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A multiphase model for exploring electrochemical Marangoni flow
(Elsevier, 2023-10-01) Karimi-Sibaki, Ebrahim; Vakhrushev, Alexander; Kadylnykova, Anastasiia; Wu, Menghuai; Ludwig, Andreas; Boháček, Jan; Kharicha, Abdellah
A multiphase numerical model based on the volume of fluid (VOF) method is proposed to simulate the transient, electrochemically-generated Marangoni flow in a system comprising a NaOH electrolyte and a eutectic gallium–indium (EGaIn) metal droplet. The model incorporates appropriate equations to accurately represent the transport phenomena, including flow, electric potential, and electric current density, within the entire system. The model includes the transient variation in the interfacial tension as a function of electric current density at the interface, leading to the generation of Marangoni flow and enabling the tracking of droplet shape evolution. Notably, the model successfully captures the elongation of the droplet towards the cathode, which is validated through comparison with available experimental data.
Thermal performance of shell-and-tube polymeric hollow fiber heat exchangers as oil coolers
(Elsevier, 2024-10-25) Astrouski, Ilja; Kůdelová, Tereza; Bartuli, Erik
Motor oil must be appropriately treated in motors, and aluminum plate heat exchangers are used to cool it. An aluminum heat exchanger is an additional part of the oil treatment module, which increases its size and weight. Two compact plastic shell-and-tube heat exchangers were tested alongside with aluminum heat exchanger to evaluate the efficiency of the plastic cooling core inside the oil module. A total of 63 experimental points were tested on three heat exchangers with good thermal balance (discrepancy of about 1,8 %), and the data were used to evaluate the heat transfer coefficients. While plastic unit PA11 showed the heat outputs exceeding the heat output of the aluminum plate unit by about 7 %, the pressure drops were about ten times higher. The unit PEEK showed good performance and pressure drops on the oil side, but the heat transfer was limited by a small heat transfer surface. Analysis of thermal resistances confirmed that the thermal resistance between the wall and the oil is dominant due to the oil's low thermal conductivity and high viscosity. The results showed that optimization of the fiber structures is needed, aiming to increase the oil flow around the fiber structures.
Potential use of blast furnace slag for filtration membranes preparation: A pilot study
(IOP Publishing, 2018-07-12) Bílek, Vlastimil; Bulejko, Pavel; Kejík, Pavel; Hajzler, Jan; Másilko, Jiří; Bednárek, Jan; Tkacz, Jakub; Kalina, Lukáš
This paper investigates the possibilities of the use of sodium hydroxide activated blast furnace slag for preparation of filtration barriers. The motivation for this research is searching for cheaper and more eco-friendly alternative to sintering, which is commonly used for filtration membranes preparation. Such an alternative could be alkaline activation, which is able to bind slag particles together. Low amount of activator, low water to slag (w/s) ratio together with pressure compaction was used to obtain microstructure with preserved continuous porosity. To confirm this presumption scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analyses were carried out.
Low Cost Membrane Contactors Based on Hollow Fibres
(EDP Sciences, 2012-04-16) Dohnal, Mirko; Veselý, Tomáš; Raudenský, Miroslav
Membrane contactors are used to solve different chemical engineering tasks (e.g. water saturation with gases). Such elements are traditionally used for bubble less oxidation of blood. However, their industrial applications are rather limited by their high investment costs. This is probably the main reason why membrane contactors are not used so widely, e.g. classical absorbers, etc. If potted bundles of hollow fibres are available, then it is a relatively simple task to design an ad hoc membrane contactor. However, it must be emphasised that to achieve the highest mass transfer efficiency requires a rather time-consuming tuning of each ad hoc designed contactor. To check the differences by water evaporation were aligned two modes, the water inside the hollow fibre membrane and fan air outside, next with the water outsides and flowing pressure air inside the membrane.
Landfills multiple goal optimization using equationless qualitative relations
(Science Publication, 2014-02-05) Dohnal, Mirko
Landfills are unique and difficult to measure. Their optimization must be solved with a severe lack of information. The privilege of not utilizing information items based on common sense cannot be afforded, as this represents an important part of the available ad hoc landfill knowledge related to e.g., economics, sociology. Therefore, a flexible, formal tool for dealing with the common sense knowledge and data of a non-numerical nature is required. The classical quantitative tools, e.g., statistics, are inefficient for dealing with such sets of non-quantitative information items as interviews. Qualitative quantification is information non-intensive. It is based on just three values-positive, zero and negative; increasing, constant and decreasing. A qualitative model can be used to generate all possible qualitative activities/scenarios. It means that the past history and future scenarios of the landfill under study are known, given the model is correct. The scenarios can be screened against the prescribed trends (maximization or minimization) of objective functions, to identify all possible ways of achieving optimal results. A case study with four mutually competing objective functions is presented in details. No prior knowledge of qualitative reasoning is required.

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