In this paper,transient and steady natural convection heat transfer in an elliptical annulus has been investigated.The annulus occupies the space between two horizontal concentric tubes of elliptic cross-section.The r...In this paper,transient and steady natural convection heat transfer in an elliptical annulus has been investigated.The annulus occupies the space between two horizontal concentric tubes of elliptic cross-section.The resulting velocity and thermal fields are predicted at different annulus orientations assuming isothermal surfaces.The full governing equations of mass,momentum and energy are solved numerically using the Fourier Spectral method.The heat convection process between the two tubes depends on Rayleigh number,Prandtl number,angle of inclination of tube axes and the geometry and dimensions of both tubes.The Prandtl number and inner tube axis ratio are fixed at 0.7 and 0.5,respectively.The problem is solved for the two Rayleigh numbers of 104 and 105 considering a ratio between the two major axes up to 3 while the angle of orientation of the minor axes varies from 0 to 90◦.The results for local and average Nusselt numbers are obtained and discussed together with the details of both flow and thermal fields.For isothermal heating conditions,the study has shown an optimum value for major axes ratio that minimizes the rate of heat transfer between the two tubes.Another important aspect of this paper is to prove the successful use of the Fourier Spectral Method in solving confined flow and heat convection problems.展开更多
基金support received from Department of Mechanical Engineering,UET Taxila,Pakistan and from King Fahd University of Petroleum&Minerals,Dhahran,Saudi Arabia is very highly appreciated.
文摘In this paper,transient and steady natural convection heat transfer in an elliptical annulus has been investigated.The annulus occupies the space between two horizontal concentric tubes of elliptic cross-section.The resulting velocity and thermal fields are predicted at different annulus orientations assuming isothermal surfaces.The full governing equations of mass,momentum and energy are solved numerically using the Fourier Spectral method.The heat convection process between the two tubes depends on Rayleigh number,Prandtl number,angle of inclination of tube axes and the geometry and dimensions of both tubes.The Prandtl number and inner tube axis ratio are fixed at 0.7 and 0.5,respectively.The problem is solved for the two Rayleigh numbers of 104 and 105 considering a ratio between the two major axes up to 3 while the angle of orientation of the minor axes varies from 0 to 90◦.The results for local and average Nusselt numbers are obtained and discussed together with the details of both flow and thermal fields.For isothermal heating conditions,the study has shown an optimum value for major axes ratio that minimizes the rate of heat transfer between the two tubes.Another important aspect of this paper is to prove the successful use of the Fourier Spectral Method in solving confined flow and heat convection problems.
