EÚ-odbor termomechaniky a techniky prostředí

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Packing versus cavity: Zone-Specific contributions to mass transfer in rotating packed bed absorption process
(ELSEVIER SCIENCE SA, 2025-08-11) Blatkiewicz, Michal; Majdzik, Małgorzata; Lewandowski, Gniewomir; Piątkowski, Marcin; Jaskulski, Maciej; Hájek, Ondřej; Malý, Milan; Gorak, Andrzej
A pilot-size rotating packed bed unit has been equipped with an infrared system for liquid phase analysis and a special interceptor that allows for online sampling of the absorbent solution at two points in the RPB: the outer periphery of the packing and the liquid outlet. Such a system allows to determine specific contributions of the packing zone and the cavity zone to the overall mass transfer. A standard chemical system of carbon dioxide and an aqueous solution of sodium hydroxide was used to determine reactive absorption efficiency under different packing and outer casing diameters, as well as varying rotational speeds, gas and liquid flow rates, and inlet absorbate concentrations. CO2 removal up to 27 % was achieved. Depending on geometrical configurations and process conditions, the cavity zone contribution in total absorption efficiency varied between 0 % and 46 %. Outer casing diameter had deciding effect on the mass transfer in the cavity zone, but it was also significantly affected by the packing size and rotational speed.
Detailed spray analysis of airblast atomization of various fuels in a reacting environment
(Elsevier, 2024-08-01) Kardos, Réka Anna; Rácz, Erika; Malý, Milan; Jedelský, Jan; Józsa, Viktor
Understanding spray evolution in a reacting environment is critical to designing advanced, clean combustion systems. The processes in the upstream region determine flame shape, stability, ignition characteristics, pollutant emission, and combustion efficiency. The developed spray is never achieved in combustion since the early regions feature primary and secondary atomization, while droplets evaporate as they approach the flame. Consequently, there is no thermodynamic equilibrium before the flame front. The principal goal of this paper is to provide detailed information to model developers on various sprays measured by a Phase Doppler Anemometer; the processed measurement data is available as supplementary material, while the raw data will be provided upon request. Four different fuels were tested: diesel fuel, aviation kerosene type JP-8, biodiesel, and a 50 % biodiesel-diesel blend by volume. The plain -jet airblast atomizer was tested at four atomization gauge pressures (0.3, 0.45, 0.6, 0.75 barg). Therefore, sixteen different sprays were measured along one spray diameter at each of four downstream distances of 15, 25, 35, and 45 mm, measured from the nozzle tip. The paper details the droplet size distribution, droplet axial velocity, fluctuations, and correlation between size and velocity to facilitate a comprehensive understanding of liquid fuel sprays. This latter measure helps identify the overshooting phenomenon, i.e., localizing the regions where the large droplets move faster than the gas phase.
Heat Flux Assessment in Reciprocating Compressor
(EPJ Web of Conferences, 2024-07-04) Rapta, Patrik; Hejčík, Jiří; Jícha, Miroslav
Heat transfer inside a cylinder and the cylinder head of a reciprocating compressor is responsible for the majority of thermodynamic losses in these devices. Both the magnitude and direction of the heat flux through the walls of those components change several times during a single revolution. They are directly dependent on the position of the piston and suction/discharge valves. A better understanding of these thermal processes could lead to better and more targeted cooling. This would result in higher efficiency of the reciprocating compressors. In this paper, two experimental methods for determining heat flux are used. The first method uses heat flux sensors to measure heat flux directly. The other one is focused on the indirect assessment of heat flux via surface-mounted thermocouples. To tie the measurement to the position of the crankshaft, both sensors are coupled to a rotary encoder. The rotary encoder sends a signal once per revolution when the piston is in the top dead center position to trigger signal acquisition. The results show signs of reaching a quasi-steady state and would most likely require sampling of the signal more times per revolution.
Flow Behaviour of Inhaled Fibres – Equations of Motion and Preliminary Results of Real Trajectories Recorded by a High-Speed Camera
(EDP Sciences, 2020-11-18) Lízal, František; Bělka, Miloslav; Malý, Milan; Cabalka, Matouš; Jedelský, Jan; Jícha, Miroslav
The ability to precisely predict the fate of inhaled fibres is important for toxicologists as well as for pharmaceutists struggling to utilize fibres as carriers of a medication. However, the complexity of fibre movement in human airways still represents a significant challenge for programmers of codes for simulation of fibre flow. This conference contribution introduces the theoretical equations of fibre motion which can be used for calculation of the fate of inhaled fibres, and also, in the second part, first results of high-speed camera recorded trajectories of fibres downstream of a realistic human airway bifurcation are presented as an illustration of the real behaviour of fibres in the lungs.
Lagrangian tracking of fibres in a channel flow
(EDP Sciences, 2018-11-13) Volavý, Jaroslav; Farkas, Árpád; Lízal, František; Elcner, Jakub; Jícha, Miroslav
Tracking of fibres in a fluid flow is much more complicated than tracking of spherical particles. In fibre motion, the orientation of fibre against the flow direction plays a very important role. In addition to the standard equation of motion, additional equations for orientation and angular velocity must be solved during the tracking of fibres. A mathematical model describing fibre motion is introduced in this work. Capabilities of this model are demonstrated through simulations of fibre transportation by air in a channel flow. The importance of the terms in the equation of angular velocity are discussed.

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