Načrtovanje visokotlačnih procesov za predelavo polimerov in izboljšave prenosa top

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.V doktorski disertaciji je predstavljeno načrtovanje visokotlačnih procesov, ki izkoriščajo »zelena topila« t.i. nadkritične fluide. Z njihovo uporabo lahko pridobivamo nove produkte z višjo dodano vrednostjo pri nizki porabi energije. Doktorska dizertacija je razdeljena na tri osrednja poglavja: procesiranje polimerov in formulacija aktivnih zdravilnih učinkovin, merjenje transportnih lastnosti iz geometrije viseče kaplje in študij prenosa toplote pri nadkritičnih pogojih. V prvem delu smo se osredotočili na uporabo biorazgradljivih polimernih materialov z namenom pridobivanja praškastih delcev in struktur za formulacijo aktivnih farmacevtskih učinkovin. Biorazgradljivi polimerni materiali so pomembni v številnih farmacevtskih aplikacijah pri nadzorovanem sproščanju zdravil. Uporabili smo patentiran visokotlačni PGSSTM postopek za formulacijo netopnih aktivnih zdravilnih učinkovin nimodipina, fenofibrata, o-vanilina in esomeprazola z namenom izboljšanja njihove biološke uporabnosti in hitrosti raztapljanja. Kot nosilni material smo uporabili biorazgradljive polimere polioksietilen stearil eter (Brij 100 in Brij 50) in polietilen glikol (PEG 4000). Preliminarno smo določili transportno-termodinamske parametre polimernima nosilcema polietilen glikolu (PEG) in polioksietilen stearil eteru (Brij S) v sistemih z nadkritičnimi fluidi. Izmerjene parametre smo uporabili za optimalno formulacijo aktivnih učinkovin. Kombinacija zmanjšanja velikosti delcev in medsebojni vpliv med aktivno zdravilno učinkovino in hidrofilnimi nosilci sta pripomogla k povečanju hitrosti raztapljanja dobljenih praškastih delcev. V drugem delu smo razvili novo visokotlačno merilno tehniko in izpeljali matematični model za določitev difuzijskih koeficientov in površinskih napetosti iz geometrije viseče kaplje. Nastanek asimetrične kapljice fluida smo preučevali z uporabo računalniškega algoritma, ki vključuje iterativno uporabo Young-Laplace-ove enačbe za opis razmerja med gravitacijsko deformacijo kapljice in površinsko napetostjo. Metodo smo umerili z meritvami površinske napetosti in difuzijskih koeficientov v sistemu voda/superkritični CO2. Določili smo površinsko napetost in difuzijske koeficiente še neraziskanemu sistemu propilen glikola/CO2 pri temperaturah 120 °C in 150 °C v tlačnem razponu od 5 MPa do 17.5 MPa. Novo metodo smo nadalje uporabili za preučitev sistemov pomembnih pri geološkem zajemanju CO2. Z namenom zmanjšanja izpustov toplogrednega CO2 v ozračje smo preučili in izmerili gostote in površinske napetosti sistemom slanica/CO2 in preučili vpliv nečistoče Ar na skladiščenje CO2 v geološke formacije. V tretjem delu doktorske naloge smo preučevali učinkovitosti prenosa toplote v bližini kritične točke CO2, etana in njune azeotropne mešanice. Izdelali smo dvocevni prenosnik toplote, ki je omogočil meritve pri povišanih temperaturah (25 °C do 90 °C) in tlakih (5 MPa do 30 MPa). Prenos toplote v sistemu z nadkritičnim fluidom smo merili v smeri iz notranje visokotlačne cevi protitočno na zunanjo cev po kateri se je pretakala voda. Izmerili smo koeficiente prenosa toplote nadkritičnemu CO2, etanu in njuni mešanici. Preučili smo učinek masnega pretoka, toplotnega toka, vzgona, tlaka in temperature na vrednosti koeficientov prenosa toplote. Za pravilno oceno potenciala in učinkovitosti azeotropne mešanice CO2 in etana smo izračunali koeficiente zmogljivosti (COP) za cikel toplotne črpalke in jih primerjali s sistemi, ki delujejo izključno na CO2

HEAT LOSSES DUE TO WATER SCALE DEPOSITS ON HEATERS OF HOUSEHOLD APPLIANCES

V diplomskem delu je predstavljena učinkovitost magnetne obdelave vode (MOV) na zmanjšanje izločanja vodnega kamna. Preučevali smo vpliv različnih hitrosti pretoka vode skozi magnetno napravo za preprečitev nastajanja vodnega kamna na grelcih bojlerjev. Prav tako smo izvedli eksperimente z in brez Mg-elektrode pri različnih pretokih. Rezultati nakazujejo, da pri eksperimentih z Mg - elektrodo in napravo z MOV ni bistvenega učinka magnetne obdelave na zmanjšanje količine izločenega vodnega kamna. Pri eksperimentih brez Mg-elektrode in vključeno napravo za MOV pa se učinek magnetne naprave povečuje s povečanim pretokom vode. Predvidevamo, da se z dodatkom Mg - elektrode vpliv MOV izrazito zmanjša.The diploma work presents the efficiency of magnetic water treatment (MWT) for scale control. The influence of different flow rate through magnetic device in order to prevent water scale precipitation on heaters was analysed. Also experiments with and without a Mg- electrode and included MWT in diffrent flow rate were carried out. The results show that a Mg-elctrode has no significant effect on scale elimination. Experiments without a Mg-electrode show increased efficiency of magnetic water treatment with increased flow rate. We assume that the presence of the Mg- electrode reduces efficiency of the magnetic device

Particle shape analysis of industrial sand using traditional and computational geometry methods

Silica sand is widely used as a raw material in the manufacture of building and construction products. Particle shape parameters such as sphericity and roundness were determined using both the Krumbein-Sloss diagram and the ImageJ processing algorithm. A total of 10 samples from production plants were comprehensibly analyzed. Olympus SZX16 microscope was used for image acquisition. Image analysis was performed separately for each grain size fraction ranging from 0.063 mm up to 2.0 mm. The microscope images showed that there was a visible difference in color and shape between manufactured sands. For sand shape parameters, the computerized method was significantly faster and with a high probability of accuracy compared to the Krumbein-Sloss diagram method

DETERMINATION OF THE SURFACE TENSION BY THE CAPILLARY RISE METHOD IN TWO-PHASE SYSTEMS

Namen magistrske naloge je bil postavitev merilne naprave in razvoj nove metode merjenja površinske napetosti s kapilarnim dvigom dvofaznih sistemov v okolici kritične točke. Za pridobitev natančnih in primerljivih meritev je bilo potrebno poznati natančni notranji premer tankih kapilar. Določili smo ga z metodo laserskega tipanja na nemški koordinatni merilni napravi ZEISS tipa UMC-850 s pomočjo merilne programske opreme CALYPSO 5.1.4. Za merjenje ravnotežne višine smo uporabili računalniški program Logger Pro, ki omogoča natančno analizo razdalj med dvema točkama. Gostote dvofaznih sistemov smo dobili iz podatkovne baze NIST ali jih izmerili s pomočjo gravimetrične metode jemanja vzorcev iz mešalnega avtoklava. Površinsko napetost smo merili v treh dvofaznih sistemih: voda/CO2, slanica/CO2 in polimer PEG/CO2 v razponu od 1 bara do 200 barov. Prve meritve smo izvedli za sistem voda/CO2 pri treh izotermah (25 °C, 45 °C in 60 °C) in jih primerjali z literaturo. Ugotovili smo, da daje naša metoda primerljive in ponovljive rezultate, ki kažejo, da se s povečanjem tlaka površinska napetost linearno zmanjšuje do območja fazne spremembe CO2, v območju višjih tlakov pa doseže konstantno vrednost. Zanimiva je tudi ugotovitev, da se površinska napetost pri atmosferskih pogojih z nižanjem temperature poveča, v območju višjih tlakov pa pada. Zaradi možnosti skladiščenja toplogrednega plina CO2 v slanico smo v avtoklavu simulirali razmere, ki potekajo pri vbrizgavanju CO2 v slane reke več kilometrov pod zemljo. Ugotovili smo, da se z višanjem koncentracije soli v vodni raztopini (od 14 g/l do 200 g/l) viša vrednost površinske napetosti. Z namenom pridobitve še neraziskanih termodinamskih podatkov v okolici kritične točke smo izmerili površinsko napetost sistema polimera PEG/CO2. Rezultati kažejo, da se je površinska napetost sistema PEG/CO2 (molske mase PEG: 200, 400, 600) s povečanjem tlaka prav tako linearno zmanjševala.The aim of the thesis was to place a measuring device for determination of the surface tension by the capillary rise method in two-phase systems at higher pressures. In order to obtain accurate and comparable measurements, it was necessary to know the exact inner diameter of the thin capillaries, which we have determined by measuring on the German coordinate machine ZEISS type UMC - 850 using a software CALYPSO 5.1.4. To measure the equilibrium height, we used a computer program Logger Pro, which enables detailed analysis of distances between two points. The densities of two-phase systems were obtained from the NIST database, or measured by the gravimetric method of taking samples from the mixing autoclave. Surface tension was measured in the three two-phase systems: water/CO2 brine/CO2 and polymer PEG/CO2 in the range from 1 bar to 200 bar. The first measurements were performed for the system water/CO2 for three isotherms (25° C, 45° C and 60° C) and compared with the literature. We found that our method provides comparable and reproducible results. As pressure increases, a decrease in the interfacial tension is observed, which is more pronounced at lower temperatures. At lower pressures surface tension decreases with rising temperatureat higher pressures the opposite effect is found. Due to the potential of storage of the greenhouse gas CO2 in brine, we simulated conditions in an autoclave, which take place when injecting CO2 into saline river several hundred meters underground. We found that by increasing the salt concentration in the aqueous solution (form 14g/l to 200g/l) the surface tension value increases. In order to obtain so far unexplored thermodynamic data, surface tension of the system polymer PEG/CO2 was measured. The results show that by increasing pressure the surface tension of the system PEG/CO2 (molar mass of PEG: 200, 400, 600) decreased linearly likewise

A Comprehensive Review of the Advances, Manufacturing, Properties, Innovations, Environmental Impact and Applications of Ultra-High-Performance Concrete (UHPC)

The article presents the progress and applications of ultra-high-performance concrete (UHPC), a revolutionary material in modern construction that offers unparalleled strength, durability, and sustainability. The overview includes the historical development of UHPC, covering its production and design aspects, including composition and design methodology. It describes the mechanical properties and durability of UHPC and highlights recent innovations and research breakthroughs. The potential integration of multifunctional properties such as self-heating, self-sensing, self-luminescence and superhydrophobicity, is explored. In addition, advances in nanotechnology related to UHPC are addressed. Beyond the actual material properties, the article presents an environmental impact assessment and a life-cycle cost analysis, providing an insight into the wider implications of using UHPC. To illustrate the environmental aspects, the determination of CO2 emissions is explained using three numerical examples. Finally, various applications of UHPC are presented, focusing on the construction of buildings and bridges. By synthesizing the above-mentioned aspects, this review paper captures the dynamic landscape of UHPC and serves as a valuable resource for researchers and engineers in the field of construction materials

Combined Effects of Metakaolin and Hybrid Fibers on Self-Compacting Concrete

There is a need to develop new construction materials with improved mechanical performance and durability that are low-priced and have environmental benefits at the same time. This paper focuses on the rheological, mechanical, morphological, and durability properties of synthetic and steel fiber reinforced self-compacting concrete (SCC) containing 5–15% metakaolin (M) by mass as a green replacement for Portland cement. Testing of the fresh mixes included a slump-flow test, density, and porosity tests. Mechanical properties were determined through compression and flexural strength. A rapid chloride penetrability test (RCPT) and the chloride migration coefficient were used to assess the durability of the samples. A scanning electron microscope (SEM) with energy dispersion spectrometry (EDS) was used to study the concrete microstructure and the interfacial transition zone (ITZ). The results show that a combination of metakaolin and hybrid fibers has a negative effect on the flowability of SCC. In contrast, the inclusion of M and hybrid fibers has a positive effect on the compressive and flexural strength of SCC. The fracture of SCC samples without fibers was brittle and sudden, unlike the fiber-reinforced SCC samples, which could still transfer a considerable load with increasing crack mouth opening deflection. Overall, the chloride migration coefficients were reduced by up to 71% compared to the control mix. The chloride reduction is consistent with the resulting compact concrete microstructure, which exhibits a strong bond between fibers and the concrete matrix

Chitosan-Based (Nano)Materials for Novel Biomedical Applications

Chitosan-based nanomaterials have attracted significant attention in the biomedical field because of their unique biodegradable, biocompatible, non-toxic, and antimicrobial nature. Multiple perspectives of the proposed antibacterial effect and mode of action of chitosan-based nanomaterials are reviewed. Chitosan is presented as an ideal biomaterial for antimicrobial wound dressings that can either be fabricated alone in its native form or upgraded and incorporated with antibiotics, metallic antimicrobial particles, natural compounds and extracts in order to increase the antimicrobial effect. Since chitosan and its derivatives can enhance drug permeability across the blood-brain barrier, they can be also used as effective brain drug delivery carriers. Some of the recent chitosan formulations for brain uptake of various drugs are presented. The use of chitosan and its derivatives in other biomedical applications is also briefly discussed

The Influences of Moisture on the Mechanical, Morphological and Thermogravimetric Properties of Mineral Wool Made from Basalt Glass Fibers

Mineral wool made from basalt fibers is frequently used as an insulating material in construction systems. In this study, both unused mineral wool and wool obtained from the softened roofing area were comprehensively analyzed in a laboratory using different characterization techniques. Firstly, the initial water content and compressive strength at 10% deformation were determined. Secondly, microstructure and surface chemical composition were analyzed by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX). To study heterogeneities near the fiber surface and to examine cross-sectional composition, a scanning transmission electron microscope (STEM) was used. Finally, to verify possible reasons for resin degradation, thermogravimetric analysis and differential scanning colometry (TGA-DSC) were simultaneously carried out. The results show that natural aging under high humidity and thermal fluctuations greatly affected the surface morphology and chemical composition of the fibrous composite. Phenol-formaldehyde and other hydrophobic compounds that protect fibers against moisture and give compressive resistance were found to be degraded