Application of artificial neural networks in performance prediction of cement mortars with various mineral additives

The machine learning technique for prediction and optimization of building material performances became an essential feature in the contemporary civil engineering. The Artificial Neural Network (ANN) prognosis of mortar behavior was conducted in this study. The model appraised the design and characteristics of seventeen either building or high-temperature mortars. Seven different cement types were employed. Seventeen mineral additives of primary and secondary origin were embedded in the mortar mixtures. Cluster Analysis and Principal Component Analysis designated groups of similar mortars assigning them a specific purpose based on monitored characteristics. ANN foresaw the quality of designed mortars. The impact of implemented raw materials on the mortar quality was assessed and evaluated. ANN outputs highlighted the high suitability level of anticipation, i.e., 0.999 during the training period, which is regarded appropriate enough to correctly predict the observed outputs in a wide range of processing parameters. Due to the high predictive accuracy, ANN can replace or be used in combination with standard destructive tests thereby saving the construction industry time, resources, and capital. Good performances of altered cement mortars are positive sign for widening of economical mineral additives application in building materials and making progress towards achieved carbon neutrality by reducing its emission

Numerical simulation of boiling crises mechanism in evaporation pipes

Predmet ovog rada je numerička simulacija i analiza trodimenzionalnog dvofaznog strujanja i istraživanje mehanizama krize ključanja u isparivačkim cevima. Kriza ključanja je nepovoljna pojava. Nagli porast temperature zida cevi izaziva termomehanička naprezanja, koja mogu dovesti do pojave prskotina i pucanja cevi pod pritiskom.Razvijen je matematički model dvofaznog strujanja u isparivačkoj cevi,koji se sastoji od jednačina održanja mase, količine kretanja i energije za obe faze. Sastoji se od sistema parcijalnih diferencijalnih jednačinakoje su rečavane za definisane granične uslove.Bilo je neophodno uvesti i modeliranje i numeričku simulaciju na mikro nivou, jer je bilo potrebno ispitati i proces pojave i rasta mehura, kao i ponašanje dvofazne mešavine na zagrejačkoj površini na makroskopskom nivou.Rezultati numeričkih simulacija su upoređeni sa raspoloživim eksperimentalnim rezultatima.The subject of this thesis is numerical simulation and analyses of three dimensional two-phase flow and mechanism of boiling crises in evaporation pipes. Boiling crises is characterized by a dried out heat surface and can bring physical destruction of the heater. A developed mathematical model of two phase flow in evaporation pipe consists of prescribed mass, momentum and energy conservation equations for liquid and vapor two-phase flow. It consists of set of partial differential equations which were solved for specific boundary conditions. Modeling of the micro scale level was necessary to take into account processes of the bubble rise and behavior of the two-phase mixture at the heating surface. Results of the numerical simulation are compared with similar available results of the experiments from the literature

Numerical simulation of boiling crises mechanism in evaporation pipes

Predmet ovog rada je numerička simulacija i analiza trodimenzionalnog dvofaznog strujanja i istraživanje mehanizama krize ključanja u isparivačkim cevima. Kriza ključanja je nepovoljna pojava. Nagli porast temperature zida cevi izaziva termomehanička naprezanja, koja mogu dovesti do pojave prskotina i pucanja cevi pod pritiskom. Razvijen je matematički model dvofaznog strujanja u isparivačkoj cevi,koji se sastoji od jednačina održanja mase, količine kretanja i energije za obe faze. Sastoji se od sistema parcijalnih diferencijalnih jednačinakoje su rečavane za definisane granične uslove.Bilo je neophodno uvesti i modeliranje i numeričku simulaciju na mikro nivou, jer je bilo potrebno ispitati i proces pojave i rasta mehura, kao i ponašanje dvofazne mešavine na zagrejačkoj površini na makroskopskom nivou. Rezultati numeričkih simulacija su upoređeni sa raspoloživim eksperimentalnim rezultatima.The subject of this thesis is numerical simulation and analyses of three dimensional two-phase flow and mechanism of boiling crises in evaporation pipes. Boiling crises is characterized by a dried out heat surface and can bring physical destruction of the heater. A developed mathematical model of two phase flow in evaporation pipe consists of prescribed mass, momentum and energy conservation equations for liquid and vapor two-phase flow. It consists of set of partial differential equations which were solved for specific boundary conditions. Modeling of the micro scale level was necessary to take into account processes of the bubble rise and behavior of the two-phase mixture at the heating surface. Results of the numerical simulation are compared with similar available results of the experiments from the literature

Simulations of the kettle reboiler shell side thermal-hydraulics with different two-phase flow models

A computational fluid dynamics approach is presented for the simulation and analyses of the kettle reboiler shell side thermal-hydraulics with two different models of two-phase flow – the mixture and two fluid model. The mixture model is based on solving one momentum equation for two-phase mixture flow and a closure law for the calculation of the slip between gas and liquid phase velocities. In the two fluid modeling approach the momentum balance is formed for each phase, while the gas-liquid interaction due to momentum exchange at the interface surface is predicted with an empirical correlation for the interface friction coefficient. In both approaches the two-phase flow is observed as two inter-penetrating continua. The models are solved for the two-dimensional geometry of the kettle reboiler shell side vertical cross section. The computational fluid dynamics numerical method based on the SIMPLE type algorithm is applied. The results of both liquid and vapor velocity fields and void fraction are presented for each modeling approach. The calculated void fraction distributions are compared with available experimental data. The differences in the modeling approaches and obtained results are discussed. The main finding is that the void fraction distribution and two-phase flow field strongly depends on the modeling of the slip between liquid and gas phase velocity in mixture model or on the interface friction model in two fluid model. The better agreement of the numerically predicted void fraction with the experimental data is obtained with the two fluid model and an interfacial friction model developed for the conditions of two-phase flows in large volumes of kettle reboilers or different designs of steam generators

Simulations of the kettle reboiler shell side thermal-hydraulics with different two-phase flow models

A computational fluid dynamics approach is presented for the simulation and analyses of the kettle reboiler shell side thermal-hydraulics with two different models of two-phase flow – the mixture and two fluid model. The mixture model is based on solving one momentum equation for two-phase mixture flow and a closure law for the calculation of the slip between gas and liquid phase velocities. In the two fluid modeling approach the momentum balance is formed for each phase, while the gas-liquid interaction due to momentum exchange at the interface surface is predicted with an empirical correlation for the interface friction coefficient. In both approaches the two-phase flow is observed as two inter-penetrating continua. The models are solved for the two-dimensional geometry of the kettle reboiler shell side vertical cross section. The computational fluid dynamics numerical method based on the SIMPLE type algorithm is applied. The results of both liquid and vapor velocity fields and void fraction are presented for each modeling approach. The calculated void fraction distributions are compared with available experimental data. The differences in the modeling approaches and obtained results are discussed. The main finding is that the void fraction distribution and two-phase flow field strongly depends on the modeling of the slip between liquid and gas phase velocity in mixture model or on the interface friction model in two fluid model. The better agreement of the numerically predicted void fraction with the experimental data is obtained with the two fluid model and an interfacial friction model developed for the conditions of two-phase flows in large volumes of kettle reboilers or different designs of steam generators

DEM analysis of the granular flow in the static mixers

Statičke mešalice se koriste za mešanje pre glavnog procesa mešanja, čime se značajno smanje vreme mešanja i potrošnja energije. U ovom radu, prikazana je upotreba metode diskretnih elemenata (engl. Discrete Element Method - DEM) na modelovanje mešanja granula u različitim konfiguracijama statičkih mešača (korišćene su različite Komax i Ross konfiguracije za mešanje). Za modelovanje protoka fluida primenjena je metoda numeričke mehanike fluida (engl. Computational Fluid Dynamic - CFD), korišćenjem Ojlerovog dvofaznog modela. Povezivanjem rezultata ove dve metode dobija se pouzdan, dovoljno tačan i adekvatan model koji daje rezultate koji odgovaraju eksperimentalnim merenjima. Statičke mešalice se široko koriste u industiji prerade hrane, farmaceutskoj ili hemijskoj industriji. Ovaj tip mešalice se koristi uglavnom kao predmešač, pre glavnog mešanja, pri čemu se značajno smanjuje vreme mešanja i štedi energija. Za potrebe ovog rada, napravljene su statičke mešalice tipa Ross i Komax od providnog pleksiglasa, dizajnirane u CAD paketu, napravljene korišćenjem CNC glodalice. Pošto su napravljeni elementi bili prozirni, praćenje procesa mešanja granula je bilo i vizuelno. Praćene su i analizirane trajektorije, brzine i ubrzanja čestica, u cilju procene kvaliteta procesa mešanja. Glavni cilj ovog članka je da određivanje ponašanja granula koje se gravitaciono transportuju u različitim konfiguracijama mešalica i odabir najbolje konfiguracije mešalice, uzimajući u obzir ukupnu trajektoriju granule, broj elemenata za mešanje i kvalitet dobijene smeše. Rezultati numeričke simulacije statičkih mešalica upoređeni su sa eksperimentalnim rezultatima, a kvalitet mešanja ispitivan je kriterijumom relativne standardne devijacije. Uticaji tipa mešalice i broja elemenata za mešanje na proces mešanja su proučavani analizom varijanse (ANOVA).Static mixer is used for premixing action before the main mixing process, for significant reduction of mixing time and energy consumption. In this article, the novel numerical approach called Discrete Element Method is used for modeling of granular flow in multiple static mixer applications, while the Computational Fluid Dynamic method was chosen for fluid flow modeling. The main aim of this article is to predict the behaviour of granules being gravitationally transported in different mixer configuration and to choose the best configuration of the mixer taking into account the total particle path, the number of mixing elements and the quality of the obtained mixture. The results of the numerical simulations in the static mixers were compared to experimental results, the mixing quality is examined by relative standard deviation criterion. The effects of the mixer type and the number of mixing elements on mixing process were studied using analysis of variance (ANOVA)

DEM analysis of the granular flow in the static mixers

Statičke mešalice se koriste za mešanje pre glavnog procesa mešanja, čime se značajno smanje vreme mešanja i potrošnja energije. U ovom radu, prikazana je upotreba metode diskretnih elemenata (engl. Discrete Element Method - DEM) na modelovanje mešanja granula u različitim konfiguracijama statičkih mešača (korišćene su različite Komax i Ross konfiguracije za mešanje). Za modelovanje protoka fluida primenjena je metoda numeričke mehanike fluida (engl. Computational Fluid Dynamic - CFD), korišćenjem Ojlerovog dvofaznog modela. Povezivanjem rezultata ove dve metode dobija se pouzdan, dovoljno tačan i adekvatan model koji daje rezultate koji odgovaraju eksperimentalnim merenjima. Statičke mešalice se široko koriste u industiji prerade hrane, farmaceutskoj ili hemijskoj industriji. Ovaj tip mešalice se koristi uglavnom kao predmešač, pre glavnog mešanja, pri čemu se značajno smanjuje vreme mešanja i štedi energija. Za potrebe ovog rada, napravljene su statičke mešalice tipa Ross i Komax od providnog pleksiglasa, dizajnirane u CAD paketu, napravljene korišćenjem CNC glodalice. Pošto su napravljeni elementi bili prozirni, praćenje procesa mešanja granula je bilo i vizuelno. Praćene su i analizirane trajektorije, brzine i ubrzanja čestica, u cilju procene kvaliteta procesa mešanja. Glavni cilj ovog članka je da određivanje ponašanja granula koje se gravitaciono transportuju u različitim konfiguracijama mešalica i odabir najbolje konfiguracije mešalice, uzimajući u obzir ukupnu trajektoriju granule, broj elemenata za mešanje i kvalitet dobijene smeše. Rezultati numeričke simulacije statičkih mešalica upoređeni su sa eksperimentalnim rezultatima, a kvalitet mešanja ispitivan je kriterijumom relativne standardne devijacije. Uticaji tipa mešalice i broja elemenata za mešanje na proces mešanja su proučavani analizom varijanse (ANOVA).Static mixer is used for premixing action before the main mixing process, for significant reduction of mixing time and energy consumption. In this article, the novel numerical approach called Discrete Element Method is used for modeling of granular flow in multiple static mixer applications, while the Computational Fluid Dynamic method was chosen for fluid flow modeling. The main aim of this article is to predict the behaviour of granules being gravitationally transported in different mixer configuration and to choose the best configuration of the mixer taking into account the total particle path, the number of mixing elements and the quality of the obtained mixture. The results of the numerical simulations in the static mixers were compared to experimental results, the mixing quality is examined by relative standard deviation criterion. The effects of the mixer type and the number of mixing elements on mixing process were studied using analysis of variance (ANOVA)

Numerical study of the hydrodynamics and mass transfer in the external loop airlift reactor

The objective of this study was to investigate the hydrodynamics and the gas-liquid mass transfer coefficient of an external-loop airlift reactor (ELAR). The ELAR was operated in three cases: different inlet velocities of fluids, different alcohols solutions (water, 0.5% methanol, 0.5% ethanol, 0.5% propanol and 0.5% butanol) and different concentration of methanol in solutions (0%, 0.5%, 1%, 2% and 5%). The influence of superficial gas velocity and various diluted alcohol solutions on hydrodynamics and the gas-liquid mass transfer coefficient of the ELAR was studied. Experimentally, the gas hold-up, liquid velocities and volumetric mass transfer coefficient values in the riser and the downcomer were obtained from the literature source. A computational fluid dynamics (CFD) model was developed, based on two-phase flow, investigating different liquids regarding surface tension, assuming the ideal gas flow, applying the finite volume method and Eulerian-Eulerian model. The volumetric mass transfer coefficient was determined using the CFD and artificial neural network model. The effects of liquid parameters and gas velocity on the characteristics of the gas-liquid mass transfer were simulated. These models were compared with the appropriate experimental results. The CFD model successfully simulates the influence of different alcohols regarding the number of C-atoms on hydrodynamics and mass transfer

Application of discrete element method for the transportat of seed in screw conveyor

Pužni transporteri imaju široku primenu u prehrambenoj industriji, građevinskim i rudarskim kompanijima, u hemijskoj, poljoprivrednoj i prerađivačkoj industriji, uglavnom za podizanje i / ili transport rasutih materijala na kratkim i srednjim rastojanjima. Uprkos njihovoj očiglednoj jednostavnosti, poboljšanje transportnih parametara je veoma zahtevan zadatak i inženjeri obično moraju da se oslanjaju na podatke dobijene empirijskim istraživanjima. U ovom radu, ispitivano je petnaest horizontalnih pužnih transportera sa konstantnim korakom pužnice, različite dužine, sa modifikovanom geometrijom. Ovi puževi su ispitivani radi mogućnosti pomoćnog mešanja tokom transporta materijala. Sva ispitivanja su rađena eksperimentalno i numerički, pomoću metode diskretnih elemenata (Discrete Element Method - DEM). Uticaji dužine puža, kao i predložene modifikacije geometrije u dizajnu pužne spirale, ipitivani su radi pomoćnog mešanja, tokom transporta granulisanog materijala kroz pužni transporter. Pomoćno mešanje (koje se koristi se za poboljšanje finalnog procesa mešanja) je postignuto tokom transporta materijala. Geometrija pužnog transportera se menja dodavanjem tri komplementarne spirale orijentisane u istom ili suprotnom smeru od pužne spirale. Čestice materijala se transportuju padaju dole sa vrha spirale do sledeće slobodne površine, i taj segment spirale je korišćen za dodatnu akciju mešanje. Prema eksperimentima i DEM analizema trajektorija čestice se povećava, sa primenjenim modifikacijama transportera, a ovakva geometrija može se koristiti za povećanje kvaliteta finalnog mešanja.Fifteen horizontal single-pitch screw conveyors with modified geometry and the different lengths were investigated for premixing action, during the transport of materials. All investigations were performed experimentally and numerically, by using Discrete Element Method (DEM). The influences of screw length, observed geometry variations and different types of screw design, on the performances of the screw conveyor-mixer during material transport were explored. The auxiliary mixing action was achieved during the transport of the material. The geometry of the screw conveyor is changed by adding three complementary helices oriented in the same or the opposite direction from screw blades. The particles of the material being transported tumble down from the top of the helix to the next free surface, and that segment of helix was used for additional mixing action. According to DEM analysis, particle path length is increased, and the improved geometry could be determined for increasing the quality of mixing

Application of discrete element method for the transportat of seed in screw conveyor

Pužni transporteri imaju široku primenu u prehrambenoj industriji, građevinskim i rudarskim kompanijima, u hemijskoj, poljoprivrednoj i prerađivačkoj industriji, uglavnom za podizanje i / ili transport rasutih materijala na kratkim i srednjim rastojanjima. Uprkos njihovoj očiglednoj jednostavnosti, poboljšanje transportnih parametara je veoma zahtevan zadatak i inženjeri obično moraju da se oslanjaju na podatke dobijene empirijskim istraživanjima. U ovom radu, ispitivano je petnaest horizontalnih pužnih transportera sa konstantnim korakom pužnice, različite dužine, sa modifikovanom geometrijom. Ovi puževi su ispitivani radi mogućnosti pomoćnog mešanja tokom transporta materijala. Sva ispitivanja su rađena eksperimentalno i numerički, pomoću metode diskretnih elemenata (Discrete Element Method - DEM). Uticaji dužine puža, kao i predložene modifikacije geometrije u dizajnu pužne spirale, ipitivani su radi pomoćnog mešanja, tokom transporta granulisanog materijala kroz pužni transporter. Pomoćno mešanje (koje se koristi se za poboljšanje finalnog procesa mešanja) je postignuto tokom transporta materijala. Geometrija pužnog transportera se menja dodavanjem tri komplementarne spirale orijentisane u istom ili suprotnom smeru od pužne spirale. Čestice materijala se transportuju padaju dole sa vrha spirale do sledeće slobodne površine, i taj segment spirale je korišćen za dodatnu akciju mešanje. Prema eksperimentima i DEM analizema trajektorija čestice se povećava, sa primenjenim modifikacijama transportera, a ovakva geometrija može se koristiti za povećanje kvaliteta finalnog mešanja.Fifteen horizontal single-pitch screw conveyors with modified geometry and the different lengths were investigated for premixing action, during the transport of materials. All investigations were performed experimentally and numerically, by using Discrete Element Method (DEM). The influences of screw length, observed geometry variations and different types of screw design, on the performances of the screw conveyor-mixer during material transport were explored. The auxiliary mixing action was achieved during the transport of the material. The geometry of the screw conveyor is changed by adding three complementary helices oriented in the same or the opposite direction from screw blades. The particles of the material being transported tumble down from the top of the helix to the next free surface, and that segment of helix was used for additional mixing action. According to DEM analysis, particle path length is increased, and the improved geometry could be determined for increasing the quality of mixing