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

The use of anodic linear sweep voltammetery analysis (ALSV) for characterization the copper anodes used for sulphur acidic waste solution treatment

This paper addresses on investigation the possibility of electrolytic treatment the sulphur acidic waste solution, obtained in the conventional electrolytic copper refining process. The copper anodes with non-standard nickel, lead, tin and antimony content were specially prepared for the refining process. Nickel content of all anodes was approximately 7.5 mass %, and the content of lead, tin and antimony was varied. Results, obtained using the standard electrochemical techniques, have indicated that the anodes could be used under the same conditions as well as in the conventional copper refining process

Analyzing the corrosion characteristics of anodes used for the sulphur acidic waste water treatment

This paper addresses on investigation the possibility of electrolytic treatment the sulphur acidic waste solution, obtained in the conventional electrolytic copper refining process. The copper anodes with non-standard nickel, lead, tin and antimony content were specially prepared for the refining process. Nickel content of all anodes was approximately 7.5 mass %, and the content of lead, tin and antimony was varied. It was observed, that anodes with O2 content lower than 200 ppm, were not passivated. Results, obtained using the standard electrochemical techniques, have indicated that the anodes with non-standard chemical composition could be used under the same conditions as well as in the conventional copper refining process

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

B chromosomes in keeled garlic, Allium carinatum L. (Liliaceae), from Tara mountain (Serbia)

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Simple point-ion electrostatic model explains the cation distribution in spinel oxides

The A2BO4 spinel oxides are distinguished by having either a normal (N) or an inverse (I) distribution of the A, B cations on their sublattices. A point-ion electrostatic model parametrized by the oxygen displacement parameter u and by the relative cation valencies ZA vs ZB provides a simple rule for the structural preference for N or I: if ZA>ZB the structure is normal for u>0.2592 and inverse for u0.2578. This rule is illustrated for the known spinel oxides, proving to be ∼98% successful. © 2010 The American Physical Society

Comparative analyses of built environment exposures relevant to health of greenhouse gas emissions reduction strategies in Serbia

Paper presents comparative analysis of residential indoor air pollutant concentration change over future specified time horizon, implementing building physical and thermal retrofit measures, thus creating pollution mitigation scenarios for existing Belgrade and Nis housing stock followed by greenhouse gas emission reduction scenarios up to 2050. Regarding specified mitigation scenarios, the set of typical housing unit models has been generated which define existing housing stock of Belgrade and Nis. Extensive monitoring of physical and thermal parameters as well as detailed socio-technical survey of selected households was performed and used as an initial modeling input. Relationship between environment pollution and building performances was investigated, with respect to indoor-outdoor sources of pollution, thermal and physical properties of the stock samples and occupant's behavior. As a final output, indoor pollutant concentrations for each of the modelled cases was obtained and validated against the available data. This housing modelling framework has been created in order to develop an assessment of present and future exposure and health impact quantity regarding single/multiple scenario interventions introduced to the housing stock. This paper provides each strategy guidelines for taking measures towards achieving the healthier indoor environments