Modeling of Transient Heat Transfer in Zinc Fixed-Point Cell

The current fixed-point calibration practice relies on furnaces that provide best achievable uniform temperature distribution, limiting the temperature gradients to about 10 mK to 20 mK along the ingot length. This paper outlines a numerical study conducted to further reveal the influences of the temperature gradients on the physical process involved and to bring some estimates for their influence on the plateau behavior. The mathematical model of the physical process is presented, along with the numerical models used through the FLUENT software package: the transient conductive heat transfer model, the discrete ordinates radiative heat transfer model, and the solidification model. The final model is reduced to axial symmetry for the sake of feasibility with the available computational resources. The convective heat transfer is neglected as it was considered to be of minor importance for the process itself. The geometrical model covers the entire fixed-point cell assembly and distinguishes each of its elements. The paper presents six cases, varying the temperature gradients in the boundary conditions and the cold-rodding. Their influence on the physical process is explained through the temperature fields presented. The study shows that a gradient of ±1K · m− 1 influences the plateau solely in its duration by either prolonging or shortening it by approximately 20 min.