Validation of the octadecane melting numerical model using a laboratory experiment

Abstract

The paper presents results of studying the melting process of octadecane, the heat-accumulating substance used in a space heat accumulator. The Stefan problem formulated for the phase transition boundary has an analytical solution only for the one-dimensional case. And in the case of the structure real geometry, it could be solved only using the numerical methods, in particular, by simulation in the ANSYS Fluent universal software system for the finite element analysis. To validate the developed numerical models, model experiments were carried out on octadecane melting in the cylindrical glass flask with heat-insulated side walls, the heater was positioned at the flask lower end. Two-dimensional and three-dimensional numerical models were investigated at the heating powers of 7.1 W and 34.2 W. The molten substance fraction dynamics in the two-dimensional and three-dimensional models was compared to the experimental data. Heat losses in heating the structure and convective heat exchange with the external media were taken into account. Results of numerical and laboratory experiments are presented, which could be used in testing the constant power heating model of a heat-accumulating substance. The results obtained show that with absolute temperature alteration in the heat-accumulating substance by an insignificant value (up to 10°C), the Boussinesq approximation provides results well verified by the experimental data.