Estimation of time-dependent heat transfer coefficient in unidirectional casting using a numerical model coupled with solidification analysis and data assimilation
Estimation of time-dependent heat transfer coefficient in unidirectional casting using a numerical model coupled with solidification analysis and data assimilation
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DOI：
10.1016/j.ijheatmasstransfer.2019.119222
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发表时间：
2020-04-01
影响因子：
5.2
通讯作者：
Ohno, Munekazu
中科院分区：
文献类型：
--
作者：
Natsume, Yukinobu;Oka, Yukimi;Ohno, Munekazu
我们最近开发了一种基于数据同化的传热系数估算方法。为了了解其在估算时效传热系数方面的作用，本文对Al-1质量%Si合金进行了单向铸造实验，得到了凝固过程中的冷却曲线。然后用实验数据验证了估计的随时间变化的传热系数。因此，可以准确地模拟实测的冷却曲线，实测曲线与模拟曲线的平均误差在0.8%以下。在冷却初期，计算得到的随时间变化的换热系数为29461.5 Wm(-2) K-1，随后迅速降至约6000 Wm(-2) K-1，随后逐渐降至约1000 Wm(-2) K-1。这些数值作为铝基合金铸件的传热系数是合理的。此外，还对数据同化设置参数的影响进行了评价。结果表明，计算中所使用的冷却曲线的位置是最重要的因素，应采用在模具表面附近位置测量的冷却曲线。该方法可以在不进行试错的情况下合理估计单向铸件的结晶器与合金液之间随时间变化的传热系数，并且可以通过凝固分析准确地再现实验测量的冷却曲线。(C) 2019 Elsevier Ltd.版权所有。
We have recently developed a method to estimate the heat transfer coefficient based on data assimilation. To understand its usefulness for estimating the time-dependent heat transfer coefficient, herein we performed unidirectional casting experiments of Al-1 mass%Si alloy and obtained the cooling curves during solidification. The experimental data were then used to validate the estimated time-dependent heat transfer coefficient. Consequently, the measured cooling curves could be accurately simulated, and the average errors between measured and simulated cooling curves were below 0.8%. The estimated time-dependent heat transfer coefficient was 29461.5 Wm(-2) K-1 at the initial stage of cooling, which rapidly decreased to about 6000 Wm(-2) K-1 and then gradually decreased to about 1000 Wm(-2) K-1 . These values are reasonable as the heat transfer coefficients for castings of Al base alloys. Additionally, the effect of the setting parameters of the data assimilation were evaluated. It was found that the position of the cooling curve(s) used in the estimation was the most important factor and a cooling curve measured at the position near the surface of the mold should be utilized. This method allows the reasonable estimation of the time-dependent heat transfer coefficient between the mold and molten alloy for unidirectional castings without using trial and error, and experimentally measured cooling curves can be accurately reproduced by solidification analysis. (C) 2019 Elsevier Ltd. All rights reserved.