NUMERICAL SIMULATION OF THERMOLUMINESCENCE QUARTZ PARTICLE

Author(s):  
Vladimir S. SHEINKMAN ◽  
Oleg A. SIMONOV ◽  
Yuliya Yu. ERINA

One of the widely used methods for studying minerals is the thermoluminescent (TL) method, which is used to date Quaternary sedimentary rocks. Usually, the difficulty in using TL dating is the lack of information about the structure of the mineral used in the experiment. For reliable interpretation of experimental data, the authors applied the digital twin method. In this case, all stages of the transformation of the mineral used are modeled from its burial in sedimentary rocks to the stimulation of the TL-signal splash in it under laboratory conditions on special installations, taking into account the unevenness heat transfer inside the sample of this mineral. The paper presents the results of numerical simulation of the TL signal from a spherical particle of natural quartz. The modeling was carried out in two stages. At the first stage, the influence of the burial time of quartz in the sedimentary rocks on its TL signal was determined. For this, the problem was posed of the accumulation of the crystal lattice quartz, information about the time of its presence in the natural radiation field. At the second stage, the TL signal from a spherical particle was simulated, which was heated in an experimental setup from the surface according to a linear law. It was found that, firstly, the burial time of quartz affects the shape of the TL-curve and, therefore, the mineral is applicable for dating. Secondly, it is necessary to control the heating mode of the quartz sample, since at high heating rates, heat transfer irregularities are significant for particles with a large radius. It also affects the shape of the TL signal and, as a result, can make it difficult to obtain age definitions or distort them. To assess the effect of non-uniformity of heat transfer, a dimensionless similarity parameter was proposed, which connects the radius of the particles and the heating rate.

Author(s):  
Robin Schmidt ◽  
Petr A. Nikrityuk

The purpose of this work was the direct numerical simulation of heat and fluid flow by granular mixing in a horizontal rotating kiln. To model particle behaviour and the heat and fluid flow in the drum, we solve the mass conservation, momentum and energy conservation equations directly on a fixed Eulerian grid for the whole domain including particles. At the same time the particle dynamics and their collisions are solved on a Lagrangian grid for each particle. To calculate the heat transfer inside the particles we use two models: the first is the direct solution of the energy conservation equation in the Lagrangian and Eulerian space, and the second is our so-called linear model that assumes homogeneous distribution of the temperature inside each particle. Numerical simulations showed that, if the thermal diffusivity of the gas phase significantly exceeds the same parameter of the particles, the linear model overpredicts the heating rate of the particles. The influence of the particle size and the angular velocity of the drum on the heating rates of particles is studied and discussed.


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