Heat transfer during diffusion-controlled unidirectional solidification of binary mixtures: effect of material advection

Autor: Abdul Najim, Shankar Krishnan
Rok vydání: 2021
Předmět:
Zdroj: Sādhanā. 46
ISSN: 0973-7677
0256-2499
DOI: 10.1007/s12046-021-01749-3
Popis: This work aims to investigate the effect of material advection on heat transfer during diffusion-controlled unidirectional solidification of binary mixtures analytically. A mathematical model was developed considering the process as a one-dimensional, two-phase, three-region Stefan problem. Two cases are considered, viz., (1) without material advection, and (2) with material advection. The mathematical model’s solution predicts the temperature distributions in the solid, mushy, and liquid region, the thickness of the mushy region, and heat flux. The analytical results were compared against experimental data from the literature at low (0.69°C/mm), medium (0.92°C/mm), and high (1.52°C/mm) temperature gradients across NH4Cl-H2O mixture. The solution of case-2 predicted the thickness of the mushy region accurately compared to case-1 for a low and medium temperature gradient. A parametric study was undertaken to investigate the effect of pulling speed and initial concentration of NH4Cl in NH4Cl-H2O mixture on heat transfer at 0.92°C/mm. The temperature profile in the system, the thickness of the mushy region, and heat flux were found to depend on the pulling speed and initial concentration of NH4Cl. However, the shape of the temperature profile was observed to depend on the pulling speed exclusively. For a fixed value of the initial concentration of NH4Cl and temperature gradient, increasing the pulling speed makes the profile progressively nonlinear in the mushy and liquid region. The increase in non-linearity of a temperature profile with pulling speed was observed to be larger in the liquid region than the mushy region due to a large increase in the Peclet number.
Databáze: OpenAIRE
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