Experimental and numerical study on forced convection heat transport in eccentric annular channels.

Abstract In the process of drilling, the tubing-casing annulus are easily to be eccentric. Heat transport phenomenon occurring in such tubes and annulus can be complex, and this paper investigates forced convection in a vertical eccentric annulus with different radius ratios and eccentricity (normalized by the radius difference). Physical experiments and numerical simulation have been conducted with constant inner tube inlet temperature and flow rate of hot water. Results show that with the increase of radius ratios, the convection heat transport coefficient increases. For a radius ratio of 1.875, the heat transport coefficient increases as the eccentricity increases when the Re > 2000 and it decreases when the Re < 2000. For a radius ratio of 2.25 and Re < 1500, the influence of eccentricity is trivial, but for Re > 1500, the increase of eccentricity strengthens the heat convection. For a radius ratio of 3.06, the heat transport coefficient increases as the eccentricity increases. An empirical correlation for Nusselt number is derived as a function of Reynolds number, Prandtl number and eccentricity. Highlights • For D o / D i = 1.875, the effect of eccentricity is identified into two zones. • For D o / D i = 3.06, the increase of eccentricity enhances the convective heat transport. • The increase of radius ratio strengthens the heat transport of annular channels. • With low eccentricity and low Reynolds number, the increase of radius ratio can hardly improve the heat exchange efficiency. • Three kind of empirical correlations are regressed through parametric analysis. [ABSTRACT FROM AUTHOR]