Natural convective heat transfer of water near its density maximum in an eccentric horizontal annulus

In order to understand the effect of eccentricity on natural convective heat transfer of water near its density maximum in a horizontal annulus, a series of two-dimensional numerical simulations from steady-state convection to oscillatory convection were performed by using finite volume method. The radius ratio of the annulus was 1.5, and density inversion parameter and eccentricity ranged from 0 to 1. Results showed that horizontal eccentricity leads to an asymmetric flow pattern, which combines the characteristic of flow in a large-gap on one side with that in a narrow-gap on another side of the annulus. For vertical eccentricity, the flow pattern has the characteristics of coupling flow in the large-gap at the bottom with that in the narrow-gap at the top of the annulus at an upward vertical eccentricity. Furthermore, when oscillatory convection appears, mechanisms of flow instability for different density inversion parameters are the same as these in horizontal concentric annulus. The variation of average Nusselt number with the Rayleigh number and the density inversion parameter is also exhibited. Based on simulation results, the heat transfer correlation for the horizontal annulus has been proposed according to the multiple linear regression technique. (C) 2012 Elsevier Masson SAS. All rights reserved.