Experimental Research On Forced Convection Heat Transfer Of Two Phase Flow In Eccentric Annulus

At present,concentric annular casing is the main research object in thermal calculation of wellbore.But because of drilling,formation creep and string bending,an eccentric shaft is appeared between tubing and casing.As a result,the heat transfer characteristic in eccentric annulus is different from that of concentric annulus.As so far,the research at home and abroad on flow and heat transfer characteristic in eccentric annulus is still not adequate,the research conclusion is inconsistent,and the research on two phase flow is much more scarce.In this paper,forced convective heat transfer in a vertical eccentric annulus with different radius ratios and eccentricity has been researched on eccentric annulus convection heat transfer laboratory furniture.The working medium is two phase flow with different air-water ratio.Research methods include experimental research and numerical simulation.The influence of radius ratio,eccentricity and air-water ratio on heat transfer characteristic is analyzed and we get forced convective heat transfer experimental correlations of air-water two-phase flow in eccentric annulus.When the eccentricity and air-water ratio are constant,increasing radius ratio can strengthen the convective heat transfer within a certain range,but the influence of radius ratio on Nusselt number is not monotonous but related to Reynolds number.When the pipe diameter is smaller,when Re > 5100,the heat transfer intensity enhances with the increase of radius ratio,when Re < 5100,the heat transfer intensity weakens with the increase of radius ratio.When diameter is larger,when Re > 4800,heat transfer intensity weakens with the increase of radius ratio,when Re < 4800,heat transfer intensity enhances with the increase of radius ratio.When the air-water ratio and radius ratio are constant,the influence of eccentricity on convective heat transfer can be divided into two parts,increasing eccentricity will weaken the convective heat transfer when radius ratio is larger and when radius ratio is smaller,it is related to the scope of Reynolds number.When Re > 5800,the heat transfer intensity enhances with the increase of eccentricity,when Re < 5800,heat transfer intensity weakens with the increase of eccentricity.When the radius ratio and eccentricity are constant,the influence of air-water ratio on convective heat transfer can be divided into two parts,increasing air-water ratio can strengthen the convective heat transfer when eccentricity is smaller and when eccentricity is larger,the convective heat transfer is increased initially and then reduced.