Energetický ústav

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Complex 3D-Printed Heat Transfer Surfaces: An Assessment and Comparison of Tools for Implicit Geometry Modelling
(AIDIC Servizi S.r.l., 2024-12-30) Zálešák, Martin; Klimeš, Lubomír; Charvát, Pavel; Špiláček, Michal
In the design of heat exchangers (HXs), an obvious effort is to maximise the heat transfer efficiency and performance while keeping the dimensions and costs of HXs as low as possible. Extended surfaces are a common technique for heat transfer enhancement, leading to an enlarged surface for the interaction of heat transfer fluids. Fins represent the most frequent extended surfaces used in the HX design. In the past, the shape of fins used in HXs was rather simple due to the limited capabilities of the available production technology. However, the rapid development of additive manufacturing (AM) and 3D printing has opened new possibilities in design and production. The AM allows for the production of HXs comprising heat transfer surfaces with a complex topology, which can possess a very high surface-to-volume ratio. In this respect, triply periodic minimal surfaces (TPMS) seem to be very promising. Gyroids and lidinoids are typical examples of such TPMS. Computer simulations are a common approach in the design of HXs. Simulations of HXs with such complex surfaces are, however, challenging. In the case of computational fluid dynamics (CFD) tools, the necessary input is the computational mesh, which is closely related to the domain geometry. The creation of the domain geometry adopting TMPS is rather demanding as TMPS are defined by implicit mathematical relationships and standard computer-aided design (CAD) modellers cannot be utilised for this purpose. The study presents an assessment and comparison of available computer tools for the implicit modelling and preparation of the TPMSbased geometry with implicit modelling. The results indicate that both commercial as well open-source tools exist for this purpose, enabling different levels of flexibility and user-friendliness.
Liquid dispersion in inner cavity of rotating packed bed
(EDP Sciences, 2024-07-04) Hájek, Jiří; Malý, Milan; Hájek, Ondřej; Cejpek, Ondřej; Rapta, Patrik; Jícha, Miroslav
Majority of power producing, and industrial processes generate a significant amount of carbon dioxide (CO2). To reduce their CO2 emissions, CCS (carbon capture and storage) can be used. One of the ways for CO2 capture is rotating packed bed (RPB), which operates on a similar principle as an absorption tower. However, in the RPB, mass transfer rate is driven by a centrifugal force, hence the RPB could be much smaller than the absorption tower, which relay on gravitational force. Also, the internal design of the RPB could affect efficiency of CO2 capture. There are several types of packing design, such as raised mesh, Zigzag, metal foam, or wire mesh. This study is focused on testing and construction of a transparent wire mesh packing, which could be used for analyse of fluid behaviour inside the packing e.g., a flow character, a liquid hold up and a liquid-gas interfacial. The operating packing speeds in the experimental part were 300 rpm, 600 rpm, 1200 rpm and 1800 rpm. The operating liquid (water) was supplied by six plain orifice nozzles with 1.44 mm diameter. Water was supplied to the system in a range of liquid flow rates from 44 to 176 kg/h. This corresponds to the jet velocity of 1.25 – 5.00 m/s. The observed area was the entry of the water jet into the wire mesh, where the atomization is the most intense. For the measurement, a high-speed camera was used. It is evident from results that with the higher jet velocity, the penetrating distance is larger, and the atomization is more intense.
Research of transport and deposition of aerosol in human airway replica
(EDP Sciences, 2010-11-24) Lízal, František; Jedelský, Jan; Elcner, Jakub; Ďurdina, Lukáš; Venerová, Tereza; Mravec, Filip; Jícha, Miroslav
Growing concern about knowledge of aerosol transport in human lungs is caused by great potential of use of inhaled pharmaceuticals. Second substantial motive for the research is an effort to minimize adverse effects of particular matter emitted by traffic and industry on human health. We created model geometry of human lungs to 7th generation of branching. This model geometry was used for fabrication of two physical models. The first one is made from thin walled transparent silicone and it allows a measurement of velocity and size of aerosol particles by Phase Doppler Anemometry (PDA). The second one is fabricated by stereolithographic method and it is designed for aerosol deposition measurements. We provided a series of measurements of aerosol transport in the transparent model and we ascertained remarkable phenomena linked with lung flow. The results are presented in brief. To gather how this phenomena affects aerosol deposition in human lungs we used the second model and we developed a technique for deposition fraction and deposition efficiency assessment. The results confirmed that non-symmetric and complicated shape of human airways essentially affects transport and deposition of aerosol. The research will now focus on deeper insight in aerosol deposition.
Hydrodynamic cavitation-enhanced activation of sodium percarbonate for estrogen removal
(IWA Publishing, 2023-12-01) Odehnalová, Klára; Přibilová, Petra; Maršálková, Eliška; Zezulka, Štěpán; Pochylý, František; Rudolf, Pavel; Maršálek, Blahoslav
The present paper investigated the potential of hydrodynamic cavitation (HC) as an effective tool for activating sodium percarbonate (SPC). The method's efficiency was demonstrated by effectively removing estrogens, which are pollutants that have adverse impacts on aquatic ecosystems. The effects of the SPC concentration, temperature of solution, and cavitation time were evaluated. After SPC/HC treatment, the removal of estrogens was monitored by LC-MS/MS. Already after 4 s of treatment and 24 h of reaction time, more than 97% of estrogens (initial concentration of 300 ng/L) were removed. The effect of post-treatment time is not considered in several papers, even though it seems to be crucial and is discussed here. The results were supported by the values of degradation rate constants, which fit the pseudo-first-order kinetic model. We also verified that HC alone was not effective for estrogen removal under the selected conditions. The sustainability of the SPC/HC system was evaluated based on electric energy per order calculation. The combination of SPC and HC is a promising approach for rapidly degrading micropollutants such as estrogenic compounds without the need for additional technological steps, such as pH or temperature adjustment.
Comparison of methods for evaluation of aerosol deposition in the model of human lungs
(EDP Sciences, 2014-03-25) Bělka, Miloslav; Lippay, Josef; Lízal, František; Jedelský, Jan; Jícha, Miroslav
It seems to be very convenient to receive a medicine by inhalation instead of injection. Unfortunately transport of particles and targeted delivery of a drug in human respiratory airways is very complicated task. Therefore we carried out experiments and tested different methods for evaluation of particle deposition in a model of human lungs. The model included respiratory airways from oral cavity to 7th generation of branching. Particles were dispersed by TSI Small-scale Powder Disperser 3433 and delivered to the model. The model was disassembled into segments after the deposition of the particles and local deposition was measured. Two methods were used to analyse the samples, fluorescence spectroscopy and optical microscopy. The first method was based on measuring the intensity of luminescence, which represented the particle deposition. The second method used the optical microscope with phase-contrast objective. A dispersion of isopropanol and particles was filtrated using a vacuum filtration unit, a filter was placed on glass slide and made transparent. The particles on the filter were counted manually and the deposition was calculated afterwards. The results of the methods were compared and both methods proved to be useful.

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