Numerical Solution And Application Of Heat Transfer Model With Phase Change

It is difficult to obtain analytical solutions for many heat transfer models with phase change. Most of them have to be solved by using numerical methods. In this paper, the finite difference method for phase change is applied to simulate the permafrost temperatures of one-dimensional model, and analyze the influence of unfrozen water on the numerical simulation results of permafrost thermal regime. What's more, the finite element method for phase change is applied to simulate the permafrost temperatures of two-dimensional model, and analyze the thermal regime of roadbed with and without insulation.This paper is divided into three parts.In the first part,the development of numerical theory are introduced simply.In the second part,it is studied to the theory and application of one-dimensional finite difference model for phase change problems. Based on the observed ground temperature data and the soil thermal and physical properties derived from Barrow, Alaska, the ground temperatures at depths of 0.29, 0.50 and 1.0m at Barrow is simulated, by using a one-dimensional finite difference model for phase change problems. Two simulation cases were conducted by considering the unfrozen water and neglecting the unfrozen water. The simulated and measured soil temperatures at different depths also were compared. The calculated results show that unfrozen water has strong influence on the numerical simulation results of permafrost thermal regime. In the third part,The theory and the application of 2-D finite element analysis for phase change problems is studied. Based on the observed ground temperature data and the soil thermal and physical properties derived from Fenghuoshan permafrost zone of Tibet, the thermal states of roadbed at Fenghuoshan permafrost zone is simulated, by using Two-dimensional finite element model for phase change problems, when the insulation is not be set in the roadbed, or it's placed at the depths of 0.5, 1.0 and1.5m. Then it is compared the four thermal regimes of the fifteenth year at the center axis of the roadbed. Furthermore, the four thermal regimes of the 30th , Octorber of the fifteenth year are done too. Based on the numerical results,it can be concluded that EPS material is effective in the frozen earth roadbed project, and the higher the insulation is placed, the more the increased heat flow from the road surface is hindered.