International Conference Fluid Power 2019
Opis: The International Fluid Power Conference is a two day event, intended for all those professionally-involved with hydraulic or pneumatic power devices and for all those, wishing to be informed about the ‘state of the art’, new discoveries and innovations within the field of hydraulics and pneumatics. The gathering of experts at this conference in Maribor has been a tradition since 1995, and is organised by the Faculty of Mechanical Engineering at the University of Maribor, in Slovenia. Fluid Power conferences are organised every second year and cover those principal technical events within the field of fluid power technologies in Slovenia, and throughout this region of Europe. This year's conference is taking place on the 19th and 20th September in Maribor.
Ključne besede: fluid power technology, components and systems, control systems, fluids, maintenance and condition monitoring
Objavljeno: 24.02.2020; Ogledov: 303; Prenosov: 23
Povezava na datoteko
High-Perssure process design for polymer treatment and heat transfer enhancementGregor Kravanja
, 2018, doktorska disertacija
Opis: The doctoral thesis presents the design of several high-pressure processes involving »green solvents« so-called supercritical fluids for the eco-friendly and sustainable production of new products with special characteristics, fewer toxic residues, and low energy consumption. The thesis is divided into three main parts: polymer processing and formulation of active drugs, measurements of transport properties form pendant drop geometry, and study of heat transfer under supercritical conditions.
In the first part, special attention is given to using biodegradable polymers in particle size reduction processes that are related to pharmaceutical applications for controlled drug release. The PGSSTM micronization process was applied to the biodegradable carrier materials polyoxyethylene stearyl ether (Brij 100 and Brij 50) and polyethylene glycol (PEG 4000) for the incorporation of the insoluble drugs nimodipine, fenofibrate, o-vanillin, and esomeprazole with the purpose of improving their bioavailability and dissolution rate. In order to optimize and design micronization process, preliminary transfer and thermodynamic experiments of water-soluble carriers (Brij and PEG)/ SCFs system were carried out. It was observed that a combination of process parameters, including particle size reduction and interactions between drugs and hydrophilic carriers, contributed to enhancing the dissolution rates of precipitated solid particles.
In the second part, a new optimized experimental setup based on pendant drop tensiometry was developed and a mathematical model designed to fit the experimental data was used to determine the diffusion coefficients of binary systems at elevated pressures and temperatures. Droplet geometry was examined by using a precise computer algorithm that fits the Young–Laplace equation to the axisymmetric shape of a drop. The experimental procedure was validated by a comparison of the experimental data for the water-CO2 mixture with data from the literature. For the first time, interfacial tension of CO2 saturated solution with propylene glycol and diffusion coefficients of propylene glycol in supercritical CO2 at temperatures of 120°C and 150°C in a pressure range from 5 MPa, up to 17.5 MPa were measured.
Additionally, the drop tensiometry method was applied for measuring systems that are of great importance in carbon sequestration related applications. The effect of argon as a co-contaminant in a CO2 stream on the interfacial tension, diffusion coefficients, and storage capacity was studied.
In the third part, comprehensive investigation into the heat transfer performance of CO2, ethane and their azeotropic mixture at high pressures and temperatures was studied. A double pipe heat exchanger was developed and set up to study the effects of different operating parameters on heat transfer performance over a wide range of temperatures (25 °C to 90 °C) and pressures (5 MPa to 30 MPa). Heat flux of supercritical fluids was measured in the inner pipe in the counter-current with water in the outer pipe. For the first time, the heat transfer coefficients (HTC) of supercritical CO2, ethane and their azeotropic mixture in water loop have been measured and compared. A brief evaluation is provided of the effect of mass flux, heat flux, pressure, temperature and buoyancy force on heat transfer coefficients. Additionally, to properly evaluate the potential and the performance of azeotropic mixture CO2-ethane, the coefficients of performance (COP) were calculated for the heat pump working cycle and compared to a system containing exclusively CO2.
Ključne besede: supercritical fluids, PGSSTM, formulation of active drugs, biodegradable polymers, transport and thermodynamic data, pendant drop method, carbon sequestration, heat transfer coefficients
Objavljeno: 28.05.2018; Ogledov: 854; Prenosov: 131
Celotno besedilo (5,51 MB)
International conference Fluid power 2017
2017, zbornik recenziranih znanstvenih prispevkov na mednarodni ali tuji konferenci
Opis: The International Fluid Power Conference is a two day event, intended for all those professionally-involved with hydraulic or pneumatic power devices and for all those, wishing to be informed about the ‘state of the art’, new discoveries and innovations within the field of hydraulics and pneumatics.
The gathering of experts at this conference in Maribor has been a tradition since 1995, and is organised by the Faculty of Mechanical Engineering at the University of Maribor, in Slovenia. Fluid Power conferences are organised every second year and cover those principal technical events within the field of fluid power technologies in Slovenia, and throughout this region of Europe. This year's conference is taking place on the 14th and 15th September in Maribor.
We wish all participants at the International Conference-Fluid Power 2017 continued successful professional work, and hope that we have yet again added another small piece within the mosaic of fluid power.
Ključne besede: fluid power technology, components and systems, control systems, fluids, maintenance, monitoring
Objavljeno: 28.09.2017; Ogledov: 601; Prenosov: 67
Celotno besedilo (19,00 MB)
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Sol-gel/Ag coating and oxygen plasma treatment effect on synthetic wound fluid sorption by non-woven cellulose materialZdenka Peršin
, Tanja Pivec
, Miran Mozetič
, Karin Stana-Kleinschek
, 2017, kratki znanstveni prispevek
Opis: Non-woven cellulose material was functionalized using two techniques, i.e. the coating with AgCl via sol-gel and oxygen plasma. The treatment effects were studied regarding the wound fluid adsorption potential using physiological saline, synthetic exudate and synthetic blood. Plasma treatment was most efficient since a significant improvement by absorbency rate and capacity was evident, less pronounced in case of synthetic blood. The combination of both treatments showed a similar trend, while the effects were less prominent, but still sufficient by managing fluid-associated as well as infected wounds.
Ključne besede: non-woven cellulose fabric, sol-gel, oxygen plasma, absorption, synthetic wound fluids
Objavljeno: 31.08.2017; Ogledov: 619; Prenosov: 287
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OLEORESINI IZ RDEČE PEKOČE PAPRIKE - EKSTRAKCIJA IN UPORABAJana Simonovska
, 2016, doktorska disertacija
Opis: Pepper (Capsicum annuum L.) as widely distributed vegetable crop in the world is an excellent source of nutritive and biologically active compounds. The characteristic compounds, capsaicinoids and carotenoids, highlight the importance of the red hot pepper varieties and their oleoresin extracts in the food and pharmaceutical industry. In the Ph.D. thesis was studied the possibility for a separate and integral utilization of the red hot pepper for obtaining the oleoresins from pericarp, placenta, seeds and stalk.
Pre-treatment of the raw material (drying, separation of anatomical structures i.e. pericarp, placenta and seeds, and determination of theirs physico-chemical
characteristics and determination of the he characteristic bioactive compounds:
capsaicinoids, carotenoids and volatiles was studied, also. The second part of the Ph.D. thesis was focused of the determination of the optimal
conditions for isolation of the bioactive capsaicinoids and coloured compounds,
through comparative following of the thermodynamical parameters by application of organic solvents and supercritical fluids. Influence of the working parameters: temperature, time, pressure, solid to liquid phase ratio, density, type of solvents, and particle size of raw material on the yield of extract and content of capsaicinoids, colour compounds and volatiles was studied. Modelling of the experimental phase data by application of mathematical methods was performed. Re-utilization of seed and stalk from red hot pepper in form of extracts for development of new formulations as edible films, biopesticides and nanoemulsions was studied, also.
Ključne besede: red hot pepper, pericarp, placenta, seed, stalk, extraction, sub- and
supercritical fluids, bioactive compounds, volatiles, re-utilization, edible films, biopesticides, nanoemulsions
Objavljeno: 08.11.2016; Ogledov: 1144; Prenosov: 95
Celotno besedilo (4,71 MB)
Supercritical fluid chromatography and scale up studyMiha Oman
, Petra Kotnik
, Mojca Škerget
, Željko Knez
, 2014, izvirni znanstveni članek
Opis: The influence of process parameters on supercritical fluid chromatography (SFC) and scale-up on to the preparative scale was investigated. In this scope, dependency of pressure, temperature, type and concentration of modifier, and type of stationary phase on the separation were examined separately. Experiments were performed on silica stationary phases in the range of pressures from 100 bar to 250 bar and temperatures from 30°C to 65°C, with use of ethanol and methanol as modifier. Results obtained on analytical scale were used for scale up on preparative (to production) scale. The aim of this study is presentation of the state-of-the-art of SFC through separate effects of process parameters on the separation and investigation of development, benefits and drawbacks of scaling-up process of the SFC.
Ključne besede: supercritical fluids, supercritical fluid chromatograpy, chromatography, scale up study, SFC
Objavljeno: 21.12.2015; Ogledov: 813; Prenosov: 74
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Pressure stability of lipases and their use in different systemsMaja Leitgeb
, Željko Knez
, 2001, izvirni znanstveni članek
Opis: For the investigation of the solvent impact on the enzymes, lipases from different sources (Pseudomonas fluorescences, Rhizopus javanicus, Rhizopus niveus, Candida rugose and Porcine pancreas) were used. Stability and activity of these lipases in aqueous medium in supercritical $CO_2$ and liquid propane at 100 bar and 40°C were studied.
On the basis of previous results lipases were used for their application in two different systems. The application of the polysulphone membrane in the continuous stirred tank membrane reactor was studied on the model system of the hydrolysis of oleyl oleate in propane at high pressure. As a catalyst the Candida rugosa lipase was used. The next utilization of lipases was the use of on silica arerogel self-immobilized lipase from Porcine pancreas as catalyst for esterification reaction in near-critical propane at 40°C and 100 bar.
Ključne besede: chemical processing, supercritical fluids, lipases, enzyme stability, high pressure membrane reactor
Objavljeno: 10.07.2015; Ogledov: 825; Prenosov: 114
Celotno besedilo (608,04 KB)
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“Thermodynamic and physical properties for high pressure process design”Maša Knez Hrnčič
, 2014, doktorska disertacija
Opis: The thesis is comprised of three main categories. The first part of dissertation covers investigations of phase equilibria of compounds from natural materials in conventional and also non conventional supercritical fluids. In details, the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion) is investigated, quantitative and qualitative analyses to evaluate and identify compounds contained after performing preliminary extraction experiments from different natural tissues are presented. The impact of operating parameters (pre-treatment of the raw material with SFE; different extraction solvents: propane, CO2, non conventional SCFs; different extraction temperatures and pressures) on extraction kinetics is observed. Following substances were taken into consideration: vanillins, caffeine, carnosoic acid extract and lecithin.
Second part of dissertation covers studies of phase equilibria of the systems bio oil/gas, which is crucial in biorefinery process design. In this part of dissertation, which covers studies of phase equilibria of binary and ternary systems, the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion) for binary system bio oil/supercritical fluid (bio oil/CO2) and (bio oil/H2) was studied. Additionally, phase behaviour of ternary systems of (bio oil/diesel/CO2) and (bio oil/tail water/CO2) under the impact of pressure and/or temperature is observed. These data are of a high importance for bio refineries as an important part of necessary sustainable development. In recent years, studies on biodiesel synthesis have focused on development of process intensification technologies to resolve some of these issues. Fundamental data to design fractionation process of components of bio oil are crucial for an efficient hydrogenation process of bio oil.
In the third part of dissertation observation of phase equilibria and determination of the parameters like diffusion coefficient, density and viscosity for the systems polymer/CO2 at elevated pressures is investigated. An overview of different methods applied to determine the parameters like diffusion coefficient, density and viscosity of the systems polymer (PEG)/CO2 at elevated pressures is offered. Observation of phase equilibria of the binary system PEG/CO2, determination of the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion), determination of thermodynamically and physically properties of the system with new applicative methods and finally, comparison of the results obtained by different methods is provided.
The interfacial tension (IFT) at the (PEG)/CO2 interface has been determined by using an experimental technique developed to study the interfacial interactions of the liquids in equilibrium with gas in a glass-windowed equilibrium cell by the means of Capillary Rise (CR) method.
Advantages and disadvantages of methods that were applied are exposed and discussed.
Ključne besede: phase equilibria, natural materials, conventional and non conventional supercritical fluids, extraction, bio oil, data for biorefinery process design, systems polymer (PEG)/CO2, diffusion coefficient, density, viscosity, surface tension, Capillary Rise (CR) method.
Objavljeno: 28.10.2014; Ogledov: 1756; Prenosov: 252
Celotno besedilo (4,46 MB)
HIGH PRESSURE PHASE EQUILIBRIUM OF THE BINARY SYSTEM TWEEN 80 AND CARBON DIOXIDENatalija Novak
, 2014, diplomsko delo
Opis: In the frame of the diploma thesis we researched the phase equilibrium of the binary system Tween 80 and CO2. Equilibrium compositions of the system have been determined with a static analytical method at temperature 40, 60 and 80 °C and pressures up to 300 bar. The obtained data was plotted in isothermal diagrams where mass percentage is presented as a function of pressure.
In this work also the viscosity of Tween 80 was determined in the temperature range between 20 and 80°C and shear rates up to 180 s-1. The measurements were obtained by using coaxial cylinder and compared with available literature data.
Ključne besede: supercritical fluids, phase equilibrium, carbon dioxide, Tween 80
Objavljeno: 22.04.2014; Ogledov: 1283; Prenosov: 64
Celotno besedilo (2,34 MB)