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    Assessment of the Influence of Input Parameters in CFD Simulation of Ventilation in an Experimental Chamber
    (IOP Publishing, 2024-07-08) Kučírek, Pavel; Šikula, Ondřej
    The aim of this paper is to evaluate the impact of selected input parameters on the accuracy and usability of CFD simulations. This paper compares the achieved results of Computational Fluid Dynamics (hereinafter CFD) simulations of air age with the ventilation results of a specific experimental box. A total of 16 variants were simulated for different simulation settings, including various computational domains and meshes in OpenFOAM, Ansys Fluent, DesignBuilder, and BlueCFD-AIR software. The paper primarily focuses on the importance of meeting the suitability criterion for the yPlus parameter used in the wall function of turbulent models k- and k- SST, and the resulting air age. Simulation with the best yPlus parameter shows the best agreement in airflow velocity and air age with the experiment. Overall, this led to an improvement in accuracy by 41 % compared to original simulation and 56 % compared to the previous our best OpenFOAM simulation.
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    Mould Risk in Technical Room in Four Underground Water Reservoirs
    (IOP Publishing, 2024-07-08) Nováková, Iva; Šikula, Ondřej
    This conference article analyses the indoor climate of a technical room in four underground water reservoirs. This indoor climate with minimal input energy is specific by high relative humidity and low air temperature, as shown in the experimental measurement. The unsteady 2D numerical simulation of the detail section (partly sub-terrain peripheral wall and floor) in software Calculation Area 4.0e calculates fluctuation of internal surface temperature and relative humidity. Finally, the empirical predictive Finnish VVT model predicts the seasonal mould risk on the internal surface of the peripheral wall.
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    Circular Free Jets: CFD Simulations with Various Turbulence Models and Their Comparison with Theoretical Solutions
    (IOP Publishing Ltd, 2019-02-25) Kmecová, Miroslava; Šikula, Ondřej; Krajčík, Michal
    The theory of turbulent free jet is fundamental for the design of comfort ventilation, as free jets frequently occur in mixing and personalized ventilation systems and their characteristics strongly influence the air quality in the breathing zone of an occupant. The aim of this research is to provide recommendations that help researchers and practitioners improve the accuracy and reliability of their computational models of ventilation systems involving circular free jets. To accomplish this, a review of existing theoretical calculation models is performed, and these models are subsequently investigated by computational fluid dynamics. The theoretical solutions of free jets are compared with CFD simulations using various turbulent models such as the standard k-epsilon model, the k-epsilon realizable model, the standard k-omega model, the shear stress transport (SST) k-omega model, and the Reynolds stress model (RSM). The simulated models are represented by profiles of the centreline velocity for a free jet emanating from a round nozzle, because such presentation of the data proved to be particularly helpful for the comparison of the turbulence models. The k-omega SST turbulence closure scheme with standard coefficients produced results of the centreline velocity closest to the average of theoretical solutions investigated, whereas the discrepancy between the simulations and the theoretical models was about 60 % with the k-epsilon standard turbulence model.
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    Energy, economic and environmental analysis of opened natural healing water source
    (EDP Sciences, 2019-08-13) Miček, Denis; Hirš, Jiří
    European´s low carbon economy is the main target in the way of the reducing greenhouse gases at the Earth´s atmosphere. The most promising way is in maximal usage of renewable sources of energy such as geothermal energy, which was in the year 2010 only 1 GWh at the Slovak republic. The paper refers to the detailed analyzation of the opened natural healing water system in the historical spa town Piešťany as one of the most perspective sources of the renewable energy in the Slovak republic primary used for healing procedures. Analysis is based on experimental measurement and numerical simulation of graphite block heat exchanger Korobon which was constructed in the year 1965 and resists highly mineralized water. The main function of this heat exchanger is to cool down the hot natural healing water with average temperature 60 °C to the 37 °C. The biggest impact is in the designing of new heat exchanger with the same quality properties as current one in accordance with the innovation of obsolete energy management at historical spa town. Such as solution allows us to save 5578 cubic meters of ground gas daily, necessary to be used for the same heat generation.
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    Energy-Pile Model Verification
    (KGH, 2020-12-31) Šikula, Ondřej; Slávik, Richard; Eliáš, Jan; Oravec, Jakub; Kašpar, Antonín
    Equipping the foundation piles with a liquid circuit pipeline makes it possible to use the advantageous thermal capacity of the soil for heating and cooling buildings at low cost. The energy performance of the energy-pile in a soil is a transient phenomenon dependent on many parameters, which could be investigate by a computational model. The contribution deals with the description and verification of a new numerical computational software based on a simpli-fied 2D and 2D rotational symmetrical heat conduction model being developed for energy-piles modeling.