Mixed convection studies of liquid metal MHD flow in a horizontal square duct subjected to a strong uniform magnetic field

Xiaodong Wu - Jie Mao - Jiawei Yan - Lang Yang

School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou, 310018, China

Abstract
The heat transfer of liquid metal blankets is one of the key issues that need to be solved in the design and manufacture of controlled thermal nuclear fusion reactors. Under actual working conditions, the buoyancy force changes the flow state of the liquid metal and thus affects the heat transfer of the blanket. In this paper, a low magnetic Reynolds number magnetohydrodynamic (MHD) solver is developed in OpenFOAM to simulate a liquid metal flow in a horizontal square duct under a transverse uniform magnetic field and surface heating. The effects of wall conductance ratio and Grashof number on the velocity, temperature, MHD pressure drop, and heat transfer are studied. The results show that the wall conductance ratio does not change the temperature distribution and heat transfer significantly, and the MHD pressure drop increases with the increase of the wall conductance ratio. The effects of the Grashof number on the mixed convection heat transfer are closely related to the critical Grashof number. When the Grashof number is less than the critical Grashof number, the flows in the duct are in a stable laminar flow state. When the Grashof number is greater than the critical Grashof number, the buoyancy force forms a transverse circulation, affects the temperature distribution followed by the broken velocity symmetry, and improves the heat transfer of the duct. The results can be referenced in the design of liquid metal blankets. Key words: Mixed convection, buoyancy force, wall conductance ratio, horizontal square duct, uniform magnetic field. Tables 2, Figs 18, Refs 21.