Cultural based preconceptions in aesthetic experience of architecture

On a broader scale, the aim of this paper is to examine theoretically the effects a cultural context has on the aesthetic experience of images existing in perceived reality. Minimalism in architecture, as direct subject of research, is a field of particularities in which we observe functioning of this correlation. Through the experiment with the similarity phenomenon, the paper follows specific manifestations of general formal principles and variability of meaning of minimalism in architecture in limited areas of cultural backgrounds of Serbia and Japan. The goal of the comparative analysis of the examples presented is to indicate the conditions that may lead to a possibly different aesthetic experience in two different cultural contexts. Attribution of different meanings to similar formal visual language of architecture raises questions concerning the system of values, which produces these meanings in their cultural and historical perspectives. The establishment of values can also be affected by preconceptions resulting from association of perceived similarities. Are the preconceptions in aesthetic reception of architecture conditionally affected by pragmatic needs, symbolic archetypes, cultural metaphors based on tradition or ideologically constructed dogmas? Confronting philosophical postulates of the Western and Eastern traditions with the transculturality theory of Wolfgang Welsch, the answers may become more available

Dynamic loads by various water hammer phenomena

Vodeni udar se može pojaviti kako u jednofaznom tako i u dvofaznom strujanju kroz cevovode. Razmatrani su osnovni mehanizmi koji dovode do pojave vodenog udara. Prikazana je i analizirana pojava dinamičkih opterećenja koja su izazvana različitim vrstama vodenih udara. Pokazano je da vodeni udar u dvofaznom sistemu može prouzrokovati mnogo veće pikove visokog pritiska nego vodeni udar u jednofaznom sistemu.Water hammer phenomena can be induced both in one-phase and two-phase systems during pipelines transients. The basic mechanisms of fluid dynamics that lead to the water hammer are presented. Dynamic loads induced by several water hammer events are presented and analyzed. It is shown that water hammers in two-phase systems can lead to much higher pressure peaks than water hammers in one-phase systems

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

Reduction of the specific surface area of porous ZnO during sintering

In this paper reduction of the specifice surface area of porous ZnO during sintering was analyzed. ZnO was sintered at temperatures from 673K to 1173K. Reduction of the specific surface area was observed as a function of the temperature and time of sintering. Analysis of sintering kintetics was done by observing reduction of the specific surface area. We used three different models, defined the appropriate parameters, and also the activation energy of sintering using the Arrhenius equation. The LSE metod was applied for determining optimum parameter values

Two-component two-phase critical flow

U radu je predstavljen model dvokomponentnog dvofaznog kritičnog strujanja dvofazne mešavine. Model je validiran poređenjem računskih rezultata sa vrednostima izmerenim na PUMA eksperimentalnoj instalaciji. Model je zasnovan na jednodimenzionalnom modifikovanom homogenom izentropskom dvofaznom strujanju tečnosti i gasa. Homogeni model je modifikovan tako što je klizanje između faza uzeto u obzir pri određivanju zapreminskog udela gasne faze u dvofaznoj mešavini, što određuje i gustinu dvofazne mešavine. Klizanje između faza je sračunato na osnovu Chisholm korelacije koja je pogodna za niže vrednosti masenog protočnog udela gasne faze kao i na osnovu Zivi korelacije koja određuje maksimalnu vrednost klizanja između faza. Na mestu kritičnog isticanja brzina dvofazne mešavine je jednaka brzini zvuka i sračunata je na osnovu takozvanog zamrznutog modela dvofaznog strujanja koji ne uzima u obzir fazni prelaz. Ostvareni rezultati su prikazani i upoređeni zajedno sa dobro poznatim Fauske modelom dostupnim u literaturi. Pokazano je da Fauske model daje više vrednosti kritičnog masenog fluksa u odnosu na izmerene vrednosti, dok model prikazan u radu daje prihvatljiva slaganja sa izmerenim podacima.A model of two-component two-phase critical flow is presented. The modelling approach is based on one-dimensional homogeneous gas-liquid two-phase isentropic flow of mixture. The homogeneous model is modified by taking into account the void fraction and two-phase mixture density dependence on velocity slip. The velocity slip is calculated using Chisholm correlation that depends on the gas phase quality and Zivi correlation for the prediction of the maximum velocity slip values. At the location of the critical flow the two-phase mixture velocity equals sonic velocity and it is calculated with the so-called ''frozen sonic velocity' model. The model is validated against data measured in air water flow at the PUMA experimental facility. Obtained results are presented together with the predictions by the well-known Fauske model. It is shown that Fauske model overpredicts measured critical mass fluxes, while the present model shows acceptable agreement with the measured data

Two-component two-phase critical flow

U radu je predstavljen model dvokomponentnog dvofaznog kritičnog strujanja dvofazne mešavine. Model je validiran poređenjem računskih rezultata sa vrednostima izmerenim na PUMA eksperimentalnoj instalaciji. Model je zasnovan na jednodimenzionalnom modifikovanom homogenom izentropskom dvofaznom strujanju tečnosti i gasa. Homogeni model je modifikovan tako što je klizanje između faza uzeto u obzir pri određivanju zapreminskog udela gasne faze u dvofaznoj mešavini, što određuje i gustinu dvofazne mešavine. Klizanje između faza je sračunato na osnovu Chisholm korelacije koja je pogodna za niže vrednosti masenog protočnog udela gasne faze kao i na osnovu Zivi korelacije koja određuje maksimalnu vrednost klizanja između faza. Na mestu kritičnog isticanja brzina dvofazne mešavine je jednaka brzini zvuka i sračunata je na osnovu takozvanog zamrznutog modela dvofaznog strujanja koji ne uzima u obzir fazni prelaz. Ostvareni rezultati su prikazani i upoređeni zajedno sa dobro poznatim Fauske modelom dostupnim u literaturi. Pokazano je da Fauske model daje više vrednosti kritičnog masenog fluksa u odnosu na izmerene vrednosti, dok model prikazan u radu daje prihvatljiva slaganja sa izmerenim podacima.A model of two-component two-phase critical flow is presented. The modelling approach is based on one-dimensional homogeneous gas-liquid two-phase isentropic flow of mixture. The homogeneous model is modified by taking into account the void fraction and two-phase mixture density dependence on velocity slip. The velocity slip is calculated using Chisholm correlation that depends on the gas phase quality and Zivi correlation for the prediction of the maximum velocity slip values. At the location of the critical flow the two-phase mixture velocity equals sonic velocity and it is calculated with the so-called ''frozen sonic velocity' model. The model is validated against data measured in air water flow at the PUMA experimental facility. Obtained results are presented together with the predictions by the well-known Fauske model. It is shown that Fauske model overpredicts measured critical mass fluxes, while the present model shows acceptable agreement with the measured data

Multi-fluid model predictions of gas-liquid two-phase flows in vertical tubes

Razvijen je potpun, stabilan, jednodimenzioni višefluidni model za predviđanje dvofaznog strujanja u vertikalnim cevima. Model je zasnovan na bilansima održanja mase, količine kretanja i energije, koji su primenjeni na svaku fluidnu struju koja je prisutna u posmatranom obliku dvofaznog strujanja, kao i na odgovarajućim konstitutivnim korelacijama za određivanje transportnih procesa na razdelnim površinama između faza. Bilansne jednačine za stacionarno stanje su transformisane u oblik pogodan za direktnu primenu numeričke metode za integraciju sistema običnih diferencijalnih jednačina. Simulirani su termohidraulički procesi duž celog isparivačkog kanala, počevši od strujanja i zagrevanja pothlađene tečnosti na ulazu u strujni kanal pa do zasušenja tečnog filma i pojave maglenog toka sa kapima uključenim u gasnu fazu na kraju kanala. Takođe, model je testiran i za uslove nekoliko parcijalnih efekata dvofaznog strujanja.A consistent one-dimensional multi-fluid model is developed for the prediction of two-phase flows in vertical pipes. The model is based on the mass, momentum and energy balance equations for every fluid stream involved in the observed two-phase flow pattern, and corresponding closure laws for interface transfer processes. The steady-state balance equations are transformed in a form suitable for a direct application of the numerical integration method for the system of ordinary differential equations. Thermal-hydraulic processes along the whole length of the boiling channel are simulated, from the flow and heating of sub cooled liquid at the flow channel inlet, and up to the liquid film dry out and gas entrained droplets mist flow at the outlet. Also, the model is tested against several partial effects of two-phase flow

Thermal-hydraulics of evaporating tubes in the forced circulation loop of a steam boiler

Elektroprivreda Srbije je u toku 2005. godine nastavila radove na izgradnji TE Kolubara B snage 350 MW, koji su započeti još davne 1989. godine. Sam kotao je toranjske konstrukcije, a za isparivač kotla predviđeno je cirkulaciono kolo sa prinudnim strujanjem. Osim toga, ekranske cevi u ložištu su ožljebljene sa unutrašnje strane, što predstavlja jedinstveni slučaj u kotlovima termoelektrana u Srbiji. Da bi se izvršile termohidrauličke analize ovog isparivača urađeni su termički proračuni kotla, kao i hidraulički proračuni isparivača za različita radna opterećenja. U ovom radu prikazana je metodologija hidrauličkog proračuna isparivača sa prinudnom cirkulacijom. Na osnovu dobijenih rezultata, za spomenuti kotao, izvršena je analiza uticaja ožljebljenja cevi na povećanje hidrauličkog otpora u cirkulacionom kolu. S obzirom da ožljebljene cevi obezbeđuju sigurniji rad isparivača, održavajući nisku temperaturu zida cevi i pri visokim sadržajima pare, vršeno je njihovo upoređivanje sa glatkim cevima za slučajeve ravnomernog i neravnomernog toplotnog opterećenja u ložištu.Rifled evaporating tubes are applied in a steam boiler with the aim to increase the steam-water mixture turbulization and to prevent tubes' wall burnout. The evaporating rifled tubes and the working fluid forced circulation are applied in the steam boiler at the Thermal Power Plant 'Kolubara B' that is being built by the Electric Power Utility of Serbia. In order to investigate operating characteristics of the steam boiler of such an advanced design, a simulation and analysis of complex coupled thermal processes on the furnace gas side and thermal-hydraulics in the evaporating tubes were performed for the whole range of the plant designed operating loads. In this paper the methodology for the hydraulic calculations of forced circulation loops is presented. The rifled tubes thermal-hydraulics is calculated. An acceptable temperature of the evaporating tube wall, even under a high void fraction of the coolant is obtained. It is shown that the rifled tubes prevent the occurrence of the critical heat transfer conditions. The obtained increased thermal safety margin of the rifled tubes is compared with the safety margin of the smooth tubes for uniform and variable heat loads between walls of the boiler furnace. The influence of the rifled tubes on the increase of the hydraulic resistance in the circulation loop is analyzed