二维方腔内HITEC熔盐熔化非稳态传热数值模拟

Abstract

本文以混合熔盐HITEC为研究对象，在内置圆形加热棒的封闭方腔内，考虑液相自然对流的情况下，建立熔盐熔化传热的数学模型。FLUENT软件被用来模拟传热过程。考虑不同功率、不同加热棒尺寸对熔盐进行加热，分别获得不同情况下熔盐熔化需要的时间。并分析在某一加热功率下，方腔内温度分布。数值模拟结果表明，自然对流不能忽视，它促进方腔上部的传热，缩短了熔盐熔化需要的时间。随着液相区不断扩大，涡流的影响范围也不断扩大。熔盐熔化过程经过三个阶段：纯导热阶段，相变阶段，自然对流主导阶段，不同阶段方腔内的温度分布差别明显。另一方面，随着加热功率增大，或者增大加热棒尺寸，液相比愈来愈呈现随时间非线性变化的规律。 A numerical study has been conducted on the heat transfer of the molten HITEC salt, in which the natural convection heat transfer of the liquid salt was considered in the closed square cavity equipped with a heating bar. The two-dimensional heat transfer model of the molten salt was es-tablished and the problem was numerically solved with the FLUENT software. The dynamic change of the molten region as well as the melting fraction in the cavity was addressed in the condition of different heating power. The numerical result has revealed that it is considered mainly caused by the buoyancy-driven fluid flow of the molten salt and the vortex would enlarge with the molten range increasing. As the result of the coupled heat transfer of the natural convection and the conduction, the process of the salt melting can be divided into three stages, i.e. the heat conduction dominated stage at the beginning, the phase changing stage in the middle period, and the convection dominated stage in the last. The temperature distribution in the square cavity is obviously different in different stage. Either increasing the heating power or enlarge the heating bar size are all helpful to the salt melting process. Nevertheless, changing the heating bar size seems to be more effective for the melting dynamics in comparison.