Modeling of electrolyte sorption – from phase equilibria to dynamic separation systems

In this thesis, general approach is devised to model electrolyte sorption from aqueous solutions on solid materials. Electrolyte sorption is often considered as unwanted phenomenon in ion exchange and its potential as an independent separation method has not been fully explored. The solid sorbents studied here are porous and non-porous organic or inorganic materials with or without specific functional groups attached on the solid matrix. Accordingly, the sorption mechanisms include physical adsorption, chemisorption on the functional groups and partition restricted by electrostatic or steric factors. The model is tested in four Cases Studies dealing with chelating adsorption of transition metal mixtures, physical adsorption of metal and metalloid complexes from chloride solutions, size exclusion of electrolytes in nano-porous materials and electrolyte exclusion of electrolyte/non-electrolyte mixtures. The model parameters are estimated using experimental data from equilibrium and batch kinetic measurements, and they are used to simulate actual single-column fixed-bed separations. Phase equilibrium between the solution and solid phases is described using thermodynamic Gibbs-Donnan model and various adsorption models depending on the properties of the sorbent. The 3-dimensional thermodynamic approach is used for volume sorption in gel-type ion exchangers and in nano-porous adsorbents, and satisfactory correlation is obtained provided that both mixing and exclusion effects are adequately taken into account. 2-Dimensional surface adsorption models are successfully applied to physical adsorption of complex species and to chelating adsorption of transition metal salts. In the latter case, comparison is also made with complex formation models. Results of the mass transport studies show that uptake rates even in a competitive high-affinity system can be described by constant diffusion coefficients, when the adsorbent structure and the phase equilibrium conditions are adequately included in the model. Furthermore, a simplified solution based on the linear driving force approximation and the shrinking-core model is developed for very non-linear adsorption systems. In each Case Study, the actual separation is carried out batch-wise in fixed-beds and the experimental data are simulated/correlated using the parameters derived from equilibrium and kinetic data. Good agreement between the calculated and experimental break-through curves is usually obtained indicating that the proposed approach is useful in systems, which at first sight are very different. For example, the important improvement in copper separation from concentrated zinc sulfate solution at elevated temperatures can be correctly predicted by the model. In some cases, however, re-adjustment of model parameters is needed due to e.g. high solution viscosity.

Application of Computational Fluid Dynamics in Modeling Blood Flow in Human Thoracic Aorta

The aim of this study was to simulate blood flow in thoracic human aorta and understand the role of flow dynamics in the initialization and localization of atherosclerotic plaque in human thoracic aorta. The blood flow dynamics in idealized and realistic models of human thoracic aorta were numerically simulated in three idealized and two realistic thoracic aorta models. The idealized models of thoracic aorta were reconstructed with measurements available from literature, and the realistic models of thoracic aorta were constructed by image processing Computed Tomographic (CT) images. The CT images were made available by South Karelia Central Hospital in Lappeenranta. The reconstruction of thoracic aorta consisted of operations, such as contrast adjustment, image segmentations, and 3D surface rendering. Additional design operations were performed to make the aorta model compatible for the numerical method based computer code. The image processing and design operations were performed with specialized medical image processing software. Pulsatile pressure and velocity boundary conditions were deployed as inlet boundary conditions. The blood flow was assumed homogeneous and incompressible. The blood was assumed to be a Newtonian fluid. The simulations with idealized models of thoracic aorta were carried out with Finite Element Method based computer code, while the simulations with realistic models of thoracic aorta were carried out with Finite Volume Method based computer code. Simulations were carried out for four cardiac cycles. The distribution of flow, pressure and Wall Shear Stress (WSS) observed during the fourth cardiac cycle were extensively analyzed. The aim of carrying out the simulations with idealized model was to get an estimate of flow dynamics in a realistic aorta model. The motive behind the choice of three aorta models with distinct features was to understand the dependence of flow dynamics on aorta anatomy. Highly disturbed and nonuniform distribution of velocity and WSS was observed in aortic arch, near brachiocephalic, left common artery, and left subclavian artery. On the other hand, the WSS profiles at the roots of branches show significant differences with geometry variation of aorta and branches. The comparison of instantaneous WSS profiles revealed that the model with straight branching arteries had relatively lower WSS compared to that in the aorta model with curved branches. In addition to this, significant differences were observed in the spatial and temporal profiles of WSS, flow, and pressure. The study with idealized model was extended to study blood flow in thoracic aorta under the effects of hypertension and hypotension. One of the idealized aorta models was modified along with the boundary conditions to mimic the thoracic aorta under the effects of hypertension and hypotension. The results of simulations with realistic models extracted from CT scans demonstrated more realistic flow dynamics than that in the idealized models. During systole, the velocity in ascending aorta was skewed towards the outer wall of aortic arch. The flow develops secondary flow patterns as it moves downstream towards aortic arch. Unlike idealized models, the distribution of flow was nonplanar and heavily guided by the artery anatomy. Flow cavitation was observed in the aorta model which was imaged giving longer branches. This could not be properly observed in the model with imaging containing a shorter length for aortic branches. The flow circulation was also observed in the inner wall of the aortic arch. However, during the diastole, the flow profiles were almost flat and regular due the acceleration of flow at the inlet. The flow profiles were weakly turbulent during the flow reversal. The complex flow patterns caused a non-uniform distribution of WSS. High WSS was distributed at the junction of branches and aortic arch. Low WSS was distributed at the proximal part of the junction, while intermedium WSS was distributed in the distal part of the junction. The pulsatile nature of the inflow caused oscillating WSS at the branch entry region and inner curvature of aortic arch. Based on the WSS distribution in the realistic model, one of the aorta models was altered to induce artificial atherosclerotic plaque at the branch entry region and inner curvature of aortic arch. Atherosclerotic plaque causing 50% blockage of lumen was introduced in brachiocephalic artery, common carotid artery, left subclavian artery, and aortic arch. The aim of this part of the study was first to study the effect of stenosis on flow and WSS distribution, understand the effect of shape of atherosclerotic plaque on flow and WSS distribution, and finally to investigate the effect of lumen blockage severity on flow and WSS distributions. The results revealed that the distribution of WSS is significantly affected by plaque with mere 50% stenosis. The asymmetric shape of stenosis causes higher WSS in branching arteries than in the cases with symmetric plaque. The flow dynamics within thoracic aorta models has been extensively studied and reported here. The effects of pressure and arterial anatomy on the flow dynamic were investigated. The distribution of complex flow and WSS is correlated with the localization of atherosclerosis. With the available results we can conclude that the thoracic aorta, with complex anatomy is the most vulnerable artery for the localization and development of atherosclerosis. The flow dynamics and arterial anatomy play a role in the localization of atherosclerosis. The patient specific image based models can be used to diagnose the locations in the aorta vulnerable to the development of arterial diseases such as atherosclerosis.

Modeling study of limestone reactions in fluidized bed conditions

Traditionally limestone has been used for the flue gas desulfurization in fluidized bed combustion. Recently, several studies have been carried out to examine the use of limestone in applications which enable the removal of carbon dioxide from the combustion gases, such as calcium looping technology and oxy-fuel combustion. In these processes interlinked limestone reactions occur but the reaction mechanisms and kinetics are not yet fully understood. To examine these phenomena, analytical and numerical models have been created. In this work, the limestone reactions were studied with aid of one-dimensional numerical particle model. The model describes a single limestone particle in the process as a function of time, the progress of the reactions and the mass and energy transfer in the particle. The model-based results were compared with experimental laboratory scale BFB results. It was observed that by increasing the temperature from 850 °C to 950 °C the calcination was enhanced but the sulfate conversion was no more improved. A higher sulfur dioxide concentration accelerated the sulfation reaction and based on the modeling, the sulfation is first order with respect to SO2. The reaction order of O2 seems to become zero at high oxygen concentrations.

LVI-suunnittelun ohjaus IPD-projekteissa

Tässä diplomityössä on tutkittu LVI-suunnittelun ohjaamista ja sen kehittämistä integroiduissa rakennushankkeissa. Tutkimuksen tavoitteena on löytää kehitysehdotuksia LVI-suunnittelun eteenpäinviemiseksi integroiduissa hankkeissa. Tutkimus on tehty hyödyntäen kirjallisia lähteitä ja haastattelemalla integroiduissa projekteissa mukana ollutta henkilöstöä. Perinteisessä rakennushankkeessa eri suunnittelualat toimitetaan useasta yrityksestä. Tässä työssä lähtökohtana on, että merkittävimmät suunnittelualat kuten arkkitehti-, rakenne- ja talotekninensuunnittelu tulevat samalta toimittajalta. Toimituslaajuuteen voidaan lisätä myös mm. rakennuttajakonsultointi- ja kiinteistönkehitysprosessi. Tutkimuksen tuloksena saatiin määritettyä kehitysehdotukset integroituihin hankkeisiin yleiseltä ja LVI-suunnittelun kannalta. Kehitystyössä tulee panostaa tietomallintamiseen, aikataulutukseen ja yhteistyöhön. Tietomallintamista voidaan parantaa koulutuksen, Yleisten tietomallivaatimusten 2012 ja tietomallien tarkasteluohjelmistojen avulla. Aikataulutus paranee, kun suunnittelijat saadaan hankkeeseen mukaan riittävän aikaisessa vaiheessa ja kun suunnittelijat pyrkivät aktiivisesti vaikuttamaan hankkeen tarjouksen- ja sopimuksentekoon. Yhteistyötä voidaan parantaa avoimen ilmapiirin korostamisella ja projektiorganisaation tiivistämisellä.

Toimintaohjeiston laatiminen HSY:n jätehuollon elinkaarimallinnuspalveluiden hankkimiseksi

Elinkaariarviointi on menetelmä, missä tuotejärjestelmän aikaiset syötteet ja tuotteet koostetaan yhteen ja tuloksena saadaan sen ympäristökuormitus. Elinkaariarviointi on päätöksentekoa tukeva työkalu. Jätelain kokonaisuudistuksen myötä elinkaariarvioinnin käyttö tullee lisääntymään kuntavastuullisessa jätehuollossa. Helsingin seudun ympäristöpalvelut -kuntayhtymä HSY:n jätehuollon tavoitteena on rakentaa elinkaarimalli, jonka avulla voidaan selvittää koko toiminnan aiheuttama ympäristökuormitus ja taloudelliset vaikutukset. HSY:n jätehuolto on päättänyt toteuttaa elinkaarimallin rakentamisen konsulttityönä. Työn tavoitteena on ollut laatia toimintaohjeisto HSY:n jätehuollon elinkaarimallinnuspalveluiden hankkimiseksi. Elinkaarimalli voidaan tehdä kaupallista ohjelmistoa käyttämällä. Tähän selvitykseen on valittu arvioitavaksi kolme elinkaariarvioinnin työkalua: EASEWASTE, WRATE ja GaBi 4.4. Ohjelmistojen ominaisuuksia on arvioitu kirjallisuuden ja haastattelun perusteella. Työssä on laadittu kriteeristö näiden ohjelmistojen arviointiin. Kirjallisuuden perusteella on selvitetty elinkaariarvioinnin soveltamiskohteet kuntavastuullisessa jätehuollossa. HSY:n jätehuollon elinkaariarvioinnin soveltamiskohteet ja mallinnustarpeet on tunnistettu haastattelemalla HSY:n jätehuollon asiantuntijoita. HSY:n jätehuollolle rakennettavan mallin päivittämistä, käyttöä ja kehittämistä tulisi hallita HSY:n jätehuollon toimesta. Kaikki työssä arvioidut ohjelmistot soveltuvat HSY:n jätehuollon tunnistamien mallinnustarpeiden laskentaan. Elinkaarimallinnuspalveluiden toimintaohjeistolla pyritään varmistamaan HSY:n jätehuollon tarpeisiin soveltuvan mallin hankinta ja jatkotoimenpiteiden suunnittelu.

Building object-oriented software with the D-Bus messaging system

Object-oriented programming is a widely adopted paradigm for desktop software development. This paradigm partitions software into separate entities, objects, which consist of data and related procedures used to modify and inspect it. The paradigm has evolved during the last few decades to emphasize decoupling between object implementations, via means such as explicit interface inheritance and event-based implicit invocation. Inter-process communication (IPC) technologies allow applications to interact with each other. This enables making software distributed across multiple processes, resulting in a modular architecture with benefits in resource sharing, robustness, code reuse and security. The support for object-oriented programming concepts varies between IPC systems. This thesis is focused on the D-Bus system, which has recently gained a lot of users, but is still scantily researched. D-Bus has support for asynchronous remote procedure calls with return values and a content-based publish/subscribe event delivery mechanism. In this thesis, several patterns for method invocation in D-Bus and similar systems are compared. The patterns that simulate synchronous local calls are shown to be dangerous. Later, we present a state-caching proxy construct, which avoids the complexity of properly asynchronous calls for object inspection. The proxy and certain supplementary constructs are presented conceptually as generic object-oriented design patterns. The e ect of these patterns on non-functional qualities of software, such as complexity, performance and power consumption, is reasoned about based on the properties of the D-Bus system. The use of the patterns reduces complexity, but maintains the other qualities at a good level. Finally, we present currently existing means of specifying D-Bus object interfaces for the purposes of code and documentation generation. The interface description language used by the Telepathy modular IM/VoIP framework is found to be an useful extension of the basic D-Bus introspection format.

Virtuaalimallin hyödyntäminen harvesteripään tuotekehityksessä

Virtuaalimallinnuksella tarkoitetaan koneen simulointia, jossa huomioidaan koneen mekaniikka, toimilaitteet ja ohjausjärjestelmä. Työn tavoitteena oli luoda virtuaalimalli harvesteripäästä. Kyseinen virtuaalimalli sisälsi harvesteripään tärkeimmät mekaaniset osat, pituusmittalaitteen hydrauliikkapiirin ja tämän ohjauksen. Luodussa virtuaalimallissa huomioitiin myös harvesteripään ja puun väliset kontaktit. Lisäksi työssä tutkittiin mahdollista virtuaalimallinnuksen implementoimista osaksi yrityksen tuotekehitysprosessia. Työssä suoritettiin verifiointimittaukset pituusmittalaitteen hydrauliikkapiirille sekä virtuaalimallin hydrauliikkakomponentit parametrisoitiin. Mittauksista saatuja tuloksia verrattiin virtuaalimallista saatuihin tuloksiin. Työssä esitellään myös ehdotus kuinka virtuaalimallinnusta kannattaisi hyödyntää osana yrityksen tuotekehitysprosessia. Virtuaalimallin eri osa-alueilla saavutetut tulokset osoittavat, että virtuaalimallinuksen hyödyntäminen tuotekehitysprosessin aikana mahdollistaa harvesteripään toimintojen tarkastelun ennen prototyypin rakentamista ja testaamista. Lisäksi hydrauliikkapiirin parametrisoimisella pystytään tutkimaan parametrien vaikutusta kokonaisuuteen.

Battery Cell Modeling for Battery Management System

Usage of batteries as energy storage is emerging in automotive and mobile working machine applications in future. When battery systems become larger, battery management becomes an essential part of the application concerning fault situations of the battery and safety of the user. A properly designed battery management system extends one charge cycle of battery pack and the whole life time of the battery pack. In this thesis main objectives and principles of BMS are studied and first order Thevenin’s model of the lithium-titanate battery cell is built based on laboratory measurements. The battery cell model is then verified by comparing the battery cell model and the actual battery cell and its suitability for use in BMS is studied.