Juraj Kosek - Academia.edu (original) (raw)

Papers by Juraj Kosek

arXiv (Cornell University), Dec 16, 2019

What is the maximum voltage of a cell with a given electrochemical reaction? The answer to this q... more What is the maximum voltage of a cell with a given electrochemical reaction? The answer to this question has been given more than a century ago by Walther Nernst and bears his name. Unfortunately, the assumptions behind the answer have been forgotten by many authors, which leads to wrong forms of the Nernst relation. Such mistakes can be overcome by applying a correct thermodynamic derivation independently of the form in which the reaction is written. The correct form of Nernst relation is important for instance in modelling of vanadium redox flow batteries or zinc-air batteries. In particular, the presence of corrosion can impact the OCV in the case of zinc-air batteries. "Thermodynamics is a funny subject. The first time you go through it, you don't understand it at all. The second time you go through it, you think you understand it, except for one or two points. The third time you go through it, you know you don't understand it, but by that time you are so used to the subject, it doesn't bother you anymore." (Arnold Sommerfeld)

In this contribution we present the extended model of the fragmentation process during the growth... more In this contribution we present the extended model of the fragmentation process during the growth of polymer particles in catalytic polymerizations of olefins. Both the catalyst support and the emerging polymer phase are represented by the agglomerate of micro-elements. The force interactions between micro-elements are calculated using the elastic or visco-elastic models (e.g., the Maxwell model) and positions of micro-elements are updated according to the Newton’s second law. The ternary microelement interactions and the improved implementation of monomer transport have been recently implemented into our model. Simple two-dimensional or three-dimensional porous structures of the catalyst support are used as the input for our simulations. Results of simulations describe qualitatively well morphogenetic processes in polymer particle, such as catalyst fragmentation, formation of hollow particles, etc.

Computer-aided chemical engineering, 2017

Abstract In this paper we present mathematical model for the development of foam morphology durin... more Abstract In this paper we present mathematical model for the development of foam morphology during the reactive foaming of polyurethane (PU). The model describes the most important physical phenomena from reaction kinetics and diffusion of blowing agents to wall drainage by capillary forces. We implemented the end group model for the PU polymerization, a bubble–shell model for the bubble growth and foam expansion and thin film model for the evolution of the wall thickness profile. The combined model can thus simulate the evolution of foam density, bubble size and wall thickness based on the foam recipe. The model allows us study the effect of physical parameters on the final foam morphology, and thus on the foam application properties.

Journal of Applied Polymer Science, Mar 13, 2017

The attempts to predict the swelling of semicrystalline polyolefins using equations of state have... more The attempts to predict the swelling of semicrystalline polyolefins using equations of state have not been successful so far and the few conducted experimental investigations have been limited to a narrow range of samples and conditions. This article presents a systematic video-microscopic study of the swelling induced in various grades of PE particles by the sorption of ethylene and co-monomers (propylene, 1-hexene) at condition relevant to gas-phase polymerization. Based on experimental data for various PE densities, the swelling factor H was evaluated, which enables the prediction of PE swelling by ethylene. The swelling data were compared with the corresponding gravimetrically measured sorption isotherms. In the case of ethylene and propylene sorption, the swelling significantly influences the evaluation of sorption isotherms. Conversely, the effect of swelling was negligible for higher hydrocarbons. The observed impact of swelling on the sorption is discussed based on the evaluated partial molar volumes of penetrants. V

Journal of Power Sources, 2022

Molecules, 2021

Despite intense research in the field of aqueous organic redox flow batteries, low molecular stab... more Despite intense research in the field of aqueous organic redox flow batteries, low molecular stability of electroactive compounds limits further commercialization. Additionally, currently used methods typically cannot differentiate between individual capacity fade mechanisms, such as degradation of electroactive compound and its cross-over through the membrane. We present a more complex method for in situ evaluation of (electro)chemical stability of electrolytes using a flow electrolyser and a double half-cell including permeation measurements of electrolyte cross-over through a membrane by a UV–VIS spectrometer. The method is employed to study (electro)chemical stability of acidic negolyte based on an anthraquinone sulfonation mixture containing mainly 2,6- and 2,7-anthraquinone disulfonic acid isomers, which can be directly used as an RFB negolyte. The effect of electrolyte state of charge (SoC), current load and operating temperature on electrolyte stability is tested. The result...

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Langmuir, 2019

The rheological behavior of particle suspensions is a challenging problem because its description... more The rheological behavior of particle suspensions is a challenging problem because its description depends on the interaction of two phases with different material properties. This interaction can lead to complex behavior due to acting forces at the solid-liquid interface such as lubrication. The goal of this work is to propose a method for the modeling of fluids viscoelasticity in the presence of spherical particles including fluid-particle interactions. To accomplish this, we employed a simplified approach using the Discrete Element Method (DEM) coupled with Computational Fluid Dynamics (CFD) to simulate a suspension of particles under oscillatory flow in a threedimensional computational domain. The choice of DEM provides versatility to customize the constitutive relations of particle-particle and fluid-particle interactions. Particularly, we focused on studying the effect of solid-liquid interaction (lubrication forces) on the viscoelasticity of the particulate system. To analyze the effect of this interfacial force, we simplified the particle-particle interaction to a non-adhesive elastic contact, thus avoiding aggregation of the particles. The work consists of two parts: The first one is a purely CFD model of the oscillatory motion applied to a Newtonian fluid (without particles), and the second is an extended version including DEM to simulate the viscoelasticity of the particles suspension. In this way, we can isolate the effect of fluid inertia on the viscoelasticity of the particulate system. The obtained results show that the model is capable to reproduce qualitatively the increase of the storage modulus as a function of the solid volume fraction and the

MethodsX, 2019

We propose a complex 4-point method for characterization of flow batteries. The distribution of o... more We propose a complex 4-point method for characterization of flow batteries. The distribution of ohmic and faradaic losses within a single-cell is evaluated from electrochemical impedance spectra and load curves of positive and negative half-cells measured with platinum wire pseudo-reference electrodes positioned in respective electrode compartment. The developed method can be used e.g., for the component screening and insitu durability studies on single-cell scale. The method was validated on a vanadium redox flow battery singlecell; however, it can be analogically employed for various chemistries of flow battery. Complex 4-point method for characterization of flow battery single-cell was developed. Method is based on electrochemical impedance spectra and load curve measurements. Direct evaluation of ohmic and faradaic losses distribution within battery single-cell by the method.

Journal of Power Sources, 2017

Hydrogen evolution reaction has a complex role during zinc electrodeposition. • Current efficienc... more Hydrogen evolution reaction has a complex role during zinc electrodeposition. • Current efficiency of zinc deposition is lowered by hydrogen evolution. • Rising hydrogen bubbles increase zinc limiting current density. • Current density ratio is not suitable as zinc morphology indicator.

Journal of Power Sources, 2019

Long-term durability of vanadium redox flow battery during 2000 cycles tested. • Two different fe... more Long-term durability of vanadium redox flow battery during 2000 cycles tested. • Two different felts tested as negative electrode under identical conditions. • Strong deactivation of PAN-based felt relates to increase of sp 3-hybridized carbon. • Stable performance of high surface area rayon-based felt with thermal activation.

Journal of Applied Polymer Science, 2017

Macromolecular Reaction Engineering, 2017

Due to hardening competition and increased focus on resource efficiency, efforts are made to deve... more Due to hardening competition and increased focus on resource efficiency, efforts are made to develop advanced industrial optimization and control systems with the goal to shift the (semi‐)batch production from recipe‐based to a state‐based approach. This study illustrates the steps needed for the implementation of optimization and on‐line control of semibatch emulsion copolymerization involving the development of process model, its validation and connection with control software, and the realization at pilot plant scale. The process model must be fast and robust enough to provide estimation of the process trajectory reliably and quickly. Moreover, in connection with nonlinear model predictive control (NMPC), the model has to be able to learn from the process and to update parameter values in real time, e.g., due to change of reactor jacket heat transfer. The Cybernetica CENIT software is employed for NMPC. The industrial pilot‐scale semibatch emulsion copolymerization of four comono...

Chemical Engineering Journal

Computer Aided Chemical Engineering

Abstract Semi-batch polymerization processes are traditionally operated according to rigidly pres... more Abstract Semi-batch polymerization processes are traditionally operated according to rigidly prescribed recipes prohibiting process optimisation and product property adjustment in real time. In this contribution, we focus on the development of computationally efficient model of 4-monomer semi-batch emulsion copolymerization for the use in model-based predictive control (MPC). We implemented a hybrid Monte Carlo approach consisting of two steps. First, the important process-product characteristics (conversion of monomers, reaction mixture temperature) are predicted by deterministic process model based on a set of ODEs; second, copolymer molecular architecture is generated using kinetic Monte Carlo simulation, utilizing state variables pre-calculated by deterministic model. The developed model was validated using various lab-scale recipes describing simultaneous copolymerisation of two hydrophilic and two hydrophobic monomers. Due to efficient implementation and program parallelization, the whole several-hours-long batch can be simulated within a few seconds resulting in a model applicable in MPC as a soft-sensor for the detailed molecular architecture of the produced copolymer.

Computer Aided Chemical Engineering, 2017

Abstract In this paper we present a multi-scale model for the prediction of ageing of heat insula... more Abstract In this paper we present a multi-scale model for the prediction of ageing of heat insulation properties of polyurethane (PU) foams. The model consists of higher scale model and lower scale model coupled together by the MoDeNa multi-scale framework. The higher scale model is responsible for the simulation of gas permeation through the foam, and thus calculation of gas phase composition in time. Heat insulation properties are determined through the surrogate model, which is automatically fitted to results of the lower scale model. The lower scale model takes into account foam morphology and both radiative and conductive contributions to heat transfer and calculates the foam equivalent conductivity. Solubility and diffusivity of gases in PU were determined experimentally. The overall model provides a valuable insight into the ageing process of PU foams.