Abstract:

Numerical investigations on the melting process of lauric acid in a horizontal annulus heated isothermally from the inside wall is presented. The simulation is verified by comparing with the results by experiment. The mechanism of heat transfer of the melting process is analyzed through the melting phase front and the average Nusselt changes with Fourier number in different boundary temperatures. The result shows that the average Nusselt decreased with the increase in Fourier number first, and then decreased gradually, the lowest point before the average Nusselt changes with Fourier number in different boundary temperatures. The result shows that the average Nusselt decreased with the increase in Fourier number first, and then decreased gradually, the lowest point before the average Nusselt increased is the transition point of heat transfer mechanism. A clear separation of melt fraction curve is manifested in comparison with the pure heat conduction model diagram. It is found that the Fourier number of the transition point from pure heat conduction to natural convection is 0.028 when Rayleigh number and Stefan number are 1.33×10⁷, 0.206 respectively.

Key words: lauric acid, annulus unit, melting, heat transfer mechanism, numerical simulation

摘要：

对月桂酸在环形单元内的熔化过程进行了数值模拟和实验研究,采用摄像法捕捉相界面的变化情况,验证了模拟计算结果的准确性。研究了月桂酸熔化过程中不同边界温度条件下环形单元内相界面的变化、平均Nusselt数及熔化速率随Fourier数的变化规律,分析了熔化过程传热机制的变化。结果表明:平均Nusselt数随Fourier数增加先下降再上升,而后逐渐下降,平均Nusselt数先下降后上升的转折点为传热机制转变点,在与纯导热模型对比图上表现为熔化分数曲线的分离,在Rayleigh数为1.33×10⁷,Stefan数为0.206时,由纯导热向自然对流过渡的转捩点的Fourier数为0.028。

关键词: 月桂酸, 环形单元, 熔化, 传热机制, 数值模拟