Experimental Study On Forced Convection Heat Transfer In Eccentric Annular Channels

In the process of injecting steam to the formation,radial heat transfer occurs between the steam which in the wellbore and the formation,through the tubing well,tubing-casing annulus,casing well and cement.In the well drilling process,the well track is not straight line but spiral line,as a result,the tubing-casing annulus is eccentric.But the heat transfer characteristics of eccentric annulus was not fully researched,and there is no mature calculation method,so the accurate calculation of eccentric annulus heat exchange process is very important.In this paper forced convection in a vertical eccentric annulus with different radius ratios and eccentricity(normalized by the radius difference)has been experimentally studied with constant inner tube inlet temperature and flow rate of hot water.The length of the pipes used in the experiment were 2000 mm and the radius ratios range from 1.875 to 3.06.The annulus inlet temperature is constant 3.7°C,and the Re range from 500 to 3500.The wall temperature of the inner pipe was measured at different points by thermocouples for the eccentric ratios 0,0.2,0.5,0.8.The analysis of experimental results indicates that with the increase of radius ratios,the convection heat transfer coefficient increases;when radius ratios is 1.875,the heat transfer coefficient increases as the eccentricity increases when the Re>2000,the heat transfer coefficient decreases as the eccentricity increases when the Re<2000;when radius ratios is 3.06,the heat transfer coefficient increases as the eccentricity increases;An empirical relation is derived for the Nusselt number as a function of the Reynolds number,Prandtl number and eccentricity.