LAUSR

Abstract In the petroleum production process, the tubing-casing annulus has been eccentric due to influence of gravity and thermal expansion, which complicates heat exchange. Forced convection heat transfer in vertical annulus with difference water-air ratios, eccentricities and radius ratios, has been experimentally studied with constant volumetric flow rate and temperature of hot fluid. The radius ratio that make Nu increase abruptly under operating conditions in this study is investigated numerically. The governing equations describing the heat transfer and flow are discretized using the Finite Element Method. Results indicate that the relation between Nu and radius ratio is non-linear. The radius ratios causing Nu to increase abruptly are 0.36 and 0.21 respectively. The coefficient of convection heat transfer increases as the radius ratios increase. For the eccentricity of 0.2, the decrease of water-air ratios enhances the heat transfer of eccentric annular space. For the eccentricity of 0.5 and 0.8, the heat transport first strengthens and then weakens with the decrease of water-air ratios. The effect of eccentricities on the Nu is affected by radius ratios and Re in the meantime. The empirical correlation is derived for the Nusselt number as a function of the Reynolds number, eccentricity and Prandtl number.