Supplier Energy Audits in Thermal Power Plants

This master’s thesis handles an operating model for an electric equipment supplier conducted sale oriented energy audit for pumping, fan and other motor applications at power plants. The study goes through the largest factors affecting internal electricity use at a power plant, finds an energy audit –like approach for the basis of information gathering and presents the information needed for conducting the analysis. The model is tested in practice at a kraft recovery boiler of a chemical pulping mill. Targets chosen represent some of the largest electric motor applications in the boiler itself and in its fuel handling. The energy saving potential of the chosen targets is calculated by simulating the energy consumption of the alternatives for controlling the targets, and thereafter combining the information with the volume flow duration curve. Results of the research are somewhat divaricated, as all the information needed is not available in the automation system. Some of the targets could be simulated and their energy saving potential calculated quite easily. At some of the targets chosen the monitoring was not sufficient enough for this and additional measurements would have been needed to base the calculations on. In traditional energy audits, energy efficiency of pump and fan applications is not necessarily examined. This means that there are good possibilities for developing the now presented targeted energy audit procedure basis further.

The evaluation of hazardous gas components caused by the thermal degradation of plant oils and animal fats

Neste Oil has introduced plant oils and animal fats for the production of NExBTL renewable diesel, and these raw materials differ from the conventional mineral based oils. One subject of new raw materials study is thermal degradation, or in another name pyrolysis, of these organic oils and fats. The aim of this master’s thesis is to increase knowledge on thermal degradation of these new raw materials, and to identify possible gaseous harmful thermal degradation compounds. Another aim is to de-termine the health and environmental hazards of identified compounds. One objective is also to examine the formation possibilities of hazardous compounds in the produc-tion of NExBTL-diesel. Plant oils and animal fats consist mostly of triglycerides. Pyrolysis of triglycerides is a complex phenomenon, and many degradation products can be formed. Based on the literature studies, 13 hazardous degradation products were identified, one of which was acrolein. This compound is very toxic and dangerous to the environment. Own pyrolysis experiments were carried out with rapeseed and palm oils, and with a mix-ture of palm oil and animal fat. At least 12 hazardous compounds, including acrolein, were analysed from the gas phase. According to the experiments, the factors which influence on acrolein formation are the time of the experiment, the sphere (air/hydrogen) in which the experiment is carried out, and the characteristics of the used oil. The production of NExBTL-diesel is not based on pyrolysis. This is why thermal degradation is possible only when abnormal process conditions prevail.

Heat Transfer in Plate Heat Exchangers

This study illustrates the different types of plate heat exchangers that are commonly used in various domestic and industrial applications. The main purpose of this paper was to devise a methodology that is capable of calculating optimum number of plates in the design of a plate heat exchanger. To obtain the appropriate number of plates, typically several iterations must be made before a final acceptable design is completed, since plate amount depends on many factors such as, flow velocities, physical properties of the streams, flow channel geometry, allowable pressure drop, plate dimensions, and the gap between the plates. The methodology presented here can be used as a general guide for designing a plate heat exchanger. To investigate the effects of relevant parameters on the thermal-hydraulic design of a plate heat exchanger, several experiments were carried out for single-phase and counter flow arrangement with two brazed plate heat exchangers by varying the flow rates and the inlet temperatures of the fluid streams. The actual heat transfer coefficients obtained based on the experiment were nearly close to the calculated values and to improve the design, a correction factor was introduced. Besides, the effect of flow channel velocity on the pressure drop inside the unit is presented.

Thermal-Hydraulic Studies on the Safety Of VVER-440 Type Nuclear Power Plants

This thesis includes several thermal hydraulic analyses related to the Loviisa WER 440 nuclear power plant units. The work consists of experimental studies, analysis of the experiments, analysis of some plant transits and development of a calculational model for calculation of boric acid concentrations in the reactor. In the first part of the thesis, in the case of won of boric acid solution behaviour during long term cooling period of LOCAs, experiments were performed in scaled down test facilities. The experimental data together with the results of RELAPS/MOD3 simulations were used to develop a model for calculations of boric acid concentrations in the reactor during LOCAs. The results of calculations showed that margins to critical concentrations that would lead to boric acid crystallization were large, both in the reactor core and in the lower plenum. This was mainly caused by the fact that water in the primary cooling circuit includes borax (Na)BsO,.IOHZO), which enters the reactor when ECC water is taken from the sump and greatly increases boric acid solubility in water. In the second part, in the case of simulation of horizontal steam generators, experiments were performed with PACTEL integral test loop to simulate loss of feedwater transients. The PACTEL experiments, as well as earlier REWET III natural circulation tests, were analyzed with RELAPS/MOD3 Version Sm5 code. The analysis showed that the code was capable of simulating the main events during the experiments. However, in the case of loss of secondary side feedwater the code was not completely capable to simulate steam superheating in the secondary side of the steam generators. The third part of the work consists of simulations of Loviisa VVER reactor pump trip transients with RELAPSlMODI Eur, RELAPS/MOD3 and CATHARE codes. All three codes were capable to simulate the two selected pump trip transients and no significant differences were found between the results of different codes. Comparison of the calculated results with the data measured in the Loviisa plant also showed good agreement.

Ydinvoimalaitoksen höyryturbiinin suorituskyvyn laskenta

Diplomityön tavoitteena on selvittää Loviisan ydinvoimalaitoksen höyryturbiinin hyötysuhteen parantamismahdollisuuksia. Työn kuvaan liittyvät oleellisesti höyryturbiinin siipivyöhykkeiden nopeuskolmioiden sekä hyötysuhteiden laskenta. Höyryturbiinien kehityskaarta sekä turbiinin häviökerrointen laskentayhtälöitä on esitetty useasta eri lähteestä ja vuosikymmeniltä. Työssä selvitettiin uusimpia ydinvoimalaitosten kostea höyryturbiinien suunnitteluperusteita lukuisista eri lähteistä. Kaikkien lähteiden mukaan kostean höyryn alueella tapahtuvaa paisuntaa on haasteellista mallintaa. Työssä on esitelty artikkeleissa tulleita eri näkökulmia höyryturbiinien suorituskyvyn parantamiseksi, sekä rakenteellisia että laskennallisia. Työssä esitellään monia turbiinin virtauksen ja suorituskyvyn laskentamenetelmiä. Esimerkiksi Baumannin säännön laskenta on yksinkertainen tapa käsitellä turbiinin suorituskykyä kostean höyryn alueella. Keskeisimpiä tehtyjä havaintoja oli se, että korkeapaineturbiinin ensimmäisestä vaiheesta löytyi mahdollista parannuspotentiaalia Loviisaan ydinvoimalaitoksen tehon lisäämiseksi. Ensimmäisessä vaiheessa on oletettu siipien olevan Laval –tyyppisiä, mutta käytännössä näin ei ole. Korkeapaineturbiinin nykyisen turbosuuttimen toimintaa voitaisiin tehostaa. Lisäksi Loviisan matalapaineturbiinin viimeisen siipivaiheen jälkeen aiheutuu suuret ulosvirtaushäviöt. Osa suurinopeuksisen virtauksen energiasta pystyttäisiin kuitenkin hyödyntämään vielä ulosvirtauskanavassa olevalla diffuusorilla.

Muutosilmiöt soodakattilakeossa

Soodakattilan sulakeon epästationaarinen käyttäytyminen sekä keon pitkä jäähtymisaika alasajon jälkeen ovat aiheuttaneet ongelmia kattilan taloudellisessa käytettävyydessä. Keon käyttäytymisestä on luotu CFD-malleja, joiden tavoitteena on havainnollistaa keon lämpötilajakaumaa ja rakennetta. Mallien ongelmana on se, että niissä huomioidaan vain keon aktiivinen pintakerros. Keon sisäosan rakennetta ja siinä tapahtuvia prosesseja ei toistaiseksi tunneta kunnolla luotettavan, koko keon kattavan mallin luomiseen. Tässä työssä tutkittiin sulakeon käytön aikana havaittuja muutosilmiöitä, jotka vaikuttavat keon rakenteeseen ja ominaisuuksiin sekä tutkittiin ilmiöiden taustalla olevia tekijöitä. Näitä tekijöitä ovat keon sisässä tapahtuvat kemialliset ja fyysiset prosessit, jotka aiheuttavat muutoksia niin lämpöteknisesti kuin fyysisesti sekä ulkoapäin tulevat tekijät, jotka aiheutuvat ajotilanteiden seurauksena tapahtuvista muutoksista. Työn kokeellisena osana luotiin sulakeon jäähtymismalli käyttäen 1-dimensionaalista ADL-mallia. Mallin pohjana käytettiin StoraEnso Oy:ltä Oulun soodakattilan sulakeosta saatua mittausraporttia. ADL-mallin avulla luotiin keon jäähtymiskäyrät lämpötilan ja syvyyden funktiona. Saadut käyrät täsmäsivät hyvin mittausraportin tuloksiin. Mallin avulla keolle saatiin muodostettua energiatase, jonka tuloksena keosta 12 tunnin aikana poistuva lämpövirta pinnalla oli noin 9.8kW/m2 ja pinnan lämmönsiirtokerroin 58.3W/m²°C. Pohjan poistuvaksi lämpövirraksi saatiin 14.1kW/m2 ja lämmönsiirtokertoimeksi 75.4W/m²°C. Termiseksi diffuusiokertoimeksi saatiin 3.9•10-7m²/s.

Thermal modelling of semiconductor switches in three-level Neutral Point Clamped Medium Voltage DTC-inverter

The aim of this thesis is to investigate the thermal loading of medium voltage three-level NPC inverter’s semiconductor IGCT switches in different operation points. The objective is to reach both a fairly accurate off-line simulation program and also so simple a simulation model that its implementation into an embedded system could be reasonable in practice and a real time use should become feasible. Active loading limitation of the inverter can be realized with a thermal model which is practical in a real time use. Determining of the component heating has been divided into two parts; defining of component losses and establishing the structure of a thermal network. Basics of both parts are clarified. The simulation environment is Matlab-Simulink. Two different models are constructed – a more accurate one and a simplified one. Potential simplifications are clarified with the help of the first one. Simplifications are included in the latter model and the functionalities of both models are compared. When increasing the calculation time step a decreased number of considered components and time constants of the thermal network can be used in the simplified model. Heating of a switching component is dependent on its topological position and inverter’s operation point. The output frequency of the converter defines mainly which one of the switching components is – because of its losses and heating – the performance limiting component of the converter. Comparison of results given by different thermal models demonstrates that with larger time steps, describing of fast occurring switching losses becomes difficult. Generally articles and papers dealing with this subject are written for two-level inverters. Also inverters which apply direct torque control (DTC) are investigated rarely from the heating point of view. Hence, this thesis completes the former material.

Combined electromagnetic and thermal design platform for totally enclosed induction machines

The aim of the thesis is to design a suitable thermal model that can be used as a tool for constructing the TEFC squirrel cage induction machine in addition to the electromagnetic model. A lumped-parameter thermal model is developed. The related problems and aspects of implementation are discussed in details. Losses are calculated analytically and the loss values are used in the thermal model. The sensitivity analysis is introduced to determine the most critical parameters of the model.

A long way to the rainbow country : understanding the foreign market expansion process of Finnish corporations into the Republic of South Africa between 1999 and 2005

De afrikanska ekonomierna växer med nära fyra procent per år och detta är en god indikation på kontinentens växande betydelse. Under kalla kriget hade afrikanska regeringar haft ett begränsat utrymme för opportunistisk köpslående, och därmed även en marginal att positionera sig strategiskt. Alltför ofta uppmuntrade och beskyddade stormakterna diktatorer och små lokala eliter som främst ville berika sig själv. I och med att globaliseringen tog fart och USA allt mera kom att dominera globalt, började en ny era i fråga om förändringar. Trots dessa förändringar på den globala arenan, har Afrika som kontinent hamnat i bakgrunden och jämfört med andra utvecklingsländer har Afrika attraherat ett fåtal utländska investeringar. Fortfarande, speciellt i Norden, finns det lite kunskap om hur utländska företag expanderar sin affärsverksamhet på den afrikanska kontinenten. Det råder brist på empiriska undersökningar om vilken inverkan afrikanska institutionella förändringar och lokala affärsmiljöer har på internationaliseringen och på de utländska företagens affärsutvecklingsstrategier på den afrikanska kontinenten. Med denna avhandling vill jag lyfta fram ett exempel på ett land (Sydafrika), som har lyckat dra nytta av de förändringar som 1990-talet förde med sig. I denna avhandling har jag intervjuat olika personer i ledande positioner inom olika finländska företag i Finland och i Sydafrika. Avhandlingen skapar en referensram för att öka förståelse och fördjupa analys av hur en kombination av olika interna och externa resurser ökar företagens konkurrenskraft och på det sättet bidrar till en framgångsrik affärsutveckling i Afrika. De politiska och sociala aktörerna samt aktörerna inom affärslivet besitter resurser som ambitiösa företag kan dra nytta av i sin strävan att erövra de nya framgångsrika marknaderna i Afrika. Gradvis ökar finländska företag sina insatser på den afrikanska kontinenten i strävan att skapa mervärde för sina kunder. Den värdeskapande processen gör att parterna måste närma sig varandra utgående från sina egna strategiska målsättningar. Hittills har finländska företag varit intresserad att sälja till Afrika men inte intresserad att köpa därifrån. Förutom de praktiska råden till olika företag, föreslår avhandlingen hur den finska staten och den sydafrikanska staten kunde agera tillsammans för att främja ömsesidigt handelsutbyte.

Höyryturbiinin käytönaikaisen suorituskyvyn seuranta

Tässä diplomityössä jatkettiin Loviisan voimalaitoksen höyryturbiinien suorituskyvyn parannuspotentiaalien tutkimusta. Tavoitteena oli kehittää laitoksen höyryturbiinien suorituskyvyn käytönaikaisia on-line-mittauksia. Selvityksessä perehdyttiin norjalaisen IFE:n kehittämään stationääritilan TEMPOohjelmaan( The Thermal Performance Monitoring And Optimisation system), sen käyttöohjeisiin ja toimintaperiaatteisiin. Työssä esiteltiin laajasti tiedon yhteensovittamisen laskentateoriaa, johon TEMPOn toiminta perustuu. Työssä tarkasteltiin turbiinin todellista paisuntaprosessia, koska sen ymmärtäminen on tärkeässä osassa turbiinin suorituskyvyn valvonnassa. Tutkimuksessa esiteltiin myös turbiineille mahdollisia vikoja sekä niiden syntymisprosesseja. Työssä tarkasteltiin TEMPOn sovittamien tulostiedostojen analysointiohjelman toimivuutta havaitsemalla itse aiheutettuja poikkeamia todellisiin mittaustiedostoihin. Analysointiohjelmalla muodostettuja kuvaajia vertailtiin todellisen prosessin ajotilanteen kuvaajiin ja tarkasteltiin, kuinka poikkeamia on mahdollista havaita kuvaajien avulla. TEMPO-ohjelmalle löydettiin tutkimuksen edetessä kehittämisehdotuksia. Näillä muutoksilla ohjelma saadaan mallintamaan Loviisan voimalaitoksen turbiiniprosessia tarkemmin ja tuloksista saadaan hyödyllisempiä.

Entrepreneurship, Service Innovation, International Expansion and Performance in SMEs: Empirical Evidence from Finnish ICT Industry

The thesis aims to clarify the mixed results of prior literature regarding the performance impacts of entrepreneurship and human capital through service innovation and international expansion. The thesis examines the factors affecting degree of internationalization (DOI) and performance in ICT SMEs. These factors are entrepreneurial orientation (EO), human capital and service innovation (SI). The data was collected via questionnaire from Finnish ICT SMEs. The results suggest that EO consist of three dimensions that have different impact in DOI and SI. Also DOI has inverted U-shaped relationship with international performance, whereas DOI-profitability relationship is linear. The results of the study suggest that SMEs should not blindly increase their DOI, and that strategic focus is important.

Thermal-Aware Networked Many-Core Systems

Advancements in IC processing technology has led to the innovation and growth happening in the consumer electronics sector and the evolution of the IT infrastructure supporting this exponential growth. One of the most difficult obstacles to this growth is the removal of large amount of heatgenerated by the processing and communicating nodes on the system. The scaling down of technology and the increase in power density is posing a direct and consequential effect on the rise in temperature. This has resulted in the increase in cooling budgets, and affects both the life-time reliability and performance of the system. Hence, reducing on-chip temperatures has become a major design concern for modern microprocessors. This dissertation addresses the thermal challenges at different levels for both 2D planer and 3D stacked systems. It proposes a self-timed thermal monitoring strategy based on the liberal use of on-chip thermal sensors. This makes use of noise variation tolerant and leakage current based thermal sensing for monitoring purposes. In order to study thermal management issues from early design stages, accurate thermal modeling and analysis at design time is essential. In this regard, spatial temperature profile of the global Cu nanowire for on-chip interconnects has been analyzed. It presents a 3D thermal model of a multicore system in order to investigate the effects of hotspots and the placement of silicon die layers, on the thermal performance of a modern ip-chip package. For a 3D stacked system, the primary design goal is to maximise the performance within the given power and thermal envelopes. Hence, a thermally efficient routing strategy for 3D NoC-Bus hybrid architectures has been proposed to mitigate on-chip temperatures by herding most of the switching activity to the die which is closer to heat sink. Finally, an exploration of various thermal-aware placement approaches for both the 2D and 3D stacked systems has been presented. Various thermal models have been developed and thermal control metrics have been extracted. An efficient thermal-aware application mapping algorithm for a 2D NoC has been presented. It has been shown that the proposed mapping algorithm reduces the effective area reeling under high temperatures when compared to the state of the art.

Application and development of numerical methods for the modelling of innovative gas cooled fission reactors

Innovative gas cooled reactors, such as the pebble bed reactor (PBR) and the gas cooled fast reactor (GFR) offer higher efficiency and new application areas for nuclear energy. Numerical methods were applied and developed to analyse the specific features of these reactor types with fully three dimensional calculation models. In the first part of this thesis, discrete element method (DEM) was used for a physically realistic modelling of the packing of fuel pebbles in PBR geometries and methods were developed for utilising the DEM results in subsequent reactor physics and thermal-hydraulics calculations. In the second part, the flow and heat transfer for a single gas cooled fuel rod of a GFR were investigated with computational fluid dynamics (CFD) methods. An in-house DEM implementation was validated and used for packing simulations, in which the effect of several parameters on the resulting average packing density was investigated. The restitution coefficient was found out to have the most significant effect. The results can be utilised in further work to obtain a pebble bed with a specific packing density. The packing structures of selected pebble beds were also analysed in detail and local variations in the packing density were observed, which should be taken into account especially in the reactor core thermal-hydraulic analyses. Two open source DEM codes were used to produce stochastic pebble bed configurations to add realism and improve the accuracy of criticality calculations performed with the Monte Carlo reactor physics code Serpent. Russian ASTRA criticality experiments were calculated. Pebble beds corresponding to the experimental specifications within measurement uncertainties were produced in DEM simulations and successfully exported into the subsequent reactor physics analysis. With the developed approach, two typical issues in Monte Carlo reactor physics calculations of pebble bed geometries were avoided. A novel method was developed and implemented as a MATLAB code to calculate porosities in the cells of a CFD calculation mesh constructed over a pebble bed obtained from DEM simulations. The code was further developed to distribute power and temperature data accurately between discrete based reactor physics and continuum based thermal-hydraulics models to enable coupled reactor core calculations. The developed method was also found useful for analysing sphere packings in general. CFD calculations were performed to investigate the pressure losses and heat transfer in three dimensional air cooled smooth and rib roughened rod geometries, housed inside a hexagonal flow channel representing a sub-channel of a single fuel rod of a GFR. The CFD geometry represented the test section of the L-STAR experimental facility at Karlsruhe Institute of Technology and the calculation results were compared to the corresponding experimental results. Knowledge was gained of the adequacy of various turbulence models and of the modelling requirements and issues related to the specific application. The obtained pressure loss results were in a relatively good agreement with the experimental data. Heat transfer in the smooth rod geometry was somewhat under predicted, which can partly be explained by unaccounted heat losses and uncertainties. In the rib roughened geometry heat transfer was severely under predicted by the used realisable k − epsilon turbulence model. An additional calculation with a v2 − f turbulence model showed significant improvement in the heat transfer results, which is most likely due to the better performance of the model in separated flow problems. Further investigations are suggested before using CFD to make conclusions of the heat transfer performance of rib roughened GFR fuel rod geometries. It is suggested that the viewpoints of numerical modelling are included in the planning of experiments to ease the challenging model construction and simulations and to avoid introducing additional sources of uncertainties. To facilitate the use of advanced calculation approaches, multi-physical aspects in experiments should also be considered and documented in a reasonable detail.