Thermogravitational and Thermocapillary Convection Heat Transfer in Concentric and Eccentric Horizontal

Laminar thermogravitational convection in concentric and eccentric horizontal, cylindrical annuli, filled with two immiscible fluids (water/air, water/silicon oil 10, water/silicon oil 100, Freon 113/ water) is studied numerically. Streamline and temperature distributions, local and average equivalent thermal conductivities are obtained over a wide range of Rayleigh number. The influence of thermocapillary convection (Marangoni convection) is similarly demonstrated for the water/air system in an annular enclosure

Theoretical and Experimental Study of Transient and Steady-State Natural Convection Heat Transfer from a Vertical Flat Plate Partially Immersed in Water

Transient and steady-state heat transfer by natural convection from a vertical flat plate has been investigated both numerically and by experiment. The plate, loaded with a uniform and constant heat flux is positioned in a square container partially filled with liquid and gas. Solutions have been obtained for one set of thermophysical property ratios and for modified Rayleigh numbers up to Ra\ast- = 108. This range has also been covered by experiments. Good agreement between calculated and measured results is obtained

Prandtl Number Effects on Natural Convection Heat Transfer in Concentric and Eccentric Horizontal Cylindrical Annuli

The influence of various Prandtl numbers on the laminar convection flow between concentric and vertically eccentric cylinders is studied numerically. To overcome the difficulties associated with the complex physical domains a numerical transformation method is used to map this region on a rectangle. Although two independent computer programs which are based on different formulations of the governing equations were used, nearly identical results were obtained. Local heat transfer results are presented for a wide range of Rayleigh numbers for the first time. Local heat transfer rates are found to depend on the Prandtl number in addition to the Rayleigh number dependence

Fast Iterative Solution of Poisson Equation with Neumann Boundary Conditions in Nonorthogonal Curvilinear Coordinate Systems by a Multiple Grid Method

A simple multiple grid (MG) technique has been used to solve the linear system of equations arising from the finite-difference discretization of the Neumann problem for elliptic Poisson equations formulated in nonorthogonal curvilinear coordinate systems. Fast, flexible, and simple solution methods for such problems are mandatory when they should act as, for example, pressure solvers in hydrodynamic codes for incompressible fluid flow. The robustness of the solution method chosen can be derived from the fact that only strong nonorthogonal grids have some influence on the asymptotic convergence rate. Problems including patched coordinate systems-for example, with interfaces describing material discontinuities-can also be handled without loss of efficiency

Analysis of the Heat Transport Mechanisms During Melting Around a Horizontal Circular Cylinder

The melting process around a heated horizontal circular cylinder embedded in a phase change material has been analyzed by means of numerical methods. Both heat conduction and convection have been taken into account to treat this moving boundary problem. Difficulties associated with the complex structure of the timewise changing physical domain (melt region) have been successfully overcome by applying a numerical mapping technique (body-fitted coordinates). Numerical solutions have been obtained for Rayleigh numbers up to Ra = 1.5 · 105, Stefan numbers in the range 0.005 ≦ Ste ≦ 0--08 and for Pr = 50. The results are discussed in detail and indicate that the influence of natural convection has to be considered in all cases

Wärmeleitung in anisotropen zusammengesetzten Körpern beliebiger Gestalt

To investigate the thermal response of composed anisotropic structures, a numerical study has been carried out. By the use of a numerical mapping technique it was possible to handle complex multi-body geometries very efficiently. Due to the transformation method the restriction of the well known finite difference method to simple solution regions is removed. For the iterative solution of the corresponding finite difference equations the Strongly Implicit Procedure (SIP) has been employed. Based on the solution methodology, several numerical examples revealing the effects of anisotropy in thermal conductivity and composite structures are presented

Numerical Analysis of Laminar Natural Convection Between Concentric and Eccentric Cylinders

A numerical analysis is carried out to investigate the local and overall heat transfer between concentric and eccentric horizontal cylinders. The numerical procedure, based on Stone's strongly Implicit method, is extended to the 3 × 3 coupled system of the governing partial differential equations describing the conservation of mass, momentum, and energy. This method allows finite-difference solutions of the governing equations without artificial viscosity, and conserves its great stability even for arbitrarily large time steps. The algorithm is written for a numerically generated, body-fitted coordinate system. This procedure allows the solution of the governing equations in arbitrarily shaped physical domains Numerical solutions were obtained for a Raylelgh number In the range 102-103, a Prandtl number of 0.7, and three different eccentric positions of the inner cylinder. The results are discussed in detail and are compared with previous experimental and theoretical results

Heat Transfer During Melting Inside a Horizontal Tube

adecane (Pr ≃ 50) as PCM. The test cell basically consists of a short tube filled with the PCM. The tube is closed with plexiglass disks on both ends, thus allowing the melting front to be recorded photographically with time. As a result, the interface positions as well as the overall and local heat transfer coefficients are presented as function of time. The agreement between experimental and numerical data is reasonably good