The analyzed heat accumulator is a key element in a hybrid heating system. In this paper, analytical and numerical models of the ceramic heat accumulator are presented.The accuracy of finite difference methods will be assessed by comparing the results with those obtained from the exact analytical solution.

In this article a three-dimensional mathematical model of radiofrequency ablation during open-heart surgery is presented. It was developed to study temperature field distribution into myocardial tissue. This model uses an anatomically correct 3D model for the left atrium, obtained by magnetic resonance imaging (MRI) processing of a patient; takes into account thermoelectric characteristic differences depending on the area of electric current application; considers cooling by the air flow. An ex-vivo experiment on the pig’s heart was performed where the depth of myocardium tissue damage was measured for the model validation. It was shown that the deviation of the model data from the experiment is within the limits of instrumental measurement error. The developed model is proposed to be used for heart ablation procedures planning, or new equipment development.

The article presents the use of computer graphics methods and computational geometry for the analysis on changes of geometrical parameters for a mixed zone in resistance-heated samples. To perform the physical simulation series of resistance heating process, the Gleeble 3800 physical simulator, located in the Institute for Ferrous Metallurgy in Gliwice, was used. The paper presents a description of the test stand and the method for performing the experiment. The numerical model is based on the Fourier-Kirchoff differential equation for unsteady heat flow with an internal volumetric heat source. In the case of direct heating of the sample, geometrical parameters of the remelting zone change rapidly. The described methodology of using shape descriptors to characterise the studied zone during the process allows to parametrise the heat influence zones. The shape descriptors were used for the chosen for characteristic timing steps of the simulation, which allowed the authors to describe the changes of the studied parameters as a function of temperature. Additionally, to determine the impact of external factors, the remelting zone parameters were estimated for two types of grips holding the sample, so-called hot grips of a shorter contact area with the sample, and so-called cold grips. Based on the collected data, conclusions were drawn on the impact of the process parameters on the localisation and shape of the mushy zone.