Numerical solutions for fully developed laminar flow in internally finned tubes with trapezoidal and triangular fin profiles were given with Finite Element Method (FEM): The heat transfer characteristics were obtained...Numerical solutions for fully developed laminar flow in internally finned tubes with trapezoidal and triangular fin profiles were given with Finite Element Method (FEM): The heat transfer characteristics were obtained and compared under the boundary conditions of uniform heat flux, uniform wall temperature, and the third boundary condition with finite wall thermal conductivity considered. The numerical results show that boundary conditions have pronounced effects on the temperature field.Furthermore, a new mechanism on the heat transfer augmentation of internally finned tubes is proposed.展开更多
The fluid flow and heat transfer characteristics of internal longitudinal finned tube were investigated experimentally,and were compared with those of circular annulus tube. It was shown that the internally longitudin...The fluid flow and heat transfer characteristics of internal longitudinal finned tube were investigated experimentally,and were compared with those of circular annulus tube. It was shown that the internally longitudinal finned tube had better heat transfer performance than the circular annulus tube with increase of pressure drop simultaneously.Numerical results based on the realized k-ε turbulence model agreed well with the experimental results.It was found that there existed a critical Reynolds number, that is, when Reynolds number was less than the critical value, the Nusselt number of internally longitudinal finned tube was smaller than that of circular annulus tube in laminar flow.In addition,the Reynolds number for the transition from laminar to turbulent flow was greatly decreased due to the existence of internal fins.展开更多
Heat transfer and fluid flow performance in internally finned tube with blocked core-tube was numerically investigated with the realizable k-ε turbulence model and wall function method.The working fluid was air.The n...Heat transfer and fluid flow performance in internally finned tube with blocked core-tube was numerically investigated with the realizable k-ε turbulence model and wall function method.The working fluid was air.The numerical method was validated by comparing the calculated results with available experimental data.It was found that there existed an optimal value for the ratio of core-tube outside diameter to outer-tube inside diameter, and this optimal value decreased with the increase of air flow rate.The optimal ratio was about 0.5—0.625 in the range of studied parameters.Meanwhile under the condition of identical pressure, the optimal ratio was also about 0.44—0.56.The conclusion is useful for the design of this kind of internally finned tubes.展开更多
文摘Numerical solutions for fully developed laminar flow in internally finned tubes with trapezoidal and triangular fin profiles were given with Finite Element Method (FEM): The heat transfer characteristics were obtained and compared under the boundary conditions of uniform heat flux, uniform wall temperature, and the third boundary condition with finite wall thermal conductivity considered. The numerical results show that boundary conditions have pronounced effects on the temperature field.Furthermore, a new mechanism on the heat transfer augmentation of internally finned tubes is proposed.
文摘The fluid flow and heat transfer characteristics of internal longitudinal finned tube were investigated experimentally,and were compared with those of circular annulus tube. It was shown that the internally longitudinal finned tube had better heat transfer performance than the circular annulus tube with increase of pressure drop simultaneously.Numerical results based on the realized k-ε turbulence model agreed well with the experimental results.It was found that there existed a critical Reynolds number, that is, when Reynolds number was less than the critical value, the Nusselt number of internally longitudinal finned tube was smaller than that of circular annulus tube in laminar flow.In addition,the Reynolds number for the transition from laminar to turbulent flow was greatly decreased due to the existence of internal fins.
文摘Heat transfer and fluid flow performance in internally finned tube with blocked core-tube was numerically investigated with the realizable k-ε turbulence model and wall function method.The working fluid was air.The numerical method was validated by comparing the calculated results with available experimental data.It was found that there existed an optimal value for the ratio of core-tube outside diameter to outer-tube inside diameter, and this optimal value decreased with the increase of air flow rate.The optimal ratio was about 0.5—0.625 in the range of studied parameters.Meanwhile under the condition of identical pressure, the optimal ratio was also about 0.44—0.56.The conclusion is useful for the design of this kind of internally finned tubes.
