Numerical and experimental simulation of convective heat transfer in a liquid metal flow in an annular pipe

Numerical simulation was performed to study the hydrodynamics and heat transfer characteristics of a curved pipe. The section of a uniformly heated pipe with a ratio of the bend radius to the pipe's inner diameter being equal to 25 is considered. The differential conservation equations of a moving continuous medium are formulated in a curvilinear coordinate system. The system of equations for a cylindrical coordinate system, which includes additional terms that arise in the ring coordinate system, is taken as a basis. The problem's geometry remains unchanged; it is still a straight pipe in cylindrical coordinates. In the simulation, a structured computational grid is used, and the influence of thermogravitational convection is considered. Experimental studies were carried out to investigate heat transfer in a liquid metal flow in a curved pipe with an inner diameter of 19 mm and a bend radius of 0.5 m. The experiments were conducted on a mercury loop at JIHT RAS in the range of the Reynolds number between 11,000 and 80,000 and at different heat loads. A probe with a correlation sensor that consists of two micro-thermopairs was used. The developed mechanism permits continuous movement of the probe in the pipe's section, which is at a distance of 76 calibers to the heating zone. In the section placed in the stabilized region of the non-isothermal turbulent flow, the averaged velocity and temperature fields were measured in detail. The parameters, presented in dimensionless form, are compared with similar numerical simulation results. It was found that inertial and gravitational forces have a strong influence on the velocity and temperature profiles of the flow, which results in significant heterogeneity in the distribution of the wall temperature around the perimeter of the considered section of the pipe. The comparison shows good agreement between experimental and calculated data.