液态金属热扩散研究

On Thermal Diffusivity of Liquid Metals

铸件凝固数值计算时高温液态金属热物理参数的选取是尚未解决的问题之一。本文在前人工作的基础上,将现场浇注(浇注圆柱形试样)与DFP参数优化结合起来,提出了一种液态金属有效导温系数α的实测方法。大量的实验与数值计算证实了该方法的可能性。有效导温系数α随液态金属温度的下降而减小。通过改变试样尺寸和浇注温度,探索了诸因素对液态金属有效导温系数的影响。

Hou [3] introduced a numerical analysis method to determine the effectivethermal diffusivity a from measured temperature distribution in a plate-shapedcasting. Because Hou did not consider the effect of convection currents, thedetermined values of a were highly scattered. The authors in this paperconsider the effect of convection currents and succeed in obtaining accuratevalues of a. The need to consider the effect of the convection currents lead the firstauthor to remember the lectures given by Professor P. N. Hansen of theTechnical University of Denmark in China in June 1987. In Hansen's lecturenotes, he pointed out: 'The trouble of measuring unsteady courses is to adjustthe most suitable value of the quantity wanted to the observation registered.This can be done by an iteration procedure of a mathematical model by meansof numerical calculations.' The authors combine Hansen's idea with the highly efficient DFP methodin mathematics [4,5]; the authors select polynomial as being suitable andsucceed in expressing a as a polynomial of temperature. The iteration for thecoefficients of the polynomial is automatically done with the aid of a speciallyprepared computer program. Computations are carried out for cylindricalcastings of pure aluminum and excellent agreement with experimental resultsis obtained. It is also found out that a decreases with decreasing temperature ofliquid metals.