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球床堆复杂的几何结构导致直接建模进行热工水力模拟非常困难,一般使用多孔介质模型简化处理,但多孔介质已有的压降和对流换热公式在熔盐冷却球床中的有效性仍待验证。本文基于固态燃料熔盐堆建立了6 cm直径小球的规则球床模型,给定球床进口熔盐流量和球壳发热功率,模拟了球床内的稳态流动与换热,计算了对应的压降和对流换热系数,并分别得到了球床压降、对流换热Nu随球床内流动Re变化的曲线。对比发现:模拟压降结果与已有公式差异较大,而模拟对流换热Nu结果与已有公式的差异相对较小。结合模拟结果和已有的公式,拟合得到了修正的压降和对流换热Nu公式。将修正公式应用于3 cm直径规则球床中,结果表明多孔介质修正模型与直接模拟结果一致。
Complex geometries of bed beds make direct modeling difficult to perform in thermal-hydraulic simulations. Porous media models are generally used to simplify handling, but the available pressure drop and convective heat transfer equations in porous media are effective in molten salt cooling of a ball bed Still to be verified. In this paper, a regular spherical bed model of 6 cm diameter pellets was established based on solid fuel molten salt heap. Given the inflow of molten salt and the heating power of the spherical shell, the steady-state flow and heat transfer in the ball bed were simulated. Pressure drop and convection heat transfer coefficient, respectively, and get the pressure drop of the ball bed, convective heat Nu with the flow of the ball inside the bed Re curve. The results show that the simulated pressure drop has a great difference with the existing one, while the difference between simulated convective heat transfer Nu and the existing one is relatively small. Combined with the simulation results and the existing formulas, the corrected pressure drop and convection heat transfer Nu formula were obtained. The modified formula was applied to a 3 cm diameter ball bed. The results show that the porous medium correction model is consistent with the direct simulation results.