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Original scientific paper https://doi.org/10.2298/TSCI19S4153KThe article presents the methodology and results of a parametric analysis performed to investigate the effects of changes in the curvature of the solar concentrator mirror on its ability to focus the radiation. Working conditions of the concentrator, i. e. possible values of radiation intensity, were adopted according to irradiance typical for Poland, and, therefore, similar to the conditions in many European countries. The curvatures of examined mirrors were obtained by modification of a parabolic curve. The calculations were conducted for two cases: when the Sun radiation falls completely directly and when it's half diffuse. The 2-D simulations were conducted in ANSYS FLUENT 18.2 software. Discrete ordinates model was employed to simulate radiation phenomenon. Also, a sensitivity analysis was carried on discrete ordinates model parameters and density of the computational mesh. The results allow stating that some of the new curvatures provide only slightly worse focus than the classical parabolic shape, but also show greater insensitivity to the increasing share of diffusive part of radiation. The presented model is a quick and proven tool for testing new curvatures of solar concentrator mirrors.

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The paper presents a two-dimensional computational fluid dynamics (CFD) model of lab-scale fixed-bed pyrolytic reactor. The goal of the work was to verify assumptions regarding construction and operating parameters of the pyrolytic reactor and examining heat transfer conditions and the final temperature distribution in the system taking into account the endothermic pyrolysis reactions occurrence. The impact of the most important numerical parameters on simulation results was also investigated. Model was prepared in ansys fluent 18.2 software. The studies have shown large temperature gradients both in the biomass deposit and at the reactor walls. The analysis has confirmed the validity of the proposed reactor construction concept and allowed to specify the range of thermal power value necessary for obtaining the pyrolysis process in a system with given properties and dimensions. Increasing the heat flux supplying the reactor from 160 to 480 W caused acceleration and intensification of biomass thermal decomposition, while the average final bed temperature after 10 min of heating in each case was reaching similar level. Low thermal conductivity of the bed and strong heat absorption due to pyrolysis suppress heat transfer through the bed, which causes significant temperature differences between the warmest and coldest regions of the bed. However, temperature unevenness and hence the unevenness of the pyrolysis process can provide favorable conditions for measuring the gas composition leaving the reactor due to the relatively balanced time stream of pyrolysis gases.

Paper present the experimental and numerical analysis of biomass photopyrolysis process. The experimental tests is performed on the solar pyrolysis installation, designed in Institute of Thermal Technology, Gliwice. It consist of the copper reactor powered by artificial light simulating sun. The paper shows the result of the solar pyrolysis of wood. The yield of the main fraction as a function of the process temperature is presented. Additionally the gas composition is determined. The numerical model is prepared in the Ansys Fluent 18.2 software, which allow at the same time for capturing geometry of the real system and easy change of input data. The results indicate that both the product yields (liquid, solid and gaseous) and gas components shares are strongly influenced by pyrolysis parameters and feedstock composition.