Numerical simulation of mixed convective heat transfer of a molten salt in a square tube with a thermally conductive wall

doi:10.12028/j.issn.2095-4239.2019.0012

Abstract

Abstract: Molten salts has been used an a regenerative working medium for solar thermal power because of their good heat transfer ability, high working temperature and temperature range, low system pressure and favorable economics. Non-uniform heating process, however, often results in temperature difference between solid heating surface and the heat transfer fluid, leading to the buoyancy effect and hence mixed convection. Heat conduction through the solid tube wall is likely to exert an effect on the mixed convective heat transfer. This paper numerically studies this effect, specifically the mixed convection process of a molten salt heated by a horizontal square tube surface under a non-uniform heating condition. The wall thickness was considered in the study. The relationship between various dimensionless numbers was analyzed. The results were compared with the flow pattern diagram and classical correlations. The results showed that there was buoyancy effect in the non-uniform heating process with the core zone located near the heating wall and the shape of the core zone changing with the increased flow distance. The Nu number increases with the increase of Re number and Ri number, and Nu_x decreases frst before rises with the depth of flow distance.Compared with the numerical simulation results for a zero wall thermal conductivity, the shape of the mainstream core region was more uniform, the local Nu_x was higher and the rising position was earlier, and the flow and heat transfer characteristics were consistent. The simulation results were in good agreement with the classical correlation.

Key words: molten salt, mixed convection, horizontal square tube, multifaceted heating

CLC Number:

TK11
TK02

YANG Cenyu, MENG Qiang, WANG Le, CHEN Mengdong, HU Xiao, XU Guizhi. Numerical simulation of mixed convective heat transfer of a molten salt in a square tube with a thermally conductive wall[J]. Energy Storage Science and Technology, 2019, 8(4): 764-771.

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