Coolant Flow and Heat Transfer in Pebble-Bed Reactor Core

This thesis gathers knowledge about ongoing high-temperature reactor projects around the world. Methods for calculating coolant flow and heat transfer inside a pebble-bed reactor core are also developed. The thesis begins with the introduction of high-temperature reactors including the current state of the technology. Process heat applications that could use the heat from a high-temperature reactor are also introduced. A suitable reactor design with data available in literature is selected for the calculation part of the thesis. Commercial computational fluid dynamics software Fluent is used for the calculations. The pebble-bed is approximated as a packed-bed, which causes sink terms to the momentum equations of the gas flowing through it. A position dependent value is used for the packing fraction. Two different models are used to calculate heat transfer. First a local thermal equilibrium is assumed between the gas and solid phases and a single energy equation is used. In the second approach, separate energy equations are used for the phases. Information about steady state flow behavior, pressure loss, and temperature distribution in the core is obtained as results of the calculations. The effect of inlet mass flow rate to pressure loss is also investigated. Data found in literature and the results correspond each other quite well, considered the amount of simplifications in the calculations. The models developed in this thesis can be used to solve coolant flow and heat transfer in a pebble-bed reactor, although additional development and model validation is needed for better accuracy and reliability.

Process intensification: From optimised flow patterns to microprocess technology

This thesis is focused on process intensification. Several significant problems and applications of this theme are covered. Process intensification is nowadays one of the most popular trends in chemical engineering and attempts have been made to develop a general, systematic methodology for intensification. This seems, however, to be very difficult, because intensified processes are often based on creativity and novel ideas. Monolith reactors and microreactors are successful examples of process intensification. They are usually multichannel devices in which a proper feed technique is important for creating even fluid distribution into the channels. Two different feed techniques were tested for monoliths. In the first technique a shower method was implemented by means of perforated plates. The second technique was a dispersion method using static mixers. Both techniques offered stable operation and uniform fluid distribution. The dispersion method enabled a wider operational range in terms of liquid superficial velocity. Using dispersion method, a volumetric gas-liquid mass transfer coefficient of 2 s-1 was reached. Flow patterns play a significant role in terms of the mixing performance of micromixers. Although the geometry of a T-mixer is simple, channel configurations and dimensions had a clear effect on mixing efficiency. The flow in the microchannel was laminar, but the formation of vortices promoted mixing in micro T-mixers. The generation of vortices was dependent on the channel dimensions, configurations and flow rate. Microreactors offer a high ratio of surface area to volume. Surface forces and interactions between fluids and surfaces are, therefore, often dominant factors. In certain cases, the interactions can be effectively utilised. Different wetting properties of solid materials (PTFE and stainless steel) were applied in the separation of immiscible liquid phases. A micro-scale plate coalescer with hydrophilic and hydrophobic surfaces was used for the continuous separation of organic and aqueous phases. Complete phase separation occurred in less than 20 seconds, whereas the separation time by settling exceeded 30 min. Fluid flows can be also intensified in suitable conditions. By adding certain additives into turbulent fluid flow, it was possible to reduce friction (drag) by 40 %. Drag reduction decreases frictional pressure drop in pipelines which leads to remarkable energy savings and decreases the size or number of pumping facilities required, e.g., in oil transport pipes. Process intensification enables operation often under more optimal conditions. The consequent cost savings from reduced use of raw materials and reduced waste lead to greater economic benefits in processing.

Varasto- ja hankintamodulin kehittäminen toiminnanohjausjärjestelmään

Tässä diplomityössä tarkoituksena on kerätä yhteen toiminnanohjausjärjestelmän varasto- ja hankintamodulin kehittämisessä tarvittavaa teoriatietoa, sekä Nestix Oy:n asiakkaiden ja joidenkin muiden yritysten tarpeita kyseiselle ohjelmistolle. Teoria ja tarpeet yhdistetään karkeaksi ohjelmiston tarvemäärittelyksi, jonka perusteella Nestix Oy toteuttaa uudet modulit toiminnanohjausjärjestelmäänsä. Tutkimuksissa havaittiin, että yrityksillä on hyvin samankaltaisia tarpeita varastojen ja hankintojen hallintaan. Varastoinnin ja hankinnan prosessit poikkeavat hyvin vähän yritysten välillä. Samoja perinteisiä logistiikan perustyökaluja käytetään miltei kaikissa yrityksissä. Tulevaisuuden houkuttelevimpana kehitysalueena voidaan pitää ohjelmistojen internet-pohjaisuutta, joka mahdollistaa ohjelmiston käyttämisen mistäpäin maailmaa tahansa ilman erillisiä ohjelmistoasennuksia. Tutkimuksen jälkeen Nestix-ohjelmistoperheeseen toteutettiin integroidut hankinnan sekä varastoinnin modulit. Ohjelmaa on kehitetty tutkimuksen tekemisen jälkeen eteenpäin ja sitä on myyty useaan Euroopan maahan osana Nestix toiminnanohjausjärjestelmää.

Personal Liberty in Psychiatric Care - Towards Service User Involvement

This study explores personal liberty in psychiatric care from a service user involvement perspective. The data were collected in four phases during the period 2000-2006 in psychiatric settings in Finland. Firstly, patient satisfaction and factors associated with user involvement were studied (n = 313). Secondly, patients’ experiences of deprivation of their liberty were explored (n = 51). Thirdly, an overview on patients’ options for lodging complaints was conducted, and all complaints (n = 4645) lodged in Finland from 2000 to 2004 were examined. Fourthly, the effects of different patient education methods on inpatients’ experiences of deprivation of liberty were tested (n = 311). It emerged that patients were quite satisfied, but reported dissatisfaction in restrictions, compulsory care and information dissemination. Patients experienced restrictions on leaving the ward and on communication, confiscation of property and coercive measures as deprivation of liberty. Patients’ experienced these interventions to be negative. In Finland, the patient complaint process is complicated and not easily accessible. In general, patient complaints increased considerably in Finland during the study period. In psychiatric care the number of complaints was quite stable and complaints led more seldom to consequences. An Internet-based patient education system was equivalent with traditional education and treatment as usual in supporting personal liberty during hospital care. This dissertation provides new information about the realization of patients' rights in psychiatric care. In order to improve patients' involvement, systematic methods to increase personal liberty during care need to be developed, the procedures for patients lodging complaints should be simplified, and patients' access to information needs to be ensured using multiple methods.

Toiminnanohjausjärjestelmät pk-yrityksissä

Tämä työ on aikaisempaan tutkimukseen ja kirjallisuuteen perustuva analyyttinen kandidaatintutkielma. Työn tavoitteena on selvittää toiminnanohjausjärjestelmien nykytilaa pk-yrityksissä. Päätavoitteena on selvittää syitä siihen miksi ja minkälaisia paineita pk-yritykset kohtaavat toiminnanohjausjärjestelmien käyttöönotossa, joka selvittää perusteita ERP-järjestelmien käyttöönotolle. Työ on rajattu siten että tarkastelussa on pk-yritykset ja niiden haasteet, ongelmat koskien toiminnanohjausjärjestelmien käyttöönottoa ja hankintaa. Pk-yritysten toiminnanohjausjärjestelmien käyttö ei liity niinkään strategisten hyötyjen saamiseen vaan päivittäisten prosessien tarkkailuun ja ylläpitoon. Perimmäinen syy järjestelmän hankkimiseen ei silti ole aivan selvä. Tutkimukset ovat osoittaneet, etteivät hankinnan pääsyyt välttämättä ole sisäisiä vaan ulkoinen tarve kuten toimittajien tai asiakkaiden kanssa verkostoituminen. Pk-yritysten kasvaessa toiminnanohjausjärjestelmän hankintakin luonnollisesti tulee entistä tärkeämmäksi. Eräs varteenotettava ratkaisu pk-yrityksen näkökulmasta on toiminnanohjauksen ulkoistaminen ASP-yritykselle. Tällöin implementointi ja ylläpito eivät vaadi yritykseltä valtavia resursseja, vaan ASP vastaa järjestelmän toiminnasta, päivityksestä sekä jakaa osan yrityksen riskistä. Vaikka ulkoistaminen saattaa vaikuttaa yrityksestä valtavalta riskiltä, koska kaikki tärkeät tiedot ovat kolmannen osapuolen hallussa, on tutkimuksissa kuitenkin tullut ilmi että ASP-yritysten tietoturvan ja luotettavuus on varsin kiitettävällä tasolla.

The Present State and a Development Plan of Cost Accounting in Batch Production of Wind Turbine Gears

The aim of this master’s thesis was to document the present state and to create a development plan for Moventas Wind’s cost accounting. The current cost accounting system was evaluated and most fundamental problems were chosen as areas of focus in development work. The development plan includes both short- and long-term development proposals for problems identified. This report presents two alternative models for product costing. Benchmarking of cost accounting practices and modern cost accounting theories were used in development of cost accounting. It was found that the current cost accounting system functions quite well and the adjustments in unit cost rate calculation have only a minor influence on costs of goods sold. An OEE-based standard cycle concept was also developed and it was found that the implementation of this new system is worthwhile in the long-term.

Strategiset allianssit: motiivit ja muodostaminen

Strategiset allianssit ovat yhteistyömuotoja, joiden taustalla on pyrkimys pitkäntähtäimen strategisten tavoitteiden saavuttamiseen. Strategisissa alliansseissa voivat toimia niin suuret ja pienet yritykset kuin julkisen sektorin organisaatiotkin. Tässä työssä strategisista alliansseista esitetään kokonaisvaltainen ja selkeä kuva. Tämän myötä niitä käsitellään omana käsitteenään ominaispiirteineen. Lisäksi strategisten allianssien toteutusvaihtoehtoja tarkastellaan taloudelliseen ja ajalliseen ulottuvuuteen rinnastaen. Motivoituneet osapuolet ovat edellytyksenä strategisen allianssin syntymiselle ja menestymiselle. Keskeisimpiä motiiveja strategiseen allianssiin ryhtymisestä tarkastellaan arvonluonnin näkökulmasta. Motiivit ovat pohjana strategisen allianssin muodostusvaiheen käynnistymiselle. Muodostusprosessia tarkastellaan kolmivaiheisen prosessin näkökulmasta, mikä kattaa päätöksenteon, kumppanin etsinnän ja valinnan sekä neuvotteluvaiheen. Työ sisältää kaksi case-esimerkkiä, joiden tarkoituksena on luoda yhteys teorian ja käytännön välille. Ensimmäisessä esimerkissä tarkastellaan pääomasidonnaista Renault – Nissan -allianssia, joka ristiinomistukseen ja yhteisyrityksiin (joint venture) perustuen toimii monipuolisena esimerkkinä. Toisessa, Sonyn ja Philipsin allianssissa, tarkastellaan ei-pääomasidonnaisen strategisen allianssin erityispiirteitä.

Lääkintähuollon ja materiaalihallinnon yhtenäisen RFID-seurannan perusteita

Tässä diplomityössä tarkastellaan radiotaajuisen tunnistamisteknologian (RFID) seurannan yhtenäisiä perusteita puolustusvoimien lääkintähuollolle ja materiaalihallinnolle. Nykytilaa selvitettiin pääpainona lääkintähuollon ja materiaalihallinnon osa-alueet ja samalla tarkasteltiin koko puolustusvoimien RFIDtekniikan käyttöä. Puolustusvoimissa RFID-teknologiaa käytetään myös vaatehuollon ja kulunvalvonnan toiminnoissa. Tämän työn teoriaosuudessa tarkastellaan RFID-tekniikkaa ja sen komponentteja sekä niiden hyödyntämistä eri sektoreilla ja logistiikassa. Työn empiirisessä osuudessa selvitetään, mitkä ovat puolustusvoimien tarpeet RFID:n käytöllä ja vaatimuksia ensihoidon kiireellisyysluokittelulle (TRIAGE) sekä materiaalihallinnon ja niiden kautta saatavalle tilannekuvalle. Työn tuloksena saadaan perusteita puolustusvoimien RFID-ratkaisujen suunnittelun pohjaksi.

Determining risk potential through accidents and near-accidents: an empirical study in a steel factory

Fatal and permanently disabling accidents form only one per I cent of all occupational accidents but in many branches of industry they account for more than half the accident costs. Furthermore the human suffering of the victim and his family is greater in severe accidents than in slight ones. For both human and economic reasons the severe accident risks should be identified befor injuries occur. It is for this purpose that different safety analysis methods have been developed . This study shows two new possible approaches to the problem.. The first is the hypothesis that it is possible to estimate the potential severity of accidents independent of the actual severity. The second is the hypothesis that when workers are also asked to report near accidents, they are particularly prone to report potentially severe near accidents on the basis of their own subjective risk assessment. A field study was carried out in a steel factory. The results supported both the hypotheses. The reliability and the validity of post incident estimates of an accident's potential severity were reasonable. About 10 % of accidents were estimated to be potentially critical; they could have led to death or very severe permanent disability. Reported near accidents were significantly more severe, about 60 $ of them were estimated to be critical. Furthermore the validity of workers subjective risk assessment, manifested in the near accident reports, proved to be reasonable. The studied new methods require further development and testing. They could be used both in routine usage in work places and in research for identifying and setting the priorities of accident risks.

Merchandising Strategies and Retail Performance for Seasonal Fashion Products

This study presents mathematical methods for evaluation of retail performance with special regard to product sourcing strategies. Forecast accuracy, process lead time, offshore / local sourcing mix and up front / replenishment buying mix are defined as critical success factors in connection with sourcing seasonal products with a fashion content. As success measures, this research focuses on service level, lost sales, product substitute percentage, gross margin, gross margin return on inventory and mark down rate. The accuracy of demand forecast is found to be a fundamental success factor. Forecast accuracy depends on lead time. Lead times are traditionally long and buying decisions are made seven to eight months prior to the start of the selling season. Forecast errors cause stockouts and lost sales. Some of the products bought for the selling season will not be sold and have to be marked down and sold at clearance, causing loss of gross margin. Gross margin percentage is not the best tool for evaluating sourcing decisions and in the context of this study gross margin return on inventory, which combines profitability and assets management, is used. The findings of this research suggest that there are more profitable ways of sourcing products than buying them from low cost offshore sources. Mixing up front and inseason replenishment deliveries, especially when point of sale information is used for improving forecast accuracy, results in better retail performance. Quick Response and Vendor Managed Inventory strategies yield better results than traditional up front buying from offshore even if local purchase prices are higher. Increasing the number of selling seasons, slight over buying for the season in order to

Improving Evaluation and Development Capability in Verification and Validation

Validation and verification operations encounter various challenges in product development process. Requirements for increasing the development cycle pace set new requests for component development process. Verification and validation usually represent the largest activities, up to 40 50 % of R&D resources utilized. This research studies validation and verification as part of case company's component development process. The target is to define framework that can be used in improvement of the validation and verification capability evaluation and development in display module development projects. Validation and verification definition and background is studied in this research. Additionally, theories such as project management, system, organisational learning and causality is studied. Framework and key findings of this research are presented. Feedback system according of the framework is defined and implemented to the case company. This research is divided to the theory and empirical parts. Theory part is conducted in literature review. Empirical part is done in case study. Constructive methode and design research methode are used in this research A framework for capability evaluation and development was defined and developed as result of this research. Key findings of this study were that double loop learning approach with validation and verification V+ model enables defining a feedback reporting solution. Additional results, some minor changes in validation and verification process were proposed. There are a few concerns expressed on the results on validity and reliability of this study. The most important one was the selected research method and the selected model itself. The final state can be normative, the researcher may set study results before the actual study and in the initial state, the researcher may describe expectations for the study. Finally reliability of this study, and validity of this work are studied.

Sinfonia piccola

Soitinnus: Ork.