International journal of simulation modelling, Feb 28, 2024
This paper presents a wear simulation-based performance evaluation of the conveyor belt transfer ... more This paper presents a wear simulation-based performance evaluation of the conveyor belt transfer chute using the DEM (Discrete Element Method). Compared to known analytical and empirical wear models, DEM simulation can significantly increase the performance of wear analysis by enabling the analysis and optimization of highly complex geometries of material handling systems such as conveyor belt transfer chutes. Only the correct design of the conveyor belt transfer chute has the potential to significantly extend its service life, resulting in considerable cost savings. Based on the parametric analysis of different angles and radius in the upper head and lower section of the transfer chute, a new geometry of the transfer chute was proposed. The wear depth of the new conveyor belt transfer chute is compared with the wear resistant and low-carbon steel of the transfer chute along with the moderate and relatively high values of the solid granules mass flow. The results show that the wear depth of the transfer chute can be significantly reduced by using the wear-resistant steel compared to the low-carbon steel, which is significantly evident in high throughput rates of the solid granules mass flow.
The article presents the problem of rapid antigen tests when they become mass waste after use. Ba... more The article presents the problem of rapid antigen tests when they become mass waste after use. Based on this, the hypothesis was made that rapid antigen tests can be recycled. Rapid antigen tests, which were used in the Covid-19 epidemic to quickly detect infections in the population or to confirm the presence of the Sars-Cov 2 virus in patients, were intended to limit the spread of the epidemic. To confirm the hypothesis of recycling for rapid antigen tests, the LFIA-REC ATP 150 project was prepared, which was selected for co-financing by the Norwegian Fund. Rapid antigen tests consist of a sample and conjugate pad, detectable or nitrocellulose membranes and absorbent pads and a plastic case. The function of the sample pad is to evenly absorb the sample (mucus, blood) and lead it to the conjugate pad with a steady flow. Gold nanoparticles (labels) are deposited on the conjugate pad. The key is that the gold nanoparticles are conjugated with capture molecules capable of binding to potentially present antibodies or virus in the sample. The scope of the research problem thus required the inclusion of various characterization techniques that must be applied to the individual material in the rapid antigen test to subsequently develop an efficient recycling process for the rapid antigen tests. The result of the research presented in this paper represents a newly developed algorithm of characterization techniques, which includes a recommended description of the preparation of samples of key materials from rapid antigen tests. This algorithm successfully achieved the characterization of gold nanoparticles from rapid antigen tests. Based on the developed algorithm, the final part of the project will validate the recycling process of rapid antigen tests, so that they can be recycled, i.e. gold nanoparticles or plastic used in new products. The paper presents the algorithm of characterization techniques with a description of the preparation of material samples from rapid antigen tests. Keywords: rapid antigen tests, recycling, characterization, nanogold, plastic V prispevku je predstavljena problematika hitrih antigenskih testov, ko le-ti postanejo po uporabi masovni odpadek. Na osnovi tega je bila postavljena hipoteza, da je hitre antigenske teste mo`no reciklirati. Hitri antigenski testi, ki so se uporabljali v epidemiji Covid 19 za hitro odkrivanje oku`b v populaciji oziroma za potrditev prisotnosti virusa Sars-Cov 2 pri testirancih, so bili namenjeni za zamejitev {irjenja epidemije. Za potrditev hipoteze recikliranja hitrih antigenskih testov je bil pripravljen projekt LFIA-REC ATP 150, ki je bil izbran za sofinanciranje s strani Norve{kega fonda. Hitri antigenski testi so sestavljeni iz vzor~ne in konjugatne blazine, zaznavne oz. nitrocelulozne membrane in vpojne blazine ter iz plasti~nega ohi{ja. Funkcija vzor~ne blazine je, da enakomerno absorbira vzorec (sluz, kri) in ga z enakomernim tokom vodi do konjugatne blazine. Na konjugatni blazini so nane{eni zlati nanodelci (oznake). Klju~no je, da so zlati nanodelci konjugirani z lovilnimi molekulami, ki so se sposobne vezati na potencialno prisotna protitelesa ali virus v vzorcu. Podro~je raziskovalnega problema je tako zahtevalo vklju~itev razli~nih tehnik karakterizacije, ki jih je potrebno uporabiti za posamezen material v hitrem antigenskem testu, da bi lahko kasneje razvili u~inkovit postopek recikliranja hitrih antigenskih testov. Rezultat raziskave, ki je predstavljen v tem prispevku, predstavlja na nov razvit algoritem tehnik karakterizacije, kjer je vklju~en priporo~ljiv opis priprave vzorcev klju~nih materialov iz hitrih antigenskih testov. Ta algoritem je uspe{no dosegel karakterizacijo nanodelcev zlata iz hitrih antigenskih testov. Na osnovi razvitega algoritma bo v sklepnem delu projekta validiran postopek recikliranja hitrih antigenskih testov, tako, da bodo lahko reciklati t.j. nanodelci zlata oziroma plastika uporabljeni v novih proizvodih. Klju~ne besede: hitri antigenski testi, recikliranje, karakterizacija, nanozlato, plastika
Sušenje je eno izmed pomembnejših in hkrati najstarejših področij procesne tehnike. Ena izmed zel... more Sušenje je eno izmed pomembnejših in hkrati najstarejših področij procesne tehnike. Ena izmed zelo uveljavljenih oblik sušenja je razpršilno sušenje, ki je zelo pogosto prisotno v živilski, farmacevtski in kemijski industriji. V danem prispevku obravnavamo karakterizacijo formiranja spreja na razpršilni šobi in izvedbo numerične simulacije z vključenim sekundarnim razpadom spreja. Karakterizacija spreja na šobi je bila izvedena na sistemu Oxfor laser, medtem ko je za izvedbo numeričnih simulacij bil uporabljen programski paket Ansys Fluent. Primerjava rezultatov je pokazala dobro ujemanje med velikostno porazdelitvijo delcev pridobljeno pri eksperimentu in pri numerični simulaciji.
V večini tehniških in naravnih sistemov je prisoten vlažen zrak. Vlažen zrak lahko pri določenem ... more V večini tehniških in naravnih sistemov je prisoten vlažen zrak. Vlažen zrak lahko pri določenem tlaku in temperaturi sprejme določeno količino vlage, pri čemer pride do točke nasičenja. Kondenzacija na stenah trdnih površin velikokrat ovira normalno delovanje v tehničnih napravah in je nezaželena. Nasproten pojav kondenzacije je uparjanje. Predstavljen je splošen matematičnofizikalni model uparjanja kapljevitega filma in njegova implementacija v obstoječi programski paket za računalniško dinamiko tekočin. Implementacija numeričnega modela uparjanja je bila preverjena na primeru simulacije pravokotnega 3D kanala in primerjana z izvedenim eksperimentom uparjanja kapljevitega filma. Zrak, ki teče nad vodno površino uparja vodo, pri čemer se vodna površina ohlaja, dokler se ne vzpostavi ravnotežje med prevodom toplote iz zraka in latentne toplote, ki se porabi za uparjanje. Spremljali smo kombiniran prenos toplote in snovi. Ugotovljeno je bilo, da je vpliv naravne konvekcije v primerja...
Lateral flow immunoassays (LFIAs) are a simple diagnostic device used to detect targeted analytes... more Lateral flow immunoassays (LFIAs) are a simple diagnostic device used to detect targeted analytes. Wasted and unused rapid antigen lateral flow immunoassays represent mass waste that needs to be broken down and recycled into new material components. The aim of this study was to recover gold nanoparticles that are used as markers in lateral flow immunoassays. For this purpose, a dissolution process with aqua regia was utilised, where gold nanoparticles were released from the lateral flow immunoassay conjugate pads. The obtained solution was then concentrated further with gold chloride salt (HAuCl4) so that it could be used for the synthesis of new gold nanoparticles in the process of ultrasonic spray pyrolysis (USP). Various characterisation methods including scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and optical emission spectrometry with inductively coupled plasma were used during this study. The results of this study showed tha...
This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the a... more This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the ultrasonic spray pyrolysis technique. They were collected in a water suspension with polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with transmission electron microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was extruded, and the injection was moulded successfully. Flexural testing of PLA/Ni/Y2O3 showed a slight average decrease (8.55%) in flexural strength and a small decrease from 3.7 to 3.3...
Sušenje vlažne snovi je ena izmed najstarejših procesnih tehnik, ki se uporablja na številnih ind... more Sušenje vlažne snovi je ena izmed najstarejših procesnih tehnik, ki se uporablja na številnih industrijskih področjih. Sušenje je zapleten fizikalni proces, ki obsega vezan večfazni prenos toplote, snovi in gibalne količine. Pri sušenju delcev, kot je na primer razpršilno sušenje, je čas sušenja odvisen od lokalnih pogojev v sušilnem plinu, in sicer na poti vsakega posameznega delca skozi sušilnik. Iz tega razloga je zelo pomembno poznavanje temperaturnega polja kot tudi polja vlažnosti v sušilniku, ki se zaradi toplotne in masne izmenjave med delci in sušilnim plinom nenehno spreminja. V prispevku je obravnavan numerični model za izračun sušenja poroznih delcev v toku sušilnega plina, pri čemer je reševanje problema izvedeno v sklopu Euler-Lagrange modela računske dinamike tekočin, in sicer z metodo robnih elementov. Povezava med delci in tokom tekočine je izvedena z nadgradnjo modela točkovnega izvora, ki upošteva konvektivni prenos toplote in snovi v sušilnem plinu. Testni izraču...
The objective of the present work is to analyze influence of temperature boundary conditions on t... more The objective of the present work is to analyze influence of temperature boundary conditions on the solidification process of NiTi alloy. Alloy is taken as an incompressible fluid where the heat is transferred by conduction and convection, including the thermal phase change phenomenon. The last one is modelled by the improvement procedure, so-called enthalpy-porosity formulation, where the liquid-solid mushy zone is treated as a porous zone with porosity equal to the liquid fraction. The numerical model is based on the finite volume method in body fitted coordinates with a SIMPLER scheme to couple the pressure and velocity fields. Simulation presents solidification for two cooling cases on the cylindrical part, where in the first case the adiabatic boundary condition is considered and in the second case the convective cooling over the wall is present. The results are presented for the velocity and temperature field as well as for the NiTi mass fraction during the solidification proc...
This paper focuses on the numerical analysis of the combustion of the liquid fuel Extra Light Fue... more This paper focuses on the numerical analysis of the combustion of the liquid fuel Extra Light Fuel Oil (ELFO) in a small combustion device. The calculation was performed by ANSYS CFX computer code for experimental optimal air-fuel ratio (λopt) and the middle power of the oil burner Weishaupt WL5/1-A (37 kW). The goal of the numerical analysis was to establish, whether the experimentally determined λopt ensured the conditions for a complete combustion in each point of the combustion chamber. The comparison of numerical results and measured values confirm the suitability of the chosen numerical model.
In this work, we developed a numerical approach based on an experimental platform to determine th... more In this work, we developed a numerical approach based on an experimental platform to determine the working conditions on a cryoplatform and to predict and evaluate the cryogenic printing of hydrogels. Although hydrogels have good biocompatibility, their material properties make it difficult to print them with high precision and shape fidelity. To overcome these problems, a cryogenic cooling platform was introduced to accelerate the physical stabilisation of each deposited layer during the printing process. By precisely controlling solidification (crystallisation), each printed material can withstand its own weight to maintain shape fidelity, and the porosity of the scaffolds can also be controlled more selectively. The thermophysical properties of gelatine hydrogels were investigated to gain a better understanding of the phase change upon freezing. The corresponding material properties and experimental observations of gelatine solidification served as the basis for developing a comp...
In the process industry, vacuum-type dryers are becoming increasingly important. A special case o... more In the process industry, vacuum-type dryers are becoming increasingly important. A special case of vacuum drying is lyophilization, where a solution, containing up to 90% of solvent (typically water), is dried under the conditions of very low temperatures and extremely low system pressures. As a container type, in which the solution is dried, a vial is frequently used. The intensity of drying is to a large extent controlled by the pressure conditions above the drying surface. The vial and the rubber stopper geometry present a significant pressure drop in the flow of sublimated solvent, but are experimentally difficult to determine. In order to produce realistic pressure conditions for the mass transfer computation, a CFD analysis of flow inside the vial-stopper channel is performed. The influence of imposing the no-slip and slip conditions on the solid surfaces on the pressure drop in the system is studied under the typical sublimation conditions. The effect of the increased partial pressure of the solvent on the sublimation rate is calculated by implementing the Maxwell-Stefan diffusion model.
To monitor the progress and prevent the spread of the COVID-19 pandemic in real time and outside ... more To monitor the progress and prevent the spread of the COVID-19 pandemic in real time and outside laboratories, it is essential to develop effective tests that can ensure rapid, selective, and reliable diagnosis of infected persons in different environments. Key in this regard is the lateral flow immunoassays (LFIAs) that can detect the presence of the SARS-CoV-2 virus quickly, with the aid of nanoparticles (NPs) and specific proteins. We report the use of gold (Au) NPs AuNPs synthesised from a gold(iii) chloride tetrahydrate precursor in a USP device and collected in a suspension composed of deionised water with polyvinylpyrrolidone as a stabiliser and cryoprotectant. In combination with freeze-drying of the AuNPs’ suspension to achieve water elimination, improved stability, and the target concentration, they exhibit the necessary properties for use as markers in LFIA rapid diagnostic tests. This was confirmed by complementary characterisation determined by using the techniques incl...
Vpliv lastnosti mikropolarnih tekočin na prenos toplote pri naravni konvekciji
V prispevku so predstavljeni numericni rezultati analize vpliva spremenljivih tokovnih razmer na ... more V prispevku so predstavljeni numericni rezultati analize vpliva spremenljivih tokovnih razmer na prenos toplote v primeru naravne konvekcije mikropolarnih tekocin v kvadratni kotanji. Za potrebe numericnega resevanja problema je bila razvita hitrostno-vrtincna formulacijo Navier Stokesovih enacb z vpeljano teorijo mikropolarnih tekocin. Izveden je bil testni primer naravne konvekcijev kvadratni kotanji za razlicne vrednosti Rayleighovih stevil vse do vrednosti ▫${10}^7$▫. Rezultati so pokazali da mikrorotacija v mikropolarni tekocini zmanjsuje prenos toplote od tople stene v kotanji in jo je tako v primeru tekocin, ki izražajo mikropolarni znacaj, pri numericnih simulacijah potrebno upostevati.
Numerično modeliranje mešanja v posodi z Rushtonovim mešalom
Strojniški vestnik, 2005
Prispevek obravnava numericno modeliranje mesanja newtonske tekocine v mesalni posodi, v kateri j... more Prispevek obravnava numericno modeliranje mesanja newtonske tekocine v mesalni posodi, v kateri je namesceno turbinsko Rushtonovo mesalo. Obravnavan je ustaljeni turbulentni tokovni rezim, opisan s casovno povprecnim Navier-Stokesovim sistemom enacb. Numericno resevanje temelji na uporabi dvoenacbnega modela turbulence in metode koncnih prostornin. Posebna pozornostje namenjena modeliranju vrtenja mesala ter izracunu mehanske moci za mesanje, kakor tudi nekaterim poenostavitvam, ki omogocajo hitrejsi izracun zahtevnih diskretnih modelov.
Journal of Drug Delivery Science and Technology, 2018
The paper reports on the development of a numerical model for the simulation of a lyophilization ... more The paper reports on the development of a numerical model for the simulation of a lyophilization process in a vial. Experimental analysis is presented of lyophilization dynamics inside a single vial in a laboratory scale lyophilizer. The problems of lyophilization modelling of a mannitol water solution are covered in detail. The effects of the small scale of the laboratory device with respect to a correct definition of boundary conditions for the numerical simulations are described, especially the effect of the comparatively high temperatures of the chamber walls. In the numerical model, a 1D vial approximation of the governing equations of heat and mass transport with moving front between the frozen and porous part of the cake is used and solved in a time stepping nonlinear iteration procedure. A water vapour diffusion model, implemented in the mass conservation equations, based on the Knudsen model of diffusivities, is applied and linked to the typical pore size of the porous cake. A front tracking scheme with moving computational grid is applied, and a dedicated sub-model of surface layer ice sublimation is introduced, based on the one-sided vapour diffusion model. The comparison of the numerical and the experimental results show that the developed numerical model is able to capture the transition points from primary to secondary drying very accurately, with accompanying accurate capturing of the temperature levels inside of the drying material.
International journal of simulation modelling, Feb 28, 2024
This paper presents a wear simulation-based performance evaluation of the conveyor belt transfer ... more This paper presents a wear simulation-based performance evaluation of the conveyor belt transfer chute using the DEM (Discrete Element Method). Compared to known analytical and empirical wear models, DEM simulation can significantly increase the performance of wear analysis by enabling the analysis and optimization of highly complex geometries of material handling systems such as conveyor belt transfer chutes. Only the correct design of the conveyor belt transfer chute has the potential to significantly extend its service life, resulting in considerable cost savings. Based on the parametric analysis of different angles and radius in the upper head and lower section of the transfer chute, a new geometry of the transfer chute was proposed. The wear depth of the new conveyor belt transfer chute is compared with the wear resistant and low-carbon steel of the transfer chute along with the moderate and relatively high values of the solid granules mass flow. The results show that the wear depth of the transfer chute can be significantly reduced by using the wear-resistant steel compared to the low-carbon steel, which is significantly evident in high throughput rates of the solid granules mass flow.
The article presents the problem of rapid antigen tests when they become mass waste after use. Ba... more The article presents the problem of rapid antigen tests when they become mass waste after use. Based on this, the hypothesis was made that rapid antigen tests can be recycled. Rapid antigen tests, which were used in the Covid-19 epidemic to quickly detect infections in the population or to confirm the presence of the Sars-Cov 2 virus in patients, were intended to limit the spread of the epidemic. To confirm the hypothesis of recycling for rapid antigen tests, the LFIA-REC ATP 150 project was prepared, which was selected for co-financing by the Norwegian Fund. Rapid antigen tests consist of a sample and conjugate pad, detectable or nitrocellulose membranes and absorbent pads and a plastic case. The function of the sample pad is to evenly absorb the sample (mucus, blood) and lead it to the conjugate pad with a steady flow. Gold nanoparticles (labels) are deposited on the conjugate pad. The key is that the gold nanoparticles are conjugated with capture molecules capable of binding to potentially present antibodies or virus in the sample. The scope of the research problem thus required the inclusion of various characterization techniques that must be applied to the individual material in the rapid antigen test to subsequently develop an efficient recycling process for the rapid antigen tests. The result of the research presented in this paper represents a newly developed algorithm of characterization techniques, which includes a recommended description of the preparation of samples of key materials from rapid antigen tests. This algorithm successfully achieved the characterization of gold nanoparticles from rapid antigen tests. Based on the developed algorithm, the final part of the project will validate the recycling process of rapid antigen tests, so that they can be recycled, i.e. gold nanoparticles or plastic used in new products. The paper presents the algorithm of characterization techniques with a description of the preparation of material samples from rapid antigen tests. Keywords: rapid antigen tests, recycling, characterization, nanogold, plastic V prispevku je predstavljena problematika hitrih antigenskih testov, ko le-ti postanejo po uporabi masovni odpadek. Na osnovi tega je bila postavljena hipoteza, da je hitre antigenske teste mo`no reciklirati. Hitri antigenski testi, ki so se uporabljali v epidemiji Covid 19 za hitro odkrivanje oku`b v populaciji oziroma za potrditev prisotnosti virusa Sars-Cov 2 pri testirancih, so bili namenjeni za zamejitev {irjenja epidemije. Za potrditev hipoteze recikliranja hitrih antigenskih testov je bil pripravljen projekt LFIA-REC ATP 150, ki je bil izbran za sofinanciranje s strani Norve{kega fonda. Hitri antigenski testi so sestavljeni iz vzor~ne in konjugatne blazine, zaznavne oz. nitrocelulozne membrane in vpojne blazine ter iz plasti~nega ohi{ja. Funkcija vzor~ne blazine je, da enakomerno absorbira vzorec (sluz, kri) in ga z enakomernim tokom vodi do konjugatne blazine. Na konjugatni blazini so nane{eni zlati nanodelci (oznake). Klju~no je, da so zlati nanodelci konjugirani z lovilnimi molekulami, ki so se sposobne vezati na potencialno prisotna protitelesa ali virus v vzorcu. Podro~je raziskovalnega problema je tako zahtevalo vklju~itev razli~nih tehnik karakterizacije, ki jih je potrebno uporabiti za posamezen material v hitrem antigenskem testu, da bi lahko kasneje razvili u~inkovit postopek recikliranja hitrih antigenskih testov. Rezultat raziskave, ki je predstavljen v tem prispevku, predstavlja na nov razvit algoritem tehnik karakterizacije, kjer je vklju~en priporo~ljiv opis priprave vzorcev klju~nih materialov iz hitrih antigenskih testov. Ta algoritem je uspe{no dosegel karakterizacijo nanodelcev zlata iz hitrih antigenskih testov. Na osnovi razvitega algoritma bo v sklepnem delu projekta validiran postopek recikliranja hitrih antigenskih testov, tako, da bodo lahko reciklati t.j. nanodelci zlata oziroma plastika uporabljeni v novih proizvodih. Klju~ne besede: hitri antigenski testi, recikliranje, karakterizacija, nanozlato, plastika
Sušenje je eno izmed pomembnejših in hkrati najstarejših področij procesne tehnike. Ena izmed zel... more Sušenje je eno izmed pomembnejših in hkrati najstarejših področij procesne tehnike. Ena izmed zelo uveljavljenih oblik sušenja je razpršilno sušenje, ki je zelo pogosto prisotno v živilski, farmacevtski in kemijski industriji. V danem prispevku obravnavamo karakterizacijo formiranja spreja na razpršilni šobi in izvedbo numerične simulacije z vključenim sekundarnim razpadom spreja. Karakterizacija spreja na šobi je bila izvedena na sistemu Oxfor laser, medtem ko je za izvedbo numeričnih simulacij bil uporabljen programski paket Ansys Fluent. Primerjava rezultatov je pokazala dobro ujemanje med velikostno porazdelitvijo delcev pridobljeno pri eksperimentu in pri numerični simulaciji.
V večini tehniških in naravnih sistemov je prisoten vlažen zrak. Vlažen zrak lahko pri določenem ... more V večini tehniških in naravnih sistemov je prisoten vlažen zrak. Vlažen zrak lahko pri določenem tlaku in temperaturi sprejme določeno količino vlage, pri čemer pride do točke nasičenja. Kondenzacija na stenah trdnih površin velikokrat ovira normalno delovanje v tehničnih napravah in je nezaželena. Nasproten pojav kondenzacije je uparjanje. Predstavljen je splošen matematičnofizikalni model uparjanja kapljevitega filma in njegova implementacija v obstoječi programski paket za računalniško dinamiko tekočin. Implementacija numeričnega modela uparjanja je bila preverjena na primeru simulacije pravokotnega 3D kanala in primerjana z izvedenim eksperimentom uparjanja kapljevitega filma. Zrak, ki teče nad vodno površino uparja vodo, pri čemer se vodna površina ohlaja, dokler se ne vzpostavi ravnotežje med prevodom toplote iz zraka in latentne toplote, ki se porabi za uparjanje. Spremljali smo kombiniran prenos toplote in snovi. Ugotovljeno je bilo, da je vpliv naravne konvekcije v primerja...
Lateral flow immunoassays (LFIAs) are a simple diagnostic device used to detect targeted analytes... more Lateral flow immunoassays (LFIAs) are a simple diagnostic device used to detect targeted analytes. Wasted and unused rapid antigen lateral flow immunoassays represent mass waste that needs to be broken down and recycled into new material components. The aim of this study was to recover gold nanoparticles that are used as markers in lateral flow immunoassays. For this purpose, a dissolution process with aqua regia was utilised, where gold nanoparticles were released from the lateral flow immunoassay conjugate pads. The obtained solution was then concentrated further with gold chloride salt (HAuCl4) so that it could be used for the synthesis of new gold nanoparticles in the process of ultrasonic spray pyrolysis (USP). Various characterisation methods including scanning electron microscopy, transmission electron microscopy, ultraviolet-visible spectroscopy and optical emission spectrometry with inductively coupled plasma were used during this study. The results of this study showed tha...
This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the a... more This study demonstrates the successful synthesis of Ni/Y2O3 nanocomposite particles through the application of ultrasound-assisted precipitation using the ultrasonic spray pyrolysis technique. They were collected in a water suspension with polyvinylpyrrolidone (PVP) as the stabiliser. The presence of the Y2O3 core and Ni shell was confirmed with transmission electron microscopy (TEM) and with electron diffraction. The TEM observations revealed the formation of round particles with an average diameter of 466 nm, while the lattice parameter on the Ni particle’s surface was measured to be 0.343 nm. The Ni/Y2O3 nanocomposite particle suspensions were lyophilized, to obtain a dried material that was suitable for embedding into a polylactic acid (PLA) matrix. The resulting PLA/Ni/Y2O3 composite material was extruded, and the injection was moulded successfully. Flexural testing of PLA/Ni/Y2O3 showed a slight average decrease (8.55%) in flexural strength and a small decrease from 3.7 to 3.3...
Sušenje vlažne snovi je ena izmed najstarejših procesnih tehnik, ki se uporablja na številnih ind... more Sušenje vlažne snovi je ena izmed najstarejših procesnih tehnik, ki se uporablja na številnih industrijskih področjih. Sušenje je zapleten fizikalni proces, ki obsega vezan večfazni prenos toplote, snovi in gibalne količine. Pri sušenju delcev, kot je na primer razpršilno sušenje, je čas sušenja odvisen od lokalnih pogojev v sušilnem plinu, in sicer na poti vsakega posameznega delca skozi sušilnik. Iz tega razloga je zelo pomembno poznavanje temperaturnega polja kot tudi polja vlažnosti v sušilniku, ki se zaradi toplotne in masne izmenjave med delci in sušilnim plinom nenehno spreminja. V prispevku je obravnavan numerični model za izračun sušenja poroznih delcev v toku sušilnega plina, pri čemer je reševanje problema izvedeno v sklopu Euler-Lagrange modela računske dinamike tekočin, in sicer z metodo robnih elementov. Povezava med delci in tokom tekočine je izvedena z nadgradnjo modela točkovnega izvora, ki upošteva konvektivni prenos toplote in snovi v sušilnem plinu. Testni izraču...
The objective of the present work is to analyze influence of temperature boundary conditions on t... more The objective of the present work is to analyze influence of temperature boundary conditions on the solidification process of NiTi alloy. Alloy is taken as an incompressible fluid where the heat is transferred by conduction and convection, including the thermal phase change phenomenon. The last one is modelled by the improvement procedure, so-called enthalpy-porosity formulation, where the liquid-solid mushy zone is treated as a porous zone with porosity equal to the liquid fraction. The numerical model is based on the finite volume method in body fitted coordinates with a SIMPLER scheme to couple the pressure and velocity fields. Simulation presents solidification for two cooling cases on the cylindrical part, where in the first case the adiabatic boundary condition is considered and in the second case the convective cooling over the wall is present. The results are presented for the velocity and temperature field as well as for the NiTi mass fraction during the solidification proc...
This paper focuses on the numerical analysis of the combustion of the liquid fuel Extra Light Fue... more This paper focuses on the numerical analysis of the combustion of the liquid fuel Extra Light Fuel Oil (ELFO) in a small combustion device. The calculation was performed by ANSYS CFX computer code for experimental optimal air-fuel ratio (λopt) and the middle power of the oil burner Weishaupt WL5/1-A (37 kW). The goal of the numerical analysis was to establish, whether the experimentally determined λopt ensured the conditions for a complete combustion in each point of the combustion chamber. The comparison of numerical results and measured values confirm the suitability of the chosen numerical model.
In this work, we developed a numerical approach based on an experimental platform to determine th... more In this work, we developed a numerical approach based on an experimental platform to determine the working conditions on a cryoplatform and to predict and evaluate the cryogenic printing of hydrogels. Although hydrogels have good biocompatibility, their material properties make it difficult to print them with high precision and shape fidelity. To overcome these problems, a cryogenic cooling platform was introduced to accelerate the physical stabilisation of each deposited layer during the printing process. By precisely controlling solidification (crystallisation), each printed material can withstand its own weight to maintain shape fidelity, and the porosity of the scaffolds can also be controlled more selectively. The thermophysical properties of gelatine hydrogels were investigated to gain a better understanding of the phase change upon freezing. The corresponding material properties and experimental observations of gelatine solidification served as the basis for developing a comp...
In the process industry, vacuum-type dryers are becoming increasingly important. A special case o... more In the process industry, vacuum-type dryers are becoming increasingly important. A special case of vacuum drying is lyophilization, where a solution, containing up to 90% of solvent (typically water), is dried under the conditions of very low temperatures and extremely low system pressures. As a container type, in which the solution is dried, a vial is frequently used. The intensity of drying is to a large extent controlled by the pressure conditions above the drying surface. The vial and the rubber stopper geometry present a significant pressure drop in the flow of sublimated solvent, but are experimentally difficult to determine. In order to produce realistic pressure conditions for the mass transfer computation, a CFD analysis of flow inside the vial-stopper channel is performed. The influence of imposing the no-slip and slip conditions on the solid surfaces on the pressure drop in the system is studied under the typical sublimation conditions. The effect of the increased partial pressure of the solvent on the sublimation rate is calculated by implementing the Maxwell-Stefan diffusion model.
To monitor the progress and prevent the spread of the COVID-19 pandemic in real time and outside ... more To monitor the progress and prevent the spread of the COVID-19 pandemic in real time and outside laboratories, it is essential to develop effective tests that can ensure rapid, selective, and reliable diagnosis of infected persons in different environments. Key in this regard is the lateral flow immunoassays (LFIAs) that can detect the presence of the SARS-CoV-2 virus quickly, with the aid of nanoparticles (NPs) and specific proteins. We report the use of gold (Au) NPs AuNPs synthesised from a gold(iii) chloride tetrahydrate precursor in a USP device and collected in a suspension composed of deionised water with polyvinylpyrrolidone as a stabiliser and cryoprotectant. In combination with freeze-drying of the AuNPs’ suspension to achieve water elimination, improved stability, and the target concentration, they exhibit the necessary properties for use as markers in LFIA rapid diagnostic tests. This was confirmed by complementary characterisation determined by using the techniques incl...
Vpliv lastnosti mikropolarnih tekočin na prenos toplote pri naravni konvekciji
V prispevku so predstavljeni numericni rezultati analize vpliva spremenljivih tokovnih razmer na ... more V prispevku so predstavljeni numericni rezultati analize vpliva spremenljivih tokovnih razmer na prenos toplote v primeru naravne konvekcije mikropolarnih tekocin v kvadratni kotanji. Za potrebe numericnega resevanja problema je bila razvita hitrostno-vrtincna formulacijo Navier Stokesovih enacb z vpeljano teorijo mikropolarnih tekocin. Izveden je bil testni primer naravne konvekcijev kvadratni kotanji za razlicne vrednosti Rayleighovih stevil vse do vrednosti ▫${10}^7$▫. Rezultati so pokazali da mikrorotacija v mikropolarni tekocini zmanjsuje prenos toplote od tople stene v kotanji in jo je tako v primeru tekocin, ki izražajo mikropolarni znacaj, pri numericnih simulacijah potrebno upostevati.
Numerično modeliranje mešanja v posodi z Rushtonovim mešalom
Strojniški vestnik, 2005
Prispevek obravnava numericno modeliranje mesanja newtonske tekocine v mesalni posodi, v kateri j... more Prispevek obravnava numericno modeliranje mesanja newtonske tekocine v mesalni posodi, v kateri je namesceno turbinsko Rushtonovo mesalo. Obravnavan je ustaljeni turbulentni tokovni rezim, opisan s casovno povprecnim Navier-Stokesovim sistemom enacb. Numericno resevanje temelji na uporabi dvoenacbnega modela turbulence in metode koncnih prostornin. Posebna pozornostje namenjena modeliranju vrtenja mesala ter izracunu mehanske moci za mesanje, kakor tudi nekaterim poenostavitvam, ki omogocajo hitrejsi izracun zahtevnih diskretnih modelov.
Journal of Drug Delivery Science and Technology, 2018
The paper reports on the development of a numerical model for the simulation of a lyophilization ... more The paper reports on the development of a numerical model for the simulation of a lyophilization process in a vial. Experimental analysis is presented of lyophilization dynamics inside a single vial in a laboratory scale lyophilizer. The problems of lyophilization modelling of a mannitol water solution are covered in detail. The effects of the small scale of the laboratory device with respect to a correct definition of boundary conditions for the numerical simulations are described, especially the effect of the comparatively high temperatures of the chamber walls. In the numerical model, a 1D vial approximation of the governing equations of heat and mass transport with moving front between the frozen and porous part of the cake is used and solved in a time stepping nonlinear iteration procedure. A water vapour diffusion model, implemented in the mass conservation equations, based on the Knudsen model of diffusivities, is applied and linked to the typical pore size of the porous cake. A front tracking scheme with moving computational grid is applied, and a dedicated sub-model of surface layer ice sublimation is introduced, based on the one-sided vapour diffusion model. The comparison of the numerical and the experimental results show that the developed numerical model is able to capture the transition points from primary to secondary drying very accurately, with accompanying accurate capturing of the temperature levels inside of the drying material.
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Papers by Matej Zadravec