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Investigation of the properties and factors affecting concentrations and size distribution of ultrafine aerosol particles during winter in the city of Zagreb
No full textUltrafine lebdeće čestice promjera manjeg od 100 nm (PM0,1) nastaju direktnom emisijom iz prirodnih/antropogenih izvora i/ili sekundarnim procesima iz plinova u atmosferi. Prvo ispitivanje ultrafinih lebdećih čestica u Zagrebu provedeno je u stvarnom vremenu primjenom skenirajućeg sustava za određivanje veličine čestica u razdoblju od 5. siječnja do 15. veljače 2024. Etalometar je omogućio mjerenja crnog ugljika u česticama (indikator izgaranja biomase i fosilnih goriva) u stvarnom vremenu dok su kaskadnim uzorkovačem sakupljene veličinske frakcije lebdećih čestica (od 10 nm do 32 μm) kojima je gravimetrijskom metodom određena masa te koncentracije organskog ugljika primjenom visokotemperaturne katalitičke oksidacije. Dobiveni podaci uspoređeni su s meteorološkim podacima te koncentracijama PM10, PM2,5, NO2, SO2 i O3. Statističkom obradom podataka omogućen je uvid u promjenjivost koncentracija ultrafinih čestica, uključujući njihove nukleacijske (PM0,02) i Aitkenove (PM0,02-0,1) frakcije te razlučivanje dominantnih utjecaja na njihovo stvaranje i starenje u gradu Zagrebu.Ultrafine aerosol particles (diameter < 100 nm, PM0,1) are emitted directly from natural/anthropogenic sources and/or formed by secondary processes from gasses in the atmosphere. The first real time investigation of ultrafine particles in Zagreb was conducted using a Scanning Mobility Particle Sizer (SMPS) system from January 5 to February 15, 2024. Real time black carbon (indicator of biomass burning and fossil fuel combustion) was measured using an aethalometer, while aerosol size fractions (10 nm to 32 μm) collected using a cascade impactor were analysed by gravimetric methods to determine the mass and by high-temperature catalytic oxidation to determine the concentration of organic carbon. The data obtained were correlated with meteorological data and concentrations of PM10, PM2.5, NO2, SO2, and O3. Statistical analysis provided insights into the variability of ultrafine particle concentrations, including their nucleation (PM0.02) and Aitken (PM0.02-0.1) fractions, and enabled identification of dominant factors influencing their formation and aging in Zagreb
Dry process of flue gas treatment in a waste power plant
No full textEnergane na otpad su postrojenja u kojima se spaljuju različiti tipovi otpada, u ovome radu analiziran je sustav za suho čišćenje dimnih plinova za energanu koja godišnje spaljuje 60000 t goriva dobivenog iz otpada. Na temelju odabranog sastava goriva postavljene su bilance dimnih plinova i izračunate su potrebne količine aditiva za neutralizaciju kiselih plinova i uklanjanje teških metala i organskih spojeva. Neutralizacija kiselih plinova vrši se pomoću sode bikarbone čija potrošnja je procijenjena na 118,6 kg/h, a za uklanjanje teških metala i organskih spojeva troši se 6,2 kg/h aktivnog ugljena. Glavna komponenta sustava za čišćenje dimnih plinova je vrećasti filtar te je za njega izrađen proračun na temelju kojeg je dobivena potrebna površina za filtraciju od 1900 m2 i odabran je materijal vreća od politetrafluoretilena (PTFE). Izrađena je shema cijelog sustava za čišćenje dimni plinova te je odabrana glavna oprema i detaljno je opisan princip rada. Zadnji dio rada obuhvaća proračun izmjenjivača topline snage 1161,4 kW koji se koristi za regeneraciju topline dimnih plinova nakon procesa čišćenja.Waste-to-energy plants are facilities where various types of waste are incinerated. This paper analyzes a dry flue gas cleaning system for a waste-to-energy plant that annually burns 60,000 tons of fuel derived from waste. Based on the selected fuel composition, flue gas balances were established, and the necessary quantities of additives for neutralizing acidic gases and removing heavy metals and organic compounds were calculated. The neutralization of acidic gases is performed using sodium bicarbonate, with an estimated consumption of 118,6 kg/h, while 6,2 kg/h of activated carbon is used to remove heavy metals and organic compounds. The main component of the flue gas cleaning system is a bag filter, for which a calculation was made, resulting in a required filtration area of 1900 m², and bags made of polytetrafluoroethylene (PTFE) were selected. A schematic drawing of the entire flue gas cleaning system was created, and the main equipment was selected, with a detailed description of the operating principle. The final part of the paper includes the calculation of a heat exchanger with a capacity of 1161,4 kW, which is used for heat recovery from flue gases after the cleaning process
Simulation model for predicting a race time of Formula Student race car on racing track
No full textRačunalne simulacije neizostavan su dio pri razvoju bolida Formule Student, omogućujući postizanje optimalnih rezultata kako u dinamičkim, tako i u statičkim testovima, kroz predstavljanje rezultat simulacija koji podržavaju donesene konceptualne odluke. Cilj ovoga rada je razviti jednostavni model za dinamičku simulaciju analize vremena kruga. U uvodnom dijelu rada dan je opis simulacije vremena kruga te su prikazani postojećih simulacijski alati. Nakon toga, prikazane su teorijske podloge za izradu modela. Model je izrađen korištenjem Matlab/Simulinka, a jedini potreban ulaz u model su GPS koordinate staze na kojoj se želi provesti simulacija. Unutar Matlab-a postavlja se matematički model staze i vozila te se kreira ciljani profil brzine, koji služi kao ulaz u dinamičku simulaciju. Na kraju, rezultati dobiveni izrađenim modelom uspoređeni su s rezultatima dobivenim ponavljanjem iste simulacije u software-u AVL VSM.Computer simulations are essential in developing Formula Student cars, helping achieve optimal results in dynamic and static tests by presenting data that supports conceptual decisions. The aim of this paper is to develop a simple model for dynamic lap time simulation. In the introductory part of the paper, a description of the lap time simulation is given, and the existing lap time simulation softwares are presented. After that, the theoretical description for the creation of the model is given. The model was created using Matlab/Simulink, and the only required input into the model is the GPS coordinates of the track on which the simulation is to be carried out. Inside Matlab, a mathematical model of the track and the vehicle is set up, and a target speed profile is calculated, which serves as an input to the dynamic simulation. In the end, the results obtained by the created model were compared with the results obtained by repeating the same simulation in the AVL VSM software
Reconstruction of the industrial refrigeration system
No full textU ovom radu je projektirano i proračunato rashladno postrojenje za skladištenje piletine i puretine u Zagrebu. Proračunata je rashladna komora dimenzija 47x23,5x4,4 m. Temperatura u komori iznosi 0 °C. U radu je proveden proračun toplinskog opterećenja komore, proračun i dimenzioniranje komponenti sustava, kao i komponente za upravljanje uljem, proračun i dizajn isparivača i kondenzatora te proračun količine punjenja radne tvari i kompresorskog ulja. Priložena je shema spajanja i automatske regulacije te dispozicijski crtež rashladnog agregata.In this thesis, a refrigeration plant for storage of chicken and turkey in Zagreb has been designed and calculated. The cooling chamber with dimensions 47x23,5x4,4 m has been calculated. The temperature maintained in the chamber is 0 °C. This thesis includes the calculation of heat load of chamber, the calculation and sizing of the system components, as well as the components for oil managment, the calculation of the quantitiy of refridgerant and compressor oil. A shematic of the connections and automatic regulation, as well as a layout drawing of the refridgeration unit, are also provide
Development of belt tensioner for bicycle with rear suspension
No full textU ovom radu prikazan je razvoj zatezača remena za bicikl sa stražnjom suspenzijom. Razvoj je
započet kratkim uvodom i prikazom problema kojeg je potrebno riješiti. Potom je provedena
analiza patenata i postojećih proizvoda na tržištu. Pomoću funkcijske dekompozicije i
morfološke matrice koja iz nje slijedi – generirana su tri koncepta zatezača remena za bicikl sa
stražnjom suspenzijom. Na temelju vrednovanja izabran je koncept za daljnju konstrukcijsku
razradu. Nakon konstrukcijske razrade model zatezača remena kontroliran je numeričkom
analizom metode konačnih elemenata. Također, proveden je i dinamički proračun sigurnosti
ležaja i tijela zatezača. Nad usvojenim modelom, nakon zadovoljavanja proračuna, proveden je
proces topološke optimizacije. Na koncu su izvršene konačne evaluacije novog modela pomoću
prethodno spomenutih metoda. Konačno rješenje je diskutirano i predloženi su eventualni
pravci daljnjeg razvoja zatezača remena.The topic of this thesis is the development of belt tensioner for bicycle with rear suspension.
The development was started with a short introduction and presentation of the problem that
needs to be solved. An analysis of patents and existing products on the market was then carried
out. By means of the functional decomposition and the morphological matrix that follows from
it – three concepts of belt tensioners for bicycle with rear suspension were generated. Based on
the evaluation, a concept was chosen for further design development. After the design
development, the belt tensioner model was controlled by numerical analysis of the finite
element method. Also, a dynamic calculation of the safety of the bearing and tensioner body
was carried out. After satisfying the engineering analysis, the topological optimization process
was carried out over the adopted model. Finally, the final evaluations of the new model were
performed using the previously mentioned methods. The final solution was discussed and
possible directions for further development of the belt tensioner were proposed
Quality control and deformation properties testing of metal materials using modern methods during plastic deformation
No full textU ovom radu provedena su ispitivanja deformacijskih svojstava suvremenim metodama digitalne korelacije slike i termografije te mogućnost korištenja suvremene metode 3D optičkog mjerenja odnosno inspekcije upotrebom automatiziranog mjernog sustava Atos Scanbox na ispitnim uzorcima za statičko vlačno ispitivanje. Dimenzijska i geometrijska kontrola ispitnih uzoraka provedena je usporedbom skeniranog (stvarnog) ispitnog uzorka bakra i njegovog CAD modela. Na ispitnim uzorcima bakra i aluminij-magnezij legure provedeno je određivanje deformacijskih svojstava metodama digitalne korelacije slike i termografije tijekom statičkog vlačnog ispitivanja odnosno plastične deformacije. Utvrđena je mogućnost inspekcije dimenzija i geometrije ispitnih uzoraka 3D optičkim mjerenjima te određivanje i usporedba deformacijskih svojstava dobivenih metodama digitalne korelacije slike i termografije tijekom plastične deformacije bakra i aluminij-magnezij legure. Usporedbom rezultata mjerenja skeniranog ispitnog uzorka bakra i CAD modela utvrđeno je da ne postoje značajna dimenzijska i geometrijska odstupanja. Metodama digitalne korelacije slike i termografije utvrđene su razlike u deformacijskim svojstvima između bakra i aluminij-magnezijeve legure.In this work, tests of deformation properties were carried out using the modern methods of digital image correlation and thermography, as well as the possibility of using modern method of 3D optical measurement, i.e. inspection using the automated measuring system Atos Scanbox on test samples for static tensile testing. The dimensional and geometric control of the test samples was performed by comparing the scanned (actual) test sample of copper and its CAD model. On the test samples of copper and aluminum-magnesium alloy, deformation properties were determined using the methods of digital image correlation and thermography during static tensile test, i.e. plastic deformation. The possibilities of dimensional and geometric inspection of the test samples with 3D optical measurements were determined. The determination and comparison of deformation properties, obtained by the digital image correlation and thermography, during the plastic deformation of copper and aluminum-magnesium alloy were determined. The comparison of the measurement results of the scanned copper test sample and the CAD model showed that there are no significant dimensional and geometric deviations. The differences in deformation properties between copper and aluminum-magnesium alloy were determined using the methods of digital image correlation and thermography
Influence of rice sample preparation on elemental composition - application of total reflection X-ray fluorescence spectroscopy
No full textRiža je namirnica koja se u velikim količinama konzumira svakodnevno diljem svijeta. Zbog zagađenosti okoliša, može biti kontaminirana teškim metalima te je stoga određivanje elementarnog sastava riže od iznimne važnosti za očuvanje ljudskog zdravlja.
Glavni cilj ovoga rada jest odrediti utjecaj različite predobrade uzoraka riže na elementarni sadržaj te usporediti učinkovitost korištenih tehnika u određivanju sadržaja metala (TXRF-Mo, ICP-MS). Prikupljeni uzorak riže prije postupka mikrovalne digestije korišten je i) bez prethodne obrade, ii) nakon što se tri puta isprao s ultra čistom vodom, iii) nakon što je usitnjen u mlinu. Svi uzorci su nakon predobrade podvrgnuti postupku mikrovalne digestije te analizirani primjenom TXRF-Mo i ICP-MS. U svim ispitanim uzorcima određeni su slijedeći elementi: željezo, bakar, mangan, cink, stroncij i nikal. Dobiveni rezultati za sadržaj elemenata u uzorcima samljevene riže i riže tri puta isprane s ultračistom vodom uspoređeni su sa sadržajem elemenata u uzorcima riže bez prethodne obrade.
Sadržaj analiziranih elemenata određenih s TXRF tehnikom usporediv je s rezultatima ICP-MS tehnike. U usporedbi s netretiranim uzorkom, rezultati analize su utvrdili da ispiranje zrna riže, za razliku od mljevenja, uzrokuje značajnije promjene sadržaja za sve određene elemente. Prethodna obrada uzorka je pokazala najveći utjecaj na sadržaj željeza, a najmanji na mangan. Unatoč tome, nije utvrđena statistički značajna razlika kod dodatne obrade uzorka te je stoga donesen zaključak kako predpriprema uzorka nije potrebna.
Analiza TXRF tehnikom iziskuje vrlo male količine uzoraka i reagensa, proizvodi malo kemijskog otpada, ne iziskuje rashladne sustave i plinove te uključuje jednostavnu kvantifikaciju dodatkom unutarnjeg standarada što ju čini bržom, jednostavnijom te ekološki i ekonomski prihvatljivijom tehnikom od ICP-MS-a.Rice is consumed daily in large quantities all over the world. Due to environmental pollution, rice can be contaminated with heavy metals, which is why controlling the elemental composition of rice grains is extremely important for the preservation of human health.
The main objective of this work is to determine the influence of different pretreatments of rice samples on elemental analysis and to compare the effectiveness of the techniques used to determine the metal content (TXRF-Mo, ICP-MS).
The rice sample collected before microwave digestion was used i) without pretreatment, ii) after washing three times with ultrapure water and iii) after milling in a mill. After processing, all samples were subjected to microwave digestion and analyzed by TXRF-Mo and ICP-MS. The following elements were determined in all analyzed samples: iron, copper, manganese, zinc, strontium and nickel. The results for the content of elements in samples of milled rice and rice washed three times with ultrapure water were compared with the content of elements in samples of rice without prior treatment.
The content of the elements analyzed with the TXRF technique corresponds to the ICP-MS element content. Compared to the untreated samples, the results showed that washing the rice grains, as opposed to milling, caused more significant changes in the content of all analyzed elements. The pre-treatment of the sample had the greatest influence on the iron content and the least on the manganese content. Regardless of this, no statistically significant difference was found with additional sample preparation, so it was concluded that pretreatment of the samples is not necessary.
Analysis using the TXRF technique requires very small amounts of samples and reagents, generates little chemical waste, does not require cooling systems or gasses and involves simple quantification with internal standards, making it a faster, simpler and more environmentally and economically acceptable technique than ICP-MS
Operating parameters of air-to-water heat pump performance in relevant environment
No full textU sklopu istraživanja IRI 2 projekta pod nazivom Razvoj dizalice topline zrak voda s prirodnom radnom tvari i naprednim sustavom odleđivanja isparivača (KK.01.2.1.02.0132), sufinanciranog sredstvima iz Europskog fonda za regionalni razvoj, ERDF, instalirana je prototipna dizalica topline u sjevernu zgradu Fakulteta strojarstva i brodogradnje, Sveučilišta u Zagrebu.
Navedena dizalica projektirana je za kondicioniranje fakultetskog prostora površine 200 m2, čime je osigurano ispitivanje dizalice topline u relevantnom okruženju. Ispitna linija opremljena je brojnim senzorima i upravljačkom opremom za što točnije i bolje praćenje parametara procesa. Eksperimentalnim mjerenjem nekoliko uzastopnih dana prikupljeni su brojni podaci te su na temelju toga izneseni bitni parametri za praćenje rada dizalice topline. Prikupljeni podaci svrstani su u kategorije, obrađeni te grafički prikazani za bolje praćenje parametara u radu.
Budući da je Sjeverna zgrada u međuvremenu obnovljena, a Fakultet zajedno sa dizalicom izmješten, bilo je potrebno provesti ponovni proračun projektnog toplinskog opterećenja prema normi HRN EN 12831 i proračun rashladnog opterećenja prema normi VDI 2078. Proračun je proveden u programu IntegraCad. Novo projektno toplinsko opterećenje iznosi 15,1 kW, dok je za sezonu hlađenja rashladno opterećenje 12,6 kW.As part of the research of the IRI 2 project entitled Development of an air-water heat pump with a natural working substance and an advanced evaporator system (KK.01.2.1.02.0132), co-financed by funds from the European Regional Development Fund, ERDF, a prototype heat pump was installed in one of the buildings at the Faculty of Mechanical Engineering and Naval ArhitectureZagreb, Univesity of Zagreb.
This heat pump was designed to condition the faculty area of 200 m2, which ensured the testing of the heat pump in the relevant environment. The test setup is equipped with numerous sensors and control system for the most accurate and better parametar monitoring. Numerous data collected through experimental measurements over several consecutive days were processed nad presented, with essential parametars for monitoring the heat pump's operation highlighted. The collected data were categorized, processed and graphically displayed for better monitoring parameters of operation.
Following the renovation of North building and relocation of the Faculty, it was necessary to recalculate the heat load according to the HRN EN 12831 standard and the cooling load according to the VDI 2078 standard. The calculation was executed in the IntegraCad. The new calculated heat load is 15,1 kW, while the cooling season requires 12,6 kW
Influence of the synthesis parameters on the morphology and application of materials derived with different drying methods
No full textGelovi, aerogelovi i kserogelovi su tri različita stanja materijala, svako od kojih posjeduje jedinstvena svojstva i primjenu. Aerogel je vrsta posebno poroznog materijala, izuzetno niske gustoće te velike poroznosti. Ističe se po svojim iznimnim izolacijskim svojstvima te velikim specifičnim površinama pa se njegova primjena očituje u području optoelektronike, zrakoplovne industrije, svemirske opreme te u mnogim drugim područjima. Celuloza, prirodni biopolimer koji se nalazi u stjenkama biljnih stanica, ističe se kao izvrstan materijal za sintezu aerogelova. Zbog svoje obnovljivosti, biorazgradivosti te biokompatibilnosti celulozni aerogelovi privlače sve više pažnje, pogotovo u području biomedicine gdje se očituje njihov značajan potencijal. Ovaj diplomski rad daje pregled sinteze i karakterizacije kserogelova i aerogelova na bazi celuloze modificiranih ureom, natrijevim kloridom i magnezijevim kloridom. Karakterizacija ovih modificiranih materijala provedena je raznim analitičnim tehnikama, uključujući pretražnu elektronsku mikroskopiju (SEM), energijski disperzivnu spektrometriju (EDS) te rendgensku difrakcijsku analizu (XRD). Primarni cilj je bio istražiti utjecaj ovih modifikacija kao i metode pripreme gela na veličinu pora, poroznost i skupljanje volumena kako bi se dobio uvid u njihovu potencijalnu primjenu u različitim područjima.Gels, aerogels, and xerogels are three distinct states of materials, each with unique properties and applications. Aerogel is a type of particularly porous material, with extremely low density and high porosity. It stands out for its exceptional insulating properties and high specific surface area, so its application is evident in the field of optoelectronics, the aviation industry, space equipment and many other areas. Cellulose, a natural biopolymer found in plant cell walls, is an excellent material for aerogel production. Due to their renewability, biodegradability and biocompatibility, cellulose aerogels are attracting more attention, especially in the field of biomedicine, where they have a significant potential. This thesis provides an overview of the synthesis and characterization of cellulose-based xerogels and aerogels modified with urea, sodium chloride and magnesium chloride. Characterization of these modified materials was performed using various analytical techniques, including scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and X-ray diffraction analysis (XRD). The primary objective was to investigate the influence of these modifications as well as the gel preparation method on pore size, porosity and volume shrinkage in order to gain insight into their potential application in different fields
Solution-based synthesis of high-entropy oxide of transition metals
No full textCilj ovog rada bila je sinteza visoko-entropijskog oksida kemijske formule (TiZrHfNbTa)O11. Korištena su četiri postupka sinteze: limunski, koprecipitacijski, sol-gel i hidrotermalni. Kao polazni reaktanti za sve četiri sinteze korišteni su kloridi niobija (NbCl5), tantala (TaCl5), hafnija (HfCl4) i cirkonija (ZrCl4) te titanijev butoksid (Ti(C4H9O)). Svi sintetizirani uzorci karakterizirani su infracrvenom spektroskopijom s Fourierovom transformacijom (FTIR) te pretražnom elektronskom mikroskopijom i energijski razlučujućom rendgenskom spektroskopijom (SEM/EDXS). Na temelju SEM/EDXS rezultata zaključeno je da su kod svih sintetiziranih uzoraka udjeli niobija, tantala, hafnija i cirkonija približno jednaki dok je titanija gotovo dvostruko više, što je vjerojatno posljedica njegove veće reaktivnosti budući da se u reakcijsku smjesu uvodi u obliku alkoksida. Uzorci visoko-entropijskih oksida koji su u
SEM/EDXS analizama pokazali najveći stupanj homogenosti i dobro poklapanje množinskih udjela pojedinih elemenata s teorijskim udjelima, dodatno su analizirani rendgenskom difrakcijskom analizom (XRD). Na temelju XRD analize zaključeno je da se dobiveni difraktogrami žarenih visoko-entropijskih oksida podudaraju s literaturnim podacima čime je potvrđeno da su svi primijenjeni postupci prikladni za sintezu HEO ciljanog sastava. Iz difraktograma prekursora dobivenog hidrotermalnim postupkom zaključeno da tim postupkom sinteze nije moguće direktno dobiti oksid bez dodatnog koraka žarenja.The aim of this work was the synthesis of high-entropy oxide with the chemical formula (TiZrHfNbTa)O11. Four synthesis methods were used: citric, coprecipitation, sol-gel, and hydrothermal. Chlorides of niobium (NbCl5), tantalum (TaCl5), hafnium (HfCl4), and zirconium (ZrCl4), as well as titanium butoxide (Ti(C4H9O)), were used as starting reactants for all four syntheses. All synthesized samples were characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDXS). Based on SEM/EDXS results, it was concluded that the contents of niobium, tantalum, hafnium, and zirconium in all synthesized samples are approximately equal, while the content of titanium is almost twice as high, likely due to its higher reactivity since it is introduced into the reaction mixture in the form of an alkoxide. High-entropy oxide samples that showed the highest degree of homogeneity in SEM/EDXS analyses and good matching of elemental molar ratios with theoretical values were further analyzed using X-ray diffraction analysis (XRD). Based on XRD analysis, it was concluded that the diffractograms of annealed high-entropy oxides match the literature data, confirming that all applied methods are suitable for the synthesis of HEO with the targeted composition. From the diffractogram of the precursor obtained by the hydrothermal method, it was concluded that this synthesis method does not directly yield an oxide without an additional annealing step