations are reduced to the ordinary differential equations. Then, these equations have been solved analytically and numerically for some values of the governing parameters, Reynolds number, Re, channel half angle, α, Prandtl number, Pr, and Eckert number, Ec, using Adomian decomposition method and the Runge-Kutta method with mathematic package. Analytical and numerical results are searched for the skin friction coefficient, Nusselt number and the velocity and temperature profiles. It is found on one hand that the Nusselt number increases as Eckert number or channel half-angle increases, but it decreases as Reynolds number increases. On the other hand, it is also found that the presence of Cu nanoparticles in a water base fluid enhances heat transfer between nonparallel plane walls and in consequence the Nusselt number increases with the increase of nanoparticles volume fraction. Finally, an excellent agreement between analytical results and those obtained by numerical Runge-Kutta method is highly noticed.
基金Project(2010CB630800)supported by the National Basic Research Program of ChinaProject(N100307003)supported by the Fundamental Research Funds for the Central Universities,China
文摘The fluid flow characteristics of the single bunch inclined jet impingement were investigated with different jet flow velocities,nozzle diameters,jet angles and jet-to-target distances for ultra-fast cooling technology.The results show that the peak pressure varying significantly from nearly 0.5 to above 13.4 kPa locates at the stagnation point with different jet diameters,and the radius of impact pressure affected zone is small promoted from 46 to 81 mm in transverse direction,and 50 to 91 mm in longitude direction when the jet flow velocity changes from 5 to 20 m/s.However,the fluid flow velocity is relatively smaller near the stagnation point,and increases gradually along the radius outwards,then declines.There is an obvious anisotropic characteristic that the flow velocity component along the jet direction is about twice of the contrary one where the jet anlge is 60°,jet diameter is 5 mm,jet length is 8 mm and jet height is 50 mm.
基金supported by the Second Stage of Brain Korea 21 Projects,Korea
文摘Numerical analysis was performed to investigate flow and heat transfer characteristics in spiral coiled tube heat exchanger. Radius of curvature of the spiral coiled tube was gradually increased as total rotating angle reached 12n. As the varying radius of curvature became a dominant flow parameter, three-dimensional flow analysis was performed to this flow together with different Reynolds numbers while constant wall heat flux condition was set in thermal field. From the analysis, centrifugal force due to curvature effect is found to have significant role in behavior of pressure drop and heat transfer. The centrifugal force enhances pressure drop and heat transfer to have generally higher values in the spiral coiled tube than those in the straight tube. Even then, friction factor and Nusselt number are found to follow the proportionality with square root of the Dean number. Individual effect of flow parameters of Reynolds number and curvature ratio was investigated and effect of Reynolds number is found to be stronger than that of curvature effect.
