engleski

Numerical study of a sphere cooling by natural convection

Two approaches for predicting the sphere cooling process were compared in terms of the accuracy of the volume averaged sphere temperature: (I) The full approach with heat conduction in the sphere and laminar natural convection in the fluid and (II) the lumped quasi-steady model approach based on Churchill’ s correlation function for steady state heat transfer. The solution of the full model depends on the Rayleigh number (Ra), the Biot number (Bi) and the sphere to fluid thermal diffusivity ratio (A). The lumped model gives fairly accurate results with respect to the full model (discrepancy in sphere temperature less than 4%) for Bi<0.05, A<50 and Ra>104. The accuracy of the lumped model decreases with increasing Bi and A and decreasing Ra.

natural convection; sphere colling; lumped model

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