Mechanical Engieering, Shahrood University of Technolgy
In this study, a mathematical model is introduced to simulate the coupled heat transfer equation and Stefan condition occurring in moving boundary problems such as the solidification process in the continuous casting machines. In the continuous casting process, there exists a two-phase Stefan problem with moving boundary. The control-volume finite difference approach together with the boundary immobilization method is selected to predict the position of moving interface and the temperature distribution. The approach is validated by some available models and the agreement is found to be satisfactory. Effects of the governing parameters such as Stefan number and casting speed on the evolution of the freezing front and temperature distributions are investigated. It is found that the variation of Stefan number has a strong influence on the growth of the shell thickness and the temperature distributions. For the same values of heat transferred from the mold, increasing Stefan number has significant results such as: accelerating the solidification process and increasing the solid thickness, enhancing the local heat flux in the liquid, and broadening the liquid zone affected by the cooling water jacket. As the casting speed becomes higher, the molten flow leaves the mold faster and the solid thickness entering the secondary cooling stage is decreased; meanwhile, the central liquid region has less time to be affected by the cooling water. Reducing casting speed results in decreasing the solid temperature; in other words, the solid layer becomes cooler.